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Post by Runic on May 29, 2013 22:40:22 GMT 5
The Golden Eagle is a very large, dark brown raptor with broad wings. However, its size is variable: it ranges from 66 to 102 cm (26 to 40 in) in length and it has a typical wingspan of 1.8 to 2.34 m (5 ft 11 in to 7 ft 8 in).[4][5][6][7] In the largest race (A. c. daphanea) males and females weigh 4.05 kg (8.9 lb) and 6.35 kg (14.0 lb). In the smallest subspecies (A. c. japonica), the sexes weigh, respectively, 2.5 kg (5.5 lb) and 3.25 kg (7.2 lb).[3] In the species overall, males may average around 3.6 kg (7.9 lb) and females may average around 5.1 kg (11 lb).[8] The maximum size of this species is a matter of some debate. Large races are the heaviest representatives of the Aquila genus. For some time, the largest known mass authenticated for a wild female was the specimen from the nominate race which weighed around 6.7 kg (15 lb) and spanned 2.55 m (8 ft 4 in) across the wings.[9] American Golden Eagles are typically somewhat smaller than the large Eurasian races but a massive female that was banded and released in 2006 around Wyoming’s Bridger-Teton National Forest is the now the heaviest wild Golden Eagle on record, at 7.2 kg (16 lb).[10] It should be noted, however, no comprehensive range of weights are known for the largest subspecies (‘’A. c. daphanea’’).[9] Captive birds have been measured up to a wingspan of 2.81 m (9 ft 3 in) and a mass of 12.1 kg (27 lb) (the latter figure was for an eagle bred for the purposes of falconry which tend to be unnaturally heavy), respectively.[9] The standard measurements of the species include a wing chord length of 52–72 cm (20–28 in), a tail length of 26.5–38 cm (10.4–15 in) and a tarsus length of 9.4–12.2 cm (3.7–4.8 in).[5] The culmen reportedly averages around 4.5 cm (1.8 in), with a range of 3.6 to 5 cm (1.4 to 2.0 in) and the bill length from the gape measures around 6 cm (2.4 in).[11][12] The long, straight and powerful hallux-claw (or hind claw, the equivalent to the big toe) can range from 4.5 to 6.34 cm (1.8 to 2.50 in), being about one centimeter more than the hallux-claw of a Bald Eagle (Haliaeetus leucocephalus) and a little more than one cm less than a Harpy Eagle (Harpia harpyja).[13][14][15] The sexes are similar in plumage but are considerably dimorphic in size. Females are rather larger than males with the differences increasing as the body size increases across the races. The large Himalayan Golden Eagles females are about 37% heavier and nearly 9% longer in wing length than the males of the race compared with the small Japanese Golden Eagles where females are a relatively modest 26% heavier and around 6% longer in wing length than males.[16][3]
Adults are primarily dark brown in color, with a paler, typically golden color (the source of the speciesÂ’ common name) on the back of the crown and nape, and some grey on the inner-wing and tail.[17] There are subtle differences in coloration among the races, described below. Unlike in other Aquila species, where the tarsal feathers are typically of a similar color to the rest of the plumage, the tarsal feathers of Golden Eagles tend to be paler, ranging from light golden to white.[3] In addition, some full-grown birds (especially in North America) have white "epaulettes" on the upper part of each scapular feather tract.[18][2] The bill is dark at the tip, fading to a lighter horn color, with a yellow cere.[19] As in many acciptrids, the bare portion of the feet are yellow. [5] This species moults gradually beginning in March or April until September or October each year. Moulting usually decreases in winter. Moult of the contour feathers begins on the head and neck region and process along the feather tracts in a general anterior-posterior direction. Feathers on head, neck, back and scapulars may be replaced annually. With large feathers of the wing and tail, moult beginning with innermost feather and proceeds outwards in a straightforward manner known as "descendant" moult.[20]
The juvenile Golden Eagle is similar to the adult but tends to be darker, appearing black on the back especially in East Asia. Compared to adults, juveniles have a more unfaded color. Young birds are white for about two-thirds of their tail length ending with a broad, black terminal band.[16] Occasionally, juvenile eagles have white patches on the remiges at the bases of the inner primaries and the outer secondaries, forming a crescent marking on the wings which tend to be divided by darker feathers.[3][21] Rarely, juvenile birds may have only trace amounts of white on the tail. Compared to the relatively consistently white tail, the white patches on the wing are extremely variable and some juveniles have almost no white visible. Juveniles of less than 12 months of age tend to have the most extensive amount of white to the plumage.[20] By their second summer, the white underwing coverts are usually replaced by a characteristic rusty-brown color. By the third summer, the upper-wing coverts are largely replaced by dark brown feathers, however not all feathers moult at once giving many juvenile birds a grizzled pattern. The tail also follows a similar pattern of maturation.[20][21] Due to the amount variability in different individuals, juvenile eagles cannot be reliably aged on sight alone.[22] Many Golden Eagles still have white on the tail during their first attempt at nesting.[23] Full adult plumage is not fully attained until the birds are between 5 and a half and 6 and a half years old.[22
Flight physiology
Golden Eagles are sometimes considered the most superlative fliers among eagles and perhaps among all raptorial birds.[24] They are equipped with broad, long wings with somewhat finger-like indentations on the tips of the wing.[5] Golden Eagles are unique among their genus in that they often fly in a slight dihedral, which means the wings are often held in a slight, upturned V.[5] When they must engage in flapping flight, Golden Eagles appear at their most labored but this flight method is generally less common than soaring or gliding flights.[3] Flapping flight usually consists of 6–8 deep wing-beats, interspersed with 2 to 3 second glides.[3] While soaring the wings and tail are held in one plane with the primary tips often be spread.[26] A typical, unhurried soaring speed in Golden Eagles is around 45–52 kilometers per hour (28–32 mph).[27] When hunting or displaying, the Golden Eagle is capable of very fast gliding, attaining up to 190 km/h (120 mph).[3][26] When diving (or stooping) in the direction of prey or in territorial displays, the eagle holds its wings tight and partially closed against their body and the legs up against tail. In a full stoop, a Golden Eagle can reach spectacular speeds of up to 240 to 320 kilometers per hour (150 to 200 mph) when diving after prey. Although less agile and maneuverable, the Golden Eagle is apparently quite the equal and possibly even the superior of the Peregrine Falcon’s stooping and gliding speeds.[2][28] This places the Golden Eagle as the one of the two fastest moving living animals on earth.[9] Although most flight in Golden Eagles has a purpose (i.e. territoriality, hunting, etc.), some flights (such as those by solitary birds or between well-established breeding pairs) seems to function merely as acts of playfulness.[29][2][24]
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Post by Runic on May 29, 2013 22:45:29 GMT 5
At least seven main hunting techniques are known to be utilized by the species, with many individual variations and the ability in most mature eagles to quickly (and sometimes cleverly) vary back and forth between methods depending on the circumstance. The first described is “high soar with glide attack”, where the Golden Eagle soars at least 50 m (160 ft) above the earth. Once it spies a prey item, the eagle partially closes its wings and enters a long, low-angled glide which can carry it over distances of 1 km (0.62 mi) or with speed increasing with wings closing more. Just prior to impact, the wings are opened, the tail fanned and feet thrust forward to grab the prey, creating a booming sound in the instant before the strike that sounds like a clap of thunder.[3] This technique is used for solitary or widely dispersed prey found in openings, such as hares or ptarmigans. A variation of the high soar where a lofty perch is used instead of a soar has been observed.[73] The next major hunting methods is the “high soar with vertical stoop”, which is used to attack birds in flight. Since they are outpaced and out-maneuvered by swift-flying birds, they can only usually attack slower flying species such as geese and cranes. The Golden Eagle also requires a height advantage over their prey for this rarely-observed technique to succeed. In one observed case, some Canada Geese (Branta canadensis) in Montana were able to avoid predation by a Golden Eagle hunting them in this way by collectively gaining flying height.[74] In another observation, a Golden Eagle was successful in knocking a ptarmigan out of a flying covey in Scotland.[75] The next hunting method is the “contour flight with short glide attack”, which is considered the most commonly utilized hunting method for Golden Eagles. This consists of a low-level quartering flight often only about 5 to 15 m (16 to 49 ft) above the ground so they do not break the sky-line when observed from the ground and they can hug the contours of the earth below. This method is useful for hunting colonial (often burrowing) prey such as ground squirrels, densely-populated leporids or birds found in concentrations, such as breeding grouse or even seabirds. The individual prey item is apparently selected in a manner of seconds before the strike.[76][74] If the first attempt fails, the eagle may fly around and attempt to ambush the prey again. The next hunting method is the “glide attack with tail-chase”, which commences with a low-angled stoop some distance from the quarry. The prey is then chased closely, whether a hare running evasively or a grouse in flight. The key to success is eagle's agility and the prey's inability to find cover. In one case, a flying Greater Sage-Grouse (Centrocercus urophasianus) was caught by a pair of eagles using this technique.[77] The next major hunting method is “low flight with slow descent attack”. In this, the Golden Eagle quarters low below the earth and then gradually swoops down on the prey. This is used for slow-moving prey, such as tortoises and hedgehogs, or any prey item with a general absence of escape behavior. This includes any potentially dangerous prey items, such as rattlesnakes and foxes.[78] When hunting mammalian carnivores, the eagle may hover for some time over the potential prey and not press the attack unless the mammal looks down.[74][76] The next is the “low flight with sustained grip attack”, which is used for hunting ungulates. Here, the Golden Eagle flies over a herd of ungulates which in turn often huddle or break into run. The eagle then selects it prey (typically young animals, though sometimes infirm or exceptionally healthy grown animals) and lands on prey's back or neck, talons gripping firmly attempting to pierce vital organs or cause shock via a crushing grip to bone and cartilage . The hunting eagle typically rides its prey for several minutes with wings outstretched and flapping to maintain balance until the prey collapses, either as result of exhaustion, shock or internal injury.[3] The final major hunting method is the “walk and grab attack”, in which the eagle walks on the ground and attempts to pull its prey out of cover. This has been used for pulling jackrabbits out of brush but has even been utilized to grab the young of large prey (i.e. deer, sheep and badgers) literally right out from under their mother’s legs.[29][79][80][3][81] Tandem hunting may be done regularly, especially with larger prey items.[82][83] Reportedly, while hunting in pairs, the male Golden Eagle flies in front of the female at a higher elevation and usually initiates the attack.[26] Breeding pairs have been recorded hunting jackrabbits cooperatively with one individual following the other at different elevations above the ground. The initial pursuer diverts prey’s attention by stooping while the second flies in unseen to make the kill.[84][85] A study in Idaho showed that the success rate was lower during tandem hunting (9%) than during solo hunting (29%), but this may have been due to the more difficult nature of the prey targeted during tandem hunts.[66] As a whole birds are reportedly more difficult prey to capture than mammals, so hunting success rates may be lower where birds outrank mammals in importance as prey.[3] Golden Eagles are not above scavenging for carrion. In fact, it makes up a significant portion (sometimes a majority) of the diet in winter, when ground squirrels are in hibernation and rabbits and hares tend to be at population lows.[3] In the Greater Yellowstone area, the Golden Eagle was one of the most frequent scavengers to attend wolf kill-sites in winter but, unlike Common Ravens (Corvus corax) and Bald Eagles, were not frequent at kills left out by human hunters.[86] In many parts of the range (i.e. Alberta, Scotland, Spain, etc.) carrion was readily fed to the young during the breeding season.[87][3][88]
Prey
While they do show strong local preferences for certain prey, Golden Eagles are first and foremost opportunists and virtually any animal of a reasonable size may be predated if encountered. Prey selection is largely determined by the local availability and abundance of the prey species. Well over 400 species of vertebrate have been recorded as golden eagle prey.[3] They normally prefer wild, native prey but can adapt easily to feeding largely on domesticated and/or exotic animals, most often when the prey returns a feral state. This is most apparent in islands that have hosted successfully nesting Golden Eagles despite having very few (or no) native land mammals, such as Corsica in Italy, Santa Rosa and Santa Cruz Islands in California and many of the Inner and Outer Hebrides of Scotland.[89][90][3] Most analysis of dietary habits of raptors results from examining the prey remains around an active eyrie at the end of the breeding season (September or October), based on pellets, skeletons and skins found. This method is not comprehensive for Golden Eagles, as particularly small prey may leave no trace and it cannot take into account the prey selected by highly nomadic juvenile eagles (which is believed to include a higher level of carrion and large prey items). However, since eye-witness accounts of hunting and close monitoring of prey brought to the nest are both rare and likely to disturb the eagles, this is the best known method of studying the eagle’s prey.[3] The complied dietary breadth (the average number of prey species found in an active eyrie) in a number of studies on the species have revealed that the average Golden Eagle nest contains 3.57 species of prey. There is considerable variation in the dietary breath across the range based on access to preferred prey, ranging from an average of a 11.2 breadth in the French Pyrenees to a mere 1.4 breadth in Alaska.[91][92] In general, the dietary breadth of Golden Eagle is greater in Eurasia than it is in North America, where eagles frequently only need to hunt two or three species throughout the nesting cycle.[3] This is a moderate dietary breadth by the standards of the ‘’Aquila’’ genus, being higher than that estimated for Steppe Eagles from Asia Minor (Aquila nipalensis orientalis) at 1.69 (with a focus on the Little Ground Squirrel (Spermophilus pygmaeus)) and the Verreaux's Eagle, with an average dietary breath of 1.79 (with a focus on the locally abundant species of rock hyrax). However, some Aquila have a higher average dietary breadth, such as the Wedge-tailed Eagle at 4.92 and the Tawny Eagle at 6.36.[3] Similarly, in southwestern Idaho, the dietary breadth was intermediate, being higher than that of Prairie Falcons (Falco mexicanus) but lower than that of Red-tailed Hawks (Buteo jamaicensis).[93] Some studies have attempted to estimate the mean weight of prey taken by Golden Eagles as well. Most prey taken appear to be around half the weight of the predating eagle, with a typical prey weight range of 0.5–4 kg (1.1–8.8 lb) but mostly in the lower half of that range.[3] If the estimated weight of the prey is broken down into categories, 24 dietary examinations have revealed the following: 2.4% of prey taken weighs under 63 g (2.2 oz); 3.3% of prey weighs from 63 to 125 g (2.2 to 4.4 oz); 4.3% weighs 125–250 g (4.4–8.8 oz); 14.2% of prey weighs 250–500 g (8.8–18 oz); 26.6% weighs from 500 to 1,000 g (1.1 to 2.2 lb); 19.5% is 1–2 kg (2.2–4.4 lb); 13.8% from 2 to 4 kg (4.4 to 8.8 lb); and 15.8% weighs over 4 kg (8.8 lb).[3] The average estimated weight of prey during the breeding season ranges from 2.27 kg (5.0 lb) in Scottish Islands (where lambs, deer fawns and rabbits are available in great numbers) to 1.39 kg (3.1 lb) in North America.[3] At a nest in Mongolia, nest site prey items appear to be heavier than those known elsewhere in the range, with an estimated mean weight of around 3 kg (6.6 lb).[94] The mean figure of these studies has shown as estimated mean prey weigh of 1.614 kg (3.56 lb) for Golden Eagles across their range.[3] Overall, prey for Golden Eagles has ranged in mass from 10 g (0.35 oz) to at least 114 kg (250 lb).[93][95] The average estimated weight of prey taken by most other Aquila species is generally much lower but the Wedge-tailed Eagle seemingly takes prey of a similar weight (both in average and range of prey weights) while the Verreaux's Eagle average prey weight is higher, probably over 2 kg (4.4 lb).[3][96] The most significant group of prey for Golden Eagles is mammals. In 59 studies of the breeding season diet across the range, 63.2% of prey remains were mammals.[3] The diet in North America is particularly skewed towards mammals with roughly 84% of a sampling of 7094 prey items from there being mammalian.[97] After mammals, other birds were most significant, comprising about 26.8% of prey.[3] Reptiles compromised about 7% of prey from across the range, with other prey groups compromising the remaining 3%.[3] All the diverse groups of prey are examined below, using mainly the aforementioned 59 dietary studies.
Leporids
The most significant prey group, by far, is the rabbits and hares of the family Leporidae. Overall, this group comprises about 32% of prey known to be taken by Golden Eagles.[3] The estimated range of weights of hares hunted by Golden Eagles is 1.36 to 3.7 kg (3.0 to 8.2 lb), whereas rabbits hunted weigh a little under 1 kg (2.2 lb) on average.[24] Where a wild or feral species of leporid is available in abundance or, especially, where two species (often a larger hare sp. And a smaller rabbit-like sp.) are common the Golden Eagle thrives. In almost every study in the contiguous western United States, leporids dominated the diet. 12 out 16 dietary studies in North America showed leporids as the most common prey group. In the northern Rocky Mountains and Northern Plains areas, the main prey species are the White-tailed Jackrabbit (Lepus townsendii) and the Mountain Cottontail (Sylvilagus nuttallii). In the more arid vicinity of the vast Great Basin, the Southwest and most of California, the main prey species are the priorÂ’s cousins, the Black-tailed Jackrabbit (Lepus californicus) and the Desert Cottontail (Sylvilagus audubonii). The Black-tailed Jackrabbit is especially important. As of 1976, the species comprised about a quarter of a sampling of 7094 prey items in North America.[97] More locally other jackrabbits and cottontails may be taken in smaller numbers. In 17 nests (sample size 503 prey items) Nevada the family compromised 85.6% of the remains and in the Four Corners area (the meeting of Arizona, Texas, Utah and New Mexico) they compromised 75.6% of 660 remains in 191 nests.[98][99] In two studies in southern Idaho, the Black-tailed Jackrabbit and the two cottontails dominated the diet, comprising 72.8% of a sampling of 311 from 74 nests and 72.6% of a sampling of 456 from 8 nests.[100][101] In nests in New Mexico, leporids made up 65.8% of the remains from 53 nests.[102] The Snowshoe Hare (Lepus americanus) is thought to be the dominant species in the Golden Eagle diet in the boreal forests of North America but there have been no dietary studies conducted there. It is known the Snowshoe, along with the larger Arctic Hare (Lepus arcticus), are some of the most significant prey species in Alaska. 17 nests along the Porcupine River in Alaska consisted of 59.1% leporids (sampling of 66).[53] In one central Alaskan nest (sample size 53) the two aforementioned hares were secondary to ptarmigan and nests (sample size 690) in Denali National Park included only 0.4% leporid remains.[103][91] Nests in Alberta and Washington had almost no leporid remains as well.[87][104][55]
19 out of 45 studies in the Palearctic listed leporids as the most common family of prey for Golden Eagles. In Scotland, the most significant prey species are the Mountain Hare (Lepus timidus) and the introduced European Rabbit (Oryctolagus cuniculus). The family represented from 10.7 to 46.9% (the highest number from the southern Inner Hebrides) of prey remains in Scotland. Surveys of nests from nine different regions of the Scottish Highlands, showed leporids averaged at 27.2% of the prey intake amongst a 1249 sample size from 217 active nests.[3] In Spain, the European Rabbit is the cornerstone of the Golden EaglesÂ’ diet, comprising from 47.6% to 66.5% of their diet in studies conducted in different regions of the country.[105][106] Again, the European Rabbit is the greatest prey item in the Central Massif of France, comprising 33.7% of a 83 specimen sample size out of 5 nests.[107] The Brown Hare (Lepus europaeus) and European Rabbit were the leading prey items in Switzerland, making up 28.8% in 65 nests with a 308 sample size.[108] Some parts of the French Alps host all three species (Brown & Mountain Hares as well as Rabbits) and they comprised 50.9% at 7 nests with a 109 sample size.[109]The Brown Hare and European Rabbit dominate the diet (48.8% and 39.6%) in two studies of the Apennine Mountains of Italy, one involving 5 nests with a 160 sample size and another 7 nests with a 149 sample size.[110][111] Brown Hare were reportedly the most common prey in Armenia though no quantitative data is available for that region.[112] In 5 nests (sample size 967) Japan, about half of all prey examined at nests was comprised by Japanese Hare (Lepus brachyurus).[113] 10 nests (with a sample size of 74) in Sicily, showed that the non-native European Rabbit was the main prey item, making up 29.7% of the remains.[114] 52 nests studied in Mali and Niger showed that Cape Hares (Lepus capensis) were the primary prey species, making up 79% of the found remains.[115]In the Bale Mountains, Ethiopian Highland Hare (Lepus starcki) dominated the diet, providing about half of the prey items.[116] In some areas leporids are secondary prey, such as Scandinavia, where the Mountain Hare comprised about 20% to of prey items, the maximum known being 28.4% in Northern Finland (in more than 50 nests with a sample size of 3766).[117] The Tolai Hare (Lepus tolai) was a secondary prey item in Mongolia, making up around 21% of prey.[94] The European Rabbit appears to be secondary in Hungary, where it comprised 14.3% out a sampling of 49 from 4 nests.[118]
Across the Golden Eagle’s range, hares and rabbits are generally known to be hunted via either “high soar with glide attack” or “contour flight with short glide attack”. Leporids are basically solitary animals but they can occur at high densities, such as when jackrabbits are at their peak numbers in brushy areas of Western North America or (historically at least) rabbits in similar brush habitats on the Iberian peninsula. The goal of the Golden Eagle while hunting hares and rabbits is to catch the prey when it is foraging out in the open. If the leporid becomes aware of the eagle’s descent upon them more than a few seconds before the strike, they invariably break into a fast, hopping run. Once contact is made, rabbits and hares will often kick or try to bite the eagle but escape is unlikely once they are pinned to the ground. In some case they are able to reach vegetative coverage and, if the said cover is sufficiently deep and dense, the eagle cannot pursue them any further. Although rare, Golden Eagles have been known to use the “walk and grab attack” to grab and yank a lagomorph out of its cover. Many hunts in Scotland of Mountain Hare involve a somewhat lengthy tail chase.[3] If the Golden Eagle is able to intercept a rabbit or hare far out in the open, a twisting and turning tail chase frequently occurs but the odds of survival for the prey are smaller the farther they are from coverage. On occasion, breeding pairs have been observed to hunt jackrabbits together, where in one will stoop on a gathering of them while the other waits out of sight and assaults one of the jackrabbits being made to run.[66]
Ground squirrels
After the leporids, the next most significant group in the diet of Golden Eagles is the ground squirrels. They comprise about 11.2% of the prey taken by this species across the range. In areas where leporids are scarce, this group of rodents seems to become more prominent. In many parts of the Golden EagleÂ’s range, ground squirrels are rare or absent, such as the British Isles, the Iberian Peninsula and some portions of central Eurasia. Nonetheless, about half of the large Spermophilus group, all species of prairie dog, three out of four species of antelope squirrel and nearly all the species of marmot has been found as Golden Eagle prey. Nests in Denali National Park in Alaska included, among a sampling of 690 remains, contained 84.2% Arctic Ground Squirrels (Spermophilus parryii).[91] Studies in Alaska have shown that the other major prey species in Alaska, the Willow Ptarmigan and the Snowshoe Hare, follow a 8 to 11 year population cycle. The locally abundant ground squirrels have less dramatic population variations and come out of hibernation in mid to late May (shortly after the eagles return from migration). The Alaskan Arctic Ground Squirrel appears to be eaten supplementally in peak years but then fill the primary niche when the ptarmigan and hare populations crash.[119][120] In Alberta, Columbian Ground Squirrels (Spermophilus columbianus) (occasionally supplemented by other species like Yellow-bellied Marmots) were the primary prey species, made up 84% of the diet of eagles nesting there.[87] In the French Alps, the most significant prey species is the Alpine Marmot (Marmota marmota) at 68.9% out of a sampling of 198 from 6 nests.[121] This is also the main prey species in the Italian Alps above the tree line, comprising 49.7% of a sample size of 79 from 12 nests.[122] In the Caspian Sea area of Kazahkstan, Yellow ground squirrels (Spermophilus fulvus) are the most important mammalian prey at 23.4% of a sampling of 468 from 36 nests.[123] Along Coastal California, California Ground Squirrels (Spermophilus beecheyi) replace Black-tailed Jackrabbits (which are scarce there) as the primary prey species.[60] In Washington state, where the Golden Eagle inhabits mainly forest openings made by humans, the Yellow-bellied Marmot (Marmota flaviventris) is the main prey species, making up 41.8% of a sampling of 47 from 2 nests and 40.3% of a sampling of 315 from 74 nests.[104][55] In many other areas, ground squirrels are secondary prey, usually ranking after lagomorphs in dietary significance. This is especially true in the contiguous Western United States outside of Washington state and coastal California where they often register as second, third or even fourth most represented family by remains. Prairie dogs feature only as supplemental prey for breeding Golden Eagles but wintering eagles reportedly prey heavily on colonies of Black-tailed Prairie Dogs (Cynomys ludovicianus).[124][125] Although rare, tree squirrels have turned up as prey in some eagle nests in both North America and Eurasia.[3][97]
Ground squirrels are generally quite social animals and some species even live in cohesive colonies. All ground squirrels live in burrows, which in species like prairie dogs can be quite elaborate. The “contour flight with short glide attack” is essentially the one and only hunting technique used by Golden Eagles on ground squirrels. Ground squirrels usually forage within running distance of one of their burrow entrances, so it is essential for the Golden Eagle to have a surprise factor. Eagles will not enter burrows, unlike some mammalian carnivores that eat ground squirrels. When they hunt ground squirrels, Golden Eagles seem to choose their victim in the last few seconds before they strike. Most of the ground squirrels targeted by the eagles are quite small, with the entire Spermophilus group and some prairie dogs weighing under 1 kg (2.2 lb). Marmots are a more challenging catch since most species weigh at least 1.5 to 3.5 kg (3.3 to 7.7 lb) in spring and about twice that by fall, which is roughly the highest weight feasible for a flying eagle to carry. Although they may locally target large numbers of juveniles, in other cases they may dismember an adult marmot after a kill so they are able to carry it to the nest.[104][3] In the Alps, it is believed to be advantageous for eagles to nest below the meadows that host their Alpine Marmot prey so they can fly downhill, a much easier flying method when carrying a heavy load.[122]
Grouse
Although absent or rare in some areas where the Golden Eagle occurs, this family can locally have an intense prey-predator relationship with the species. They are by far the most significant family of birds in the diet of Golden Eagles, making up 10.3% of their known prey.[3] In Scandinavia and the Baltic States, grouse are in fact the primary prey for these eagles, displacing mammals altogether. The main prey species in most of this sizeable area is the largest species of grouse, the Western Capercaillie (Tetrao urogallus), supplemented by its cousins, the Black Grouse (Tetrao tetrix) and the Hazel Grouse (Tetrastes bonasia). However, in the northernmost parts of Scandinavia, these species are replaced in the diet by the smaller-bodied but often abundant Willow Ptarmigan (Lagopus lagopus) and Rock Ptarmigan (Lagopus muta). Grouse make up 63.3% of the diet in northern Sweden (sampling of 2803 from 105 nests), 54% in another study of northern Sweden (sampling of 2792 in 105 nests), 55.5% of the diet in south Finland (sampling of 1796 from more than 50 nests), 47.6% of the diet in north Finland (sampling of 3766 from more than 50 nests) and 53% in Norway (sampling of 469 from 37 nests).[126][127][128][117][129] From a sampling of 749 from more than 10 nests in Belarus, grouse were the most common family of prey at 47.8%.[130] In Estonia, the prey base is more varied, but grouse were still the most represented bird family, comprising 18.1% of a sampling of 133 from 4 nests.[131] The Red Grouse, a race of Willow Ptarmigan (Lagopus lagopus scotica), and the Rock Ptarmigan (there simply called the Ptarmigan) also occur heavily in the Golden EagleÂ’s diet in parts of Scotland, up to 47.8%, as recorded in the East Highlands (28 nest, 143 sample size).[3] One paper in Alaska showed that the two ptarmigan species (primarily the more abundant Willow) made up 49.1% of the remains in a Golden Eagle pairÂ’s nest, making it the only known study in North America where birds were more prevalent in the diet than mammals.[103]Other reports from Alaska show the Willow Ptarmigan as secondary prey.[119] In some other areas, grouse are also taken as supplemental prey. In the Italian Alps (above tree line), Black and Hazel Grouse (and an occasional Rock Ptarmigan) made up 19.4% of the remains in 12 nest (79 sampling), being the most common avian prey there.[122]In eastern Washington state, Sooty Grouse (Dendragapus fuliginosus) were the second most significant prey species (at 13%) after Yellow-bellied Marmot.[55] It seems likely that every species of grouse is prey of the Golden Eagle as the Black-billed Capercaillie (Tetrao parvirostris) and the Siberian Grouse (Falcipennis falcipennis), the only two not mentioned in literature regarding the eagleÂ’s diet, both overlap in distribution with Golden Eagles and occur outside of areas where the Golden Eagle has been closely studied.[3]
Golden Eagles generally hunt grouse using the “contour flight with short glide attack” method, since grouse are often found in small groups. The usual response of the grouse to the eagle is to take off in flight, in unison if found in a group. They can, despite their short wingspans, take flight directly from the ground with considerable power. Frequently, a Golden Eagle will abandon the hunt after the grouse has flown, since it is unlikely to overtake such prey in the air unless it gains height over its quarry extremely fast. If it is able to surprise the grouse, the eagle frequently has a split second to grab the prey before it flies off. As previously described, Golden Eagles are sometimes, in fact, able to gain the appropriate height to tail chase a grouse or even catch it while flying high using the “High soar with vertical stoop attack”. In a few cases, in an atypical behavior, Golden Eagles will drop a rock near the grouse (as was recorded with a juvenile eagle unsuccessfully hunting Dusky Grouse (Dendragapus obscurus) in Idaho), possibly with the goal of spooking the bird into flight and then overtaking it with a flying height advantage.[132] Although they are equally likely to attack both males and females, the fact that all cock grouse display in spring, often loudly and spectacularly, on “leks” may renders them more distracted and more easily found. The Golden Eagle appears to use a different tactic with the exceptionally large adult cock Western Capercaillie, which are quite aggressive when on a lek. A video taken in Norway shows a Golden Eagle of roughly similar size to its prey landing between two feuding cock capercaillies and facing off with one of the two males. For a moment the cock calls angrily at it and then both the capercaillie and the Golden Eagle present their sharp claws, but the cock is ultimately outmatched and is pinned down and killed. The dead cock’s rival stays nearby calling angrily and then tries to confront the eagle with the same unfortunate outcome for itself.[133] In Sweden, most of the capercaillie remains appeared to be those of the more modestly-sized adult females.[127]
Pheasants
In generally warmer areas of the Eurasian continent, the diverse pheasant family replaces the grouse as the significant group of birds in the Golden Eagle’s diet. Across the range, pheasants make up 5.7% of the diet of this species. Unlike grouse, pheasants are not known to comprise more than half of the nest remains in any study, but they can be important nonetheless. This is especially true in Spain, where most studies show that the pheasants at 22.8-28.7% of the diet, mainly the Red-legged Partridge (Alectoris rufa), are the second most prominent prey species after the European Rabbit, with the Red-legged Partridge and the Rabbit collectively making up to more than 90% of the prey remains in several nests there.[105][106]The Red-legged species, along with the Rock Partridge (Alectoris graeca) and Grey Partridge (Perdix perdix), are the leading prey group in the French Pyrenees at 15.8% of a sampling of 114 from 10 nests.[92] In Hungary, the Common Pheasant (Phasianus colchicus) appears to be the favored prey species, making up 26.6% of the prey of a sampling of 49 from 4 nests there.[118] In Japan, the Copper Pheasant (Syrmaticus soemmerringii) is the second most common single prey species, making up 17.8% of the remains (sample size of 967 from 5 nests).[113] In the Caspian Sea area of Kazakhstan, the most common bird species (and third most common overall prey species) is the Chukar (Alectoris chukar), representing 19.5% of a sampling of 468 from 36 nests.[123] Chukar and Caspian Snowcock (Tetraogallus caspius) are reportedly the primary avian prey species in Armenia.[112] In the Himalayan region, two very large pheasants, the Himalayan Monal (Lophophorus impejanus) and the Himalayan Snowcock (Tetraogallus himalayensis), are reportedly among the most significant prey for eagles.[44] Moorland Francolin (Scleroptila psilolaemus) were reportedly the most common bird prey species in Ethiopia’s Bale Mountains, comprising 10% among a sample size of 49 at 4 nests.[116] North America has fewer native pheasants species but introduced species such as Grey Partridge, Ring-necked Pheasant and, especially, Chukar are readily hunted (native quail seem to be largely or entirely ignored as prey by Golden Eagle, perhaps because of their small size or dense thicket-dwelling habits).[134][135][55][97] The Chukar is the most significant bird species in the diet in Nevada (at 5.4%) and the second most significant bird species in Washington state (at 11.8%).[98][104][55] One native North American “pheasant” known to be occasionally hunted is the Wild Turkey (Meleagris gallopavo), the largest species of galliform. The Golden Eagle is the only major avian predator of adult turkeys. The hunting techniques used on pheasants are probably similar to those used for grouse. On a wildlife monitoring camera in Tennessee, a Golden Eagle was filmed assaulting an adult Turkey, appearing to use a “contour flight with short glide attack” but the quarry in this case appears to successfully avoid the strikes by running and then ultimately flying away.[136] Breeding pairs of eagles have been known to hunt turkeys cooperatively.[137]
Ungulates
The contribution of ungulates to the diet of Golden Eagles has long since been the most controversial and debated aspect of the species’ whole biology. In total, deer comprise about 4.97% of all Golden Eagle food, bovids about 4.92%, pigs about 0.71% and pronghorns much less than even that.[3]That this species occasionally hunts domestic stock and preferred game species has frequently has been used as the justification for wanton poisoning, shooting and trapping of the great eagles. Sheep farmers in Scotland have historically claimed that they up to 80% of deaths in their flocks of Domestic sheep (Ovis aries) were caused by eagles, clearly a wild exaggeration. [24][138] Leslie Brown claimed, to the opposite extreme, that it was “physically impossible” for a Golden Eagle to kill any ungulate scaling several times their own weight.[24] The truth lies somewhere in between. Almost all predation on live ungulates is directed at lambs, fawns or kids and these mostly in the first few months of life.[139] Once they exceed a certain size, it is not practical for breeding eagles to predate the growing ungulates not only due to the difficult and dangerous nature of the kill but also the fact it would be too heavy to carry to the nest. Sheep are sometimes eaten in considerable numbers, especially in the Inner and Outer Hebrides of Scotland where 25.9% and 26.8% of the remains at nests were comprised by sheep. Differentiating whether a lamb has been caught and killed while alive or scavenged as a carcass can be difficult, but if the remains are in good condition is it possible via the placement and depth of talon wounds, the amount of bruising in the pelt and the apparent amount of external bleeding. In one examination of remains in appropriate condition in Scotland, it was found that out of the remains of 10 lambs at Golden Eagle nests, 3 had been taken alive and 7 after they had died.[24][140] This indicates most lambs are taken as carrion, a fact often borne out by the fact that much ungulate carrion found around active nest sites in Scotland is already in a malodorous and putrid state.[3] Domestic goats (Capra aegagrus hircus) are occasionally predated as well. Goats slightly outnumbered sheep in the diet of eagles breeding on Corsica, with both domesticated animals making up 20.5% of the diet there and being the most important food source.[89] In North America, lambs and goats were found to comprise less than 1.4% of all prey items.[141] In Montana, it was found that most predation on lambs by Golden Eagles was committed by juvenile eagles or eagles that failed to breed (which have no need to carry prey to a nest). There it was found that the hunting of domestic stock peaks during wet, cold springs that seemed to adversely effect the local abundance of jackrabbits.[142] Pigs (including feral and domestic varieties) are occasionally taken, especially in insular populations. Pigs (most certainly taken as carrion) made up to 13.3% of the diet in Corsica (out of a sampling of 332 from 16 nests) and 43.1% on Santa Cruz Island, California (out of a sample size of 161 from 6 nests) before the prey was eradicated from the latter.[89][90] Few wild pigs co-exist with Golden Eagles but Wild Boar (Sus scrofa) (likely only as piglets or carrion) have been taken in Bulgaria.[143]
Of wild species of ungulate, certainly deer are the preferred family. In nests found below the tree line in the Italian Alps area, the most common prey species of all was the European Roe Deer (Capreolus capreolus), which made up 32.2% of 168 remains from 10 nests there.[122] The Roe Deer was also a prominent prey item also in the French Pyrenees (14.9%) and Switzerland (14.6%), respectively.[92][144] In several parts of the Scottish Highlands, Red Deer (Cervus elaphus) are eaten with some regularity, making up 22.3% of prey remains in the Northwest Highlands. In North America, several deer species, but mainly Mule Deer (Odocoileus hemionus) fawns, were significant in the diet in Washington state (14.3%) and California (12.7%).[145][73] Around the Himalayas, the small Himalayan Musk Deer is reportedly a favorite prey item (though no quantitative analysis are known).[44] In the near Arctic regions of Scandinavia, reindeer (Rangifer tarandus) of both semi-domestic and wild stock are fed on with some regularity. Nests in the mountain tundra of Northern Sweden bore reindeer as 11.4% of 2803 prey items from 105 nests.[126] In the sub-Arctic areas of Alaska, Golden Eagles are more scarce than in equivalent areas of Scandinavia and only rarely hunt the sizeable local herds of wild reindeer.[146] Partial moose (Alces alces) remains were even found at a nest in Sweden.[127] Once again, fawns are the main live prey items and carrion probably comprised most of the Golden EagleÂ’s take of deer (certainly in larger-bodied species such Red Deer). Among wild bovids, eagles are reportedly the main predator of Saiga Antelope (Saiga tatarica) calves in Mongolia and are regularly reported to take Chamois (Rupicapra rupicapra) and Alpine Ibex (Capra ibex) calves in Europe.[147][148][149] Mongolian gazelles (Procapra gutturosa) comprised about 15% of the remains found at a nest in Mongolia (sample size of 78).[94] Up to 7 wild species of goat, 5 other wild species of sheep and at least 2 wild gazelle species are confirmed Golden Eagle prey.[3] In North America, Pronghorn (Antilocapra americana) are occasionally hunted by Golden Eagles.[83]
As previously described, the “low flight with sustained grip attack” is the main method of predation used on ungulates and can take anywhere from a few seconds to at least 15 minutes to kill the prey.[150][3] The average lamb or reindeer calf found in Golden Eagle nests is estimated to weigh 5 kg (11 lb).[127][3] The average Chamois calf and Roe Deer fawn taken to nests in the Alps were both estimated at 3.7 kg (8.2 lb).[151][122] The average weight of Odocoileus deer fawns taken to nests in Washington was estimated at 3.63 kg (8.0 lb).[55] The average piglet taken on Santa Rosa Island in California was estimated to weigh 2.5 kg (5.5 lb).[90] In each case, the estimated weights given for ungulate prey is roughly similar to the average newborn weight for that respective species, and most ungulates taken are about the same weight as a Golden Eagle.[3] The taking of larger ungulates is exceptional but has been verified in several cases. This kind of attack is most likely to happen in late winter or early spring, when other available prey tends to be at a population low, and (in most of the range) eagles are not concerned with carrying prey to a nest. In Scotland, Golden Eagles have been confirmed to kill Red Deer calves of up to 20 kg (44 lb) in mass and have been captured on film attacking an adult Red Deer but not carrying through with the hunt.[152][153] Both adult and kid Chamois and Ibex have been confirmed as prey and, in some cases, have been forced off of cliff edges to fall to their deaths, after which the eagle can dismember and feed on the remains.[148][154][151] At a Mongolian nest, an apparently live-caught, dismembered adult Mongolian Gazelle was observed.[94] Adult pronghorns of a mass of 27 to 32 kg (60 to 71 lb) in mass have successfully attacked and killed by Golden Eagles.[83][155] Unsuccessful attacks on both adult Mule[156] and White-tailed Deer (Odocoileus virginianus)[157] have been recently filmed but there is only a single account that mentions predation on an adult White-tailed Deer[77]. Adult Roe Deer, being relatively modestly-sized, are possibly taken with some regularity unlike adults of other deer species.[3] A handful of confirmed attacks on adult sheep, exceptionally including healthy adults, estimated to weigh around 52 to 70 kg (110 to 150 lb) have occurred in Scotland.[3] Reindeer calves, of an estimated average weight of 12 kg (26 lb), were routinely killed in Finland per one study.[158] More remarkably, adult female reindeer weighing 60 to 70 kg (130 to 150 lb) have been killed in 3 cases in central Norway.[159] Few records of predation on domestic cattle are known but a detailed examination of calf remains has shown that Golden Eagles in New Mexico, mainly wintering migrants, killed some 12 and injured 61 weighing from 41 to 114 kg (90 to 250 lb) from 1987 to 1989 .[95] A record of a Golden Eagle killing a calf weighing 227 kg (500 lb) may need further confirmation.[160] Certainly, no other living bird of prey has been verified to kill prey as heavy as these, although Wedge-tailed, Martial and Crowned Eagles have been confirmed to kill prey estimated to weigh up to 50 kg (110 lb), 37 kg (82 lb) and 30 kg (66 lb), respectively.[161][5]
Other mammals
Mice, rats and their allies can occasionally comprise an important portion of the Golden Eagle’s diet, making up 3.05% of prey throughout the range.[3] Most mouse-sized mammals are too small to serve as regular prey but in marginal habitats, they can become more important. On Santa Rosa Island and Santa Cruz Islands, the North American Deer Mouse (Peromyscus maniculatus) is fairly important prey, comprising up to 11.6% of the prey remains collectively.[90]In northern Sweden, murids were fairly significant, especially Norway lemming (Lemmus lemmus), making up to 11.7% of the remains from 105 nests (2803 sample size).[126] Brown Rat (Rattus norvegicus) are semi-regular secondary prey in Scotland, comprising up to 10.9% of the remains at nests (a sampling of 274 from 29 nests) in the North Highlands.[3] In more arid parts of the range, assorted rat-sized rodents may be important secondary prey. In the Caspian Sea region of Kazahkstan, Great Gerbils (Rhombomys opimus) were one of the most important prey species for Golden Eagles, making up 18.7% of the remains.[123] In the Bale Mountains, grass rats, especially Blick's grass rat (Arvicanthis blicki), are the second most important prey group, making up approximately 26% of the diet, with the Big-headed mole rat (Tachyoryctes macrocephalus) being another semi-regular prey item there.[116] Mammalian carnivores can compete for some of the same prey as Golden Eagles but can also become prey for the eagles themselves. The main prey family of carnivores is the canids. 12 species of canid are known to have been hunted by Golden Eagles and they collectively make up about 2.8% of the diet from all surveyed Golden Eagle nests. For the most part, foxes are the preferred prey. Among these kits (young) are usually targeted as prey, though foxes of any age or condition, including adult male Red Foxes (Vulpes vulpes) heavier than the eagles themselves, may be hunted.[162] Across much of both species’ ranges, Red Fox co-exist with Golden Eagles and eagles hunt them in small numbers. In Sicily, Red Foxes make up 13.5% and, in the Republic of Macedonia, they make up 5.9% of a sampling of 85 from 19 nests.[163] In a nest in Mongolia, Corsac Fox (Vulpes corsac) were surprisingly the main prey species, making up 38% of a sampling of 78 remains.[94] Kit Fox (Vulpes macrotis), Swift Fox (Vulpes velox), Gray Fox (Urocyon cinereoargenteus) and Island Fox (Urocyon littoralis) are readily predated in North America.[164][165][90][97] The other family of carnivores that turns up with some regularity in the Golden Eagle’s diet are the mustelids, at about 2.3% of the diet.[3] Everything in this diverse family from Least Weasels (Mustela nivalis) to Wolverines (Gulo gulo), have turned up as prey in Golden Eagle nests.[166][127] Most prevalent of this family are probably the martens, with species like American Marten (Martes americanus), Pine Marten (Martes martes) and Beech Martens (Martes foina) having been been found with some regularity around Golden Eagle nests. The young of larger species are also occasionally hunted in Scotland and Ireland, including Eurasian Otters (Lutra lutra) and Eurasian Badgers (Meles meles).[3] Similarly, amongst Wolverines, “young and inexperienced” specimens are usually targeted as prey by Golden Eagles.[167] In North America, full-grown large mustelids, including American Badgers (Taxidea taxus) and Fishers (Martes pennanti), have also turned up as prey.[97][168] The largest percentage of mustelids was 13.2% in a nest was in central Alaska.[103] Mustelids, mainly martens, turned up in large numbers in the French Alps where they made up 10.1% of the remains from 7 nests (109 sample size).[109] Cats are rarer in the diet, occasionally turning up in the diet of European eagles, such as in the French Alps where 3.4% of the remains were felid and the Republic of Macedonia where 2.2% was from cats.[163] Mainly domestic cats (Felis catus) are taken but Wildcats (Felis silvestris) are also known to be hunted.[3] Rarely, the Bobcat (Lynx rufus) have been reported as prey in North America[97] and the remains from the much larger Eurasian Lynx (Lynx lynx) (age undetermined) have been found in a nest in Sweden.[127] Among the more bizarre carnivores reported in the diet come from a handful of accounts from North America and Scandinavia of Golden Eagles hunting and flying off with small cubs of American Black (Ursus americanus) and Brown Bears (Ursus arctos), of an estimated weight of 3 to 5 kg (6.6 to 11 lb).[169] Similarly, the pups of Spotted seals (Phoca largha) and Harbor seals (Phoca vitulina) have reportedly hunted.[170][171] The only other family of mammals to be important in the Golden Eagle’s diet is the hedgehogs, making up 1.5% of the diet throughout the range, though only known as prey in Europe. The European Hedgehog (Erinaceus europaeus) appears to be the most important prey species on the Swedish island of Gotland, making up 42.5% of a sampling of 645 from 3 nests.[172] In Estonia, the Southern white-breasted hedgehog (Erinaceus concolor) was the most significant prey species at 28.6% of a sampling of 133 from 4 nests.[131] The latter species was the most important mammalian prey at 13.8% of the remains 2 nests (sample size 65) in the Sarena Srenda Mountains of Bulgaria.[143] Previously unmentioned families of mammals which comprise less than 1% of prey for Golden Eagles include: dormice (maximum representation being 10.9% of prey below the tree line in the Italian Alps) [122], pocket gophers (up to 2.1% of prey in Arizona)[173], moles (maximum being 1.4% of prey in the Massif Central of France)[107], raccoons (maximum being 1.3% in New Mexico)[174], horses (up to 1.2% of the prey in the Republic of Macedonia)[163]), kangaroo rats (maximum representation being 1.1% in Idaho), porcupines (maximum being 0.6% of prey in Italy’s Apennine Mountains)[111], shrews, pikas, and, rather bizarrely, chinchillas (reported as 0.1% of prey in Idaho from far outside their native range)[101].
Other birds
Although quantitatively outnumbered by mammals, birds are the most diverse class of prey in the Golden Eagle’s diet, as more than 200 species have been identified at eagle nests. Little analysis has gone into how regularly Golden Eagles will attack the nestling and fledglings of other birds, although it has been interpreted that this behavior is not uncommon.[2] Nestling-aged Rock Pigeons (Columba livia) have been observed as prey in Golden Eagle nests.[175] The first record of a Golden Eagle eating eggs was recorded when a Golden Eagle was observed consuming Canada Goose (Branta canadensis) eggs in eastern Idaho.[176] After large galliforms, the next most significant group of prey among birds is the corvid family, making up 4.1% of the diet from around the range. Most prevalent among these are magpies and the large-bodied Corvus (crow and raven) genus. On Santa Rosa and Santa Cruz Islands in California, Common Raven became the most common prey species after feral pigs were eradicated from the latter, making up 24% of a 454 sample size from 14 nests.[90] The Raven was also the most prevalent bird prey in central Arizona, in a sampling of 1154 from 119 nests.[173] The Black-billed Magpie (Pica hudsonia) was an important prey item in Washington state, making up 9.7% of the remains there, and was the most significant avian prey in Montana.[104][177] In 10 studies in Europe, corvids made up more than 5% of the prey remains, usually represented by Carrion Crows/Hooded Crows (Corvus corone/cornix), Rooks (Corvus frugilegus),Alpine Chough (Pyrrhocorax graculus), Ravens or Eurasian Magpies (Pica pica). Smaller species such as jays and nutcrackers only occasionally turn up as prey, mainly in North America, though the Eurasian Jay (Garrulus glandarius) has also been known as prey.[97][127][3] The next best represented family of birds are the waterfowl, making up approximately 1.4% of the Golden Eagle’s breeding season diet. Waterfowl of all sizes from Green-winged Teal (Anas crecca)[127] to Trumpeter Swans (Cygnus buccinator)[97], Tundra Swans (Cygnus columbianus)[178] and Mute Swans (Cygnus olor)[129] have been successfully hunted by Golden Eagles. Moderately-sized species, including larger Anas ducks such as Mallards (Anas platyrhynchos) and geese such as Bean Goose (Anser fabalis) are perhaps most often recorded. Waterfowl are mostly recorded during the nesting season in Northern Europe, comprising 15.4% of prey in Gotland and 14.4% of prey in Belarus.[172][130] In some years at Malheur-Harney Lakes Basin in Oregon, Anas ducks can make up to 20% of the prey consumed by the local nesting eagles.[179] Mostly in the United States, wintering Golden Eagles may become habitually predators of wintering and migrating groups of waterfowl, with species such as Canada Geese, Cackling Geese (Branta hutchinsii), Snow Geese (Chen caerulescens), and Ross's Geese (Chen rossii). Since these are found in large concentration during frigid conditions, they can be hunted with relative ease.[55][180][181] Waterfowl are typically hunted using the “contour flight with short glide attack” technique, in order to surprise the prey before it can take flight or dive. In one case, a Golden Eagle was able to capture a Mallard as it took off in flight. Other water birds are rarer as prey but may become regular in the diet in marsh-like Northern regions and coastal areas. Scotland, being surrounded by coasts and possessing quite a wet climate, often hosts water birds which become prey such as colonies of petrels (largely Northern Fulmar (Fulmarus glacialis), making up to 17% of the recorded prey in 26 nests with a 119 sample size in the Outer Hebrides), migrating throngs of sandpipers and plovers (up to 5.9% and 2.8% in 25 nest in the northern Inner Hebrides) and gulls (making up a whopping 23% of prey recorded in 25 nests in the West-Central Highlands).[3] Among shorebirds, usually only larger types such as godwits, curlews, Tringa sp., stone-curlews andoystercatchers turn up as prey as smaller species are probably too flighty and agile to catch.[3][182] Eurasian Cranes (Grus grus) are regularly predated in Northern Europe, turning up at 6.8% of nests in Estonia and 5.8% of nests in southern Finland.[131][128] Hooded Cranes (Grus monacha) are reportedly prey for Golden Eagles in China.[183] Demoiselle Cranes (Anthropoides virgo) have been caught in mid-air as they migrate over the Himalayas and both Sandhill (Grus canadensis) and Whooping Cranes (Grus americana) may be hunted in North America.[184][185] The last known breeding pair of Golden Eagles in Maine (which did not return after 1999) were reported to hunt an unusually large number of herons, specifically Great Blue Herons (Ardea herodias) and American Bitterns (Botaurus lentiginosus). Elsewhere, herons are basically neglible in the diet.[3] Other water birds recorded as prey include cormorants (up to 8.6% of the recorded prey in Santa Rosa and Santa Cruz Islands), auks, grebes and loons.[3][90]
Other raptorial birds can sometimes become semi-regular prey, such as various hawks which are recorded largely in North America at locations such as Oregon (8.8% of prey remains) and Arizona, owls almost across the range (maximum being 2.9% in Oregon) and, more rarely, falcons.[3] Rock Pigeons may be hunted regularly in some parts of the Golden Eagle’s range (other pigeons and doves have been recorded as prey but are typically rare in the diet). The common feral pigeon was the second most prevalent prey species in Sierra Espuña Regional Park in Spain, making up 18.8% of a sampling of 99 from 5 nests.[88] The species was also prevalent in Slovakia, making up 7.4% of remains at nests there.[3] Non-corvid passerines are usually ignored as prey but large thrushes such as Song Thrush (Turdus philomelos), Mistle Thrush (Turdus viscivorus) and Common Blackbird (Turdus merula), are semi-regularly recorded as prey in Europe. This family is most prevalent in Sicily, making up 8.1% of a sampling of 74 from 10 nests there[114], 7.7% in Central Spain[105] and 7.2% in the French Alps.[109] The smallest-bodied bird family recorded as semi-regular prey are pipits. Meadow Pipits (Anthus pratensis) is the most represented species and are taken mainly in Scotland, making up to 3.5% of prey in the Inner Hebrides.[3][186] Other bird families rarely recorded as Golden Eagle prey (making up less than 1% of prey in all studied nests) include starlings (maximum being 4.8% in the French Alps, neglible elsewhere), larks (maximum is 2.3% in the West-Central Highlands of Scotland), emberizid sparrows (up to 1.7% in central Alaska), woodpeckers (up to 1.5% in Alberta), cuckoos, bustards, icterids, shrikes and finches.[3]
Reptiles and amphibians
As they are often the most diverse and widely-distributed reptiles in temperate regions of the world, it is perhaps no surprise that snakes are the most common group of reptiles in the Golden Eagle’s diet, making up about 2.9% of the remains from all studied Golden Eagle nests.[3] In Japan, snakes (largely Elaphe and Rhabdophis sp.) are apparently quite regularly hunted, making up 27.5% of the prey found in 5 nests (967 sample size).[113] Similar species, mainly the Green whip snake (Coluber viridiflavus), are very common as prey in Sicily, making up 25.7% of the remains in 10 nests.[114] In central Arizona, gopher snakes (Pituophis catenifer), make up 14.9% of the remains from 119 nests.[173] In Kazakhstan, the Eastern Four-lined Snake (Elaphe quatuorlineata) made up 9.7% of the remains from 36 nests.[123] The French Pyrenees also showed a large percentage of snakes from various species in the diet, making up 9.7% of the remains from 10 nests.[92] Usually colubrid snakes (sometimes called “harmless snakes”) are hunted but venomous species are also occasionally taken, especially the Prairie Rattlesnake (Crotalus viridis) in North America and the European Adder (Vipera berus) in Europe.[3] Less widely reported but even more locally important in the diet than snakes are tortoises. In fact, tortoises displace mammals and birds as the most important prey group in most of Southeastern Europe as well as the Caucasus.[3] Hermann's tortoises (Testudo hermanni) and Greek tortoises (Testudo graeca) made up 55.4% of the prey in two nests in Bulgaria and 52.9% of the prey in 19 nests in Macedonia.[163][143] The same species are also prevalent in the diet of eagles from Greece, but no quantitative analysis is known from that country.[187] Russian Tortoises (Agrionemys horsfieldii) made up 31.9% of the prey in 5 nests in Turkmenistan and 25.4% of the prey in 36 nests in Kazakhstan.[123][188] When hunting tortoise, Golden Eagles engage in an unique technique, they pick up the tortoise and take flight, flapping up to at least 20 m (66 ft) above the rocky ground, in order to drop the tortoise onto the terrain below in the hope of smashing open their hard shells.[3] Among all other birds, the only other species confirmed to hunt vertebrates in this way is the Lammergeier (Gypaetus barbatus) which also uses the technique when it hunts tortoises (parallel to the way the latter species cracks open ungulate bones to access marrow). Gulls may use a similar technique on hard-shelled prey such as mussels.[5] The larger Desert Tortoise (Gopherus agassizii) of North America has occasionally turned up as prey there.[189] Other turtles are rarely reported as being hunted, such as painted turtles (Chrysemys picta) in Washington state and baby Loggerhead sea turtles (Caretta caretta) in Corsica, but are essentially a negligible part of the diet.[55][89] Lizard turn up with some regularity as prey in some of the hotter, drier portions of the Golden Eagle’s range. In Europe, lizards made up to 13% of the prey remains in the French Pyrenees and 12.7% in the Italian Apennines.[92][111]Fairly large lizards, including the monitor lizards, tend to make the most significant contribution to the Golden Eagle diet.[190] The most important lizard prey in Europe is the Lacerta genus, i.e. the Ocellated Lizard (Lacerta lepida).[191] Another lizard genus of particular note in the Golden Eagle’s diet is the spiny-tailed lizards of the genus Uromastyx. Reportedly, spiny-tailed lizards are the single most important prey for Golden Eagles in Northeast Africa.[3] In the particularly sparse Negev Desert of Israel, the Egyptian Spiny-tailed Lizard (Uromastyx aegyptia) apparently comprised 89% of the diet, the most a single species has been reported to dominate a Golden Eagle’s diet locally.[192][193] Amphibians, specifically Rana frogs, have been reported in only two locations across the Golden Eagle’s range: in the French Pyrenees, where they made up 2.7% of the diet, and the West-Central Highlands of Scotland, where they made up 0.7% of the diet.[92][3]
Other prey
Fish have not been mentioned as prey in Eurasia in dietary studies of nesting Golden Eagles. However, they have been reported in nests in North America. The two largest known reports are from coastal California and along the Porcupine River in Alaska, with fish making up 3.6% and 3.5% of the diets, respectively.[73][2] Most reported species are trout and salmon from the Salmo and Oncorhynchus genera, although other species have also been hunted, including suckers (Catostomus), Sacramento perch (Archoptiles interruptus) and the Northern Pike (Esox lucius).[73][3][2] Fish have apparently been captured in Scotland on rare occasions, although they have not been reported in the breeding season diet.[3] Golden Eagles have been observed around the Sea of Okhotsk (especially along Northern Japan) to join large numbers of White-tailed Eagles (Haliaeetus albicilla) and Steller's Sea Eagles (Haliaeetus pelagicus) in winter to scavenge and capture various, locally abundant fish amongst ice-floes. Perhaps the most improbable prey reported in the Golden EagleÂ’s diet are insects. TheyÂ’ve been reported in small quantities in the French Pyrenees, the Italian Alps and Bulgaria.[92][122][143] There is no information on how Golden Eagles capture insects or what kind of insects they hunt, although slower, larger, terrestrial insects like large beetles seems likely.[3]
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Post by Runic on May 29, 2013 22:49:38 GMT 5
Interspecific predatory relationships
One of the most fascinating, though relatively little studied, aspects of the Golden EagleÂ’s biology is how it interacts with other predators in a natural environment, especially other large predatory birds. The Golden Eagle is a powerful hunter with few avian rivals in size or strength, although what it gains in these areas it loses somewhat in its agility and speed. Golden Eagles are avian apex predators, meaning a healthy adult is not generally preyed upon. There are several other large birds of prey that inhabit the Northern Hemisphere that may be attracted to the same prey, habitats and nesting sites as the Golden Eagles. Two examples are the Common Raven and Peregrine Falcon (Falco peregrinus) as these are two fairly large-bodied, mostly predatory birds that co-exist with Golden Eagles in almost every part of their range, although the former occurs in much larger numbers and the latter has a much larger natural distribution in more varied habitats. Both the Raven and the Peregrine are often attracted to much the same precipitous habitat as the Golden Eagle. However, both are generally dominated by the much larger eagle and will activity avoid nesting in the same area as a Golden Eagle pair.[194][195][196] Ravens and Peregrine Falcons have both been robbed of food on a few occasions by Golden Eagles.[197][198][199] Both species have turned up widely in the diet of Golden Eagles, much more so the Raven than the Peregrine.[90][200] However, these conspecific species follow no set "rules". Ravens often vigorously and successfully displaces Golden Eagles from their nesting territories.[201] Peregrine Falcons have also displaced Golden Eagles from their nesting territories and, in one instance in Utah, even killed a Golden Eagle that had breached the area of their nest.[202] In another case, a Peregrine Falcon kleptoparasitized a Willow Ptarmigan from a Golden Eagle.[203] In a study of 4 cliff-nesting raptor species in Spain, the Golden Eagle was not observed to engage in agnostic encounters with the other species but the Peregrine Falcons but were dominated by and occasionally killed by a relatively small race of Eurasian Eagle-Owls (Bubo bubo hispanus).[204] Both Ravens and Peregrine Falcons appear to easily outmaneuver Golden Eagles in flight.[3]
Other raptors, large and small, are often outright dominated by Golden Eagles. In Eurasia, the relative paucity of mid-sized "Buteo" species is thought to be due to the radiation of large "Aquila" eagles that already occupied the large raptor niche and outcompeted them. In North America, where there are no "Aquila" eagles other than the Golden Eagle, "Buteo" species are more diverse with at least 3 large hawks (the Red-tailed, Swainson's ("Buteo swainsoni") and Ferruginous Hawks ("Buteo regalis")) that occur in similar habitats and sometimes eat similar prey as both each other and Golden Eagles.[3] On occasion, Golden Eagles will kleptoparasitize or even predate these three "Buteo"s.[76][179][205] Other small to medium-sized diurnal raptors are known to occasionally be hunted by Golden Eagles, including Ospreys[206], Hen Harriers[177], Eurasian Sparrowhawks (Accipiter nisus)[3], Cooper's Hawks (Accipter cooperii)[97], Northern Goshawks[127], Red-shouldered Hawks (Buteo lineatus)[207], Common Buzzards (Buteo buteo)[3], Long-legged Buzzards (Buteo rufinus)[190], Upland Buzzards (Buteo hemilasius)[94], Rough-legged Buzzards[127], Eurasian Kestrels (Falco tinnunculus)[122], American Kestrels (Falco sparverius), Merlins (Falco columbarius)[208], Prairie Falcons[73] and Gyrfalcons (Falco rusticolus)[45]. Occasionally, Golden Eagles may even boldly predate these smaller species as in flight during migration, as was recorded at Hawk Mountain Sanctuary with a Red-shouldered Hawk.[209] It is thought that on rare occasions, more nimble, smaller raptors like Rough-legged Buzzards and Harriers can kleptoparatisize Golden Eagles.[210]
Due to the potential danger to themselves and their offspring, almost every other type of raptorial bird readily mobs Golden Eagles.[45] Gyrfalcons (Falco rusticolus), skuas, and Buteos like Rough-legged Buzzards, which are normally fierce competitors with each other, have worked together to group-mob Golden Eagles that have passed their adjacent nesting areas.[45] Occasionally smaller raptors, especially large falcons, will drive eagles to the ground. The eagle typically ignores attacks from smaller species or at least leaves their home ranges, but will occasionally roll and extend talons toward chasing individual without displaying predatory behavior. If physical contact occurs, it sometimes ends in injury, death and/or consumption of the attacking species.[211] Remarkably, the nest defense by Golden Eagles themselves is often rather passive towards other raptorial birds, perhaps since other species may fear predation on themselves if they approach a Golden Eagle territory. There are exceptions to this, however, when particularly bold, large raptorial birds seemingly range too far into a pairÂ’s home range. One pair of Golden Eagles killed but did not eat 3 Great Horned Owls (Bubo virginianus), implying that they were killed in nest defense and not in predation.[29] In one of the few cases of a Golden Eagle killing but not eating another large raptor, an adult Golden Eagle was observed killing a Ferruginous Hawk which apparently came too close to its nest.[212]
Golden Eagles, being habitual scavengers at carrion, come into conflict with scavenging birds as well. They may encounter corvids at carrion sites and the large passerines are often highly cautious, either feeding some distance from the eagle or waiting until the eagle is done eating least they be predaceously grabbed.[3] Occasionally, however, corvids may behave more boldly around Golden Eagles. In one case, a group of three Black-billed Magpies were observed to rob a Golden Eagle of its prey.[213] Golden Eagles also usually dominate both New World and Old World vultures. Smaller species like Black Vulture (Coragyps atratus) in North America and Egyptian Vulture (Neophron percnopterus) in Eurasia are known to be occasionally hunted by Golden Eagles.[214][215] Besides the Steller's Sea Eagle, the larger species of Old World vulture and the California Condor (Gymnogyps californianus) are the only noticeably larger raptorial birds that a Golden Eagle may encounter. The relationship between these large vultures and Golden Eagles can be highly contentious, with most sources favoring victory for the eagle due to its more aggressive disposition, much stronger feet and sharp talons. In one case, a colony of Griffon Vulture (Gyps fulvus) was exceptionally able to displace a pair Golden Eagles from a cliff where they were trying nest so they could nest there themselves.[216] On the other hand, a 5-year-old Griffon Vulture reintroduced into the wild in Bulgaria was thought to have been killed by a Golden Eagle.[217] The Golden Eagle is a potential predator of the Lammergeier which is often attracted to much the same habitat and prey as the eagle but often feeds largely on bone marrow from carcasses.[218] It has been observed that both Golden Eagles and Lammergeiers will readily pirate food away from each other.[219] In the Southwestern United States, several conflicts between huge California Condors and Golden Eagles have been observed. At carrion, victory during conflicts can go either way apparently.[220][221][222] Recent observation have suggested that the critically endangered California Condors do not seem to actively defend their nesting territories from Golden Eagles but have been recorded gaining incidental protection from Prairie Falcons and Common Ravens, which both aggressively displaced the eagles from their own adjacent territories.[223] The Golden Eagle is considered an occasional predator of California Condors (especially fledglings) but there seems to be little in the way of eye-witness accounts to confirm this. It is possible that (as in the Bulgarian Griffon Vultures) the California Condors have lost their natural cautiousness around eagles due to having been reintroduced from captivity.[224]
Owls, which may have dissimilar periods of activity, are not entirely exempt from Golden Eagle predation either.[225][226] Several species have been recorded as prey, especially in Northern Europe, Slovakia (where owls make up 2.4% of prey remains) and some parts of the Western United States.[3] Species hunted have ranged in size from tiny Eurasian Pygmy-Owl (Glaucidium passerinum) and Little Owl (Athene noctua) to the formidable, large Great Horned and Great Gray Owls (Strix nebulosa).[127][94] Barn Owls (Tyto alba) have been predated by Golden Eagles in both North America and Eurasia.[97][105] On Santa Rosa and Santa Cruz Islands, Barn Owls made up 4.5% of the diet, the largest known occurrence of that species in the eaglesÂ’ diet.[90] However, the Great Horned Owl is the owl species that occurs most regularly in the diet of North American Golden Eagles.[97][177] The primary owl species hunted in Europe appears to be the Tawny Owl (Strix alucco).[227] Few eye-witness accounts are known of owl predation, but one violent mid-day confrontation between a Golden Eagle and an adult Great Horned Owl was witnessed in Jefferson County, California. Although this owl was about a third of the eagleÂ’s weight, it was able to land some damaging blows on the larger bird. In the end, despite its wounds, the eagle was victorious over the dead owl.[228] A case of kleptoparasitism by a Golden Eagle on a Great Horned Owl has been recorded.[229]
In the Palearctic, the Golden Eagle co-exists with several other large raptorial birds called eagles. Unlike in their relationship with smaller raptors, Golden Eagles are rarely reported to hunt other eagle species. Most conflicts between different eagles are over kills or carrion, though some species will defend nesting territories from each other. When it comes to carrion and kills, usually the “aggressor” (that is the eagle who initiates the agnostic behavior) is victorious over the other eagle.[230] Considering that that they overlap considerably in both distribution and prey selection, there is remarkably almost no known accounts from Eurasia of Golden Eagles behaving aggressively with other Aquila eagles. This is possibly due to differing habitat preferences between these species, with Lesser and Greater Spotted Eagles being essentially woodland or wooded wetland-dwelling birds, Spanish and Eastern Imperial Eagles inhabiting fragmented, open woods and Steppe Eagles generally living in flat, often treeless steppe and desert-like habitats. In central Asia, where Golden Eagles and other Aquila species are rare or absent, Steppe Eagles sometimes nest in mountainous rock formations like Golden Eagles.[3] Compared to these eagles, the Bonelli's Eagle appears to have a more contentious relationship with Golden Eagles, as they are often attracted to similar prey (largely rabbits and gamebirds) and occur in abutting habitats. The larger Golden Eagle is apparently dominant and, in at least one case, has killed and consumed a Bonelli's.[231][232] The two species defend their territories from one another exclusively, in the same way they defend them from others of their own species. Both will use nests built by the other species, more so the Golden using Bonelli's nests than vica versa.[233] In Israel, Bonelli's and Golden Eagles compete as well. In the dry, barren Negev Desert, Golden Eagles nests were found 13 km (8.1 mi) apart and Bonelli's were scarce. In the Judaean Desert, which has more annual rainfall and more available prey, the distance between Golden Eagle nests averaged 16 km (9.9 mi) and the Bonelli's Eagle easily outnumbered them. Apparently, the Bonelli's Eagle exceptionally outcompeted its larger cousin here due to a subtle topographic variation in the habitat.[234] Still, in areas without unnatural human pressures, the gradation between these species is still adequate enough that they can exist without serious negative effect on either population.[235] In Japan, Golden Eagles were observed to hunt Mountain Hawk-Eagles (Nisaetus nipalensis), despite the fact that the local race of hawk eagle is around the same mass as a Japanese Golden Eagle.[236][237] The Bale Mountains of Ethiopia is arguably the richest biosphere the Golden Eagle is known to inhabit and there, this species may potentially interact with more than 10 other eagle species and nearly 30 other acciptirid species, including both migratory and resident breeding species. These are often supported by an exceptionally diverse, dense population of rodents there. The Bale Mountains Golden Eagles were recorded kleptoparatisizing Steppe Eagles, Augur Buzzard (Buteo augur), Pallid Harrier (Circus macrourus) and Lanner Falcons (Falco biarmicus) and the eagles were themselves kleptoparatisized by Steppe Eagles on three occasions. The Golden Eagles were also observed to chase Tawny and Steppe Eagles out of their nesting territories. In the Bale Mountains, the Golden Eagle overlaps with perhaps its closest living relative, the Verreaux's Eagle. The Golden Eagles appear to vigorously defend their territories from the Verreaux's Eagles and, as in its relationship with the Bonelli's, the two species appear to maintain exclusive territories. Several chases involving the Golden chasing Verreaux's were witnessed but only one where a Verreaux's chased off the Golden. Despite several reported agnostic interactions, no other raptors were found as prey in the Bale Mountains nests of Golden Eagles.[116]
Perhaps the most formidable raptorial birds that the Golden Eagle co-exist with are the large Northern Haliaeetus sea or fish eagles. Two species, the White-tailed Eagle and the Bald Eagle, overlap in distribution frequently with Golden Eagles. Both are marginally heavier on average than the Golden, especially the White-tailed Eagle, which tends to have a slightly longer wingspan as well. There is much different in the dietary biology of these species as they primarily eat fish, occasionally supplemented by water birds or other semi-aquatic prey, and obtain more of their food via scavenging of dead or injured animals or via kleptoparasitism than Golden Eagles do. They also prefer nesting in large trees by the shore of a body of water, often in lowland areas, quite different from the upland, often mountainous nesting habitat preferred by Golden Eagles.[238] However, conflicts between the great eagles do occur, especially at carrion or kills. In most cases, the Golden Eagle is reportedly dominant over White-tailed Eagles at food, reportedly being more aggressive and a more agile and swift flier.[230] However, in some cases, White-tailed Eagles have dominated Golden Eagles at carrion or kills.[239][240] Competitions between Golden and Bald Eagles in North America can reportedly go either way, depending on the size and disposition of the eagles involved.[45][241] In Arizona, Bald Eagles were successful in 25% of attempts to rob Golden Eagles of their prey.[242] Conflicts between White-tailed Eagles and Golden Eagles over nesting sites occur with some frequency in some areas, but are unknown in other areas. In one instance in Norway, a pair of Golden Eagles harassed a newly-formed pair of White-tailed Eagles so persistently that the White-tails abandoned their nesting attempt.[243] This relationship between the two eagle species is particularly aggressive in Scotland where the White-tailed has recently been reintroduced. In the Scottish Highlands, a White-tailed Eagle was found dead with talon piercings in its skull likely from a female Golden Eagle it had been interacting with the previous day.[244] There are at least two known instances of Scottish White-tailed Eagles fiercely attacking Golden Eagles in apparent territorial bouts, in one instance pulling the Golden down into shallow coastal waters to drown.[245] White-tailed Eagles are able to survive on a great breadth of food and have longer guts so can live on less food for a longer time than Golden Eagles. Thus, the White-tailed may locally outcompete the Golden Eagle in terms of populating a given area.[230] In North America, few such contentious relations have been reported between Bald and Golden Eagles but Golden Eagles were reported to avoid the vicinity of active Bald Eagle nests.[29] Even in areas where conflicts between White-tailed and Golden Eagles do occur it is thought that, since the species are very different in their preferred foods and nesting sites, they do not adversely affect the other at a population level.[246] A much more passive interspecies guild of eagles have been observed in a wooded area of Kazakhstan, consisting of White-tailed, Eastern Imperial and Golden Eagle. This guild was seen to freely use abandoned nests built by the other two species. Unlike in Scotland and Norway (or in a guild of Buteos in the American Midwest), no aggression or conflicts were reported between the three large eagle species even though they sometimes nested within 475 m (1,558 ft) of one another. All observed conflicts in the Kazakhstani woods were amongst others of their own species.[247] On the Scottish Isle of Mull, Golden and White-tailed Eagles also nested in close proximity without any observed aggressive encounters.[248] The Steller's Sea Eagle co-exists with Golden Eagles in coastal Japan and Russia. This species is the heaviest living eagle and may weigh twice as much as the small-bodied Japanese Golden Eagles.[237] Occasionally, both Golden and White-tailed Eagles join Steller's Sea Eagles to feed on fish caught along ice floes in the Sea of Okhotsk. The Steller's, being more aggressive in disposition than its Bald and White-tailed cousins[2], appears dominant over Golden Eagles here and has been photographed repeatedly displacing them from fish.[249][250] The smaller Pallas's Sea Eagle (Haliaeetus leucoryphus) also overlaps in range with Golden Eagles but there is no published information on their relationship.[2]
Mammalian carnivores are potential competitors with Golden Eagles for food. Foxes may prey on the same species in a given area but, as they are occasionally hunted by the eagles and are mainly nocturnal, they tend to avoid direct conflicts.[3][122][90] Though rare, Golden Eagles may sometimes pirate prey from various species of fox.[251][151] In North America, Coyotes (Canis latrans) may engages in agnostic interactions with Golden Eagles. Despite being around three times as heavy, lone coyotes are seemingly dominated by Golden Eagles at many carrion or kill sites.[252][253][254] In the Greater Yellowstone, Golden Eagles were ranked as the second most dominant scavenger at wolf kills during winter (when bears are hibernating) after coyote packs but above Bald Eagles.[86] In one instance, a healthy adult male coyote was attacked and killed by a Golden Eagle. This coyote weighed 13.5 kg (30 lb) after the eagle had consumed some of its internal organs.[255] Conflicts between Golden Eagles and Scottish Wildcats have been reported on rare occasions. In one instance, a Golden Eagle trying to hunt some wildcat kittens was intercepted by the mother wildcat. In the ensuing violent battle, the wildcat mother and the eagle both died.[245] In Northern California, Golden Eagles have pirated lambs killed by bobcats, a species which has itself occasionally turned up in the eagleÂ’s diet.[256][97] Per one anecdote from the Himalayas, a Golden Eagle reportedly tried to predaceously attack a Snow Leopard (Panthera uncia) but was killed by the much larger felid, although this could have actually been a case of an overly-bold eagle trying to displace a large predator from its own home range.[257] Adult wolverines appear to be one of the few conspecific mammal carnivores to actively pose a threat to Golden Eagles. Wolverines were observed to prey on nestling Golden Eagles in Denali National Park.[54] During incubation in Northern Sweden, an incubating adult Golden Eagle was killed on its nest by a Wolverine.[258] Grizzly Bear (Ursus arctos horribilis) have also reportedly killed and eaten Golden Eagle nestlings in Denali National Park.[45] The Grizzly is reportedly one of the few mammals to trigger a strong aggressive reaction from the parent eagles when spotted close to the nest, as eagles have been observed to strike the bruins about the head and neck with their talons.[259][45]
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