page_title: Steppe eagle
section_title: Dietary biology
hierarchical_section_title: Steppe eagle / Dietary biology
caption_attribution_description: Long-tailed Ground Squirrel Urocitellus undulatus (syn. Spermophilus undulatus), Olkhon, Lake Baikal, Russia.
context_page_description: The steppe eagle is a large bird of prey. Like all eagles, it belongs to the family Accipitridae. The steppe eagle’s well-feathered legs illustrate it to be a member of the subfamily Aquilinae, also known as the “booted eagles”. This species was once considered to be closely related to the non-migratory tawny eagle and the two forms have previously been treated as conspecific. They were split based on pronounced differences in morphology and anatomy; two molecular studies, each based on a very small number of genes, indicate that the species are distinct but disagree over how closely related they are.
  The steppe eagle is in many ways a peculiar species of eagle. It is a specialized predator of ground squirrels on the breeding ground, also taking other rather small mammals and other prey, doing so more often when ground squirrels are less consistently found. In rather treeless areas of the steppe habitats, these eagles tend to nest on a slightly rise, often on or near an outcrop, but may even the flat, wide-open ground, in a rather flat nest. They are the only eagle to nest primarily on the ground.
context_section_description: The steppe eagle is an opportunistic predator like other Aquila eagles but has a number of dietary and foraging peculiarities. They prey mainly on small-sized mammals, with some birds and reptiles and (mostly in winter) frequently insects and carrion. Despite their opportunistic nature, the steppe eagle is a somewhat specialized predator on particular mammals such as ground squirrels while breeding and, during non-breeding times, feeds on various foods but is often peculiarly narrow in dietary selection, preferring massed food sources that require little effort for them to obtain. Various other small or medium-sized mammals can be become the most significant prey locally on the breeding grounds, such as voles, pikas and zokors and, generally more secondarily, marmots, hares, gerbils, hedgehogs and others. During the breeding season, one resource claimed that prey mostly weighs 50 to 250 g (1.8 to 8.8 oz). Another account estimated that about 95% of prey weighed less than 250 g (8.8 oz), although predominantly over 63 g (2.2 oz). However, yet another resource claimed that staple prey for steppe eagles could weigh anywhere from 50 g (1.8 oz) up to 1,500 g (3.3 lb). Even the latter estimate may be conservative in size range, with prey species varying widely in size from very small insects from colonies to unexpectedly large mammals (and seldom birds) apparently killed near nests. On the other hand, a preference has indeed been detected for smaller burrowing mammals (i.e. probably under 250 g (8.8 oz) or so). Studies have determined where only larger species of burrowing mammals are predominant (even the larger species of ground squirrel), the steppe eagles appear to attain comparatively sparse nest densities, only occurring in high densities where the smaller burrowers are profuse. Ecological partitioning to limit interspecific competition may be a factor that dictates the steppe eagle’s preference for relatively small prey. The breeding steppe eagle mainly hunts in a low soaring or gliding flight, at a maximum of 200 m (660 ft), diving or making short, accelerated stoops onto their prey. Usually, they tend to capture their prey on the ground. Steppe eagles have been recorded in both Kazakhstan and Mongolia to tactfully avoid casting a shadow before descending onto prey and may drop stones to provide a distraction, a probable form of tool use. In the Kazakh observation, the steppe eagles quickly became used to agricultural activity adjacent to prey accesses while they hunted. They also may hunt in any season on the ground, moving with a shambling gait as necessary, and may give chase on foot to both vertebrate and insect prey. Steppe eagles can often ambush prey by standing in wait next to burrows, suddenly pouncing quickly onto the quarry upon its emergence. Steppe eagles have been seen in China to buzz through locust swarms on the wing as well as to taking avian prey from over 200 m (660 ft) above the ground in a dive. Tandem hunting by pairs has been recorded during the breeding season while, in winter and migration, these may be the most social of all eagles, often sharing by up to the dozens abundant food sources. The non-breeding steppe eagle flocks may even seem to assist one another in procuring prey from which they themselves are not likely to be able to directly profit and may repeatedly assist each other until all flock members are satiated. If confirmed, this mutually beneficial foraging strategy between presumably unrelated eagles is truly unique. Much like the tawny eagle, the steppe eagle will readily rob other raptors of their catches, approaching from any angle and pursuing closely until the victim is forced to land or drop its food.
caption: Ground squirrels like long-tailed ground squirrels are often the most important prey for breeding steppe eagles.
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