ground and bird's eggs are sometimes consumed. While the main prey is largely quite small rodents and similar mammals, on occasion larger prey is taken. Alternate prey can extend to those weighing over such as willow ptarmigan (Lagopus lagopus) and Daurian hedgehog (Mesechinus dauuricus), and occasionally much larger such as woolly hare (Lepus oiostolus), weighing some , and Tibetan snowcock (Tetraogallus tibetanus), weighing some . Additionally, this buzzard was recorded as an occasional likely predator of Mongolian gazelles (Procapra gutturosa), born weighing about . Another impressive prey species reported for the upland buzzard is the corsac fox (Vulpes corsac), which when fully grown weighs about as much as a newborn Mongolian gazelle, but it is not known whether full-grown adults are counted amongst their prey. Upland buzzards often feed extensively on the same prey and in the same habitats as Eurasian eagle-owls (Bubo bubo), however the eagle-owl is considerably larger and more powerful and sometimes additionally hunts the upland buzzards. Additionally, upland buzzards have been known to fall victim to golden eagles (Aquila chrysaetos). The upland buzzard breeds between April and August, with egg laying tending to occur in May. Nests tend to be located on outcrops, crags and ledges of cliffs, usually in locations blocked from the elements by rocks or vegetation. Some nests additionally are placed on steep rocky slopes. The nest is constructed with sticks and well lined, often with wool, grass, dry dung and, perhaps detrimentally, human garbage. This species normally lays a clutch of 2 to 4 eggs and, if an entire clutch is lost, they are capable of laying a replacement clutch. In Mongolia, clutch sizes have been recorded exceptionally varying up to 8, with an average clutch size reported as 3.49. Incubation lasts 36 to 38 days, although previously reported at only about 30 days. The chicks bear greyish-brown down and develop fairly slowly, fledgling at around 45 days. In western and central Mongolia, brood size averaged 1.95. Commonly, two young often fledge from upland buzzard, though up to four fledglings have been recorded. Breeding success is known to be food based and higher sibling competition and perhaps siblicide have been reported in instances where stable prey such as voles decline in population. References External links The Ineternet Bird Collection Upland buzzard upland buzzard Birds of China Birds of Mongolia Birds of Tibet upland buzzard Taxonomy articles created by Polbot