Rough-legged Buzzard

The rough-legged buzzard is a member of the genus Buteo, a group of moderately large raptors exhibiting broad wings, short tails and wide robust bodies. Four subspecies of Buteo lagopus are accepted: * B. l. lagopus is the nominate subspecies. It breeds in northern Europe and Asia and has relatively dark plumage. The dorsal feathers are a homogeneous brown colour, contrasting well with the paler head. * B. l. menzbieri breeds in northeastern Asia. * B. l. kamtchatkensis breeds in Kamchatka. It has paler plumage when compared with B. l. sanctijohannis and it is, on average, the largest of the subspecies. * B. l. sanctijohannis breeds in North America. It has pale, speckled dorsal plumage and is slightly smaller than B. l. lagopus.

The rough-legged buzzard breeds in tundra and taiga habitats of North America and Eurasia between the latitudes of 61° (locally south to 48° in Newfoundland and 58° N in southern Norway) and 76° N. Those occurring in North America migrate to southern Canada and into the central United States for the winter, while Eurasian birds migrate to central Europe and Asia, with small numbers west to eastern parts of Great Britain; most winter between latitudes of 43° and 58° N. It is the only member of its diverse genus found in all three of the northern continents, having a complete circumpolar distribution. During the winter months, from October to April, preferred habitats include marshes, moorland, prairies and agricultural regions where rodent prey is most abundant. Breeding sites are usually located in areas with plenty of unforested, open ground. Depending on snow conditions, migrants arrive at breeding grounds during April and May. Home ranges vary with food supply but are commonly reported to be during the winter, but little is known about home ranges during the breeding season. Although frequently attacked in skirmishes by other highly territorial birds such as gyrfalcons and skuas, the rough-legged buzzard is not strongly territorial. However, wintering rough-legged buzzards may behave aggressively towards common buzzards in Sweden, and both species will try to keep the other off a fixed hunting range.

===Diet=== This species is carnivorous, typically feeding on small mammals, which make up 62–98% of its diet. Lemmings and voles are the major prey items of this species, seasonally comprising up to 80–90% of their prey but this varies with seasonal availability. In northwest Russia, rough-legged buzzards may feed on small rodents in the years when rodent density is high, and shift to alternative prey (ptarmigans and hares) in the years when small rodents are scarce. The rough-legged buzzard will also supplement its diet with mice, rats, gerbils, pikas, shrews, squirrels of the genera Spermophilus and Tamias, and insects. Like most Buteo species, rough-legged buzzards have been reported both still-hunting (watching for prey from a perch and then stooping) and watching for prey while in flight. Unlike most other large raptors, they may engage in hovering flight above the ground while searching for prey.

The length of the activity period of Rough-legged buzzards is strongly influenced by day length, with activity duration increasing as daylight extends. When day length increases from 7.2 to 24 hours, their activity duration expands from 13.1 to 19.0 hours. Consequently, while their total daily energy expenditure rises, the rate of energy expenditure per hour decreases. This allows them, particularly during the Arctic breeding season under polar day conditions, to allocate more energy toward reproduction while maintaining a lower hourly energy expenditure. At the same time, their activity levels fluctuate throughout the day. Rough-legged buzzards exhibit an increasing activity pattern, meaning that their daytime activity strongly depends on local light conditions, particularly sun elevation. Their activity levels change in sync with the sun's movement, resulting in a season-specific activity slope.

Rough-legged buzzard is a migratory raptor that breeds in the Arctic tundra and moves to temperate regions for the winter. Its migration patterns are influenced by food availability, weather conditions, and breeding success. In autumn, Rough-legged buzzards leave their breeding grounds in late September and migrate southward to their wintering areas. This movement is primarily driven by the inaccessibility of small rodents in the Arctic during winter due to continuous snow cover and polar night, during which they are unable to hunt. By late April, they return to their breeding sites. Their migration follows a distinctive "foxtrot" pattern, characterized by alternating quick and slow phases. The initial quick phase occurs over approximately two weeks, during which the birds cover about 1,500 km. This stage takes them over forested regions, which are largely unsuitable for foraging due to the scarcity of small rodent prey. Upon reaching open landscapes such as grasslands and agricultural fields, their pace slows. The subsequent slow phase extends throughout winter, during which they gradually move southwestward, covering around 1,000 km by midwinter. This movement is primarily influenced by snow accumulation, which limits access to prey. While the quick phase of migration occurs at a speed of approximately 100 km per day, the slow phase is about ten times slower, with birds covering around 10 km per day. In the latter half of winter, Rough-legged buzzards begin their return migration, retracing their route in reverse. The slow phase occurs first, as they move northeastward toward the forest boundary, followed by a rapid flight across the forest zone back to the tundra and forest-tundra regions. However, this pattern varies depending on the breeding and wintering regions, which differ in snow cover dynamics. During spring migration, Rough-legged buzzards use snow presence as a cue to time their arrival at their breeding grounds. They return to areas that were suitable for breeding in the previous season. This includes sites where they successfully nested the previous year or locations they discovered during prospecting movements following unsuccessful breeding in the previous year. In rare cases, if these areas are no longer viable, they may continue searching for suitable breeding sites in spring before settling.

]] Sexual maturity is reached at about two years old. Breeding generally occurs during May but is variable depending upon dates of arrival at breeding grounds. The rough-legged buzzard is thought to be monogamous, mating with a single individual for multiple years. Nests are built soon after arrival to breeding grounds and require 3–4 weeks to complete. Twigs, sedges, and old feathers are used as building materials. Nests are in diameter and in height.

Rough-legged buzzards that survive to adulthood can live to an age of 19 years in the wild; however, perhaps a majority of individuals in the wild do not survive past their first two years of life. The threats faced by young rough-legs can include starvation when prey is not numerous, freezing when Northern conditions are particularly harsh during brooding, destruction by humans, and predation by various animals. The chances of survival increase incrementally both when they reach the fledging stage and when they can start hunting for themselves. Death of flying immatures and adults are often the result of human activity, including collisions with power lines, buildings, and vehicles, incidental ingestion of poison or lead from prey, or illegal hunting and trapping. Other reasons for nestling mortality are earth-slides of the river-banks, where rough-legged buzzards often build their nests, and chilling.

Adult rough-legged buzzards will give alarm calls when intruders approach a nesting site. It is described as a downward slurring whistle, sounding like kiu wiyuk or a lengthy descending kee-eer similar to that of the red-tailed hawk. This cry is given in flight or from a perch every 15–30 seconds. During courtship, both sexes have been recorded to give a whistling sound that changes to a hiss. Following copulation, females will give a cluck-like sound and males give a whistling noise. Fledglings will give begging calls while waiting for parents to provide food.