The birds of Pasvik / E. I. Khlebosolov, O. A. Makarova, O. A. Khlebosolova [et al. ; English transl. Nikita Chernetsov]. - Ryazan : Golosgubernii, 2007. - 175 с. : ил., портр.

The Northern Hawk-Owl occurs in loose forests, peat bogs w ith groups o f trees, at old fire sites and clearings w ith young trees. It forages on m ice and voles. Sometimes small birds are taken (B ianchi & Koshkina 1960, Sem enov-T ian- Shansky & Gilyazov 1991, Butyev et al. 2005). When foraging, N o rth e rn Hawk- Owls use variable techniques, and combine waiting and search flights. Usually they look for prey perched in a tree. Fo r this solitary trees are used, usually dead ones or with a dead top. A N orthern Hawk-Owl rem ains about 30 m inu tes at such a w atch ­ ing point, then it flies to ano ther one. Sometimes N o rth e rn Hawk-Ow ls hover, like other birds o f prey that hunt mainly in open habitats. It may also glide. Starting from the tree -top , a bird glides towards the ground w ith wings nearly immobile. It may cover up to 100 m and more before ascending near th e next perch. D uring such flight, when flying low (several m etres) above the ground, th e bird may roll in the air and catch prey on the ground (Pukinsky 1977). Great Grey Owls inhabit boreal forests. They often settle in m atu re pine forests but prefer areas adjacent to old fire sites, clearings and o p en spaces o f peat bogs rather than large non-fragm ented stands (Pukinsky 1977, Sem enov-T ian -Shan sky & Gilyazov 1991, Butyev et al. 2005). T heir food is m ainly voles and lemm ings. Sometimes a G reat G rey Owl can capture squirrels, hares, birds (Butyev et al. 2005). The main foraging technique o f the G reat G rey Owl is looking for perched prey. If a perch is located at a poo r site, the bird moves to a n o th e r place by slow flight, starts to turn its head and listens. If the density o f rod en ts is low, hunting from a perch is alternated with patrolling. The owl slowly flies across its range (clearings, peat bogs, old fire areas) 2 .5 - 5 m above the g round . Patrolling flights are usually interrupted by a sudden grab o f the prey (Butyev et al. 2005). All the three owl species o f Pasvik feed on small rodents. However they use dif­ ferent habitats, and use species-specific search and foraging techn iques. The S h o rt­ eared Owl lives in the most open habitats and m ainly uses patro lling when search ­ ing for prey. The N orthern Hawk-Owl prefers sparse forests and forages by waiting on a perch and patrolling. The G reat G rey Owl inhabits den ser forests and mainly remains perched when looking for prey. These life history features allow these owls to occupy different ecological niches and to co-exist in th e n atu ral ecosystems o f Pasvik. 2 .4 .3 . Grouse G rouse are sedentary and occu r in the study area th ro u g h o u t th e year. They are specialised for feeding on parts o f herbs and trees and possess a num ber o f behav­ ioural, ecological and morphophysiological adapation s th a t allow th em to survive 90