Snow buntings Plectrophenax nivalis : the behavioural ecology and site use of an itinerant flock species in the non-breeding season

• Main Author: Smith, Richard D.
• Published: University of Glasgow 1994
• Subjects: 598.8; QL Zoology
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.618338

This thesis examines how extrinsic and intrinsic factors affect dispersal, foraging, aggression and energy reserves in a winter population of a small, migratory flocking bird, the Snow Bunting Plectrophenax nivalis. Previous observations of this species, and consideration of its northern ground-feeding open country niche, suggested that Snow Buntings were less likely to show as strong a degree of site fidelity as many other winter-studied species. This may therefore have led to opportunities for the Snow Bunting's winter behavioural ecology to diverge from that of more sedentary species. The distribution of age and sex categories of wintering Snow Buntings was examined at eleven sites in North-East Scotland which varied markedly in altitude (and consequently habitat and climate). The proportions of adult males and adult females trapped at these sites increased with altitude, whilst the proportion of juvenile females decreased. Because males are the larger sex, and adult birds have the advantage of previous experience, the distribution of age and sex categories suggested that the more elevated sites were of higher quality. Consequently, I suggest several environmental factors (reduced competition, fewer predators, and similarity to breeding conditions) which may be responsible for altitudinal segregation and argue that these may also help explain intraspecific latitudinal segregation patterns in this and other species. More detailed observations of Snow Bunting numbers and behaviour were made at one high altitude site, Cairn Gorm during 1987/88 to 1992/93. There was evidence that, even within this site, birds selected higher altitude feeding areas when possible. However, snowfalls caused some birds, particularly young or naive individuals or females, to leave the site, although population composition recovered during subsequent thaws.