Partial migration as an adaptation to nest-site scarcity and vole cycles in Tengmalm's owl Aegolius funereus

Call Number:

Keywords:

Abstract:

Tengmalm’s Owl, Aegolius funereus is the second smallest and one of the most common owl species in Fennoscandia. It is distributed over the Holarctic coniferous forest belt and feeds mainly on voles. Thus the owl subsists on food which fluctuates highly in abundance, the interval between peaks being several (principally 3-5) years. Based on the regional asynchrony of vole peaks, Mysterud presented a hypothesis that Tengmalm's Owls are highly mobile; both sexes and all age classes move more or less at random between different feeding and breeding areas in the large taiga region between the Scandinavian Peninsula and the Ural Mountains. On the other hand, Tengmalm's Owls originally breed in holes (especially in cavities excavated by Black Woodpeckers Dryocopus martius), which by contrast, should favour the evolution of resident habits. One could therefore suspect a serious conflict between these opposing selective pressures. Lundberg suggested that as a response to the conflicting selective forces the strategy of partial migration has evolved for Tengmalm's Owls; i.e. males are resident, while females and young birds are migratory. Recent results from breeding owls, although based on quite limited field data, supported Lundberg's suggestion. In addition Korpimäki, basing his conclusion on wing lengths of irruptive owls at Falsterbo bird station, southern Sweden, suggested that migrants are either females and/or young birds. In the present study we test Lundberg's assumption by sexing migrants using known differences in body dimensions, by ageing them from moult data and by presenting data on site tenacity in breeding Tengmalm's Owls.

Notes:

Reference Code: A86KOR03IDUS

Full Citation: Korpimäki, E., and H. Hongell 1986. Partial migration as an adaptation to nest-site scarcity and vole cycles in Tengmalm's owl Aegolius funereus. Vår Fågelvärld Supplementum 11: 85-92.

Location: ANIMAL EF: AEGOLIUS FUNEREUS