AVIS-IBIS

Birds of Indian Subcontinent

Breeding dispersal of Eurasian kestrels Falco tinnunculus under temporally fluctuating food abundance

Publication Type:Journal Article
Year of Publication:2011
Authors:Vasko, V, Laaksonen, T, Valkama, J, Korpimaki, E
Journal:Journal of Avian Biology
Volume:42
Issue:6
Date Published:2011
ISBN Number:1600-048X
Keywords:bias, Falco, Falco tinnunculus, Falconidae, Finland, Tinnunculus
Abstract:Costs and benefits of dispersal can vary in space and time, depending on environmental factors and individual state. Plastic, condition-dependent dispersal strategies, in which individuals rely on external cues such as food abundance to adjust their dispersal distances, are therefore expected to evolve in temporally fluctuating environments. We examined factors affecting breeding dispersal distances in Eurasian kestrels Falco tinnunculus subsisting on multi-annually and cyclically fluctuating voles as their main food. We attempted to avoid traditional bias in dispersal studies by having large study areas and by taking detection probabilities into account. We observed 320 dispersal events of male and 215 events of female kestrels from our study areas in western Finland during 24 yr. After correcting for distance-specific detection probability, the estimates of mean dispersal distances increased two-fold being still clearly higher for females than males. Vole abundance in the spring of settlement was more important in determining average dispersal distances than vole abundance in the previous autumn. At the population level (cross-sectional model), both males and females dispersed longer distances when the spring abundance of their main food (voles) was low compared to when it was abundant, as predicted by the food depletion hypothesis. At the individual level (longitudinal model), only females responded to the food situation by dispersing more when food abundance was low in the spring of settlement. Females also dispersed longer when vole abundance in the previous autumn had been high. Individual males did not respond to vole abundance, which implies that the population level response in males might have been caused by long-distance dispersers, which breed in the study area only in good vole years. Our results show that the dispersal distances of kestrels at northern latitudes depend both on individual properties (gender, age, and possibly individual tendency to disperse) and environmental conditions (temporal variation in main food abundance).
URL:http://dx.doi.org/10.1111/j.1600-048X.2011.05351.x
Short Title:Journal of Avian Biology
Scratchpads developed and conceived by (alphabetical): Ed Baker, Katherine Bouton Alice Heaton Dimitris Koureas, Laurence Livermore, Dave Roberts, Simon Rycroft, Ben Scott, Vince Smith