Pre-Migratory Movements by Juvenile Burrowing Owls in a Patchy Landscape

Abstract

Dispersal is a fundamental aspect of population dynamics, and can have direct implications on processes such as the colonization of habitat patches. Pre-migratory movements, landscape fragmentation, and body condition have all been hypothesized as key factors influencing dispersal in birds, but little direct evidence exists to support these ideas. We used radio-telemetry and supplementary feeding to test if body condition or landscape pattern influenced pre-migratory movements of juvenile Burrowing Owls (Athene cunicularia) in a fragmented landscape. We categorized grassland patches as either large (≥95 ha) or small and isolated (≤58 ha and ≥1.5 km to next nearest grassland patch), and young owls were either provided supplemental food as nestlings or not. Owlets receiving supplemental food and residing in large grassland patches moved a greater maximum distance from their nest than similarly fed owlets residing in small patches (large = 1605 ± 443 m; small = 373 ± 148 m). In contrast, non-supplemented owlets from large and small patches did not differ in their maximum distance moved from the nest (large = 745 ± 307 m; small 555 ± 286 m). Only two of 32 individuals from small patches moved >800 m, whereas ten of 23 owlets from large patches moved >800 m. In addition, owlets from large patches continued to move farther and farther from their nest before migration, whereas owlets in small, isolated patches ultimately moved 800 m, tandis que 10 des 23 cheveches provenant de grandes parcelles l’ont fait. De plus, les cheveches provenant de grandes parcelles se sont eloignees de plus en plus de leur Biology Department, University of Regina, Royal Saskatchewan Museum, Integrated Landscape Management Group, University of Alberta, Environment Canada, Canadian Wildlife Service Prairie and Northern Region Avian Conservation and Ecology Ecologie et conservation des oiseaux 2(2): 4 http://www.ace-eco.org/vol2/iss2/art4/ nid avant la migration, tandis que celles provenant de parcelles petites et isolees se sont finalement deplacees sur <400 m de leur nid avant la migration, meme si elles avaient amorce leur dispersion de la meme facon que les cheveches provenant de grandes parcelles. Nos resultats, en parallele aux resultats obtenus dans les etudes anterieures, montrent la reticence ou l’incapacite qu’ont les jeunes Cheveches des terriers nees dans de petites parcelles a franchir la matrice cultivee dans un paysage fragmente.