Gap Crossing Decisions by Forest Songbirds during the Post‐Fledging Period

Gaps in forest cover, created by agriculture, forestry, and other anthropogenic activities, are assumed to impede the movements of many forest songbirds. Little is known, however, about the reluctance of different species of birds to cross habitat gaps. We studied this by inducing birds in the post-fledging period to cross gaps of varying widths and to choose between routes through woodland or across open areas by attracting them to a recording of mobbing calls by Chickadees (  Parus atricapillus). In 278 experiments conducted in boreal forest and agricultural landscapes near Quebec city, 157 birds or flocks of birds of five species were attracted. Overall, birds were twice as likely to travel through 50 m of woodland than through 50 m in the open to reach the recording. When given a choice of traveling through woodland or across a gap, the majority of respondents preferred woodland routes, even when they were three times longer than shortcuts in the open. However, species differed greatly in their response to gaps. Our results show that woodland links significantly facilitate movements of birds across fragmented landscapes. Es considerado que los claros en la cobertura forestal creados por la agricultura y otras actividades antropogenicas impiden los movimientos de muchas especies de aves paserinas. De cualquier manera, se conoce poco acerca de la renuencia de diferentes especies de aves a cruzar claros en los habitats. Estudiamos esto, induciendo aves en el periodo post-juvenil a cruzar claros de diversas dimensiones y a escoger rutas a traves de areas boscosas o abiertas, mediante la atraccion por llamadas grabadas de parvadas de Parus atricapillus. En 278 experimentos conducidos en paisajes de bosque boreal y agricultural, cercanos a la ciudad de Quebec, 157 aves o parvadas de cinco especies fueron atraidas. En general, las aves fueron mayormente atraidas a viajar a traves de 50 m de area boscosa que a traves de 50 m de claro, para encontrar la grabacion. Cuando se dio la opcion de viajar a traves de bosque o claro, la mayoria de las aves que respondieron prefirieron las areas arboladas, aun cuando estos viajes fueron tres veces mas largos que atajos por las areas abiertas. Sin embargo, las especies respondieron de diferente manera a los claros. Nuestros resultados muestran que uniones de areas boscosas facilitan significativamente los movimientos de aves a traves de paisajes fragmentados.