Abstract
Natal dispersal affects many processes such as population dynamics. So far, most studies have examined the intrinsic and extrinsic factors that determine the distance between the place of birth and of first breeding. In contrast, few researchers followed the first steps of dispersal soon after fledging. To study this gap, we radio-tracked 95 barn owl nestlings (Tyto alba) to locate their diurnal roost sites from the fledging stage until December. This was used to test whether the age of nest departure, post-fledging movements and dispersal distance were related to melanin-based coloration, which is correlated to fitness-related traits, as well as to corticosterone, a hormone that mediates a number of life history trade-offs and the physiological and behavioural responses to stressful situations. We found that the artificial administration of corticosterone delayed the age when juveniles left their parental home-range in females but not in males. During the first few months after fledging, longer dispersal distances were reached by females compared to males, by individuals marked with larger black feather spots compared to individuals with smaller spots, by larger individuals and by those experimentally treated with corticosterone. We conclude that the onset and magnitude of dispersal is sensitive to the stress hormone corticosterone, melanin-based coloration and body size.
Highlights
Natal dispersal, the movement between the places of birth and of first reproduction, has crucial effects on population biology, ecology and evolution [e.g. 1, 2]
We explored the departure and the first part of the transient phase of dispersal in nestling barn owls (Tyto alba)
We modified post-natal rearing conditions through experimentally increasing corticosterone for a short period of time during the nestling stage [58]. This artificial increase in corticosterone levels temporally hampered growth but did not affect survival until fledging and body mass at fledging [45]. We investigated whether these short-term stressful developmental conditions have long-lasting effects on natal dispersal behaviour and on post-fledging survival and whether these effects vary between individuals showing different melanin-based coloration
Summary
The movement between the places of birth and of first reproduction, has crucial effects on population biology, ecology and evolution [e.g. 1, 2]. An individual’s decision to disperse depends on extrinsic factors, such as environmental condition [9,10,11], predation risk [12, 13], social interactions [12, 14], sex ratio [reviewed in 15], and on intrinsic phenotypic traits such as sex [8, 16, 17], behavioural phenotypes [reviewed in 18] and colour morph [13, 19,20,21].
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