A1 Refereed original research article in a scientific journal

Juvenile Barn Swallows Hirundo rustica L. from late broods start autumn migration younger, fuel less effectively and show lower return rates than juveniles from early broods




AuthorsRaja-Aho S, Eeva T, Suorsa P, Valkama J, Lehikoinen E

PublisherWILEY

Publishing placeHOBOKEN

Publication year2017

JournalIbis

Journal name in sourceIBIS

Journal acronymIBIS

Volume159

Issue4

First page 892

Last page901

Number of pages10

ISSN0019-1019

eISSN1474-919X

DOIhttps://doi.org/10.1111/ibi.12492(external)

Web address 10.1111/ibi.12492


Abstract
Long-distance migratory passerines may exhibit different post-fledging rearing times between their early and late broods due to limited time and energy resources. This could affect the migratory fuelling behaviour, condition and fitness of juvenile birds. We analysed long-term (13-year) biometric data (body mass, fat score) on Barn Swallows ringed at the nest and later recaptured during their initial stages of autumn migration. The return rates of early-and late-born juveniles after overwintering in Africa were further compared to estimate their fitness. We found that juveniles from late broods started migrating south on average 11 days younger compared with juveniles from early broods. Body masses of nestlings did not differ between early and late broods, but juveniles from late broods were in better condition after leaving the nest, possibly due to a longer period of parental care. Having started migration, juveniles from late broods were, however, less efficient in accumulating energy than juveniles from early broods. A younger departure age, together with less efficient fuelling of late brood juveniles, may partly explain the 39% lower return probability and hence lower fitness value of late-brood juveniles. Our study is the first to show that juveniles from the early and late broods exhibit different fuelling behaviour and departure strategies (in terms of age and timing), which may be reflected in the fitness value of offspring.



Last updated on 2024-26-11 at 20:56