Costs of long-term carrying of extra mass in a songbird

Atema, E., van Noordwijk, A. J., Boonekamp, J. J. and Verhulst, S. (2016) Costs of long-term carrying of extra mass in a songbird. Behavioral Ecology, 27(4), pp. 1087-1096. (doi: 10.1093/beheco/arw019)

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Abstract

Iteroparous organisms face a trade-off between reproduction and survival, but knowledge of whether how and when costs of long-term increases in workload are paid is scant. We increased locomotion costs for a whole year by equipping male great tits with a backpack during breeding, removing the backpacks 1 year later. We applied 3 different treatments: control (without backpack), light (“empty” backpack, 0.1g), and heavy (“full” backpack, 0.9g, ~5% of body mass). Backpacks were administered in 3 cohorts, and we monitored effects on mass of nestlings and the male, wing length, reproduction, and survival. Added mass had a negative effect on nestling mass in both the starting year of the experiment and 1 year later, but not on production of fledglings or recruits. In winter and the next breeding season, males equipped with heavy backpacks had a higher (net) body mass and had shorter third primary feathers than the other 2 groups. Heavy backpack males were less likely to sleep in a nest box in winter. Nest boxes are optimal roosting sites, and we interpret this finding as a treatment effect on success in competition over this resource. However, there was no effect of the manipulation on survival. Overall, we found no long-term fitness consequences, and we discuss possible explanations and implications for the “starvation–predation theory” of optimal body mass. However, we found short-term effects of carrying extra weight suggesting that behavioral studies using small devices should consider the effects of equipping small non-migratory passerines with devices such as transmitters.

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Boonekamp, Dr Jelle
Authors: Atema, E., van Noordwijk, A. J., Boonekamp, J. J., and Verhulst, S.
College/School:College of Medical Veterinary and Life Sciences > Institute of Biodiversity Animal Health and Comparative Medicine
Journal Name:Behavioral Ecology
Publisher:Oxford University Press (OUP) for International Society for Behavioral Ecology
ISSN:1045-2249
ISSN (Online):1465-7279
Published Online:17 February 2016

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