Ecological and demographic correlates of helping behaviour in a cooperatively breeding bird
Article first published online: 24 JAN 2013
© 2013 The Authors. Journal of Animal Ecology © 2013 British Ecological Society
Journal of Animal Ecology
Volume 82, Issue 2, pages 486–494, March 2013
How to Cite
Hatchwell, B. J., Sharp, S. P., Beckerman, A. P., Meade, J. (2013), Ecological and demographic correlates of helping behaviour in a cooperatively breeding bird. Journal of Animal Ecology, 82: 486–494. doi: 10.1111/1365-2656.12017
- Issue published online: 18 FEB 2013
- Article first published online: 24 JAN 2013
- Manuscript Accepted: 1 OCT 2012
- Manuscript Received: 9 JUL 2012
- Natural Environment Research Council
- Nuffield Foundation
- Association for the Study of Animal Behaviour and the University of Sheffield
- Leverhulme Trust Research Fellowship
- cooperative breeding;
- ecological constraints;
- kin selection;
- nest predation;
- social evolution
The evolution of cooperation is a persistent problem for evolutionary biologists. In particular, understanding of the factors that promote the expression of helping behaviour in cooperatively breeding species remains weak, presumably because of the diverse nature of ecological and demographic drivers that promote sociality.
In this study, we use data from a long-term study of a facultative cooperative breeder, the long-tailed tit Aegithalos caudatus, to investigate the factors influencing annual variation in helping behaviour. Long-tailed tits exhibit redirected helping in which failed breeders may become helpers, usually at a relative's nest; thus, helping is hypothesised to be associated with causes of nest failure and opportunities to renest or help.
We tested predictions regarding the relationship between annual measures of cooperative behaviour and four explanatory variables: nest predation rate, length of the breeding season, population-level relatedness and population density.
We found that the degree of helping was determined principally by two factors that constrain successful independent reproduction. First, as predicted, cooperative behaviour peaked at intermediate levels of nest predation, when there are both failed breeders (i.e. potential helpers) and active nests (i.e. potential recipients) available. Second, there were more helpers in shorter breeding seasons when opportunities for renesting by failed breeders are more limited.
These are novel drivers of helping behaviour in avian cooperative breeding systems, and this study illustrates the difficulty of identifying common ecological or demographic factors underlying the evolution of such systems.