Age at first breeding and fitness in goshawk Accipiter gentilis
Article first published online: 19 JAN 2005
Journal of Animal Ecology
Volume 74, Issue 2, pages 266–273, March 2005
How to Cite
KRÜGER, O. (2005), Age at first breeding and fitness in goshawk Accipiter gentilis. Journal of Animal Ecology, 74: 266–273. doi: 10.1111/j.1365-2656.2005.00920.x
- Issue published online: 19 JAN 2005
- Article first published online: 19 JAN 2005
- Received 12 March 2004; accepted 30 July 2004
- delayed maturity;
- life-history evolution;
- territory quality
- 1Age at first breeding has a large influence on fitness and hence is crucial to the evolution of life-history strategies. Goshawks Accipiter gentilis start breeding aged 1–4 years. Using 30 years of data and both lifetime reproductive success (LRS) and lind as a fitness estimate for 74 female goshawks, I showed that the optimal age at first reproduction was 3 years in this population.
- 2Females that started to breed earlier had lower LRS and lind, not because of reduced life span, but because of lower reproduction at early ages.
- 3The constraint hypothesis, which states that foraging or other skills improve with age was the most likely explanation for the higher reproduction with increasing age.
- 4Incorporating habitat heterogeneity provided the mechanism that explained not only the fitness cost to early maturity, but also why this cost was heterogeneous. Females starting to breed aged 1 suffered a very high fitness cost if they were in a bad-quality territory, but fitness costs were small when they were in a good-quality territory. This explains why I found evidence for a nonlinear selection pressure on age at first breeding.
- 5Population density also affected whether a female started to breed early or not: over the study period, population density increased and the percentage of females starting to breed aged 1 decreased.
- 6The optimal age at first breeding seems to be a trait affected by a complex interplay between cost and benefits of early reproduction mediated by habitat heterogeneity and population density.