Long-term breeding demography and density dependence in an increasing population of Golden Eagles Aquila chrysaetos
Article first published online: 12 MAY 2011
© 2011 The Authors. Ibis © 2011 British Ornithologists’ Union
Volume 153, Issue 3, pages 581–591, July 2011
How to Cite
FASCE, P., FASCE, L., VILLERS, A., BERGESE, F. and BRETAGNOLLE, V. (2011), Long-term breeding demography and density dependence in an increasing population of Golden Eagles Aquila chrysaetos. Ibis, 153: 581–591. doi: 10.1111/j.1474-919X.2011.01125.x
- Issue published online: 14 JUN 2011
- Article first published online: 12 MAY 2011
- Received 23 November 2009; revision accepted 2 April 2011. Associate Editor: Rob Simmons.
- buffer effect;
- habitat heterogeneity;
- Italian Alps;
- long-term study;
- population dynamics;
- population regulation
Few studies have quantified the dynamics of recovering populations of large raptors using long-term, spatially explicit studies. Using data collected over 37 years in the western Italian Alps, we assessed the trends in distribution, abundance, fecundity and breeding population structure of Golden Eagles Aquila chrysaetos. Using the spatial distribution of territory centroids in 2007, we found that the spatial distribution of eagle territories was over-dispersed up to 3 km. Although population size and total productivity increased from 1972 to 2008, the proportion of pairs that laid eggs showed a strong decline, falling to no more than 50% after 2003. On average, 15% of successful nests produced two fledglings, and productivity also declined over time. No significant relationship between population growth rate and total population size was detected, but the percentage of pairs that bred and breeding success showed evidence of density dependence, as they declined significantly with increasing density. Our results suggest that density dependence, operating across heterogeneous habitats, is currently regulating this population, while the carrying capacity may still be increasing. This may explain the apparent paradox of reduced breeding effort despite increasing total productivity.