Age‐dependent reproductive performance in Northern Goshawks Accipiter gentilis

• Published in: Ibis
• Main Authors: Tøttrup Nielsen, Jan, Drachmann, Jan
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2002
• Subjects: Accipiter gentilis
• Online Access: http://dx.doi.org/10.1046/j.1474-919x.2003.00127.x; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1046%2Fj.1474-919X.2003.00127.x; https://onlinelibrary.wiley.com/doi/pdf/10.1046/j.1474-919X.2003.00127.x

The age‐specific reproductive performance of Northern Goshawks Accipiter gentilis was studied over 22 years in Denmark. The age of the breeding female in relation to the number of young raised was known in 929 breeding attempts, while the age of both the male and the female was known in 496 breeding attempts. The number of fledglings raised per breeding attempt increased with both male and female age, but only for females was it possible to conduct a detailed analysis of this age‐dependent relationship. The annual production of fledglings increased with female age from 1 to 7 years of age, whereupon it started to decline. A longitudinal analysis showed that this mean population trend could be attributed to similar age‐related trends in individual females. Previous breeding experience did not influence the number of fledglings produced by individual females, and poorly performing females apparently survived with the same probability as well performing ones. The most likely explanation for the age‐dependent reproductive performance in the observed Goshawk population appeared to be age‐related improvements in competence, such as foraging efficiency.