Age-dependent diet choice in an avian top predator

Area of Science:

• Ornithology
• Behavioral Ecology
• Life-History Theory

Background:

• Age-dependent breeding performance is well-documented in birds, but the underlying reasons are unclear.
• Lack of foraging skills in young individuals is a proposed cause for poorer breeding success.
• The northern goshawk (Accipiter gentilis) is a powerful raptor where males provide food for their family.

Purpose of the Study:

• To investigate if young male northern goshawks exhibit poor foraging skills, particularly for their primary prey, the feral pigeon (Columba livia).
• To determine if hunting efficiency and prey choice improve with age in male goshawks.
• To explore the link between age-dependent foraging ecology and reproductive performance.

Main Methods:

• Utilized a 'natural experiment' during the expansion of an urban northern goshawk population with minimal intraspecific interference.
• Analyzed dietary data from individually identified male breeders to track prey composition.
• Examined the relationship between male age and the proportion of pigeons in their diet.

Main Results:

• The proportion of pigeons in the diet of male northern goshawks significantly increased with male age, at least for the first three years.
• This finding supports the hypothesis that young males lack experience in hunting their primary avian prey.
• Prey choice, reflecting hunting skills, was demonstrated to be age-dependent in this raptor species.

Conclusions:

• Age-dependent foraging skills, specifically improved pigeon hunting, are a key factor in the breeding performance of male northern goshawks.
• The study provides the first evidence of age-dependent prey choice in a raptor, linking foraging ecology to reproductive success.
• Understanding these age-related patterns is crucial for life-history theory and conservation efforts for raptor populations.