Copulatory behaviour in the Bonelli´s Eagle: Assessing the paternity assurance hypothesis

Area of Science:

• Ornithology
• Behavioral Ecology
• Conservation Biology

Background:

• Bonelli's Eagle (Aquila fasciata) is a vulnerable raptor species.
• Understanding breeding behavior is crucial for conservation efforts.
• Paternity assurance hypotheses provide a framework for studying avian reproductive strategies.

Purpose of the Study:

• To examine the copulatory behavior of Bonelli's Eagles.
• To test predictions of the paternity assurance hypothesis.
• To evaluate the adaptive significance of their mating system.

Main Methods:

• Field observations of 15 Bonelli's Eagle pairs over three breeding seasons (2010-2012).
• Recording copulatory attempts, timing, and success rates.
• Analyzing data in relation to breeding density, female fertile period, and mate attendance.

Main Results:

• Copulation commenced approximately 69 days before egg-laying, with high success rates (96%).
• Average copulation frequency was 0.86 per day, with a bimodal daily pattern peaking in the evening.
• Paternity assurance predictions were largely rejected; mate attendance did not increase during the fertile period, but mate-guarding correlated with copulation frequency.

Conclusions:

• Bonelli's Eagles exhibit partially adaptive paternity assurance behaviors, with moderate copulation rates and limited mate-guarding.
• The increase in within-pair copulations during the female fertile period aligns with sperm competition hypotheses.
• Frequent copulations may also serve as territorial signaling to conspecifics and other raptor species.