Nest predation increases with parental activity: separating nest site and parental activity effects

Area of Science:

• Ecology
• Behavioral Ecology
• Evolutionary Biology

Background:

• Alexander Skutch proposed that increased parental activity elevates nest predation risk.
• Studies have shown varied results regarding the relationship between parental activity and nest predation.
• Nest site characteristics are also known to influence predation rates.

Purpose of the Study:

• To test Skutch's hypothesis on parental activity and nest predation risk in ten open-nesting bird species.
• To investigate the role of nest site characteristics in modulating nest predation.
• To understand the interplay between parental activity and nest site effects on predation.

Main Methods:

• Field study of ten open-nesting bird species in Arizona, USA.
• Quantified parental activity during incubation and nestling stages.
• Conducted experiments using previous year's nest sites to isolate nest site effects.

Main Results:

• Parental activity was higher during the nestling stage (feeding) than incubation.
• Nest predation did not consistently increase with parental activity between stages across species.
• Nest site characteristics significantly and repeatably affected predation risk, with poor sites incurring rapid predation.
• Predation risk was higher during incubation than nestling stages when nest site effects were considered.
• Once nest site effects were accounted for, nest predation increased with parental activity during the nestling stage.

Conclusions:

• Nest site characteristics and parental activity have opposing influences on nest predation risk.
• Both nest site selection and parental behavior are crucial factors in understanding nest predation patterns.
• Nest predation is a significant source of natural selection, shaped by both environmental and behavioral factors.