Passive and active parental food allocation in a songbird

Area of Science:

• Behavioral Ecology
• Evolutionary Biology
• Animal Behavior

Background:

• Parent-offspring conflict over food allocation is explained by passive (scramble competition) and active choice (signaling) models.
• Empirically distinguishing between these models is challenging, necessitating detailed analysis of parental feeding decisions.

Purpose of the Study:

• To investigate how nestling traits (cryptic quality, size, signals, location) interact to predict parental feeding responses in pied flycatchers.
• To differentiate between passive and active choice models of food allocation by examining parental decision-making processes.

Main Methods:

• Experimental manipulation of nestling cryptic quality (via vitamin E) in even-sized, small pied flycatcher broods.
• Analysis of food allocation and prey-testing by parents based on nestling traits and spatial competition dynamics.

Main Results:

• Heavier, vitamin E-supplemented nestlings grew faster and accessed better nest locations, but competition was mild.
• Pied flycatcher fathers used nestling position and begging order for food allocation.
• Mothers employed a more complex active choice mechanism, considering postural begging intensity, order, position, and treatment.

Conclusions:

• Parental feeding allocation in pied flycatchers is influenced by both nestling traits and parental sex.
• Sex differences in food allocation rules may arise from differing time constraints and decision-making strategies.