Avian brood reduction and parent-offspring "conflict".

Area of Science:

• Evolutionary biology
• Behavioral ecology

Background:

• Avian brood reduction is often considered a source of parent-offspring conflict.
• Empirical evidence suggests parents initiate competitive asymmetries and rarely intervene in sibling aggression, challenging the conflict hypothesis.

Purpose of the Study:

• To examine parent-offspring conflict over brood reduction using a game model.
• To determine conditions under which brood reduction is an evolutionarily stable strategy (ESS).

Main Methods:

• A simple game model was developed to simulate parent-offspring interactions regarding brood size and parental effort.
• Two resource allocation policies were analyzed: equal distribution and despotic distribution based on sibling hierarchy.

Main Results:

• Both conflict and cooperation over brood size can be evolutionarily stable strategies (ESS).
• Despotic resource allocation slightly diminished parental fitness but also reduced the risk of parent-offspring conflict.
• When conflict occurred, fitness costs and benefits were modest, especially under despotic allocation.

Conclusions:

• Parent-offspring conflict and cooperation are both possible ESS in avian brood reduction.
• Despotic allocation may favor cooperation by minimizing conflict, even with "insurance" offspring.
• Sibling rivalry can be the proximate cause of infanticide, masking potential parental-offspring agreement on eliminating redundant young.