Avian Siblicide

Siblicide, the act of one sibling killing another, is a natural behavior in many bird species and is closely tied to brood reduction—an evolutionary strategy where more chicks hatch than parents can reliably feed.

In species like eagles, herons, and boobies, the first-hatched chick often grows faster and dominates food access, sometimes aggressively attacking or starving smaller siblings.

This ensures that at least the strongest chick survives when food is scarce.

Siblicide can be obligate (almost always occurs) or facultative (only under resource stress), helping parents optimize their reproductive success relative to environmental conditions.