Obligate Brood Reduction
Definition
Obligate brood reduction is a reproductive strategy unique to crested penguins (Eudyptes) in which two eggs are laid but only one chick is raised. The first egg is typically 20-40% smaller than the second and is almost invariably lost through ejection, starvation, or sibling competition. This puzzling strategy may have evolved as insurance against egg loss, or the first egg may serve as a hormonal primer for the larger second egg. Regardless of the mechanism, the functional result is that Eudyptes species produce only one chick per breeding season, limiting their ability to recover from population declines.
Related Terms
Related Species
Species where obligate brood reduction is especially relevant.
Frequently Asked Questions
What does obligate brood reduction mean in penguin biology?
Obligate brood reduction is a reproductive strategy unique to crested penguins (Eudyptes) in which two eggs are laid but only one chick is raised. The first egg is typically 20-40% smaller than the second and is almost invariably lost through ejection, starvation, or sibling competition. This puzzling strategy may have evolved as insurance against egg loss, or the first egg may serve as a hormonal primer for the larger second egg. Regardless of the mechanism, the functional result is that Eudyptes species produce only one chick per breeding season, limiting their ability to recover from population declines.
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Glossary entries define the language. FAQ answers common questions; guides carry the longer Survival Lab arguments.
More in reproductionWhere this definition comes from
Reference bodies behind the reproduction terminology. Links last checked August 5, 2026.
- British Antarctic Survey - Antarctic penguin ecology, diving, and sea-ice context.
- Australian Antarctic Division - Antarctic species profiles, breeding, and environmental context.
- Smithsonian Ocean Portal - Penguin biology, anatomy, and breeding explainers.