Clutch Size
Definition
Clutch size is the number of eggs laid in a single breeding attempt. Most penguin species lay a clutch of two eggs, but emperor and king penguins consistently lay only one. In the crested penguins (Eudyptes), two eggs are laid but the first egg is significantly smaller and is almost always lost, a phenomenon called obligate brood reduction. Clutch size represents a trade-off between the number of offspring and the resources each receives. Single-egg species invest heavily in one chick, while two-egg species hedge their bets but provide less per offspring.
Related Terms
Obligate brood reduction is a reproductive strategy unique to crested penguins (Eudyptes) in which two eggs are laid but only one chick is raised.
Incubation is the period during which a parent penguin keeps the egg at a constant temperature (approximately 36-38 °C) to allow embryonic development.
Related Species
Species where clutch size is especially relevant.
Frequently Asked Questions
What does clutch size mean in penguin biology?
Clutch size is the number of eggs laid in a single breeding attempt. Most penguin species lay a clutch of two eggs, but emperor and king penguins consistently lay only one. In the crested penguins (Eudyptes), two eggs are laid but the first egg is significantly smaller and is almost always lost, a phenomenon called obligate brood reduction. Clutch size represents a trade-off between the number of offspring and the resources each receives. Single-egg species invest heavily in one chick, while two-egg species hedge their bets but provide less per offspring.
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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.