Why do these penguins lay two eggs only to discard the first one?
In short: The erect-crested penguin is a mysterious seabird that exhibits a strange reproductive habit: it lays two eggs, but the first is almost always lost or intentionally discarded. Despite decades of study, scientists remain baffled by why this species and its kin invest energy in a doomed first egg.
The erect-crested penguin (Eudyptes sclateri) is a striking member of the crested penguin genus, defined by vibrant yellow plumes that sweep back from its bill above each eye. Standing up to 67 cm tall, these birds are among the largest of their kind. While they roam the Southern Ocean, their breeding grounds are restricted to the Antipodes and Bounty Islands near New Zealand.
Their reproductive cycle is marked by a peculiar phenomenon known as egg-size dimorphism. In October, pairs typically lay two eggs, with the first being significantly smaller than the second. Observations suggest that parents may even tip the smaller, first egg out of the nest as the second arrives. While some theories suggest this is an evolutionary holdover from a time when the genus laid only one egg, the exact biological driver remains an open question.
The species faces a precarious future. Since the late 1970s, populations have plummeted; for instance, breeding pairs on the Bounty Islands dropped from 115,000 in 1978 to just 28,000 by 1998. Since 2000, the IUCN has classified the erect-crested penguin as endangered. Researchers have ruled out hunting and introduced predators as causes, yet the precise reason for this ongoing decline remains unknown, leaving conservationists searching for answers in the remote subantarctic.
Life for these penguins is defined by extreme environments. Chicks are raised in simple nests of mud and rock, or sometimes on bare stone, and eventually join crèches for protection while parents forage. Despite their resilience, the lack of successful breeding evidence on Campbell and Auckland Islands since the 1980s highlights the fragility of their current status. Understanding these birds requires untangling the complex interplay between their unique evolutionary traits and the shifting pressures of their isolated island habitats.
Opens the Intellect+ feed with this card first. Swipe up for the next one.
Sources
- Summary by Intellect · source: Erect-crested penguin | Antarctic Bird Species | Britannica
- Also: Crested penguin
To cite this card, link to https://intellectplus.co.uk/app/nature-crested-penguin.
How we source, check and correct cards: Editorial standards.
General information, not professional advice. Spotted an error? Flag the card or see corrections and complaints.
Intellect Plus is a visual educational discovery platform for exploring fascinating facts and ideas. Brain Food, Not Brain Rot. What is Intellect Plus?
Related
More in Vertebrates · More in Nature · Latest · A–Z · All topics
