Penguin parenting: Here’s why this stylish endangered species ignores its first egg, but raises its second

DUNEDIN, New Zealand — So much for picking favorites. The erect-crested penguin not only sports a wild spiky hairdo, but also has questionable parenting skills — at least from afar. Scientists reveal in a new study, this extraordinary endangered species of penguin destroys or ignores its first egg and only raises its second one.

They believe that only the second egg is reared because it is bigger and has a better chance of survival. The erect-crested penguin is the least studied of all penguin species and it lives on two isolated islands south-east of New Zealand, the Antipodes and Bounty Islands.

Why do these penguins ignore their first egg?

What little is known about the erect-crested penguins comes from a study in 1998 by Professor Lloyd Davis and colleagues from the University of Otago, New Zealand. The researchers went to observe their highly unusual courting and egg laying habits, where the female lays a small egg and then a larger one around five days later.

As these observations are still the most recent and extensive data collected on this species of penguin, Professor Davis and his colleagues decided to reanalyze them in order to learn more about the birds’ strange behavior and to provide a basis for future conservation efforts.

“This study highlights the paradox that such an intriguing and endangered penguin species should be so little known in this day and age that the best data we have comes from nearly a quarter of a century ago,” says Davis, in a statement. “When three of us went to the Antipodes Islands in 1998 to conduct research on the erect-crested penguin, it was by far the least studied penguin species.

Eggs of the erect-crested penguin
The difference in sizes of eggs within a clutch of erect-crested penguins is the largest for any bird, with the first-laid egg being far smaller than the second-laid egg.
(Credit: Lloyd Davis Photography (, CC-BY 4.0)

“Sadly, the situation remains unchanged: the very few studies conducted since then have been involved mostly with just counting the numbers of erect-crested penguins breeding on the Bounty and Antipodes Islands south-east of New Zealand,” adds Davis. “These studies have documented further drastic declines in the population of erect-crested penguins on the Antipodes Islands from those that we had observed in 1998.”

The researchers suggest that erect-crested penguins have retained the reproductive habit of their ancestors, which laid and hatched two eggs, but sacrifice their first egg as they can’t provide enough food for both chicks. Producing more eggs than is possible to rear is called brood reduction and other species of birds do so as a form of insurance, whereby a second egg is laid in case the first chick dies.

Why the erect-crested penguin sacrifices its first egg, is still under debate. Davis and colleagues said there has not yet been a satisfactory answer as to why they do this, they suggest it may be because females begin to form their first egg while still at sea and their second egg after reaching land.

What happens to the first egg?

This means the chick in the second egg is larger and therefore less likely to starve so it becomes the favorite. Typically, the first egg is lost either before or soon after the second egg is laid, and parents sometimes deliberately break or reject it.

Around 40 percent of mating penguin pairs do not even bother to incubate the first egg, with steady incubation occurring only after the second egg is laid. Blood samples taken from the penguins also showed how hormones affect the birds’ behavior.

During laying, females had testosterone levels that were as high as the males, but they dropped during incubation and rose in males, which may help the males to protect the nest and guard the incubating females from bullying by other birds.

The future of erect-crested penguins

The population has declined sharply in the last 50 years and evidence suggests that climate change is negatively impacting their breeding on the Antipodes Islands, with greater numbers of storms and mudslides in recent decades wiping out parts of colonies and killing nesting penguins.

Rising ocean temperatures have already caused the population of eastern rockhopper penguins to crash and they are likely affecting the erect-crested penguin’s ability to reproduce and feed as well.

Davis and colleagues cautioned that without more research attention the species will continue to decline until threatened with extinction and suggested that conservation marketing, raising public awareness and advocating for more research, could help conservation efforts.

“Remaining an enigma will not change the plight of erect-crested penguins. Research priorities increasingly determine prospects for survival of many species around the world,” the authors write in their paper. “Although not typically considered to be part of the conservation science toolbox, conservation marketing could be used to influence the outcome for a troubled species like the erect-crested penguin.”

“Without prioritizing conservation market for erect-crested penguins, we are likely to be limited, as here, to describing continued declines in the species and, in essence, drafting an obituary for nature,” say authors of the study.

The study was published in the journal PLOS ONE. 

South West News Service writer Danny Halpin contributed to this report.