{"id":22487,"date":"2022-11-14T15:20:09","date_gmt":"2022-11-14T14:20:09","guid":{"rendered":"https:\/\/www.discoverwildlife.com\/?p=70827"},"modified":"2022-11-14T15:33:12","modified_gmt":"2022-11-14T14:33:12","slug":"why-erect-crested-penguins-lay-one-and-a-half-eggs","status":"publish","type":"rss_feed","link":"https:\/\/c01.purpledshub.com\/bbcwildlife\/rss_feed\/why-erect-crested-penguins-lay-one-and-a-half-eggs\/","title":{"rendered":"Why erect-crested penguins lay one and a half eggs"},"content":{"rendered":"

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By Stuart Blackman\n \t\t<\/p>

Published: Monday, 14 November 2022 at 12:00 am<\/p>

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Some birds lay 20 eggs per clutch; others lay just one. Most fall somewhere in between. And yet there\u2019s a little-known species of penguin<\/a> that lays one and a half.<\/p>\n

Erect-crested penguins are, according to Lloyd Davis of New Zealand\u2019s University of Otago<\/a>, \u201cthe forgotten penguins,\u201d largely because of the inaccessibility of their breeding colonies on the uninhabited Bounty and Antipodes islands 800km off New Zealand.<\/p>\n

\u201cNo one visits them,\u201d says Davis. \u201cSure, every now and then, in the past, you\u2019d get shipwrecked sailors or sealers there. But the only people visiting those islands these days are scientists who have gone through the rigorous permitting process, which is basically a fence to keep people out. Virtually no work has ever been done on them and you never see them on documentaries, because no one\u2019s allowed to go there and film.\u201d<\/p>\n

For his latest research on the species, published in PLOS One<\/em><\/a>, Davis and his colleagues drew on data collected on a rare visit to the colonies in 1998.<\/p>\n

More related content:\u00a0<\/strong><\/p>\n

Penguin guide: how to identify each species and best places to see<\/a><\/p>\n

Emperor penguin guide: where they live, how they breed and how they survive the cold<\/a><\/p>\n

King penguin guide: species facts and where they live<\/a><\/p>\n

Penguin: A Story of Survival<\/a><\/p>\n

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This has revealed that erect-crested penguins employ a highly unusual egg-laying strategy, in which the first of the two eggs they lay is only about half the size of the second. Davis says the difference is more pronounced than in any other bird. The smaller egg is not brooded by the parents and never hatches.<\/p>\n

Davis believes that this bizarre situation represents a snapshot in a process of transition between a two-egg and a one-egg strategy. He says that while most penguins raise two chicks, species that nest far from their feeding grounds tend to reduce their clutch to a single egg. Emperor<\/a> and king penguins<\/a>, for example, stop laying after the first egg.<\/p>\n

For the erect-cresteds, though, it\u2019s not so simple, because for some reason they put all their effort into the second egg rather than the first.<\/p>\n

\u201cThe problem is that you can\u2019t lay a second egg until you\u2019ve laid a first egg,\u201d says Davis. \u201cSo all you can do is reduce the investment in the first egg as much as you can.\u201d<\/p>\n

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More egg-cellent facts<\/h4>\n