(ORDO NEWS) — Large crested penguins, whose numbers are already constantly declining, have a strange habit: lay the first egg, leave it to its fate and hatch only the second, which appears after a few days. Now scientists have finally figured out why birds do this.
Of all the penguin species, scientists know the least about the crested penguin ( Eudyptes sclateri ), probably because these birds breed only on the Antipodes and Bounty Islands southeast of New Zealand.
Despite their remoteness from civilization, over the second half of the 20th century, the number of these birds decreased by about half, and today large crested penguins are listed as endangered species.
Back in 1998, scientists visited penguin nesting sites, where they collected unique data on their reproductive behavior.
Among the unusual features of their reproduction was the strange habit of getting rid of one of the two eggs laid by the female during the breeding season.
Sometimes the first laid egg simply rolled out of the nest, sometimes it was broken and eaten, and most often it did not incubate at all and died from the cold.
The second egg, laid about five days later, almost always hatched.
Although all crested penguins have two-egg clutches, scientists suggest that great crested penguins reduce the number of eggs per clutch in order to ensure the survival of the most promising chick in conditions of scarce food resources.
The fact is that the first egg is formed in the body of the female when she is still at sea, heading towards the nesting sites, so it is relatively small.
The second egg is formed already on land, and it is much larger, so that the chick hatched from it has a better chance of survival.
The strange behavior of penguins is accompanied by equally unusual changes in the hormonal background: analysis of blood samples taken from these birds showed that during the laying of eggs, the level of “male” testosterone in the female is almost the same as in the male, but it decreases in females and increases in males during clutch incubation.
It is likely that initially a pair needs a high level of testosterone to recapture the nesting site from other penguins, while later on its protection falls almost entirely on the shoulders of the male while the female incubates the egg.
The authors of the work emphasize that this little-studied species (after all, the most “fresh” data on its behavior was obtained a quarter of a century ago) still needs to be studied.
Climate change negatively affects the penguin population: more frequent storms and the landslides they cause destroy entire areas of the colonies.
Therefore, unless urgent action is taken to conserve them, the survival of great crested penguins may eventually be in jeopardy.
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