Natures wonders: problems in penguin migration (Introduction)

by David Turell @, Thursday, October 01, 2015, 18:11 (1477 days ago) @ David Turell

Travelling 4,000 kilometers has problems for young penguins:

http://www.the-scientist.com/?articles.view/articleNo/44087/title/Ocean-Sentinels/

"Each year around April, as the Southern Hemisphere winter approaches, the Magellanic penguins, also known as Patagonian penguins, leave their breeding grounds in southern Argentina. They migrate northward to wintering grounds in the coastal waters of northern Argentina, Uruguay, and southern Brazil in search of food. (Some southernmost breeders also head along Chile's Pacific shores, but that route is less well studied.) It's a monumental journey: a round-trip of up to 4,000 kilometers that coincides with the seasonal spawning of anchovies, a staple of the penguins' diets. The birds face many challenges along the way, and some run out of strength, winding up on Brazil's beaches in serious need of help.

"Birds like these appear every year, while others continue their travels even farther north. Researchers are still trying to understand exactly why some birds end up farther from home than ever before.

***

“'Most of them are juveniles that we think cannot eat as well as the adults, so they beach,” she says. “And some are caught by nets.” But for the most part, the circumstances that lead to the penguins' arrival on Brazilian beaches are still mysterious.

"Recent years have been tough for Magellanic penguins along the Atlantic coast of South America. In 2008, more than 3,000 birds were found stranded along the coast of Brazil—almost all of them juveniles. Nearly 15 percent of the birds were smothered in oil, and about a third were dead.

"Pablo García Borboroglu, a researcher at Argentina's National Research Council and president of the Global Penguin Society, and collaborators studied what happened with the penguins in 2008 and reported their findings in a 2010 Marine Pollution Bulletin article: the penguins had strayed far north of their normal winter migration path (60:1652-57). A few nearly reached the Equator. Most of the birds that went as far as northern Brazil were juveniles. Many were dehydrated, anemic, hypothermic, and emaciated, García Borboroglu says. He notes one factor that may have contributed to the anomalous migration is that year's unusually cold sea-surface temperatures around the time that the anchovy were spawning, which may have depleted the penguins' key prey base.

***

"P. Dee Boersma, a collaborator of García Borboroglu who heads the University of Washington's Center for Penguins as Ocean Sentinels, says that temperate-zone penguins, even while pairs are incubating eggs and taking turns feeding at sea, are swimming 60 km farther north from their nests than they did a decade ago. This change likely reflects “shifts in prey in response to climate change and reductions in prey abundance caused by commercial fishing,” she says. “These temperate penguin species, marine sentinels for southern oceans, demonstrate that new challenges are confronting their populations.'”

Comment: following shifting food supply. But an amazing journey for swimming birds.


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