After a bad winter in the ocean, female Magellanic penguins suffer most, study shows

Date:  November 7, 2018

Source:  University of Washington

Every autumn in the Southern Hemisphere, Magellanic penguins leave their coastal nesting sites in South America. For adults, their summer task -- breeding, or at least trying to -- is complete. Newly fledged chicks and adults gradually head out to sea to spend the winter feeding. They won't return to land until spring.

Yet life for these birds when they winter offshore is largely a mystery to the scientists who study Magellanic penguins -- and who advocate for their conservation amid declining population numbers.

"The winter period is something of a black box for us in terms of understanding Magellanic penguins," said Ginger Rebstock, a University of Washington research scientist. "We know the least amount about this part of their year."

But research by Rebstock and P. Dee Boersma, a UW professor of biology and founder of the Center for Ecosystem Sentinels, is starting to pry open that black box and discover how Magellanic penguins from one nesting site, Punta Tombo in Argentina, fare during the winter months. In a paper published Aug. 9 in the journal Marine Ecology Progress Series, they report that the Río de la Plata -- which drains South America's second-largest river system after the Amazon -- strongly influences oceanographic conditions in the Magellanic penguins' winter feeding waters. Those oceanographic features, they report, show up in the body conditions of Magellanic penguin females, but not males, when the penguins return to their nesting grounds in spring.

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Which snowy owls thrive in Saskatchewan's winters?

Date: August 31, 2016

Source: Central Ornithology Publication Office

Snowy Owls capture the imagination, but ornithologists know surprisingly little about how these birds of the far north fare during the harsh winters they endure. The researchers behind a new study in The Auk: Ornithological Advance strapped and tracked Snowy Owls wintering in Canada and found that while age and sex affect the birds' condition, most do fairly well, showing few signs of starvation and some even putting on weight over the winter months.

Female Snowy Owls are bigger than males, and Alexander Chang and Karen Wiebe of the University of Saskatchewan expected that their dominant behavior would give females access to greater food resources during the challenging winter season. Their results bore this out -- females tended to be in better condition than males, and adults, with their greater hunting experience, tended to be in better condition than juveniles.

It's widely believed that Snowy Owls that winter south of the Arctic tend to be struggling, starving birds that only move south because they can't find enough to eat at home, but few of the adults captured in the wild showed signs of starvation. Surprisingly, many of the adult birds in the study actually increased their fat stores slightly over the course of the winter. Well-insulated against the cold and not distracted by the demands of reproduction, Snowy Owls may use winter as a time to recharge and build up their reserves before returning to their breeding grounds.

Continued