Thursday, January 3, 2019

In findings published on Wednesday in Ecological Applications, scientists from the University of Washington and Center for Ecosystem Sentinels examine the reason for the plummeting numbers of female Magellanic penguins (Spheniscus magellanicus) that have been reported at the birds’ breeding sites in South America for over twenty years.

“Two decades ago, there were about 1.5 adult male Magellanic penguins for every adult female at Punta Tombo,” postdoctoral researcher and study co-author Natasha Gownaris said in a press release. “Today, it’s approaching three males for every female.” The findings showed that a disparity in the death rate of juvenile and adult penguins, not differences in chick survival, account for this difference.

Punto Tombo is one of the annual breeding sites for the species; it is in Argentina. The penguins travel thousands of miles each year to reach these sites.

The work involved building population models out of over thirty years of data collected by tagging individual penguins. Findings also suggested that the pronounced sex disparity might make population models used to predict survival among other birds with a more even gender balance inappropriate for use on Megallanic penguins.

The overall population of Magellanic penguins in Punto Tombo at one of their annual breeding sites in Argentina has declined 40% since 1987, and the male-to-female ratio has gone up a great deal.

Since 1983, the research team has been putting stainless steel bands on tens of thousands of chicks hatched at the Punta Tombo breeding site in Argentina and noting which juvenile and adult birds make it back to the site the next year and extrapolating how many lived and died. Among juveniles, there was a 17% survival rate for males and 12% for females. Among adults, it was 89% and 85%. These effects became compounded every year, reaching as high as six males to one female among older penguins.

The researchers noted implications for penguin conservation: “Over the years, this team has helped preserve the land and waters around breeding colonies like Punta Tombo,” said Gownaris. “But now we’re starting to understand that, to help Magellanic penguins, you have to protect waters where they feed in winter, which are thousands of miles north from Punta Tombo.”

Wikinews caught up with Natasha Gownaris to learn more.

((Wikinews)) What prompted your curiosity about Magellanic penguins?

Natasha Gownaris:

((WN)) How did you approach putting together such a large-scale study?

NG:

((WN)) How much time did you end up spending in Argentina? What was it like at the breeding site?

NG:

((WN)) Do you have any theories on why more female juveniles die at sea? You mention starvation; what might be the causes of that, and are there other possible explanations you can think of?

NG:

((WN)) You suggest conservation efforts should look at protection of feeding grounds. What sort of measures do you think might be beneficial?

NG:

((WN)) What do you think might be causing pressure on food sources for the penguins?

NG:

((WN)) Have you noticed differences in behavior among the penguins as the ratios become increasingly skewed?

NG:

((WN)) Your release mentioned sexing the penguins was problematic; how did you achieve it with confidence?

NG:

((WN)) How well can you extrapolate population trends at Punta Tombo based on the birds you tagged? More broadly, how well do you think this work represents global populations?

NG:

((WN)) In your opinion, for how much longer are penguin populations sustainable without intervention?

NG:

((WN)) What are your next plans moving forward with your work?

NG:

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