Declining Penguin Populations Turn Heads Toward Coastal Currents
Magellanic penguins are one of the few species of penguins that live in warmer, non-polar waters. They breed along the coasts of Argentina, Chile, and the Falkland Islands. In the winter, these penguins take to the sea and spend the colder months along the shallower continental shelf. Recent observations of river outflow have shown that oceanic winds and currents can mean good or bad winters for the penguins, but only the females.
Ecologists and biologists have turned their attention toward these tiny penguins in recent years due to human threats to their breeding grounds. Although there are still millions of Magellanic penguins along the South American coastlines, oil spills pose a hazard to large breeding colonies, particularly along the shores of Argentina. Every year, 20,000 adults and 22,000 chicks succumb to oil spills.
Climate change has also caused a decline in the Magellanic penguin population. Warming oceans have displaced fish populations, driving them away from their historic ranges. During the breeding season, this means that hunting penguins have to swim up to 50 miles farther to find food while their mates sit starving on their nests.
A River Flows Through It
The Rio de la Plata meets the South Atlantic Ocean between Argentina and Uruguay, dumping nutrient-rich water and sediments into the surrounding sea. Wind patterns along the coast disperse the outflow. The microorganisms in the water attract fish. Low winds mean that the fish and their food supply stay relatively close to the mouth of the river, whereas stronger current carries them along the coast for miles, dispersing the fish.
Magellanic penguins feed on these fish during their winters at sea. When the winds are low and the food is concentrated, the penguins are healthier-looking in the springtime and more fit to have a productive mating season. If currents thin the fish populations, the penguins suffer, though scientists noted that only the female Magellanic penguins seemed to feel the effects.
Like many species, Magellanic penguins exhibit sexual dimorphism, which is a visual difference between the two sexes. Male penguins of this species are larger than the females, and scientists believe that may play a key role in discovering why the males don’t seem as affected by changes in the currents. The larger male penguins are thought to have more stamina and a greater ability to hunt at depths that the females cannot reach. As a result, they have access to more food when the river outflow is dispersed than the female penguins do.
Studying the habits of these little birds has been a challenge because of where they spend their winters. Satellite technology and digital trackers are making it easier to scientists to understand what Magellanic penguins do when they’re away from land. Before biologists compared the satellite imagery of the Rio de la Plata with the penguins’ unusual health fluctuations, the reason was left to much tricker guesswork. As we continue to blend technology into all facets of science, we are better able to study the world around us and understand how we can help it as habitats change and the climate shifts.
For now, the population seems to be doing alright. That’s not the case for other wildlife in the seas, with populations decreasing by up to 50% over the past forty years.