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On the shallow shores of Australia’s Phillip Island, a shriek like a broken whistle fills the air. A tiny penguin, only 1 foot tall and 3 pounds, fights for the life of its chicks from its burrow. The island’s crows attack them.
Crows observe small penguin burrows, also known as fairy penguins, for several days before attacking. They work in pairs, with the larger penguin distracting the parent penguin while the smaller penguin burrows into the burrow from above and steals the eggs and chicks. In one particularly violent attack, researchers witnessed a pair of crows throw a parent penguin off a cliff before attacking its burrow. However, BirdLife Australia’s Kasun Ekanayake said the crows typically harass the penguins for several hours before giving up hope.
This was not always the case. In fact, it was only about 20 years ago that researchers noticed that crows, which arrived from mainland Australia in the 1970s, began preying on the island’s penguins, which are about the same size. Now, as each species develops new strategies to outwit the others, researchers hope to find a way to stop crow attacks before they start impacting penguin populations. are competing with
Little penguins, which live on the southern coasts of Australia and New Zealand, are not endangered, but the colony on Phillip Island, with more than 40,000 breeding birds, is the largest of them. Island ecosystems exist in a delicate state of equilibrium, and one small change can upset that harmony.
“As far as we know, other penguin colonies do not seem to suffer from such crow attacks,” said Professor of Wildlife and Conservation Biology at Melbourne’s Deakin University, who has researched the phenomenon. Mike Weston says. “This suggests that there is a local crow population that has learned this behavior, and the risk of this behavior spreading is real.”
Understudied and underappreciated predators
Invasive foxes were once the biggest threat to Phillip Island’s penguin colony, killing more than 3,000 penguins, but a concerted eradication effort finally wiped them out from the island in 2015. (Watch the “Penguin Parade” of little penguins Phillip Island to help fund research and conservation efforts. )
The Ravens, on the other hand, have a more complicated challenge.
Crows have been “hugely underestimated as wildlife predators,” Weston said. Their ability to thrive in urban areas, eat a variety of plants and animals, and their incredible intelligence makes the threat they pose particularly difficult to mitigate. These characteristics also explain why their numbers are increasing. The problem gets even more complicated. No one really knows why crows started preying on small penguins in the first place, or how it spread.
A 2021 study proved that predatory behavior comes from social learning rather than genetics, but there are still many unknowns. “It’s likely that there was some kind of innovation that spread throughout the population. Ravens are very smart, and some crows know to learn just by watching other ravens solve puzzles. ,” said study co-author Weston.
In 2013, researchers found that more than 60 percent of the penguin colonies they monitored were attacked or destroyed. After just two years, only 30 percent of observed clutches were attacked, suggesting that penguins were adapting to crow attacks to make their burrows safe. So far, the island’s penguin population has remained stable since 2015.
The rate at which crows raid penguin burrows varies from year to year, depending in part on the availability of alternative food sources, according to research by Laura Tan of BirdLife Australia.
Crow’s “unkindness”
Weston, Tan and colleagues also tested whether penguin DNA could be detected in crow feces. This could give researchers better insight into how widespread penguin predation is among the island’s crows. Although the technique did not prove as useful as the researchers had hoped, it did show that crows eat far more birds and mammals than previously realized.
So the increasing number of crows is a concern not only for sun penguins, but also for other endangered species, especially other ground-nesting birds, Tan said.
“What struck me was the pure breathiness of the raven’s diet,” Weston says. “Their versatility is amazing.”
Crows have also been known to use their sharp beaks to blind livestock and stab other sandpipers to death before eating them. These behaviors lend credence to the collective characterization of crows. A group of crows is called “unfriendly”.
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