A surprising new study by South Korean researchers finds that Antarctic seabirds might recognize individual humans after they’ve met them a few times.

It is not unusual for intelligent bird species with frequent human interactions to recognize people. That crow in the park, for example, could recognize you (and not just your sandwich) from your daily lunch break.

But brown skuas, Antarctic seabirds known to scientists as Stercorarius antarcticus, hardly ever interact with humans, yet they were able to recognize individual human researchers studying their breeding habits after just a few visits.

"It is amazing that brown skuas, which evolved and lived in human-free habitats, recognized individual humans just after 3 or 4 visits,” said one of the study’s researchers, Won Young Lee. “It seems that they have very high levels of cognitive abilities."

The humans had come to study brown skua nests and eggs, but when the scientists from the Korea Polar Research Institute got too close to the birds' nests, the skuas attacked them.

More surprisingly, the attacks didn’t end when researchers changed their appearances.

"When I was with other researchers, the birds flew over me and tried to hit me," said PhD student Yeong-Deok Han. "Even when I changed my field clothes, they followed me. The birds seemed to know me no matter what I wear."

When confronted with one researcher who had previously approached their nests and another researcher who was unknown to them, seven out of seven breeding pairs chose to attack the repeat visitor while ignoring the new person, even when both individuals acted the same.

How did these isolated birds learn to distinguish between humans?

Because the brown skuas responded the same way to researchers regardless of clothing, and because Antarctica is such a windy and cold place that smells are unlikely to have tipped the birds off, researchers believe that the birds identify intruders by visual traits.

According to their published findings, the birds could have learned to identify humans in one of two ways.

One, they might just be unusually smart creatures. Researchers who approached the nests of other bird species near the research station found that no other bird species discriminated between repeat "invaders" and neutral humans.

Their other hypothesis is that the birds had learned enough about humans from repeated contact over their lifetimes that they were prepared to defend against human nest “invaders.”

There are 11 Antarctic stations on King George’s Island, where the study took place, and about 60 to 80 researchers at South Korea’s King Sejong Station every summer.

"Since this area has been inhabited by humans only after the Antarctic research stations were installed,” said Dr. Lee, “we think that the skuas could acquire the discriminatory abilities during a short-term period of living near humans."

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Whatever the reason, researchers say that the brown skuas’ cognitive abilities are likely to be a factor.

The study was published in the journal Animal Cognition this month.