Antarctic brown skuas are large brownish birds that eat fish and other small animals, and they have been known to steal prey from other predators. They've even been observed pilfering sips of breast milk from nursing elephant seals. Living life as a food thief, or a kleptoparasite as biologists call it, requires a relatively high level of intelligence.
But brown skuas (Stercorarius antarcticus) may be even smarter than we thought. A study published in March in the journal Animal Cognition found that these large birds can recognize individual people.
Korean scientists at a research station on King George Island, off the tip of the Antarctic Peninsula, embarked on a study of seven brown skua nests, to see if the birds were breeding and how many young they were having. However, they noticed that the birds would begin to act much more aggressively and even attack—swooping in on researchers and hitting them on the head with their feet—after the researcher had visited the nest a couple times.
But it didn't stop there. "When I was with other researchers, the birds flew over me and tried to hit me," said Yeong-Deok Han, a doctoral student at Inha University, in a statement. "Even when I changed my field clothes, they followed me. The birds seemed to know me no matter what I wear."
This strongly suggested that the brown skuas were recognizing Han. Other birds such as crows, ravens and magpies have already been shown to recognize individual humans. However, this ability remains rare among birds, so far as we know. To further explore this possibility, the scientists set up an experiment in which a pair of researchers—one who had approached the nest before (labeled as the "intruder), and one who hadn't—walked toward the nest and waited for a few seconds as the birds flew toward them. They then walked in different directions (away from the nest). In each case, for all seven breeding pairs of birds tested, the skuas followed the intruder and ignored the newcomer.
"It is amazing that brown skuas, which evolved and lived in human-free habitats, recognized individual humans just after three or four visits," said Won Young Lee, a senior researcher from Korea Polar Research Institute. "It seems that they have very high levels of cognitive abilities."
Since the change of clothes didn't deter the birds, it suggests they are able to recognize humans by looking at their face, or perhaps recognizing differences in body posture and gait, according to the study.
Most birds that can recognize human individuals, like crows, have lived in the same area as humans for longer, so it's possible that evolution could have helped select for this human-identifying ability. With brown skuas, however, they have only been exposed to humans since the 1950s, so evolutionary pressures almost certainly haven't played a role in developing this ability, the researchers wrote.
