May 19, 2009
Study Shows How Mockingbirds Can Tell People Apart
Researchers say mockingbirds can tell humans apart and are quick to react to those they don't like, The Associated Press reported.
The study in Tuesday's edition of Proceedings of the National Academy of Sciences suggested that birds rapidly learn to identify people who have previously threatened their nests "” even sounding alarms and attacking those people, while ignoring others nearby.
Douglas J. Levey, a professor in the zoology department of the University of Florida, said the study shows that birds are much more perceptive of their environment than people had previously suspected.
"We are a part of their environment and we are a concern to them," he added.
The mockingbirds were being studied as part of an effort to better understand how species adapt to urbanization, as more and more areas are being converted into towns and cities.
Levey said in a telephone interview with AP animals that adapt well seem to be those that are especially perceptive about their environment.
"We do not think mockingbirds evolved a specific ability to respond to humans, rather we think that mockingbirds are naturally perceptive about their environment, especially threats to their nests," he said.
Levey said one of his graduate students involved in the research on bird nesting found that when she made repeat visits to peoples' yards the birds would alarm and attack her, yet they seemingly ignored other people nearby who weren't perceived as a threat.
The birds even seemed to recognize her car, which led her to begin parking around the corner.
The team soon began their own tests around the university campus, where subjects would approach mockingbird nests, touch the nest, and then move on.
Levey said the study involved 10 people who varied in age, sex and amount of hair and facial hair, and dressed differently on different days.
The individuals approached a total of 24 mockingbird nests from different directions and at various times of day.
For four consecutive days the same student would approach and touch a nest, and then leave. By day three, the birds began reacting to them in advance by fleeing the nest, sounding alarms and dive-bombing the trespassers.
However, the birds didn't respond in advance on the fifth day, when a different student would approach the mockingbird nest.
Levey said the researchers were surprised that the response was as rapid and dramatic as it was.
He said such behavior might be expected from more highly intelligent bird species like crows, ravens and parrots, but not from songbirds living in a natural setting.
The team even noticed that the mockingbirds ignored dozens of other passers-by even on the days when they were attacking a person they perceived as a threat.
Levey noted that past studies have sought to determine if birds could choose between two individuals, or pictures of individuals, to get a food reward.
But his research focused on whether birds needed to pick out one person they had seen before that was not always dressed the same or coming from the same direction, while other people were in the general vicinity.
The study showed how the birds succeeded in doing this after having seen the person just twice.
"You may be walking by a bird and think it's just minding its own business. But if there is a nest nearby, you are its business," Levey said.
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