Tuesday, May 19, 2009

Mockingbirds Can Recognize Individual Humans

Here comes another example of birds being smarter than popular culture recognizes. Northern Mockingbirds are able to distinguish whether an individual human is a likely threat based on its memory of that person's past behavior.

Mockingbirds are among the most common birds on the University of Florida campus in Gainesville, where they nest in trees and shrubs close to the ground. For the research, student volunteers walked up to the nests, reached through the foliage and gently touched the nests' edges, then walked away. The same volunteers repeated the same visits again the next day, and again for two more days. On the fifth day, however, different volunteers approached the nests. All told, 10 volunteers tested 24 nests at least five times last spring and summer, during the mockingbird nesting season....

On the third and fourth days, the birds flushed from their nests more rapidly each time the increasingly familiar students appeared -- even though the students took different paths toward the nests on successive days and wore different clothes. The birds also gave more alarm calls and flew more and aggressively each succeeding day, with some especially defensive birds even grazing intruders' heads -- not exactly deadly, but annoying, because the birds tend to hit the same spot repeatedly, Levey said.

And yet when different students approached the nests on the fifth day, the birds hardly ruffled their feathers, waiting to flush until last moment. They also gave fewer alarm calls and attacked much less than on the previous day with the familiar intruder.

On a campus of 51,000-plus students, paths are filled with students walking back and forth from class all day every weekday -- so it's no stretch to say that thousands of different people come within a few feet of mockingbird nests during the breeding season.

And yet, the mockingbirds in the study were clearly able to recognize and remember a single individual, based on just two brief negative encounters at their nest.
The authors suggest that the ability to remember and recognize specific individuals helps explain why mockingbirds are so successful at adapting to urban environments, like a major university campus. This certainly would give mockingbirds an edge over less perceptive species. The same would probably apply to other urban species as well. Starlings, for example, seem to be pretty smart, and corvids have proven themselves adept at using tools and trickery to obtain food.

However, I find myself less interested in the discovery's implications for urban ecology and more in what it says about our relationship with birds. According to the Florida study, this very common and familiar bird has intellectual capacities that no one seems to have noticed until now. Already this week, I have seen other cases of abilities going unnoticed, such as Pine Siskins mimicking other species and House Sparrows hawking insects. It makes me wonder what else we do not know.