In this test on the university campus, the mockingbirds ignored most passers-by, but took to the air when they recognised people who had approached their nest days before.
(Image: Lou Guilette/PNAS)
The study was prompted by a series of bird attacks. A graduate student involved in research on bird nesting noticed that when she would make repeat visits to peoples’ yards the birds would alarm and attack her, while they would ignore people gardening or doing other things nearby…. Indeed, it seemed they could even recognize her car, and she had to start parking around the corner [AP]. So the researchers designed an experiment to investigate whether the birds really could identify an individual person.
For the study, published in the Proceedings of the National Academy of Sciences, the researchers identified 24 mockingbirds watching over egg-filled nests on the University of Florida campus in Gainesville. For each nest, they had one volunteer approach and touch the eggs over the course of four days, but on each day the volunteer approached at a different time, came from a different direction, and wore different clothes. Still, with every visit, the bird grew more agitated. At first, the mother bird waited until the person came close and then flew to a nearby bush to shout out alarms calls, a behavior called flushing that birds do to distract predators in the wild. But by day four, mom was up and out of her nest when the volunteer was almost 14 meters away–and she or her mate dive-bombed the volunteer’s head [ScienceNOW Daily News]. When a new volunteer approached the nest on the fifth day and touched the eggs, the mother bird started the get-to-know-you process from scratch, and merely called alarms from a nearby bush.