For several days, student volunteers walked up to the nests, gently touched them and then walked away.

Writing in the Proceedings of the National Academy of Sciences, UF biology professor Doug Levey said that on the third and fourth days, the birds flushed from their nests more rapidly each time the increasingly familiar students appeared.

This occurred even though the students took different paths toward the nests on successive days and wore different clothes.

But when different, unfamiliar students approached the nests on the fifth day, the birds hardly ruffled their feathers until the last moment.

It’s believed that the ability to recognize individual humans who might threaten their nests is one way the species has adapted and thrived in urban environments.

Photo: Lou Guillette - University of Florida