Blue Jays and Ants

I witnessed blue jays taking large red ants in their bills and rubbing them under their wings and on other parts of their bodies. Why would they do this?

—Thomas Kintz, Homosassa Springs, Florida

George: Blue jays and many other species will use crushed ants to rid their bodies of parasites. The ants contain formic acid that will kill parasites or cause them to abandon birds. Some birds will also roll on anthills to obtain the same relief from parasites.