A Male Bluebird engaged in either sunbathing or "anting."
Photo by Debbie Leone of St. Francisville, LA
This male Eastern Bluebird is either sunbathing (which may help drive off mites or lice), or doing what is called passive "anting." They fly down onto the lawn and strike a possum-like pose, lying on the ground with their wings extended and fluffed out, and their heads cocked to one side. Sometimes they actually lie on their sides. They stay in this position for one to several minutes. Afterwards they may preen their belly and wing feathers.
I saw a Black-capped Chickadee doing this on a black shingle roof. I thought it was dead until it flew off. It was probably sunning or sunbathing. (House Sparrows have also been seen doing this on rooftops.) Sunbathing helps absorb solar radiation. The heat may cause feather parasites to mobilize, making it easier for the bird to locate and remove them during preening.
Anting has been observed in more than 250 species of birds (mostly passerines) worldwide. (It has not been seen in Western Bluebirds. Whitaker, who did a resume of anting in 1957, listed all other North American thrushes except bluebirds as anting.) When birds (e.g., Starlings) engage in passive anting over an ant hill, they may first disturb it with their feet or belly. Apparently they want the ants to crawl on them. They don't eat them. Some people believe this is because the formic acid emitted by ants as a defense mechanism may affect mites which pester them. Bluebirds do not place ants on their feathers like other members of the thrush family (Krieg 1971.)
In other cases, birds actually pick up ants (called "active anting"), kill them, and then rub them on their plumage. Researchers disagree as to why they do this. According to John Eastman in Birds of Forest, Yard, and Thicket: "The traditional view is that ants' formic acid acts as an insecticide or fungicide against feather and skin parasites. Anting often occurs during periods of high humidity, lending weight to the fungicidal theory. But other investigators find no correlation between anting and parasite or fungal presence; they speculate that anting, like sunning, is simply a comfort activity, stimulating the skin, especially during summer molt. A recent theory suggests that anting forces the insects to expel their formic acid, thus making them more palatable to consume."
A bluebird, famous for the scrap of sky
Borne on his back - an indigo so bright
That just a glimpse of his distinctive flight,
All swoop and flurry, captivates the eye ... - George Bradley, "New Yorker" Mar. 19, 2001
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