Thursday, February 21, 2013

Black-billed Cuckoo

In an American folk songwe are told “the coo coo, she's a pretty bird...she never says coo-coo ‘till the fourth day July…” There may be some truth here—Black-billed Cuckoos time their nesting to correlate with caterpillar, particularly tent caterpillar, outbreaks. Cuckoos consume up to a dozen caterpillars per minute. Cuckoo stomachs often contain several hundred caterpillars, so many that the lining of their digestive tracts become coated with caterpillar spines. When the spines obstruct digestion, “the entire stomach lining is sloughed off and is regurgitated as a pellet” (Hughes 2001).
Black-billed Cuckoos declined during the 1900s, with severe drops in the 1980s and 1990s. Caterpillar outbreaks are now controlled with pesticides. These poisons are probably detrimental to both insects and birds. In any case, cuckoos are now rarely seen but singly. Older accounts report flocks of cuckoos “descending on caterpillar-laden trees and not departing until every insect was consumed” (Hughes 2001). These photos are from Rice County, Minnesota—the Black-billed Cuckoo from Dundas and the caterpillars from the Carleton Arboretum.

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