Scientific American predicts a lively summer 2021, with the noisy emergence of Brood X – three species of 17-year cicadas – filling the air with noise and with well-fed young birds, whose populations should skyrocket thanks to the insect bounty… at least temporarily:
“In response to this superabundance of food, a lot of the predator populations have outrageously good years,” says Richard Karban, a University of California, Davis, entomologist who studies periodical cicadas. “But then the next year, and in the intervening years, there’s no food for them, so their populations crash again.”
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A 2005 analysis of 24 bird species in hardwood forests in the eastern U.S., based on 37 years of North American Breeding Bird Survey data, revealed that 15 species saw population changes associated with periodical cicada emergences. In that study, Walter Koenig, a research zoologist now emeritus at the University of California, Berkeley, and Andrew Liebhold, a research entomologist at the U.S. Forest Service, found that populations of red-bellied woodpeckers, brown-headed cowbirds, blue jays and common grackles increased significantly one to three years after cicada emergences and that their populations then dropped back down to normal. But the behavior of some species changed in an unexpected direction. Populations of American crows, tufted titmice, gray catbirds and brown thrashers dropped below normal during the cicada emergence year—and then increased the following year, after which they stabilized.
The results of the same 2005 study also suggest that most bird species do not travel to take advantage of cicada emergences, Liebhold says. They live and eat in the same areas year after year, picking off the insects opportunistically instead of traveling to the cicada motherlode. Koenig points out that cuckoos are an exception: they migrate to take advantage of insect outbreaks all over the country.