Effects of periodical cicada emergences on abundance and synchrony of avian populations

Abstract

We used 37 years of North American Breeding Bird Surveys to test for effects of periodical cicada (Magicicada spp.) emergences on the abundance and spatial synchrony of 24 species of avian predators in hardwood forests of the eastern United States. Fifteen (63%) of the bird species exhibited numerical changes in abundance apparently associated with emergences of the local periodical cicada brood, and intraspecific spatial synchrony of bird abundance was significantly greater between populations sharing the same cicada brood than between populations in the ranges of different broods. Species exhibited at least four partially overlapping temporal patterns. (1) Cuckoos (Coccyzus spp.) occurred in high numbers only during emergence years and subsequently declined in abundance. (2) Red-bellied Woodpeckers (Melanerpes carolinus), Blue Jays (Cyanocitta cristata), Common Grackles (Quiscalus quiscula), and Brown-headed Cowbirds (Molothrus ater) increased significantly 1-3 years following emergences and then declined. (3) Red-headed Woodpeckers (Melanerpes erythrocephalus), American Crows (Corvus brachyrynchos), Tufted Titmice (Baeolophus bicolor), Gray Catbirds (Dumetella carolinensis), and Brown Thrashers (Toxostoma rufum) were found in significantly low numbers during emergence years, underwent significant numerical increases in the following year, and then stabilized. (4) Wood Thrushes (Hylocichla mustelina), Northern Mockingbirds (Mimus polyglottos), Northern Cardinals (Cardinalis cardinalis), and House Sparrows (Passer domesticus) exhibited significantly deviant population numbers 1-2 years prior to emergences, below the long-term mean in the first two species and above the long-term mean in the latter two. These results suggest that the pulses of resources available at 13- or 17-year intervals when periodical cicadas emerge have significant demographic effects on key avian predators, mostly during or immediately after emergences, but in some cases apparently years following emergence events. © 2005 by the Ecological Society of America.