Periodical cicadas, which spend most of their lives underground and occasionally emerge en masse, may time their appearances with periodic dips in predator numbers.
Why several species of the insect (Magicicada spp; pictured) surge to the surface of North American forests after 13 or 17 years underground has been a mystery. Walt Koenig at Cornell University in Ithaca, New York, and Andrew Liebhold of the US Department of Agriculture Forest Service in Morgantown, West Virginia, analysed data on the population sizes of 15 bird species between 1966 and 2010 to estimate the predation pressure on the insects. They conclude that the cicadas somehow set their predators' populations into cycles that reduce bird numbers during their next foray above ground.
This could be explained by the insects' long-lasting effect on forest ecology influencing factors such as nutrient levels and tree growth for several years after their emergence, the authors suggest.
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Cicadas emerge when predators decline. Nature 493, 274 (2013). https://doi.org/10.1038/493274a
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DOI: https://doi.org/10.1038/493274a
