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Evolution, Ecology, and Behavior News

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In times of ecological uncertainty, brood parasites hedge their bets

Some birds lay their eggs in the nests of other bird species and let the host parents raise their young. A new study finds that in times of environmental flux, these brood parasites “diversify their portfolios,” minimizing the risks of their unorthodox lifestyle by increasing the number and variety of hosts they select as adoptive parents.

“We found that, in unstable environments, brood parasites choose to not put all their eggs in one basket,” said study lead author Nicholas Antonson, a Ph.D. student at the University of Illinois, Urbana Champaign. “Our results are consistent with the idea that brood parasites diversify their reproductive risk in areas that are ecologically, behaviorally or environmentally unpredictable.”

Antonson led the study with Mark Hauber, a U. of I. professor of evolution, ecology and behavior; Dustin Rubenstein, a professor of environmental biology at Columbia University; and Carlos Botero, a professor of biology at Washington University in St. Louis. They report their findings in the journal Nature Communications.

“This research begins to answer a longstanding question about how species first interact and then coevolve in environments that are also changing,” Hauber said. “Theory suggests that in unpredictable environments, predators and parasites should rely on a greater number and variety of prey hosts. But with so many variables in flux, this is a challenging thing to study.”

Brood parasite success depends on the host’s acceptance of the outsider’s eggs and its ability to raise the young. Some birds learn to recognize that the foreign eggs are different and eject them or build new nests. Others seem not to notice. They incubate, hatch and care for the parasitic offspring as if they were their own.

Several other factors could influence how many hosts and which host species a brood parasite targets. The host must be in egg-laying mode when the interloper comes to call. If only one foster parent is involved in taking care of the young, its nest might not succeed as well as one with two parents present. But having two parents around makes it more difficult for parasites to get into the nest to lay their eggs.

Read the full article at the Illinois News Bureau

Publication Date: 08/24/2020
Photo credits: L. Brian Stauffer
Editor: Diana Yates