Study Suggests That Difficulty of Pecking Hole in Parasitic Egg for Gripping Purposes May Explain Why Most Host Birds Fail to Eject Foreign Eggs from Nest

Avian brood parasites lay their eggs in the nests of other bird species, forcing the hosts to do the hard work of raising the unrelated young. A team of scientists wanted to simulate the task of piercing an egg – a tactic that only a minority of host birds use to help grasp and eject the foreign eggs. Their study offers insight into some of the physical challenges the discriminating host birds face. The new findings were published on March 5, 2021 in the Journal of Experimental Biology. The article is titled “Nest Substrate and Tool Shape Significantly Affect The Mechanics and Energy Requirements of Avian Eggshell Puncture” ( Take cowbirds, for example. Their eggs look nothing like the host birds’ eggs, “yet most of their hosts do not reject the parasite eggs,” said study co-author Mark Hauber (, PhD, Professor of Host-Parasite Interaction in the Department of Evolution, Ecology, and Behavior at the University of Indiana and a brood parasitism expert. “One explanation is that the cowbird eggshell is too thick and strong for a small host’s beak to pierce.” To determine whether the difficulty of piercing a brood parasite’s egg played a role in whether the host bird tried to eject it, Daniel Clark, an undergraduate student working in Hauber’s laboratory, teamed up with an Assistant Professor in the same department, Philip Anderson, PhD, an expert in the biomechanics of piercing, slashing, and stabbing. Dr. Anderson has previously studied the characteristics that contribute to the cutting and crushing ability of teeth and the piercing power of viper fangs ( and cactus spines (
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