eWestern BirdsThe Quarterly Journal of Western Field Ornithologists
Vol. 49, No. 4
Western Field Ornithologists
Egg Destruction by Males in the Western Grebe and Clark's Grebe
Floyd E. Hayes, Dylan G. Turner, Nathan D. Zimmerly, Manuel B. Peralta, Bryan J. McIntosh, and Mychal E. Hellie
ABSTRACT: Destruction of eggs in nests of a bird’s own species has been reported in many species of birds, including three species of grebes of the family Podicipedidae. We report for the first time four incidents of egg destruction by Western Grebes (Aechmophorus occidentalis) and three by Clark’s Grebes (Aechmophorus clarkii) in mixed breeding colonies at Clear Lake, Lake County, California, from 2014 to 2017. All incidents occurred during the late stage of nesting within a colony. Five incidents of egg destruction occurred at three recently vacated nests in which the previous eggs had been removed by mammalian predators <24 hours earlier; the other two incidents occurred at nests with an unknown history. Egg destruction was perpetrated only by males. The eggs may have been destroyed to usurp nests or to prevent brood parasitism or cuckoldry. Because none of the eggs or adults were marked and no tissue samples were taken, it was impossible to be certain of the relationships among adults and eggs, and whether egg destruction was intraspecific or interspecific.