The northern flying squirrel (Glaucomys sabrinus) as a potential predator of marbled murrelet (Brachyramphus marmoratus) eggs
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Marbled murrelet (Brachyramphus marmoratus) populations have been declining in North America for over a decade. As a result, the bird, which nests most often in forest canopies of average height 57.4-73 m, in Washington, Oregon and California, was listed as threatened in this region by the U.S. Fish and Wildlife Service in 1992. Nest predation has been posed as one reason for the decline, and several forest rodents, including northern flying squirrels (Glaucomys sabrinus), are potential nest predators. Investigations were made to determine whether the northern flying squirrel was capable of preying upon eggs similar in size to marbled murrelet eggs, and whether sex or age at capture from the wild affected a squirrel's tendency to attack an egg. In multiple experiments, a captive colony of northern flying squirrels was exposed to single eggs from bobwhite quail (Colinus virginianus), blue grouse (Dendragapus obscurus), pigeon (Columba livia), and chicken (Gallus domesticus), placed in simulated marbled murrelet nests; chicken eggs are the most similar in size to marbled murrelet eggs. Age at capture and sex of squirrels did not influence predatory behaviour. The flying squirrels were only able to break through eggs of quail size and smaller, so they are unlikely to be predators of marbled murrelet eggs. Both gape of the mouth and eggshell thickness could limit egg predation, so eggs with thinner shells and eggs smaller than quail eggs are potential prey for flying squirrels.