Male and female black-throated blue warblers, a bird species common in the northeast U.S., have a reputation for practicing monogamy and sharing in the raising of their young. However, the mere presence of a fertile female in the nest next door can be enough to cause a male to stray, leaving his female mate unguarded, according to a paper scheduled for publication in the July issue of Auk, the journal of the American Ornithologists' Union, authored by a doctoral candidate at the University at Buffalo and an assistant professor of biological sciences.