Introduction

The White-throated Sparrow, a familiar passerine, is found throughout much of North America at some season south of tree line and principally east of the Rocky Mountains. To many people, its distinctive whistled song is synonymous with the northern wilderness. During migration and throughout its winter range, this species is a common visitor at feeding stations.

White-throated Sparrows exhibit plumage polymorphism (white-striped and tan-striped morphs) during the breeding season (see color photos), associated with a difference in their chromosomes. Such differences in plumage and genetic material are maintained by negative assortative mating—each morph nearly always mates with its opposite. These plumage differences are paralleled by differences in behavior, with white-striped males being more aggressive, territorial, and apt to seek matings outside the pair bond than their tan-striped counterparts, and with tan-striped females providing more parental care than their counterparts.

Although such genetic, plumage, and behavioral differences are apparently unique among birds, in other respects the natural history of the White-throated Sparrow is much like that of other sparrows. Apart from research on the color morphs, White-throated Sparrows have been widely used for studies of breeding biology, vocalizations, territoriality, migration, circadian rhythms, physiology, and winter behavior and ecology, making this species one of the best studied songbirds in North America.