Introduction

The American Tree Sparrow is a familiar migrant and winter visitor in many settled areas of North America, where winter flocks frequent backyard feeders and are important consumers of weed seeds. “American Tree Sparrow” is somewhat of a misnomer for this species, as most individuals breed in remote northern areas, often north of the treeline. The name was given by early European settlers for the superficial resemblance of this species to the Eurasian Tree Sparrow (Passer montanus).

In summer, males sing persistently to proclaim possession of territory. Individual males sing only a single song type each, although song types are widely shared among males. Females build a nest on the ground and incubate the eggs alone. Both parents help to raise the single brood of 4 to 6 young.

Although many aspects of the behavior and natural history of American Tree Sparrows are well studied, gaps still exist in our knowledge of this species; little is known of population structure, population regulation and dynamics, and dispersal, for example. In addition, most studies of the breeding biology of this species have been conducted in northern Manitoba. As American Tree Sparrows breed over a wide geographic area, it is likely that aspects of their biology may differ across their range.