ABSTRACT
The field sparrow (Spizella passerina) is a common species in the eastern US Its range extends from Minnesota, Michigan, southern Quebec, and southern Maine south to southern Texas, the Gulf Coast, and southern Florida. Because the field sparrow is not sexually dimorphic, distinguishing between males and females is impossible unless either the male is singing or the female is building a nest or incubating. Females may nest in different regions of larger territories during successive nestings, resulting in clusters of observations clumped around each nest. The detectability of field sparrows depends on the mating status of the male and on the stage in the nesting cycle. The spot map method has both advantages and disadvantages when used to census field sparrow populations during the breeding season. Male field sparrows are easily captured immediately after their spring arrival and before they have paired.
