White-throated Sparrow

White-throated Sparrows are one of the most abundant breeding birds in New Hampshire’s northern and higher elevation conifer and mixed forest, but only occur in scattered locations (often bogs) south and east of Concord. In winter, however, this pattern is reversed, and white-throats are concentrated in the southeast and the major river valleys. But while still common, this sparrow is in long-term decline in New Hampshire and the Northeast in general. The reasons for this decline are not well understood, but could include loss of shrubby edge habitat to forest succession. It is also a frequent victim of window collisions during migration, and studies have demonstrated lowered physiological performance after prolonged exposure to pesticides.

At the same time, winter data for New Hampshire show a slight and very gradual increase possibly a result of bird feeders, gradually moderating climate, or a combination of both. Winter data from farther south show the same declines as the breeding data, albeit not as dramatic, so the increases in New Hampshire almost certainly reflect a slight northward shift of the non-breeding range.

White-throated Sparrows come in two color morphs, a bright one with bold white stripes on its head (hereafter white-striped) and a dull one where the stripes are tan (tan-striped). These differences are not based on sex, meaning that both males and females can be of either morph. In fact, each morph almost always mates with the opposite one, meaning that you’ll rarely encounter a pair consisting of two white-striped birds. So contrary to popular perception, white-striped birds are not necessarily males and tan-striped ones females.

These morphs result from a gene change in a single chromosome pair and are correlated with consistent behavioral differences. White-striped birds are more aggressive, sing more (including the females), and exhibit less parental care (particularly the males) than tan-striped birds. If you have White-throated Sparrows at your feeders in the winter, you can observe interactions between the two morphs – chances are you’ll see the brighter birds chasing off the duller ones more than the other way around.