Prairie Warbler

The Prairie Warbler is a species of sparse shrubby areas, not extensive grasslands as its name would suggest. Like other shrubland species it benefitted from extensive clearing of forests following European colonization, which allowed it to expand north into New Hampshire by the late 1800s. By the 1980s it was well-established in the Merrimack Valley and southeast, where much of its spread was attributed to its use of early successional habitat in power line corridors. At this point, the Prairie Warbler’s population trajectory diverges significantly from those of other shrubland species like towhees and thrashers. While most such species declined since the Breeding Bird Atlas, the Prairie Warbler has continued to expand and is now found north to the Conway area and west to the Connecticut River in southwestern New Hampshire.

Declines in shrubland birds are generally attributed to loss of habitat, as either forests or houses reclaim disturbed land. Given this reality, the persistence and increase in the Prairie Warbler remains something of a mystery. Their preferred habitats in the state remain pine barrens and powerline corridors, areas still used by declining species like towhees and Field Sparrows. Perhaps it’s just that Prairie Warblers expanded slowly and thus filled habitat as it became available rather than overextending themselves only to decline as habitat became rare. Either way, it will be interesting to see what the coming decades bring for this species in the state. There are still areas in the west where it’s rare, and there is certainly room for expansion up the Connecticut Valley. Alternatively, its fortunes will turn, and Prairie Warbler will follow other shrubland species into slow and steady decline.

Prairie Warblers build their small cub nests within 3-8 feet of the ground in dense shrubs or saplings, sometimes even in brambles. Detailed research on this species found that the height of nests increased over the breeding season. They incubate their 3-5 eggs for 12 days and the young leave the nest 8-11 days later. If a pair gets an early start and is successful on their first nest they will sometimes raise a second brood. In the winter, most Prairie Warblers migrate to Florida and the islands in the western Caribbean, where they continue to use shrubby or edge habitats and can be quite abundant.