Saltmarsh Sparrow
Saltmarsh Sparrow
For some folks, sparrows are merely an afterthought — those “little brown jobs” that inhabit our neighborhood yards and bushes. Certain ones, such as the ubiquitous Song Sparrow, nest in a broad range of habitat types across the continent. Being true generalists, or birds with broad adaptability to diverse habitats, Song Sparrows (and American Robins) are strong contenders as our most plentiful songbirds. Many other species aren’t so flexible in their nesting requirements, though. That’s why outlying species with specialized nesting needs must rely on pockets of suitable habitat.

South Thomaston’s Weskeag Marsh is listed as one of Maine’s 22 Important Bird Areas, unique or specialized habitat areas in the state that are important for bird breeding, wintering and migration activities. In particular, Weskeag provides essential grassland and salt marsh habitats for several species with restricted nesting requirements.

New England’s grassland nesting areas have declined significantly in recent decades. Likely factors such as reforestation and intensification of agricultural practices have contributed to the current trend. The resulting declines in Northern Harriers, Eastern Meadowlark and Bobolink populations are quite evident.

This is where Weskeag merits one of its “IBA” designations. Portions of the upland field areas are managed to support grassland nesters such as those Bobolinks and meadowlarks I mentioned. Another grassland nester, the small streaky Savannah Sparrow continues to do well in this grass habitat. Savannahs have a short tail, crisp streaking to mid-belly area and a variable yellow stripe above the eye. Unlike many other sparrows, Savannahs are not particularly shy. They perch openly on weed stalks or fence wires and chip aggressively whenever their nest site is approached by intruders.

With more highly specialized nesting requirements, two species of marine sparrows are found along Weskeag’s river ditches and dike terrain. The Nelson’s Sparrow and Saltmarsh Sparrow’s spiky tail tips create an impression of “sharpened” tail feathers. Of these two closely related species, the Nelson’s is far more numerous. These skulky sparrows might go totally unnoticed unless you heard the Nelson’s dry trilled song that resembles a pressurized escape of steam.

A limited number of Saltmarsh Sparrows share the marsh, and Weskeag may well be their northernmost outpost for successful breeding. The Saltmarsh species has an unusual mating system for a songbird, with males simply roving about looking for females rather than defending a nesting territory. The males take no part in caring for the eggs or young. A species of special conservation concern, Saltmarsh birds are rapidly disappearing from the eastern United States. Fifteen years ago their population was estimated at more than 250,000. Today those numbers have plummeted to less than one-fifth and continue to drop by 9 percent a year. At the present rate, the species would become extinct by 2050.

Aside from creeping habitat losses, their main survival challenge involves rising tide levels that disrupt nesting activity. Nests are usually placed just above normal high tide mark, but some nests are destroyed by more frequent extreme tides. UConn researcher Chris Elphick explains the situation: “The birds’ nesting cycle lasts about 23 to 24 days—just a few days less than the 28-day tidal cycle influenced by the moon’s gravity. If the flooding only happens every 28 days or so, then they can just about fit their nesting cycle between two sets of really high tides,” Elphick says. If high tides are more frequent, the 28-day window collapses; eggs either float away or the chicks drown.” Although eggs may withstand a brief dunking in soaking seawater, the nest is doomed if tidal water levels rise over the nest rim.