WatchList Species Account for Swainson’s Warbler (Limnothlypis swainsonii)

Qualifies for the list as a Declining Yellow List Species

 

Swainson's Warbler by Greg Lavaty
Photo: Greg Lavaty

Although the outline of its breeding range covers nearly the entire Southeastern United States, the Swainson’s Warbler’s secretive nature and use of the densest areas of vegetation available make it among the least known and most rarely observed members of its family. Far more often heard than seen, it uses two distinct habitat type for breeding. Most use canebrakes and other thick mid-level vegetation on slight ridges in river bottom hardwood forests, with smaller numbers in rhododendron thickets and cove hardwoods in the Appalachians. These habitat types, particularly the former, were decimated in the late 19th and early 20th centuries, and Swainson’s Warbler populations presumably plummeted as a result. Recently, however, conditions have stabilized and since the onset of the Breeding Bird Survey, trends in this species show gradual increases.

 

Because it is still a rare (and rarely seen) species with territory sizes and habitat quality needs exceeding those of other co-existing passerines, it is often used as a focal species for bottomland hardwood conservation planning.

 

Very little is known regarding its status in similarly dense vegetation on its wintering grounds in the Bahamas, Cuba, Jamaica, and the Yucatan Peninsula. Research on the breeding biology of the species is underway, in particular at one of its densest breeding sites, the Great Dismal Swamp of southeastern Virginia. This work indicates that the species is especially vulnerable to flooding because it forages on the ground; one prescription for habitat management for the species is to keep the water table at subsurface levels from late March through September.