A project of

Swainson's Thrush

North Woods Songster

Perhaps best known for its silvery, ascending song, Swainson's Thrush is an increasingly common bird of our mountain forests, even as its populations elsewhere in North America have declined.

The State of Swainson’s Thrush

Regionally: Increasing

Swainson’s Thrush numbers have increased since Mountain Birdwatch began. Annual fluctuations are evident, but overall counts of this species have increased steadily.

Recent growth

Swainson’s Thrush numbers in the study area have been steady or rising since 2011. Faded bars estimate the uncertainty in the estimate of abundance.

Past growth

The average number of Swainson’s Thrush counted increased during the first 10 years of Mountain Birdwatch.

Globally: Decreasing

Swainson’s Thrush numbers have decreased across Canada and the United States according to the Breeding Bird Survey. Points indicate annual estimate of relative abundance; higher numbers mean more Swainson’s Thrush were counted in that year. Solid black lines above and below indicate the uncertainty around estimates of relative abundance. Figure provided by the United States Geological Survey.

Data collected by the Breeding Bird Survey indicate declines in Swainson’s Thrush, although populations appear to have leveled off since 2000. Other data sources also suggest that overall numbers of Swainson’s Thrush are dwindling. They have disappeared from many locales that they once inhabited in California, for example in coastal areas and in some of the major interior valleys. Counts of this species made at several migratory stopover sites have declined as well.

Opportunities for Conservation

Some populations of Swainson’s Thrush are increasing – like those in the mountains of the northeast – whereas others are decreasing. These kinds of local and regional differences in population trajectories suggests that different populations face different threats. It may be that no single, general factor can explain population declines.

What We Can Do to Help

Continued research and monitoring is necessary to understand the factors driving population change in Swainson’s Thrush. Until scientists identify specific opportunities for conservation, Swainson’s Thrush will benefit from the general activities that help all birds: protecting habitat, changing window design and lighting policies to reduce collisions with buildings and other structures during migration, reducing pesticide use, and reducing predation by domestic and feral cats.

State of Mountain Birds