The wood thrush is a medium-sized North American thrush. It is a fairly common breeder in eastern North America. Its natural habitat is moist, shaded deciduous forests.
What does a wood thrush look like?
The wood thrush is a plump bird with strong legs and a fairly long tail. Adults have brown upperparts with bright white underparts and black spots on the breast, sides and flanks. Their head is blackish-brown with white eye-rings. Males and females look alike.
Wood thrushes are 20–23 cm in length with a wingspan of 29–32 cm and weigh 40–65 g. Among standard measurements, the wing chord is 10.8 to 13 cm, the tail is 7.2 to 8.8 cm, the culmen is 2 to 2.6 cm and the tarsus is 2.9 to 3.2 cm.
Size
The wood thrush is a medium-sized thrush, similar in size to the American robin. Adults weigh between 40-65 g.
Coloration
Adult wood thrushes have brown upperparts and white underparts with black spots on the breast, sides and flanks. Their heads are blackish-brown with prominent white eye-rings.
Sexual dimorphism
Males and females look alike (sexually monomorphic). Juveniles may have buff spotting on their wings.
Where does the wood thrush live?
The wood thrush breeds in eastern North America from southern Canada to northern Florida and as far west as Texas and eastern Nebraska. Its breeding habitat is moist, shady deciduous forests, especially with tall trees. It winters in Costa Rica and south to western Panama.
Breeding range
The wood thrush breeds in the eastern United States and southern Canada. Its breeding range extends from southeastern Manitoba east to southern Quebec and Nova Scotia, and south to northern Florida and eastern Texas.
Wintering range
The wood thrush winters in Central America, primarily in lowland areas from southern Mexico (Oaxaca and eastern Veracruz) south through Guatemala, Belize, Honduras and Nicaragua to Costa Rica and western Panama.
Migration
Wood thrushes are long-distance nocturnal migrants. They migrate through the eastern US to their Central American wintering grounds. Spring migration occurs March to May. Fall migration occurs August to October.
What kind of habitat does the wood thrush prefer?
The wood thrush inhabits mature, shady deciduous and mixed forests, especially those with tall trees. Its preferred breeding habitat includes:
- Forest interiors and edges
- Riparian woodlands
- Floodplain forests
- Swamp forests
- Upland forests of various types (oak-hickory, beech, maple-basswood)
They favor moist, rich soil environments that support trees, shrubs and leaf litter. In winter, they occur in tropical lowland evergreen and semi-evergreen forests, second growth, shade coffee plantations and wooded gardens.
Breeding habitat
On the breeding grounds, wood thrushes most often inhabit mature, deciduous forests with a closed canopy and dense understory. They favor moist habitats near creeks, swamps or riparian areas.
Winter habitat
On the wintering grounds, wood thrushes occur in tropical lowland evergreen forests, semi-evergreen forests, taller second growth, and shaded plantations. They are often found near forest edges and openings.
What does the wood thrush eat?
The wood thrush is omnivorous, with a diet consisting of insects, fruits and berries. They forage by hopping on the ground or picking prey from vegetation. Their diet includes:
- Insects and other invertebrates (beetles, caterpillars, spiders, snails, millipedes, centipedes)
- Fruits and berries (dogwood, wild grape, poison ivy, blueberry, blackberry, raspberry, strawberry)
- Seeds
- Nuts
They glean insects from leaf litter and probe in soil. They also sally from perches to pick insects from foliage. Wood thrushes play an important role dispersing the seeds of forest plants.
Foraging behavior
Wood thrushes forage primarily by hopping on the ground turning over litter, or picking prey from low vegetation. They also capture insects by flycatching or hovering.
Diet composition
Wood thrush diet is 61% animal matter (insects, spiders) and 39% vegetable matter (wild fruits and berries), according to one study.
Feeding habitat
Wood thrushes forage mainly on the ground in leaf litter, but also in low bushes and small trees. They use a wider range of forest strata in migration and winter.
How does the wood thrush nest and breed?
The wood thrush builds an open cup nest on a horizontal tree branch, near the trunk or in a fork. The nest is made of grass, bark strips, stems, rootlets and lined with dead leaves. The female lays 3-5 eggs. Pairs raise one or two broods per breeding season. Other nesting and breeding behaviors include:
- Clutch size is typically 3-5 eggs
- Incubation period is 12-14 days
- Fledging period is 10-16 days
- Nest height is typically under 16 feet
- Wood thrushes are mostly monogamous
- Pairs may raise one or two broods per season
Both parents incubate the eggs and feed the nestlings. Wood thrushes may reuse a nest later in the breeding season for a second brood.
Nest
The wood thrush builds an open cup nest out of bark, grasses, stems, and leaves. It is constructed on a horizontal branch, near the tree trunk, usually under 16 feet high.
Eggs
The female lays 3-5 pale blue eggs with reddish-brown spotting. Egg size ranges from 27–33 mm x 19–23 mm.
Incubation and nestlings
The female incubates the eggs for 12-14 days. Both parents feed the altricial nestlings until they fledge at 10-16 days old.
What are the greatest threats to wood thrush populations?
Wood thrush numbers have declined significantly in recent decades, primarily due to habitat loss on their breeding and wintering grounds. Other major threats include:
- Habitat loss and degradation
- Forest fragmentation
- Predation by cats, raccoons, snakes, etc.
- Brown-headed cowbird brood parasitism
- Collisions with buildings and towers during migration
Protection and restoration of mature forest habitats is vital for conserving wood thrush populations across their range.
Habitat loss
The conversion of forests to agriculture, logging, development and other uses has led to pervasive habitat loss across the wood thrush’s range.
Forest fragmentation
The wood thrush is forest interior specialist. Fragmentation of forests creates more forest edge and degraded breeding habitat. It also increases nest parasitism and predation.
Brood parasitism
Brown-headed cowbirds often lay eggs in wood thrush nests. Cowbird nestlings outcompete thrush young, lowering reproductive success.
What is the conservation status of the wood thrush?
The wood thrush has experienced significant population declines in recent decades and is identified as a Species of Conservation Concern:
- Partners in Flight Watch List Red Score = 14/20
- State listings: Endangered (VT), Threatened (MI), Special Concern (CT, DE, FL, GA, NH, NJ, NY, NC, PA, RI, VA)
The estimated global breeding population is 12 million, with 95% spending some part of the year in the U.S. BBS data indicates a population decline of 63% from 1966-2015.
Population estimates and trends
Population Estimate | 12 million |
---|---|
Percentage in U.S. | 95% |
BBS 1966-2015 Trend | -63% |
The significant long-term population decline and ongoing threats qualify the wood thrush as a species of conservation concern.
Conservation designations
The wood thrush is considered a Species of Continental Concern by Partners in Flight. Several states list it as Endangered, Threatened or Special Concern.
Why are wood thrushes declining?
Wood thrush populations have declined significantly since the 1960s, primarily due to habitat degradation and forest fragmentation on the breeding grounds. Contributing factors include:
- Habitat loss and fragmentation
- Nest predation and brood parasitism
- Agricultural intensification on wintering grounds
- Mortality during migration
These threats reduce reproductive success and survival throughout the wood thrush’s annual cycle. Conservation efforts are needed across their breeding, migration and wintering range.
Habitat loss and degradation
Widespread loss, fragmentation, and degradation of mature, shaded deciduous forest habitats on the breeding grounds is a major cause of wood thrush declines.
Nest predators and cowbirds
In fragmented forests, wood thrush nests experience higher rates of predation and brood parasitism by brown-headed cowbirds, significantly reducing nesting success.
Threats on wintering grounds
Habitat conversion for agriculture and silviculture in Central America negatively impacts wood thrush overwinter survival.
How can we help wood thrush populations recover?
To stabilize and restore wood thrush populations, conservation efforts focused on protecting and improving forest habitats are recommended, including:
- Preserve large forest tracts and improve connectivity
- Implement sustainable forestry practices
- Protect forests on wintering grounds
- Reduce collisions during migration
- Support shade coffee initiatives
Monitoring and research are also needed to better understand their full annual cycle and guide effective conservation actions across their breeding, migration and wintering range.
Protect and restore forest habitats
Preserving large, contiguous tracts of mature forest will provide high quality breeding habitat. Improving connectivity helps offset threats from fragmentation.
Sustainable forestry
Sustainable forestry practices, such as thinning rather than clear-cutting, can maintain wood thrush habitat quality on managed land.
Shade coffee partnerships
Promoting shade coffee production helps protect wintering habitat. Migratory Bird Joint Ventures facilitate partnerships between coffee producers and conservation groups.
Conclusion
In summary, the wood thrush is a Species of Conservation Concern due to significant population declines primarily resulting from habitat loss and fragmentation across its range. Ongoing efforts to protect and restore mature, shady deciduous forest habitats are crucial to conserve these vulnerable songbirds. Monitoring, research and international partnerships are also key components for maintaining wood thrush populations into the future.