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Wood Thrush

Wood Thrush photo by Michael Stubblefield.

In 1852, after pondering on the distinctive song emanating from the forests of the eastern U.S., naturalist David Thoreau penned, “Whenever a man hears it, he is young, and Nature is in her spring … He sings to make men take higher and truer views of things.” The flute-like melody belonged to the Wood Thrush (Hylocichla mustelina), a close relative of the American Robin (Turdus migratorius). Paired with its song, its autumn-colored back and characteristic white and bold brown underside made the Wood Thrush a recognizable presence in eastern deciduous forests from northern Florida to southern Canada. Richly abundant in the days of Thoreau, Wood Thrush songs are heard less and less as mature forests are lost and fragmented. The changing landscape has resulted in a decline of nearly half the population since the mid-1960s. We now recognize that large acreages of the remaining mature forests – especially in the Appalachians - must be preserved and even expanded to stabilize the population.

Habitat
Every spring as temperatures and green growth slowly creep back, the Wood Thrush returns from its wintering grounds in the tropical forests of Central America to breeding grounds in the interior mature and mixed forests that extend throughout the lands east of the Mississippi River. Males arrive first to claim territories and soon begin belting out a multi-part flute-like song that rings out ‘ee-oh-lay’ to attract their female counterparts. Their distinctive song derives from a divided syrinx – the vocal organ of birds – that can create two separate notes simultaneously.

Upon mate selection, the female begins building a nest consisting of all types of material – from bark and moss to dead leaves, grass, and even mud. The nest is generally hanging from the fork of a branch in the lower midstory of a forest, with sheltering foliage providing shade and cover. Nests are predominately located in the interior of mature deciduous and hardwood forests where trees are tall, open areas are plentiful, and the understory vegetation is dense.

Decline and Status
Threats to Wood Thrush survival and nesting success increase considerably when roads, energy development, and urbanization fragment large patches of forest. On the edges of fragmented habitat, acid precipitation has a greater impact on this species by depleting invertebrate prey compared to individuals nesting in the forest interior. Similarly, Brown-headed Cowbird (Molothrus ater) nest parasitism significantly lowers nesting success in edge habitats. Female cowbirds lay their eggs in the nests of other songbirds, including the Wood Thrush. Cowbird eggs typically hatch sooner and the faster-growing cowbird nestling will often push other nestlings out of the nest and demand more food. The loss of large tracts of mature forests has lead Wood Thrush to more frequently inhabit secondary forest, where understory is not as dense, leading to higher predation rates from small mammals. Finally, the population declines experienced in their breeding range is coupled with destruction of habitat in Central American wintering grounds.

Our Work
Studies have shown Wood Thrushes thrive in large blocks of mature forests with open canopies and natural gaps that allow sunlight in. Historically, the Appalachians contained a sizeable amount of such grounds. However, the connectivity and condition of mature forests in the Appalachians have changed drastically over the last century and much of the forested landscape is comprised of densely packed, single-aged trees with a closed canopy structure.

Working with partners, the AMJV is expanding the range of habitats that are more suitable for Wood Thrush and other species of conservation concern with similar habitat requirements. Through Best Management Practice recommendations based on sound science and proven techniques, AMJV and partners are training foresters to implement habitat management practices that allow for both sustainable timber harvesting, while recreating more of the conditions that were present prior to the extensive logging of the 20th century. Large land acquisitions made by our partners and supported by the partnership’s coordination and leveraging efforts are increasing the amount of land protected in the Appalachians that will benefit all birds.

The AMJV is also bringing together experts interested in participating in a Wood Thrush Working Group. Various agencies and individuals across the Americas have participated in Wood Thrush conservation, research, and outreach projects in the past. There is increasing interest for experts to meet to share information, identify research gaps, and begin working on a conservation plan for the species.

Targeting reforestation and forest management efforts in the Appalachian Mountains is a crucial step in protecting and conserving important Wood Thrush breeding habitat, however we must consider the full life-cycle of this migratory species. Therefore, we are working closely with the Chiapas Regional Alliance (CRA) – a partnership among several conservation organizations in the Chiapas region of Mexico that are focused on protecting Neotropical birds and their habitats - to develop a strategy and joint action for conserving shared bird species. For example, the AMJV is helping to develop an online data sharing and collaborative mapping tool for ProNatura Sur in Chiapas, Mexico (a CRA member organization) that will help to share information, advance planning, and improve conservation outcomes. Researchers in Chiapas will be able to spatially and temporally reference Wood Thrush sightings and monitor information that will better visualize efforts, limit redundancy of conservation information, and keep members up to date on recent activities.