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    Wood Thrush Life History

    Habitat

    Habitat ForestsWood Thrushes breed throughout mature deciduous and mixed forests in eastern North America, most commonly those with American beech, sweet gum, red maple, black gum, eastern hemlock, flowering dogwood, American hornbeam, oaks, or pines. They nest somewhat less successfully in fragmented forests and even suburban parks where there are enough large trees for a territory. Ideal habitat includes trees over 50 feet tall, a moderate understory of saplings and shrubs, an open floor with moist soil and decaying leaf litter, and water nearby. Favored understory species include southern arrowwood, smooth blackhaw, spicebush, coast pepperbush, rhododendron, and blueberry. In their winter range, they are most abundant in the interior of mature, shady, broad-leaved and palm tropical forests in lowlands. As in their temperate range, they will also inhabit forest edges and the denser understory of second-growth forests. Back to top

    Food

    Food InsectsWood Thrushes feed mostly on leaf-litter invertebrates and fruits from shrubs. Their summer diet is predominantly invertebrates, including adult beetles and flies, caterpillars, spiders, millipedes, woodlice, and ants. Insects, snails, and salamanders found in trees are occasional prey. Fruits like spicebush, fox grape, blueberry, holly, elderberry, jack-in-the-pulpit, Virginia creeper, pokeweed, dogwood, black cherry, and black gum make up most of the rest of their diet. Parents feed chicks soft invertebrates and pre-softened fruits. In late summer and fall, after breeding season, Wood Thrushes shift their diet toward fruits (particularly fatty fruits) in preparation for the demands of migration. Fruits remain important on migration and in winter, though Wood Thrushes remain omnivorous, eating a wide variety of insects as well. Back to top

    Nesting

    Nest Placement

    Nest TreeThe nest is usually in the lower branches of a sapling or shrub, where a fork provides good support and twigs or foliage provide shade and cover. The male may call attention to a spot by calling or by placing nest materials nearby, but the final decision is the female's.

    Nest Description

    The female begins nest building by laying down a platform of dead grass, leaves, stems, and sometimes paper or plastic. She weaves walls 2–6 inches high using the same materials, ending up with a cup that’s 4–6 inches across. She stamps the floor tight and uses the weight of her body to mold a 3-inch inner cup. Then she lines the cup with mud which she smoothes with her breast. She finally adds a covering of rootlets to bed the eggs. The process takes 3–6 days. A pair often raises two broods of youngsters per season, but may need 3 or 4 attempts to do so. A second nest after a successful first is often within 300 feet, but an unsuccessful nest may provoke a wider search for a new site.

    Nesting Facts
    Clutch Size:3-4 eggs
    Number of Broods:1-2 broods
    Egg Length:0.9-1.1 in (2.3-2.8 cm)
    Egg Width:0.7-0.8 in (1.7-2.1 cm)
    Incubation Period:12-15 days
    Nestling Period:12-15 days
    Egg Description:Turquoise-green with no marking.
    Condition at Hatching:Helpless, eyes closed, with only wisps of gray down.
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    Behavior

    Behavior Ground ForagerOne of the first songsters to be heard in the morning and among the last in the evening, the male sings his haunting ee-oh-lay song from an exposed perch in the midstory or lower canopy. He uses the song, which carries through dense forest, to establish a territory that averages a few acres. Within days, a female initiates pairing by enticing him to chase her in silent circular flights 3–6 feet above the ground. Between flights, the prospective pair shares a perch. After pairing, the female helps defend the territory from intruders. Low-level threat gestures like breast puffing, crest raising, and wing and tail flicking are usually enough. Among the alarm calls they give is a distinctive, sharp machine-gun-like sound that can be heard from far off. Wood Thrushes forage by hopping through leaf litter on the forest floor, tossing leaves to expose insects or probing for litter-dwelling prey. While foraging, they frequently bob upright for a look around. Foraging is largely solitary, though they may form mixed flocks on their wintering grounds, where they sometimes cautiously feed at the periphery of an army ant swarm. Pairs are socially monogamous, though extra-pair copulations are common. New pairs form each year. Back to top

    Conservation

    Conservation DecliningWood Thrush are still common throughout the deciduous forests of eastern North America, but populations declined by almost 2 percent per year between 1966 and 2015 resulting in a cumulative decline of 62% percent, according to the North American Breeding Bird Survey. Partners in Flight estimates a global breeding population of 11 million with 94% spending part of the year in the U.S., 39% in Mexico, and 6% breeding in Canada. Wood Thrush is a U.S.-Canada Stewardship species, and rates a 14 out of 20 on the Continental Concern Score. It is listed as a Tri-National Concern species and is on the 2016 State of North America's Birds' Watch List, which includes bird species that are most at risk of extinction without significant conservation actions to reverse declines and reduce threats. The Wood Thrush is one of the most prominent examples of declining forest songbirds in North America. Some of the steepest declines have been in Atlantic Coast and New England states where Wood Thrushes are most common. Some areas of the Midwest have seen increases. One partial reason for declines is thought to be habitat fragmentation in both breeding and wintering grounds. Fragmented habitats may offer poorer food or expose nests to predators such as raccoons, jays, crows, and domestic or feral cats, and to the Brown-headed Cowbird, which is a nest parasite. However, in some studies habitat fragmentation has not hampered nest success. Wood Thrushes are also susceptible to the effects of acid rain, which can leach calcium from the soil, in turn robbing the birds of vital, calcium-rich invertebrate prey. In Central America, the loss of lowland tropical forests shrinks their winter habitat.Back to top

    Backyard Tips

    Wood Thrushes are forest-interior birds and are unlikely to come to feeders. However, they are still common and may be audible from your yard if you live near small woodlots.

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    Credits

    Evans, Melissa, Elizabeth Gow, R. R. Roth, M. S. Johnson and T. J. Underwood. 2011. Wood Thrush (Hylocichla mustelina), version 2.0. In The Birds of North America (P. G. Rodewald, editor). Cornell Lab of Ornithology, Ithaca, New York, USA.

    Evans, W. R. and M. O'Brien. 2002. Flight calls of migratory birds: eastern North American landbirds [CD-ROM]. Mecklenburg, NY: Old Bird Inc.

    Kroodsma, D. 2005. The singing life of birds: The art and science of listening to birdsong. New York: Houghton Mifflin.

    Lutmerding, J. A. and A. S. Love. Longevity records of North American birds. Version 2015.2. Patuxent Wildlife Research Center, Bird Banding Laboratory 2015.

    Sauer, J. R., D. K. Niven, J. E. Hines, D. J. Ziolkowski, Jr., K. L. Pardieck, J. E. Fallon, and W. A. Link. 2017. The North American Breeding Bird Survey, results and analysis 1966–2015. Version 2.07.2017. USGS Patuxent Wildlife Research Center, Laurel, Maryland, USA.

    Sibley, David Allen. 2014. The Sibley guide to birds, second edition. Alfred A Knopf, New York.

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