The wood thrush (Hylocichla mustelina) is a North American passerine bird in the family Turdidae and is the only species placed in the genus Hylocichla. It is closely related to other thrushes such as the American robin and is widely distributed across North America, wintering in Central America and southern Mexico. The wood thrush is the official bird of the District of Columbia.
The wood thrush is a medium-sized thrush, with brown upper parts with mottled brown and white underparts. The male and female are similar in appearance. The song of the male is often cited as being the most beautiful in North America.
The wood thrush is an omnivore, and feeds preferentially on soil invertebrates and larvae, but will also eat fruits. In the summer, it feeds on insects continuously in order to meet daily metabolic needs. It is solitary, but sometimes forms mixed-species flocks. The wood thrush defends a territory that ranges in size from . The wood thrush is monogamous, and its breeding season begins in the spring; about 50% of all mated pairs are able to raise two broods, ranging in size from two to four chicks.
Taxonomy
The wood thrush was formally described in 1789 by the German naturalist Johann Friedrich Gmelin in his revised and expanded edition of Carl Linnaeus's Systema Naturae. He placed it with the thrushes in the genus Turdus and coined the binomial name Turdus mustelinus. Gmelin based his account on the "Tawny thrush" that had been described in 1785 by the Welsh naturalist Thomas Pennant in his book Arctic Zoology. The wood thrush is now the only species placed in the genus Hylocichla that was introduced in 1864 by the American naturalist S.F. Baird. The species is monotypic: no subspecies are recognised. The species name comes from the Latin mustela "weasel".
This thrush is closely related to the other typical American thrushes of the genus Catharus, and is sometimes merged into that genus. The wood thrush also appears to be fairly closely related to the large Turdus thrushes, such as the American robin. "Wood thrush" is the official common name given to the species by the International Ornithologists' Union (IOC). The longest known lifespan for a wood thrush in the wild is 8 years, 11 months. Other brownish thrushes have finer spotting on the breast. American naturalist Henry David Thoreau wrote:
<blockquote>Whenever a man hears it he is young, and Nature is in her spring; wherever he hears it, it is a new world and a free country, and the gates of Heaven are not shut against him.</blockquote>
While the female is not known to sing, the male has a unique song that has three parts. The first subsong component is often inaudible unless the listener is close, and consists of two to six short, low-pitched notes such as bup, bup, bup. The middle part is a loud phrase often written ee-oh-lay, and the third part is a ventriloquial, trill-like phrase of non-harmonic pairs of notes given rapidly and simultaneously.
The male is able to sing two notes at once, which gives its song an ethereal, flute-like quality. Each individual bird has its own repertoire based on combinations of variations of the three parts. Songs are often repeated in order. The bup, bup, bup phrase is also sometimes used as a call, which is louder and at a greater frequency when the bird is agitated. allowing them to find their direction from the stars and orient themselves by detecting the Earth's magnetic field.
The wood thrush prefers deciduous and mixed forests for breeding. It prefers late-successional, upland mesic forests with a moderately-dense shrub layer. It favors areas with running water, moist ground, and high understorey cover. Along with many other species, this thrush faces threats both to its North American breeding grounds and Central American wintering grounds. Forest fragmentation in North American forests has resulted in both increased nest predation and increased cowbird parasitism, significantly reducing their reproductive success. A study by the Cornell Laboratory of Ornithology was the first large-scale analysis that linked acid rain to this thrush's decline. Continued destruction of primary forest in Central America eliminated preferred wood thrush wintering habitats, likely forcing the birds to choose secondary habitats where mortality rates are higher. In spite of this, the wood thrush is considered to be Least Concern.
Behavior
thumb|A wood thrush singing in [[Central Park, New York City]]
The wood thrush is primarily solitary, but occasionally forms mixed-species flocks in the winter. Its breeding territory ranges from in size, and are used for nesting, gathering nest materials, and foraging. The nest is usually sited in a dense patch of vegetation in a tree or shrub that provides concealment and shade. It is usually made of dead grasses, stems, and leaves, and lined with mud, and placed in a fork at a horizontal branch. The nest is not reused. Usually, two broods are attempted, although three to four separate nests may be built before a pair succeeds. Two to four pale blue eggs are laid at the rate of one per day. The eggs are incubated by the female only for 11 to 14 days, with the average being 13 days. Like all passerines, the chicks are altricial at hatching, mostly naked with closed eyes. The female broods the chicks during the first four days after hatching. Both parents feed the nestlings and remove fecal sacs from the nest. The chicks fledge 12–15 days after hatching, but the parents continue to feed them until they become independent and leave the parents' territory at 21–31 days old.
The young wood thrush is able to begin breeding the next summer. Most females lay their first eggs in mid-May, but older females may begin laying sooner. Pairs usually attempt to rear a second brood no later than late July, with the last of the young fledging around mid-August.