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wood thrush

Hylocichla mustelina

What do they look like?

Wood thrushes are small songbirds. They are 19 to 21 cm long and weigh 40 to 50 g. They are cinnamon-brown on the top of their head and back of their neck. Their back, wings and tail are olive-brown. Their breast and belly are white with big dark brown spots. They have a dull white ring around their eye, a brown bill, and pink legs.

Male and female wood thrushes look very similar. Young wood thrushes look similar to adults, but they have spots on their back, neck and wings as well. (Bertin, 1977; Roth, et al., 1996)

  • Sexual Dimorphism
  • sexes alike
  • Range mass
    40 to 50 g
    1.41 to 1.76 oz
  • Range length
    19 to 21 cm
    7.48 to 8.27 in

Where do they live?

The breeding range of wood thrushes (Hylocichla mustelina) extends from southern Canada to northern Florida and from the Atlantic coast to the Missouri River and the eastern Great Plains. Wood thrushes spend winters in Mexico and Central America, mostly in the lowlands along the Atlantic and Pacific coasts. (Roth, et al., 1996)

What kind of habitat do they need?

Wood thrushes live in deciduous and mixed forests. They prefer older forests with shrubs in the understory. They also like to have trees taller than 16 m, moist soil and leaf litter on the ground. Wood thrushes also like areas where there is running water. They can breed in small patches of forest, but large areas of forest keep them safer and allow them to raise more chicks.

Wood thrushes spend the winter in the understory of old tropical forests. However, they may also be found along the edges of forests, and in younger forests. (Bertin, 1977; Roth, et al., 1996)

  • Range elevation
    1325 (high) m
    4347.11 (high) ft

How do they reproduce?

Wood thrushes are monogamous (one male mates with one female). Breeding pairs form in mid-April and early-May. They usually stay together for most of the summer, and often raise two broods together. Most wood thrushes find a new mate each year. (Roth, et al., 1996)

Male wood thrushes begin arriving in the spring a few days before the females. A few days after arriving, they set up territories and begin to sing to attract a mate. Once breeding pairs have formed, they begin searching for a nest site.

The female usually chooses the nest site and builds the nest. The nest is located in a tree or shrub, and is built of dead grasses, stems or leaves, and lined with mud. The female lays 2 to 4 eggs, and incubates them for about 13 days. When the chicks hatch, they are naked and helpless. The female broods the chicks for the first four days or so to keep them warm and protect them. Both parents feed the nestlings and remove their fecal sacs from the nest. The chicks leave the nest (called fledging) when they are 12 to 15 days old. The parents continue to feed them until they are about 21 to 31 days old.

Most breeding pairs try to raise two broods in one season. The first eggs are laid in mid-May, and the second clutch of eggs are laid in July. Wood thrushes begin breeding when they are about one year old. (Roth, et al., 1996)

  • How often does reproduction occur?
    Wood thrushes breed once per year. They may raise one or two broods per breading season.
  • Breeding season
    Wood thrushes breed between April and August.
  • Range eggs per season
    2 to 8
  • Average eggs per season
    3
    AnAge
  • Range time to hatching
    11 to 14 days
  • Average time to hatching
    13 days
  • Range fledging age
    12 to 15 days
  • Range time to independence
    21 to 31 days
  • Range age at sexual or reproductive maturity (female)
    1 to 1 years
  • Range age at sexual or reproductive maturity (male)
    1 to 1 years

The female usually chooses the nest site and builds the nest. The female also incubates the eggs and broods the chicks for the first four days after hatching. Both parents feed the chicks and remove fecal sacs from the nest. (Roth, et al., 1996)

  • Parental Investment
  • altricial
  • pre-fertilization
    • provisioning
    • protecting
      • male
  • pre-hatching/birth
    • protecting
      • female
  • pre-weaning/fledging
    • provisioning
      • male
      • female
    • protecting
      • male
      • female
  • pre-independence
    • provisioning
      • male
      • female

How long do they live?

The oldest known wood thrush lived to be at least 8 years and 11 months old. Most wood thrushes do not live to be that old. (Roth, et al., 1996)

How do they behave?

Wood thrushes migrate between breeding areas in North America and wintering grounds in Mexico and Central America. The average distance that wood thrushes migrate is 2,200 km. Wood thrushes usually arrive in the spring by mid-April. They begin leaving their breeding grounds for the fall migration around mid-August. Wood thrushes migrate at night.

Wood thrushes are usually solitary, though they sometimes join flocks of other birds in the winter. They defend territories that are 0.08 to 2.8 ha in size. They use their territories for nesting, gathering nest materials, and foraging. Wood thrushes defend their territory from others by singing and flicking their wings and tail. They don't usually fight each-other physically. (Roth, et al., 1996)

  • Range territory size
    800 to 28000 m^2

How do they communicate with each other?

Wood thrushes communicate using song and body signals. Male wood thrushes sing a very unique song that sounds like a flute and ends in a trill. Female wood-thrushes do not sing. Wood thrushes also use calls, such as "bup, bup" or "tut, tut" to signal that they are agitated. (Roth, et al., 1996)

What do they eat?

Wood thrushes are omnivorous. They prefer soil invertebrates and larvae, but they will eat fruits in late summer, fall, and winter. Occasionally they feed on arboreal insects, snails, and small salamanders. In late summer, wood thrushes begin eating fruits with a lot of fat in them. This helps them to store up energy for their fall migration

Wood thrushes feed mostly on the forest floor. They can be seen hopping around in leaf litter and on the ground under the forest canopy, gleaning insects and probing the soil with their bills. They use their bill to turn over leaves in search of prey. (Roth, et al., 1996)

  • Animal Foods
  • amphibians
  • insects
  • terrestrial non-insect arthropods
  • mollusks
  • terrestrial worms
  • Plant Foods
  • fruit

What eats them and how do they avoid being eaten?

Eggs and chicks are vulnerable to predation by chipmunks, raccoons, blue jays, American crows, black rat snakes, brown-headed cowbirds, common grackles, southern flying squirrels, gray squirrels, least weasels, white-footed mice, domestic cats, great horned owls and sharp-shinned hawks. Adults are probably taken primarily by hawks and owls.

When predators are nearby, adult wood thrushes become alert and responsive to sounds. When their nests or young are threatened, adults respond with agitated calls and chases, escalating into dives and strikes.

What roles do they have in the ecosystem?

Wood thrushes affect the populations of the insects and other animals they eat. They may help to disperse the seeds of the fruits they eat. They also provide food for their predators.

  • Ecosystem Impact
  • disperses seeds

Do they cause problems?

How do they interact with us?

The benefits of wood thrushes toward humans are unknown.

Are they endangered?

Wood thrushes are becoming less common. This is probably because the forests that they breed in are being cut down, or divided up into smaller patches. Wood thrushes prefer large patches of forest over small patches. They are able to raise more chicks is large forests because predators are less common. They can also raise more chicks in large forests because nest parasites, such as brown-headed cowbirds are less common.

Wood thrushes are protected under the U.S. Migratory Bird Act. There are about 14,000,000 wood thrushes in the world. (Bertin, 1977; Hoover and Brittingham, 1993; Hoover, et al., 1995; Roth, et al., 1996)

Contributors

Kari Kirschbaum (author, editor), Animal Diversity Web.

Michelle Lesperance (author), University of Michigan-Ann Arbor, Terry Root (editor), University of Michigan-Ann Arbor.

Glossary

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

Neotropical

living in the southern part of the New World. In other words, Central and South America.

World Map

acoustic

uses sound to communicate

altricial

young are born in a relatively underdeveloped state; they are unable to feed or care for themselves or locomote independently for a period of time after birth/hatching. In birds, naked and helpless after hatching.

arboreal

Referring to an animal that lives in trees; tree-climbing.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends.

chemical

uses smells or other chemicals to communicate

diurnal
  1. active during the day, 2. lasting for one day.
endothermic

animals that generate their own body heat through metabolic processes.

forest

forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

migratory

makes seasonal movements between breeding and wintering grounds

monogamous

Having one mate at a time.

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

omnivore

an animal that mainly eats all kinds of things, including plants and animals

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

seasonal breeding

breeding is confined to a particular season

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

solitary

lives alone

tactile

uses touch to communicate

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

terrestrial

Living on the ground.

territorial

defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement

tropical

the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

visual

uses sight to communicate

References

Bertin, R. 1977. Breeding habitats of the wood thrush and veery. The Condor, 79: 303-311.

Hoover, J., M. Brittingham, L. Goodrich. 1995. Effects of forest patch size on nestling success of wood thrushes. The Auk, 112: 146-155.

Hoover, J., M. Brittingham. 1993. Regional variation in cowbird parasitism of wood thrushes. Wilson Bulletin, 105: 228-238.

Roth, R., M. Johnson, T. Underwood. 1996. Wood thrush (*Hylochicla mustelina*). Pp. 1-28 in A Poole, F Gill, eds. The Birds of North America, Vol. 246. Philadelphia, PA: The Academy of Natural Sciences and Washington, D.C.: The American Ornithologists' Union.

 
University of Michigan Museum of ZoologyNational Science Foundation

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Lesperance, M. 2002. "Hylocichla mustelina" (On-line), Animal Diversity Web. Accessed April 25, 2014 at http://www.biokids.umich.edu/accounts/Hylocichla_mustelina/

BioKIDS is sponsored in part by the Interagency Education Research Initiative. It is a partnership of the University of Michigan School of Education, University of Michigan Museum of Zoology, and the Detroit Public Schools. This material is based upon work supported by the National Science Foundation under Grant DRL-0628151.
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