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Toxostoma rufumbrown thrasher

By Phillip Gray

Geographic Range

Brown thrashers are found from southeastern Canada through eastern, central, and southeastern United States. Brown thrashers are the only thrasher species east of the Rocky Mountains and central Texas. During the breeding season brown thrashers primarily inhabit areas of southern Canada south to east central Texas. Migration is over short distances and at night. In winter, these birds migrate from the northern parts of their range into the southern parts of their range. (Howard and Moore, 1991; Robbins, et al., 1983)

Habitat

Brown thrashers are found in warm, dry habitats, such as warm forest edges and dense thickets. They are also found in suburban and agricultural areas. (Cavitt and Haas, 2000; Peterson, 1999; Peterson, 2001)

Physical Description

Adults have rufous upperparts and white underparts with a long, black tail. They have long, straight bills and yellow eyes. Males and females are alike in size and coloration. They are from 23.5 cm to 30.5 cm long, with wingspans of 9.4 to 11.1 cm long. The young appear the same except their upperparts are spotted and their eyes are gray. There are two sub-species, brown thrashers (T. rufum rufum) and long-billed thrashers (T.rufum longirostre). Long-billed thrashers are unique in their dull upperparts, gray head, orange eye, and long, straight bill. (Cavitt and Haas, 2000; Dunning, 1993; Godfrey, 1986)

  • Sexual Dimorphism
  • sexes alike
  • Range mass
    89 (high) g
    3.14 (high) oz
  • Average mass
    68.8 g
    2.42 oz
  • Range length
    235 to 305 mm
    9.25 to 12.01 in
  • Range wingspan
    94 to 111 mm
    3.70 to 4.37 in

Reproduction

When males arrive at the breeding grounds they establish a territory. In the southern parts of their range breeding starts in February and March, in the northern parts, breeding starts in May and June. Soon after this, pairs are formed and they begin to build a nest. Mates find each other with calls, most commonly using a call similar to a "tick" or "tchuck". Once the bond is formed and the nest is built, the pair will mate. (Cavitt and Haas, 2000; Fergus, 2004)

Brown thrasher breeding seasons vary with geographic region. Birds in the southern region breed from February to March; while those in the northern region breed from May to June. Brown thrashers lay three to five eggs each breeding season. Incubation takes about two weeks, once the eggs have hatched, nestlings take from 9 to 13 days to fledge. Independence is reached 17 to 19 days later. (Cavitt and Haas, 2000; Ehrlich, et al., 1988)

  • Breeding interval
    Brown thrashers breed once yearly.
  • Breeding season
    Breeding season varies geographically. Southern populations breed in February and March, northern populations birds breed in May and June
  • Range eggs per season
    3 to 5
  • Average eggs per season
    4
    AnAge
  • Range time to hatching
    11 to 14 days
  • Range fledging age
    9 to 13 days
  • Range time to independence
    17 to 19 days

Both parents incubate, brood, and feed nestlings. They incubate by sitting tightly on the nest and slip off when disturbed. During the incubation period, the female does the majority of the incubating. Both parents feed the chicks. (Cavitt and Haas, 2000; Ehrlich, et al., 1988)

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

Lifespan/Longevity

Year-to-year survival is age dependent for brown thrashers. Survival rate is approximately 35% for their first and second years, 50% between second and third years, and 75% between third and fourth years. Limitations to lifespan include disease (for example Salmonella tymphimurium), parasitism, and sometimes exposure to cold temperatures. The longest known lifespan in the wild is twelve years and in captivity, ten to twelve years. (Cavitt and Haas, 2000; Ehrlich, et al., 1988)

  • Range lifespan
    Status: wild
    12 (high) years
  • Range lifespan
    Status: captivity
    10 to 12 years
  • Typical lifespan
    Status: wild
    11.34 to 17.61 years
  • Average lifespan
    Status: wild
    14.14 years
  • Average lifespan
    Status: captivity
    12 years

Behavior

These birds are usually territorial and are found in pairs or with offspring during the breeding season. They compete with other birds for habitat and nesting areas. This competition results in hostile encounters with birds like gray catbirds (Dumetella carolinensis). Most often these encounters are instigated by males. During winters brown thrashers often displace other birds from their feeding areas. The name "thrasher" may come from the bird's habit of thrashing ground litter with its bill. Migration is over short distances and at night. (Cavitt and Haas, 2000; Fergus, 2004)

  • Range territory size
    5000 to 11300 m^2

Home Range

Territory-mapping studies indicate variation in territory densities. Most activites of a pair are confined to territories. (Cavitt and Haas, 2000)

Communication and Perception

Brown thrashers communicate mainly with vocalizations. They use mimicry extensively as well and are well known for their songs. Males have the largest documented song repertoire of all North American bird. This includes over 1100 types of songs. At young ages, birds most commonly use "alarm noises". Primary modes of perception include visual and tactile. Brown thrashers use mainly vision to find food and their tactile abilities to search for and manipulate food. (Cavitt and Haas, 2000; Ehrlich, et al., 1988)

  • Other Communication Modes
  • mimicry

Food Habits

Brown thrashers eat insects, primarily beetles and other arthropods, fruits, and nuts. They forage for food on the ground in leaf litter below trees and shrubs. These birds sweep the soil and leaf litter with rapid side-to-side movements that scatter leaves. After sweeping a few times, they will probe the soil and litter with their beaks. (Cavitt and Haas, 2000)

  • Animal Foods
  • insects
  • Plant Foods
  • seeds, grains, and nuts
  • fruit

Predation

Gray catbirds (Dumetella carolinensis) have been documented visiting brown thrasher nests to break the eggs. Two hypotheses are proposed to explain this heterospecific egg destruction behavior: resource competition and egg predation. These birds both live in shrubs and have similar timing in breeding. They compete for the resources of this habitat. Once the catbird has broken the egg, usually it will consume the contents. This egg consumption is consistent with the proposed egg predation hypothesis. The eggs of brown thrashers are also preyed on by many species of snakes. Adults and nestlings are preyed on by falcons. (Cavitt and Haas, 2000; Rivers and Sandercock, 2004)

To respond to predation, brown thrashers have a few natural defenses. Adults are aggressive and often chase predators from the nest. Adults will use their bill to hit predators, these are large birds and they can cause significant damage to small and medium-sized predators. Other defenses include flapping theirwings and vocalizations. (Cavitt and Haas, 2000; Rivers and Sandercock, 2004)

Ecosystem Roles

Ecosystem roles include competition with other birds for nesting sites and resources. Also these birds are prey for many snakes and other birds. (Cavitt and Haas, 2000; Ehrlich, et al., 1988; "Mockingbirds", 1985; Fergus, 2004)

Commensal/Parasitic Species
  • ticka (Ixodes dentatus)
  • hematophagous larvae (Protocalliphora metallica, P. shannoni)

Economic Importance for Humans: Positive

Brown thrashers are one of the best and most spectacular singers of all North American birds. Avid bird watchers enjoy the chance to see and hear these birds. (Ehrlich, et al., 1988)

  • Positive Impacts
  • ecotourism
  • research and education

Economic Importance for Humans: Negative

Brown thrashers can be significant pests in fruit orchards and crop fields. (Cavitt and Haas, 2000; Cavitt and Haas, 2000)

  • Negative Impacts
  • crop pest

Conservation Status

Brown thrashers are not listed as threatened or endangered in any part of their range. No management actions are known to increase or maintain populations. Dangers include pesticides, collisions with structures, and some degradation of habitats. These effects have yet to become harmful enough to cause concern. (Cavitt and Haas, 2000)

Other Comments

Brown thrashers belong to the mimic thrush family, Mimidae. They are among the most vocal birds and often mimic other species. Other birds in this group include northern mockingbirds (Mimus polyglottos) and gray catbirds (Dumetella carolinensis).

The best time to observe these birds is in April, before nest sites are established. During this time males sing on high branches to attract mates. (Cavitt and Haas, 2000; Ehrlich, et al., 1988; Fergus, 2004)

Contributors

Tanya Dewey (editor), Animal Diversity Web.

Phillip Gray (author), Kalamazoo College, Ann Fraser (editor, instructor), Kalamazoo College.

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

acoustic

uses sound to communicate

agricultural

living in landscapes dominated by human agriculture.

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.

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. Synapomorphy of the Bilateria.

chemical

uses smells or other chemicals to communicate

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

humans benefit economically by promoting tourism that focuses on the appreciation of natural areas or animals. Ecotourism implies that there are existing programs that profit from the appreciation of natural areas or animals.

endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

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

mimicry

imitates a communication signal or appearance of another kind of organism

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.

riparian

Referring to something living or located adjacent to a waterbody (usually, but not always, a river or stream).

scrub forest

scrub forests develop in areas that experience dry seasons.

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

suburban

living in residential areas on the outskirts of large cities or towns.

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

visual

uses sight to communicate

References

Equinox (Oxford) Ltd. 1985. Mockingbirds. Pp. 360-361 in C Perrins, A Middleton, eds. The Encyclopedia of Birds. New York: Facts On File Publications.

Cavitt, J., C. Haas. 2000. Toxostoma rufum brown thrasher. Pp. 1-28 in The Birds of North America, Vol. 14, 541-560 Edition. Philadelphia, PA: The Birds of North America, Inc..

Dunning, J. 1993. CRC handbook of avian body masses. Boca Raton, FL: CRC Press.

Ehrlich, P., D. Dobkin, D. Wheye. 1988. The birder's handbook a field guide to the natural history of north american birds. New York, New York: Simon and Schuster Inc..

Fergus, C. 2004. "Gray Catbird, Northern Mockingbird and Brown Thrasher" (On-line). Pennsylvania Game Commision. Accessed November 12, 2006 at http://www.pgc.state.pa.us/pgc/cwp/view.asp?a=458&q=150398.

Godfrey, W. 1986. The Birds of Canada. The Birds of Canada, Rev. ed. Edition. Ottawa, ON: National Museum of Natural Science.

Howard, R., A. Moore. 1991. A Complete Checklist of the Birds of the World. San Diego, CA: Academic Press Inc..

Peterson, A. 2001. Predicting species’ geographic distributions based on ecological niche modeling. The Condor, 103 3: 599-605. Accessed October 15, 2006 at http://0-www.bioone.org.ariadne.kzoo.edu/perlserv/?request=get-document&doi=10.1650%2F0010-5422%282001%29103%5B0599%3APSGDBO%5D2.0.CO%3B2#I0010-5422-103-3-599-PETERSON2.

Peterson, A. 1999. Sensitivity of distributional prediction algorithms to geographic data completeness. Ecological Modeling, 117: 159-164.

Rivers, J., B. Sandercock. 2004. Predation by gray catbird on brown thrasher eggs. The Southwestern Naturalist, 49/1: 101-103.

Robbins, C., B. Bruun, H. Zim. 1983. A guide to filed identification birds of North America. New York, New York: Western Publishing Company, Inc..

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