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.
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.
- Habitat Regions
- temperate
- terrestrial
- Terrestrial Biomes
- forest
- scrub forest
- Other Habitat Features
- suburban
- agricultural
- riparian
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.
- Other Physical Features
- endothermic
- homoiothermic
- bilateral symmetry
- Sexual Dimorphism
- sexes alike
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.
- Mating System
- monogamous
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.
- Key Reproductive Features
- iteroparous
- seasonal breeding
- gonochoric/gonochoristic/dioecious (sexes separate)
- sexual
- oviparous
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.
- Parental Investment
- altricial
-
pre-fertilization
- provisioning
-
protecting
- female
-
pre-hatching/birth
-
provisioning
- female
-
protecting
- male
- female
-
provisioning
-
pre-weaning/fledging
-
provisioning
- male
- female
-
protecting
- male
- female
-
provisioning
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.
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.
- Key Behaviors
- terricolous
- flies
- diurnal
- motile
- migratory
- territorial
Home Range
Territory-mapping studies indicate variation in territory densities. Most activites
of a pair are confined to territories.
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.
- Communication Channels
- acoustic
- 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.
- Primary Diet
- omnivore
- 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.
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.
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.
- 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.
- Positive Impacts
- ecotourism
- research and education
Economic Importance for Humans: Negative
Brown thrashers can be significant pests in fruit orchards and crop fields.
- 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.
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.
Additional Links
Contributors
Tanya Dewey (editor), Animal Diversity Web.
Phillip Gray (author), Kalamazoo College, Ann Fraser (editor, instructor), Kalamazoo College.
- 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.
- native range
-
the area in which the animal is naturally found, the region in which it is endemic.
- 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.
- forest
-
forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.
- scrub forest
-
scrub forests develop in areas that experience dry seasons.
- suburban
-
living in residential areas on the outskirts of large cities or towns.
- agricultural
-
living in landscapes dominated by human agriculture.
- riparian
-
Referring to something living or located adjacent to a waterbody (usually, but not always, a river or stream).
- 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.
- 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.
- monogamous
-
Having one mate at a time.
- 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).
- 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
- oviparous
-
reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.
- 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.
- diurnal
-
- active during the day, 2. lasting for one day.
- motile
-
having the capacity to move from one place to another.
- migratory
-
makes seasonal movements between breeding and wintering grounds
- 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
- acoustic
-
uses sound to communicate
- mimicry
-
imitates a communication signal or appearance of another kind of organism
- 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.
- omnivore
-
an animal that mainly eats all kinds of things, including plants and animals
- visual
-
uses sight to communicate
- tactile
-
uses touch to communicate
- acoustic
-
uses sound to communicate
- chemical
-
uses smells or other chemicals to communicate
References
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..
Equinox (Oxford) Ltd. 1985. Mockingbirds. Pp. 360-361 in The Encyclopedia of Birds . New York: Facts On File Publications.