Content for this page researched and created by Marshall Utiss

The Brown Thrasher (Toxostoma rufum) is a medium sized Mimidae of North America. (Field Guide To North America). On average its length roughly measures from 9.1 to 11.8 inches with a wingspan of 11.4 to 12.6 inches, and usually weighs between 2.2 to 3.1 grams (Cornell Laboratory). Both female and male Brown thrashers are very similar in appearance (Conserve Wildlife Foundation). They have long rounded tails, short wings and slightly curved bills. Coloring is also similar for both sexes with both being Reddish brown on the back and wings with a white underbelly containing black streaks and yellow eyes. Juveniles differ from adults in the coloring of

their eyes (they are greyish brown until there first winter) (Oiseaux-Birds).

The Brown Thrasher is found in many parts of the United States and occurs in very large populations in states such as Louisiana, Florida, Georgia and the Carolinas all year round (50 states). It is the only Thrasher species to be found east of Texas (Field Guide To North America).

Brown Thrashers live in thickets or open woodlands that contain lots of brush and shrubs. However, they have been known to come into suburban areas and agricultural areas. They prefer wild, thicket areas because of their solitary nature and because of the quick access to a number of places to find cover if disturbed. Sometimes the Brown Thrasher has been observed to bathe in puddles on the sides of roadways and then roll in sandy substances to dry and remove insects (Oiseaux-Birds). The population of Brown Thrashers and many other shrub breeding birds have been declining for a number of years

in North America, this population decline is believed to be caused by the loss of habitats due to agricultural and suburban expansion. Because large cleared areas are needed for agriculture many of the small woodland areas and shrubs in which this thrasher species thrives are destroyed to make way for crops and livestock. When this happens the birds are forced to move into already occupied habitats which greatly increases competition and stress. Increased mortality often results from this amplified competitive matrix. A similar story is seen when suburban areas expand into previously wild habitats. Large areas cleared for new housing plans and other suburban development force many birds to relocate, although some thrashers have been observed to continue to live in these new suburban areas   (Christopher J. W. McClure).

Individuals in western populations of the Brown Thrasher are larger in size than their eastern counterparts and have less streaking. The Brown Thrasher should not to be confused with Long Billed Thrasher of southern Texas whose bill is less curved and is greyer in color. Another way to distinguish between the two would be the Long Bill’s red eyes versus the Brown Thrasher’s yellow eyes (National Geographic). Some Brown Thrashers have displayed growth defects which have caused bill abnormalities such as extreme bending (Goertz). Another important distinguishing trait of the Brown Thrasher is its size in comparison to other Mimidaes.

While in their shrub habitats Brown Thrashers establish a feeding range from 2 to 10 acres in size. Inside of this range they feed mainly on the ground in fallen leaves and eat a number of insects and berries (Georgia Nongame Endangered Wildlife Program). Some of the insects that the Brown Thrasher has been found to eat are beetles, grubs, wire worms, army worms, gut worms, tent caterpillars, cicadas, grass hoppers, crickets, wasps, and bees. Although more than half of the Brown Thrasher’s diet comes from insects (Audubon) they do consume some plant life such as blueberries, huckleberries, holly berries, elderberries, hackberries, Virginia creeper, sour gum, bay berry, raspberry, grape cherry, and strawberries. The Brown Thrasher also eats small lizards and snakes (Cornell Laboratory).

Even though the Brown thrasher Is a ground feeding bird it has been observed to leap into the air to catch insects and will even take some human handouts. Once its feeding territory is claimed the Brown Thrasher has also been seen to chase other birds out of feeding territory very aggressively (Georgia Nongame Endangered Wildlife Program). One study found that when Brown Thrashers territory is established near gun ranges lead poisoning levels increase dramatically in these birds. This was believed to be caused by the birds eating shot pellets from the ranges that they confuse with the berries that are in their regular diet. The Thrashers were the only birds in this study to actually consume the pellets  (L. A. Lewis).

During mating the Brown Thrasher exhibits  number of different behaviors. The first behavior involves the male producing a large number of songs. The male Brown Thrasher has the largest song collection of all North American birds with a “play list” of more than 1100. Once a female has been attracted she will normally approach the male with twig and hop towards to male while fluttering her wings rapidly. The male usually then responds by picking up a leaf and hoping towards her. Breeding can then take place (Georgia Nongame Endangered Wildlife Program).

The Brown Thrashers nesting habits differ from most birds in that they normally establish nests very close to or on the ground (Conserve Wildlife Foundation Of New Jersey).  Nesting lasts for 9 to 13 days with a normal clutch size of 2 to 6 eggs. Eggs are 0.7 to 0.8 inches in size and usually are a glossy pale blue or sometimes marked with red or brown spots (Cornell Lab). Brown Thrasher nests are constructed in a cup shape with a mixture of leaves, twigs and sometimes even paper. The inside of these nests are lined with some roots (Georgia Nongame Endangered Wildlife Program).

A study measured the feeding patterns and nesting attendance for the male and female Brown Thrasher in relation to the nesting age and time of day with variable weather. This study found that males incubated eggs 29% of the time whereas the females 71% of time. Males also were found to feed 63% of the times vs. female 37%. Both sexes assisted in egg brooding and time at nest decreased 5 days after eggs hatched and feeding increased on the 6^th day  (Heagy). Already being a solitary bird the Brown Thrasher is a very aggressive and fierce protector of its nest. They have been observed to fiercely fight surrounding birds with nests in the area and to attack other larger potential threats such as dogs or humans (Oiseaux-Birds). Even with these highly aggressive tendencies nest predation accounts for 50% of nest failure in some areas. With the nests being close to or on the ground vulnerability of these nests is very high to predators (Conserve Wildlife Foundation Of New Jersey) and as expected shorter rate of nest occupancy was found to raise predation rates significantly (Murphy).

 

The Brown Thrasher is infected by a parasite known as Collyriculm faba. These adigenetic

flatworm parasites have been observed in the wings of dead birds (Byrd, Elon E.). Once in the bird they produce a number of cysts and wounds which normally heal over time and cause little to no problem for the bird. In some cases however, when more than 50 cysts are present birds show anemia, emaciation, defecating problems and death (Biomedcentral).

The Brown Thrasher is also the largest bird whose nests are parasitized by the brown-headed cowbird (Georgia Nongame Endangered Wildlife Program). The brown-headed cowbird affects a large number of North American birds especially in east. Most Brown Thrasher females remove cowbird eggs within 3 days of their being placed. This can vary however and recognition of the eggs is believed to be dependent on the mother’s previous experience with the cowbird. Even though there are many instances of cowbird parasitism there has been no linkage to it actually causing any significant population declines in thrashers (Haas). Another bird that consistently battles with the Brown Thrasher is the Catbird. Catbirds have been observed destroying Brown Thrasher eggs on a number of occasions. This is believed to be caused by the two birds having similar nesting periods and relatively similar demands for resources (Rivers James W.).

 

General References

Audubon, John James. “Georgia State Bird – Brown Thrasher – Turdus rufus.” 2016. 50 States. Web. 21 September 2016. <http://www.50states.com/bird/georgia.htm>.

Bouglouan, Nicole. “Brown Thrasher.” n.d. Oiseaux-Birds. Web. 23 Spetember 2016. <http://www.oiseaux-birds.com/card-brown-thrasher.html>.

“Brown Thrasher.” 2015. All About Birds: The Cornell Lab of Ornithology. Web. 21 September 2016. <https://www.allaboutbirds.org/guide/brown_thrasher/lifehistory>.

“Brown Thrasher.” 2006. National Geographic. Web. 20 September 2016. <http://animals.nationalgeographic.com/animals/birding/brown-thrasher/>.

Davenport, Michael J. “New Jersey Endangered and Threatened Species Field Guide.” 2011. Conserve Wildlife Foundation Of New Jersey. Web. 22 September 2016. <http://www.conservewildlifenj.org/species/fieldguide/view/Toxostoma%20rufum/>.

Dick, Gary Owen. “Field Guide To North America.” 2013. What Bird.com. Web. 22 September 2016. <https://identify.whatbird.com/obj/679/_/Brown_Thrasher.aspx>.

Herrmann, Jenny. “Brown Thrasher.” n.d. Wisconsin Bird Conservation Plan. Web. 20 September 2016. <http://www.wisconsinbirds.org/plan/species/brth.htm#>.

Johnson, Terry. Brown Thrasher. Forsyth : Georgia Nongame Endangerd Wildlife Program , n.d. Web.

Kaufman, Kenn. “Brown Thrasher.” 1 March 2016. Audubon Guide to North American Birds. Web. 20 September 2016. <http://www.audubon.org/field-guide/bird/brown-thrasher>.

Petr Heneberg, Anna Faltýnková, Jiří Bizos, Milena Malá, Juraj Žiak, Ivan Literák. “Parasites & Vectors.” 8 February 2015. biomedcentral.com. Web. 30 11 2016. <https://parasitesandvectors.biomedcentral.com/articles/10.1186/s13071-015-0646-3>.

 

Scientific References

Byrd, Elon E. “The Brown Thrasher, Toxostoma rufum (L.), as a Host for Collyriclum faba (Bremser).” The Journal of Parasitology. Vol. 56. Allen Press, 1970. 1 vols. 195-196. Web. 23 September 2016. <http://www.jstor.org/stable/3277486?pq-origsite=summon&seq=1#page_scan_tab_contents>.

Christopher J. W. McClure, Brian W. Rolek, Geoffrey E. Hill. “Seasonal use of habitat by shrub-breeding birds in a southeastern national forest.” The Wilson Journal of Ornithology. The Wilson Ornithological Society, 2013. 731-743. Web. 22 September 2016. <http://www.bioone.org/doi/abs/10.1676/13-038.1>.

Dunkin, Stacy W., Fred S. Guthery. “Bird Nesting in Chickasaw Plum Related to Age of Plum in Oklahoma.” The American Midland Naturalist. University of Notre Dame, 2010. 151-156. Web. 22 Septmeber 2016. <http://www.bioone.org/doi/abs/10.1674/0003-0031-164.1.151>.

Goertz, John W., Elmer E. Mowbray. “Brown Thrasher with a Bill Abnormality.” The Southwestern Naturalist. Vol. 14. Southwestern Association of Naturalists , 1969. 2 vols. 254-255. Web. 22 September 2016. <http://www.jstor.org/stable/3668883?pq-origsite=summon&seq=2#page_scan_tab_contents>.

Haas, Carola A., Katherine H. Haas. “Brood Parasitism by Brown-Headed Cowbirds on Brown Thrashers: Frequency and Rates of Rejection.” The Condor. Vol. 100. Blacksburg: Cooper Ornithological Society, 1998. 3 vols. 535-540. Web. 22 September 2016. <http://www.jstor.org/stable/1369720?pq-origsite=summon&seq=1#page_scan_tab_contents>.

Heagy, Patricia A,. Louis B. Best. “Factors Affecting Feeding and Brooding of Brown Thrasher Nestlings.” The Wilson Bulletin . Vol. 95. Wilson Ornithological Society, 1983. 2 vols. 297-303. Web. 22 September 2016. <http://www.jstor.org/stable/4161764?pq-origsite=summon&seq=1#page_scan_tab_contents>.

A. Lewis, et al. “Lead Toxicosis and Trace Element Levels in Wild Birds and Mammals at a Firearms Training Facility.” Archives of Environmental Contamination and Toxicology. Springer-Verlag New York Inc, 2001. 208–214. Web. 22 September 2016. <http://search.proquest.com/docview/1517452954?pq-origsite=summon&accountid=13158>.

Murphy, Michael T., Robert C. Fleischer. “Body Size, Nest Predation, and Reproductive Patterns in Brown Thrashers and Other Mimids .” The Condor. Vol. 88. Cooper Ornithological Society, 1986. 4 vols. 446-455 . Web. 22 September 2016. <http://www.jstor.org/stable/1368270?pq-origsite=summon&seq=2#page_scan_tab_contents>.

Pacifici Krishna, Theodore R. Simons, Kenneth H. Pollock. “Effects of Vegetation and Background Noise on the Detection Process in Auditory Avian Point-Count Surveys.” The Auk. Raleigh: The American Ornithologists’ Union, 2008. 600-607. Web. 22 September 2016. <http://www.bioone.org/doi/abs/10.1525/auk.2008.07078>.

Rivers James W., Brett K. Sandercock. “Predation by Gray Catbird on Brown Thrasher Eggs.” The Southwestern Naturalist . Vol. 49. Manhattan: Southwestern Association of Naturalists, 2004. 1 vols. 101-103. Web. 22 September 2016. <http://www.jstor.org/stable/3672276?pq-origsite=summon&seq=1#page_scan_tab_contents>.

Image References