Brown Thrasher (Toxostoma rufum) Raymond J. Adams Jr.

Manistee Co., MI. 6/21/2009 © Darlene Friedman This species sponsored by the Audubon Society of Kalamazoo

(Click to view a comparison of Atlas I to II)

Anyone familiar with the Brown Thrasher townships with a near universal distribution in the southwestern counties. The prevalence of during the breeding season is well aware of its thrashers in southwestern Michigan is pugnacity. This colorful mimid presents a fierce associated with their preference for deciduous- demeanor when threatened by potential nest mixed shrub upland, shrubby old field and shrub predators as I learned at an early age. The wetland (Eastman 1991). In addition, this area Brown Thrasher readily throws itself at humans, of the state has extensive farmland bordered by dogs, snakes and other birds (pers. obs.). This hedgerows and tree lined fencerows, which thrasher is easily identified as few species are provide alternative nesting cover. Elsewhere in similar in appearance. There are a handful of the LP, the Brown Thrasher is fairly uniform in thrushes with comparable patterns, but all lack distribution. In the eastern third of the LP from the long graceful tail and yellow eye. The only Lenawee and Monroe counties all the way to the species which might cause confusion is the Straits of Mackinac there is a north/south similar Long-billed Thrasher which overlaps corridor where this species is sometimes absent. with the Brown Thrasher in south Texas. The The causes for these gaps in occurrence are not Brown Thrasher breeds from the East Coast to obvious from looking at a map. During MBBA the Rocky Mountains and from the Canadian I, the Brown Thrasher was present in every Prairie Provinces and the south edge of the township in Oakland and Livingston counties. boreal forest to the Gulf Coast. In winter it In MBBA II this species was unrecorded in 21 retires to the southern third of the United States townships in these same two counties. with a few birds overwintering each year into Urbanization, human population increases, and the northern U.S.. This species breeds the accompanying loss of habitat likely explain throughout Michigan, although it is less losses of Brown Thrasher in these two counties common in the Upper Peninsula and rare on Isle (and effort decreased there from 1,739 hours in Royale. MBBA I to 901 hours in MBBA II). But

distribution gaps away from large population Distribution centers are more difficult to explain. On careful examination of the Michigan atlas map for the Brown Thrasher, this species is widespread in the LP; reported from 73% of the

© 2011 Kalamazoo Nature Center Brown Thrasher (Toxostoma rufum) Raymond J. Adams Jr.

In the Upper Peninsula, the Brown Thrasher was 19th and 20th centuries. It undoubtedly recorded in 270 blocks and 221 townships in benefitted from the increase in human MBBA I, but only 228 blocks and 186 settlement and lumbering as suggested by Gibbs townships in MBBA II. The overall distribution (1879) “breeds in all half-cleared localities in in the UP in MBBA II has changed little from LP.” Most of the comments regarding the previous survey. This bird is widely abundance are vague. Whether you read distributed north of Wisconsin, especially in Barrows (1912) “summer resident of all parts of Menominee, Dickinson, Marquette and Iron the state…most abundant in the southern half” counties. Elsewhere in the UP, the distribution or Payne (1983) who described it as “common is clumped with large regions where the species in the Lower Peninsula, more local and less is apparently absent. Presumably, because the common in the Upper Peninsula”, exactly how “earlier shrub stages of plant succession” they common was it? require are missing (Eastman, 1991). It probably reached its peak abundance in the Breeding Biology late 1800s following forest clearing. There is The adage “timing is everything” is certainly little data on actual numbers in Michigan during relevant when surveying for the Brown the early 20th century, but in Illinois the Brown Thrasher. When the species returns, typically Thrasher declined 74% from 1909 through 1958 by mid April in southern Michigan, sometimes (Cavitt and Haas 2000). With the increased use earlier, the male is extremely vocal spending of pesticides following the war there is every hours singing from the taller perches in suitable reason to expect that trend continued. Federal habitat counter singing with other males while BBS routes from 1966 through 2007 indicate a advertising for a female which typically arrives decline of more than 80% of Brown Thrasher later (Bent, 1948). The song period is not long numbers in Michigan (Sauer et al. 2008), while in duration (Cavitt and Haas 2000), but at this Kalamazoo County BBS surveys suggest an time it is easy to locate this thrasher especially 86% drop from 1970 through 2006. Michigan when multiple males are present. Interestingly, Breeding Bird Atlas data from 1983-2008 also males sing less frequently when competition is indicate a decline. During MBBA I, there were lacking (pers. obs.). Brown Thrashers renew nearly 4,100 pairs found in over 2,500 blocks, singing prior to the second brood or following while the MBBA II results total about 3,500 an initial nest failure. Once nesting starts the pairs in 1,845 blocks. Clearly, the Brown male helps incubate and feed the young (Cavitt Thrasher is on a downward trend. and Haas 2000) and the Brown Thrasher becomes much less conspicuous. It is not until Conservation Needs the young fledge and begin following the adults While the Brown Thrasher is neither threatened around for food, that the thrasher again is more nor endangered, the rapid population decline easily located. Clutch size ranges from 2-6 eggs over the past 50 to 100 years is cause for alarm. and may vary seasonally and regionally. As with other declining species which occupy similar habitat or rely on similar food, a number Abundance and Population Trends of hypothesizes have been proposed for the (Click to view trends from the BBS) causes. Following the expansion of pesticide The Brown Thrasher has likely been present in use after World War II the Brown Thrasher Michigan well before the time of European suffered increased visible mortality as well as settlement. It was present when Sager published indirect mortality in and around agricultural the first state bird list in 1839 and was listed by operations (Cavitt and Haas 2000). This no each of the authors throughout the rest of the doubt continues today. Collisions are known to

© 2011 Kalamazoo Nature Center Brown Thrasher (Toxostoma rufum) Raymond J. Adams Jr. be another serious mortality factor. While and Geographical Survey of the Territories stationary objects such as towers and windows 5:481-497. are well known obstacles, automobiles and Payne, R.B. 1983. A Distributional Checklist trucks cause heavy mortality. During Atlas of the Birds of Michigan. MP 164. surveys in southwestern Michigan, Brown University of Michigan Museum of Thrasher road kills including young were noted Zoology. Ann Arbor, MI. frequently (pers. obs.). Because this bird is a Sager, A. 1839. Report of Doctor Abraham short distance migrant it is less likely to be Sager, zoologist of Geological Survey. exposed to severe weather in migration. Harsh House Documents of the State of Michigan: winters in the south have been known to cause 410-421. major impacts. Habitat degradation and loss Sauer, J.R., J.E. Hines, and J. Fallon. 2008. may be the greatest problem of all. The North American Breeding Bird Survey, Results and Analysis 1966-2007. Version Habitat protection may be the most important 5.15.2008. USGS Patuxent Wildlife management opportunity; protecting hedgerows, Research Center. Laurel, MD. fallow fields, providing brush cover along agricultural field edges and designing housing Suggested Citation developments where portions of the natural areas are salvaged. Because roadside mortality Adams, R.J. 2011. Brown Thrasher (Toxostoma has become an issue, finding ways to alter rufum). In Chartier, A.T., J.J. Baldy, and roadsides so that wildlife is provided greater J.M. Brenneman (eds.). 2010-2011. The protection would help many bird species, not Second Michigan Breeding Bird Atlas. just the Brown Thrasher. For many species, Kalamazoo Nature Center. Kalamazoo, MI. every bird that we can save is important. Accessed online at: . Literature Cited

Barrows, W.B. 1912. Michigan Bird Life. Special Bulletin. Michigan Agricultural College. Lansing, MI. Bent, A.C. 1948. Life Histories of North American Nuthatches, Wrens, Thrashers, and Their Allies. U. S. Natl. Mus. Bull. 195. Cavitt J.F., and C.A. Haas. 2000. Brown Thrasher (Toxostoma rufum). In The Birds of North America, No. 557 (A. Poole and F. Gill, eds.) The Birds of North America, Inc., Philadelphia, PA. Eastman, J. 1991 Brown Thrasher. In Brewer, R., G.A. McPeek, and R.J. Adams Jr. (eds.). 1991. The Atlas of Breeding Birds of Michigan. Michigan State University Press. East Lansing, MI. Gibbs, M. 1879. Annotated list of the birds of Michigan. Bulletin of the US Geological

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