Hylocichla mustelina

See Winker and Rappole (1988) for discussion of evidence indicating that the wood thrush does not warrant recognition as a genus (i.e., Hylocichla) separate from Catharus

Large range in eastern North America; many occurrences; long-term decreasing population trend (per BBS data) but still common in many areas; threatened by forest fragmentation and resulting increases in brood parasitism by cowbirds and nest predation.

BREEDING: southeastern North Dakota and central Minnesota across the northern U.S. and adjacent southern Canada to Nova Scotia; south to eastern Texas, the Gulf Coast, and northern Florida; and west to eastern South Dakota, central Nebraska, central Kansas, and eastern Oklahoma. Casual breeder to southern Manitoba, southwestern North Dakota, and central South Dakota (AOU 1983). NON-BREEDING: southern Texas south through eastern Mexico and Middle America to Panama and northwestern Colombia (AOU 1983).

Many occurrences, with Partners in Flight (2013) estimating 11 million individuals globally.

Habitat degradation and fragmentation are commonly cited as the biggest threats. With loss of habitat and increased conversion to agriculture and pine plantations, both brood parasitism and nest predation increase. The Brown-headed Cowbird (MOLOTHRUS ATER) is by far the most serious threat, causing significant population declines throughout much of the range. Despite the fact that cowbirds are such a problem, control of cowbird numbers rarely has been attempted. Rate and impact of cowbird parasitism is highest in the Midwest, lowest in the Northeast (Hoover and Brittingham 1993). In forest fragments in northern Indiana, 90% of 278 nests contained an average of 2.4 cowbird eggs/parasitized nest; there was no relationship between size of forest fragment and cowbird parasitism but the entire landscape "appeared to be part of a regional sink for Wood Thrushes" (Fauth 2000). Data were collected from fragmented forests in Illinois by Robinson (1992), where thrushes also suffered extraordinarily high rates of brood parasitism. Of 19 nests found, all were parasitized with an average of 1.2 host eggs per nest, and an average of 4.6 cowbird eggs per parasitized nest; thrushes raised far more cowbirds than they did wood thrushes. Of 15 thrush nests found during the incubation period, only a single thrush fledgling was produced. One nest had 12 cowbird eggs in it. Similar results have been found for the Shawnee National Forest of southern Illinois, although parasitism rates are somewhat lower--89% of 83 nests contained an average 3.2 cowbird eggs per parasitized nest (Robinson and Wilcove 1994). On four separate occasions, Hoover (1992) witnessed common grackles (QUISCALUS QUISCULA) preying on all of the eggs in four different nests (blue jay [CYANOCITTA CRISTATA] and American crow [CORVUS BRACHYRHYNCHOS] were likely to be other avian nest predators). Brood parasitism by cowbirds was less prevalent in Hoover's (1992) study, 18% and 6% of all nests being parasitized in 1990 and 1991, respectively. Nest records for 896 nests (Cornell Laboratory of Ornithology) indicated that rates of brood parasitism differed significantly among the Midwest (42.1%), the mid-Atlantic (26.5%), and the Northeast (14.7%) regions of the U.S. Because of the high abundance of cowbirds, high percentages of nests parasitized, and high numbers of cowbird eggs per parasitized nest, the effects of cowbird parasitism are particularly detrimental to populations in the Midwest. Another possible threat includes loss of forest undergrowth due to overgrazing by high deer populations. On the other hand, dense herbaceous growth resulting from waste-water irrigation is detrimental (Rollfinke et al. 1990). Loss of tropical forests also may contribute significantly to regional declines in temperate North America.