Breeding Habitat:Woodland
Nest Type:Open-cup nesting passerine
Migration Status:Short distance migrant
Nest Location:Mid-story- canopy nesting
Breeding Varied Thrushes are associated with humid coastal and montane coniferous forests in northwestern North America. Their breeding range extends from northeastern California and central Idaho north along the Rocky Mountains, Cascades, and coastal ranges into Alaska (AOU 1983). Most BBS data are obtained from the southern portion of this range, north to central British Columbia. The more northerly populations are not currently monitored by the BBS.
Within its BBS coverage, Varied Thrushes tend to be most numerous in British Columbia and adjacent portions of the United States (Relative Abundance Map). Their population trends are generally positive during 1966-1979, including significant increases in Washington, Canada, and for the entire survey area (Trend List). In contrast, their trends are generally negative after 1980, including significant declines in Washington, the Cascade Mountains (S67) stratum, and the United States. These conflicting trends produce non-significant estimates for all states/provinces, strata, and regions during the entire survey period. The trend map exhibits a mixed pattern of increases and declines, with declines prevailing in southern British Columbia and Washington (Trend Map).
This temporal pattern in trends is also reflected in the survey- wide annual indices, with increases through the mid-1980s followed by declines (Survey-wide Annual Indices). Similar patterns are exhibited in British Columbia, Washington, and the Southern Pacific Rainforests (S93) stratum (British Columbia Annual Indices). (Washington Annual Indices). (S. Pacific Rainforests Annual Indices). Oregon populations are generally stable (Oregon Annual Indices). Increases are evident in Montana while the Idaho indices are variable but generally declining. (Montana Annual Indices). (Idaho Annual Indices). Note that exceptionally high population levels occur in most of these states/provinces and strata during 1984 and 1986. There are no apparent explanations for these influxes of breeding Varied Thrushes into the southern portion of its breeding range during these years. Since they occurred relatively early during the interval, these influxes combined with the subsequent return to more normal population levels are largely responsible for the declining population trend estimates during 1980-1994.
American Ornithologists Union. 1983. Check-list of North American
birds, 6th ed. Allen Press, Lawrence, KS. 877 pp.