Breeding Habitat:Grassland
Nest Type:Open-cup nesting passerine
Migration Status:Neotropical migrant
Nest Location:Ground-low nesting
Lark Buntings are conspicuous occupants of short-grass and mixed- grass communities of the Great Plains. In North Dakota, their optimum habitats are sage prairies, although they are found in other mixed-grass communities as well as fallow fields, weedy roadsides, and hayfields (Stewart 1975). In Colorado, they are most numerous in short-grass prairies but also occupy sagebrush habitats in mountain parks (Andrews and Righter 1992).
Like many other grassland birds, habitat destruction has been responsible for declines in Lark Bunting populations since the nineteenth century (Andrews and Righter 1992). However, this species is fairly nomadic during the breeding season, and short- term movements can obscure or accentuate long-term trends. For example, Lark Buntings are normally scarce residents of eastern South Dakota, but large numbers appeared in that portion of the state during 1964. They remained numerous through 1970, but then returned to their previous abundance (SDOU 1978). Similar fluctuations have been reported elsewhere, but are normally of shorter duration. Annual fluctuations in precipitation levels and its influence on habitat conditions are believed to be primarily responsible for these nomadic movements. Along BBS routes, Lark Buntings are normally most numerous on the central and western Great Plains from eastern Colorado and western Kansas north to Montana and North Dakota (Relative Abundance Map). Their numbers rapidly diminish towards the peripheries of their range. Despite their nomadic movements, population declines predominate throughout most of their range (Trend Map). Increasing populations tend to be small and localized, except for portions of Montana and Alberta. The BBS trend estimates tend to be imprecise, but are generally in a negative direction. The regional trends are generally non-significant declines during 1966-1994; there are no significant increases while significant declines are evident in 3 states/provinces and 2 physiographic strata (Trend List). Population declines during 1966-1979 are largely responsible for these long-term trends. The only significant increase during this interval occurred in Montana, while significant declines occurred in 3 states/provinces, 3 strata, the Central BBS Region, U.S., and survey-wide. The trend estimates become more positive after 1980, when the regional trends are generally non-significant increases and all significant trends in states/provinces and strata are increases.
The BBS annual indices tend to be quite variable, and few temporal patterns are apparent. The survey-wide indices show a declining tendency through 1975, and a slight increasing tendency after 1985 (Survey-wide Annual Indices). In the Central BBS Region, declines are most evident during 1970 and 1971 with considerable population fluctuations during the mid- 1980s (Central BBS Region Annual Indices). Indices for the Western BBS Region are fairly stable, but show definite peaks during 1988 and 1992 (Western BBS Region Annual Indices). Indices for states/provinces and strata tend to be extremely variable and do not exhibit any obvious temporal patterns.
During the winter months, Lark Buntings are most prevalent in the southwestern deserts from south Texas to southern Arizona and south into Mexico. They occupy weedy, barren habitats within these desert communities (Phillips et al. 1964). They are also quite nomadic during these months, apparently in response to food availability. Throughout their winter range, Lark Buntings can be locally numerous one year and nearly absent the next. These fluctuations in abundance are responsible for very imprecise trend estimates based on data from CBCs, although these data suggest that their populations are also declining.
Andrews, R., and R. Righter. 1992. Colorado birds. Denver Mus.
Natur. Hist., Denver, CO. 442 pp.
Phillips, A., J. Marshall, and G. Monson. 1964. Birds of Arizona.
Univ. of Arizona Press, Tucson, AZ. 212 pp.
South Dakota Ornithologists Union. 1978. The birds of South
Dakota: an annotated check list. South Dakota Ornithologists
Union, Vermillion, SD. 311 pp.
Stewart, R.E. 1975. Breeding birds of North Dakota. Harrison
Smith, Lund Press, Minneapolis, MN. 295 pp.