Eastern Meadowlark Habitat Model
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Eastern meadowlark, Sturnella magna
Use of Study Area Resources:
Reproduction in all of study area except northwest Maine; winters as far north as southern Maine.
Cover. Meadowlarks feed and nest in native grasslands, pastures, and savannas, hay and alfalfa fields, roadsides, golf courses, and shrubby overgrown fields (Hull 2001, DeGraaf and Rappole 1995, Lanyon 1995, NBS web site). They prefer dense graminoid cover (Vickery et al. 1994). Late seasonal mowing of hayfields is the preferred management (Lanyon 1995). They may winter in old fields and salt marshes (Forbush 1929, Bent 1958).
Nests are located on the ground in fairly dense vegetation, often in a shallow depression (Lanyon 1995). These are constructed of dry grasses, herbaceous stems, or fine bark and may be arched or roofed with runways providing access (Lanyon 1995). In Maine, Vickery et al. (1994) found abundance was correlated with plant species richness, larger patch size, high grass/graminoid cover, and shrubs up to 60 cm. A Habitat Suitability Index constructed by Schroeder and Sousa (1982 in Hull 2001) found ideal vegetation heights for nesting were between 25 and 50 cm, and vegetation shorter than 2.5 cm or taller than 76 cm was unsuitable.
Forage. Eastern meadowlarks feed largely on insects, especially crickets and grasshoppers, as well as caterpillars; weed seeds, grains, and other vegetable matter comprises roughly a quarter of their diet, varying with season and availability (Lanyon 1995).
Area. Meadowlarks appear area sensitive, selecting large grazed and ungrazed pastures (Hull 2001). In Illinois meadowlarks were encountered more than twice as often at sites of 20 to 100 ha than at sites less than 20 ha (Herkert 1991 in Vickery et al. 1994). However, Samson (1980 in Vickery et al. 1994) observed meadowlarks in all four sites of less than 10 ha that he inspected. In Maine blueberry barrens Vickery et al. (1994) found meadowlark incidence increased with area. Birds incidence increased from about 20% to 70% as the area of sites increased from 100 to 1000 ha, while fewer than 10% of sites less than 10 ha had meadowlarks. Minimum sized territories (which may have been in larger fields) in Wisconsin and New York were about 3 ha (Lanyon 1995). Herkert (1994a in Hult 2001) estimated minimum area requirement for meadowlark at 5 ha.
We further examined minimum area by measuring the size of grassland patches near meadowlark occurrences along Breeding Bird Survey Routes for 1999 and 2000, within the study area. We identified the largest patch within each .25 mile observation buffer, then identified the minimum patch associated with these 30 sites; this was 5.8 ha. Accordingly, we used 5 ha as a minimum suitable patch size.
Disturbance and threats. Meadowlarks are very sensitive to human disturbance, including irrigation and mowing, and readily desert a nest. Eggs and young may also be lost to trampling by livestock or by predation by fox, coyotes, dogs, cats, snakes, skunks, raccoons, or other small mammals. Meadowlarks typically do not renest if a nest or young are lost (Lanyon 1995). Brown-headed cowbirds are common brood parasites. Late seasonal mowing of hayfields (delaying until August) is the preferred management (Lanyon 1995).
The meadowlark range within the study area was delineated by selecting all USDA Forest Service Ecological subunits (Keys et al. 1995) in which meadowlarks were known to occur. Subsequent mapping and testing of the model was restricted to these areas. The grassland cover type (see table, below) was selected, and scores were adjusted according to the patch size. Patches over 30 ha were regarded as optimal; patches from 10 through 30 ha have half that suitability, while patches of 5 ha and over but less than 10 ha were scored 0.2. Grasslands smaller than 5 ha were scored 0.
|Cover Types||Cover Suitability
(0 - 1 scale)
|Upland deciduous forest|
|Upland coniferous forest|
|Upland mixed forest|
|PEM, L2EM||Lake/pond, emergent vegetation|
|PFOcon||Palustrine forest, conifer|
|PFOdec||Palustrine forest, deciduous|
|PSSdec||Palustrine scrub shrub, deciduous|
|PSScon||Palustrine scrub shrub, conifer|
|PAB, L2AB||Lake/pond, aquatic vegetation|
|L1UB, PUB||Lake/pond, unconsolidated bottom|
|L2US||Lake, unconsolidated shore|
|L2RS||Lake, rocky shore|
|R1UB||Riverine subtidal unconsolidated|
|E1AB||Estuarine subtidal vegetated|
|E1UB||Estuarine subtidal unconsolidated bottom|
|E2AB||Estuarine intertidal algae|
|E2EM||Estuarine intertidal emergent|
|E2RS, R1RS||Estuarine, tidal river rocky shore|
|E2SS||Estuarine intertidal shrub|
|E2US||Estuarine intertidal unconsolidated shore|
|M1AB||Marine subtidal vegetated|
|M1UB||Marine subtidal unconsolidated bottom|
|M2AB||Marine intertidal algae|
|M2RS||Marine intertidal rocky shore|
|M2US||Marine intertidal unconsolidated shore|
The meadowlark occurrences along Breeding Bird Survey routes throughout the study area were used to test the habitat map. We compared the presence of habitat near a random set of 774 upland points in the meadowlark range to habitat occurrences at Breeding Bird Survey stops at which meadowlark were observed in 1990, 1997, or 1998. Of the 56 sites with birds, 53 had mapped habitat, while only 180 sites out of the 774 randomly distributed sites had habitat. The Chi-square was highly significant, indicating that the overall model does indicate localities useful to meadowlark.
DeGraaf, R.M. and J.H. Rappole. 1995. Neotropical Migratory Birds: Natural History, Distribution and Population Change. Comstock Publishing Associates, Ithaca, NY. 676 pp.
Herkert, J.R. 1991. An ecological study of the breeding birds of grassland habitats within Illinois. Ph.D. thesis. University of Urbana-Champaign, IL.
Hull, S.D. 2000. Effects of management practices on grassland birds: Eastern Meadowlark. Northern Prairie Wildlife Research Center, Jamestown, ND. Jamestown, ND: Northern Prairie Wildlife Research Center Home Page. http://www.npwrc.usgs.gov/resource/literatr/grasbird/fpeame/fpeame.htm (Version 16JUN2000).
Keys, J.E., Jr., J.C. Carpenter, S. Hooks, F. Koenig, W.H. McNab, W. Russell and W. Smith. 1995. Ecological units of the eastern United States - first approximation (map and booklet of map unit tables), USDA Forest Service. Atlanta, GA.
Lanyon, W.E. 1995. Eastern Meadowlark. The Birds of North America, 160.
NBS web site on Eastern Meadowlark: http://www.mbr-pwrc.usgs.gov/bbs/grass/a5010.htm
Samson, F.B. 1980. Island biogeography and the conservation of prairie birds. Proceedings of the North American Prairie Conference 7:293-305.
Vickery, P.D., M.L. Hunter, Jr. and S.M. Melvin. 1994. Effects of habitat area on the distribution of grassland birds in Maine. Conserv. Biol. 8(4):1087-1097.