1994 Proceedings
North American Conference on Savannas and Barrens

Historically the grasslands of central North America and the extensive eastern forests came in contact in a broad crescent-shaped zone that included parts of Alberta, Manitoba and Saskatchewan in Canada, and Arkansas, Illinois, Indiana, Iowa, Minnesota, Missouri, Nebraska, Oklahoma, Texas, and Wisconsin in the United States (Anderson 1983). This transition-zone occupied a sizable area in the Midwest with estimates for savanna habitat alone accounting for more than 11 million ha at the time of European settlement (Nuzzo 1986). Agricultural and urban development and the elimination and control of periodic fires, however, has led to the near complete elimination of this transitional habitat from the Midwest, with current estimates suggesting that considerably less than 1% of this habitat remains (Nuzzo 1986).

Because of the extensive loss of this habitat in the Midwest, wildlife inhabiting the transition-zone between prairie and deciduous forests may have been hit particularly hard by changes in the Midwestern landscape.

Birds may be a particularly good group of species to use to examine the effect this loss of habitat has had on wildlife populations because birds are a well studied group of organisms. The historical record of Midwestern bird populations is well documented and includes accounts of early naturalists in Midwestern prairies and woodlands (e.g., Ridgway 1873, 1889) as well as quantitative data on bird populations collected shortly after the turn of the century (e.g., Forbs 1908; Forbs and Gross 1922). In this paper I compare the early accounts and data with present day bird population data to assess the affects of landscape changes on transition-zone breeding bird populations in the Midwest.

RESULTS AND DISCUSSION

Two hundred and seventy-seven species of birds presently breed in the Midwestern states of Iowa, Illinois, Indiana, Michigan, Minnesota, Missouri, Ohio, and Wisconsin (Green and Janssen 1975, Mumford and Keller 1984, Bohlen 1989, Peterjohn 1989, Brewer et al. 1991, Kent and Bendorf 1991, Robbins 1991, Robbins and Easterla 1992). Of these species, 83 (30%) breed in the transition-zone between grasslands and deciduous forests (Appendix I), including 53 species that are primarily restricted to the transition-zone and 30 species that are approximately equally abundant in transition-zone and deciduous forest habitats (Appendix I).

Despite the immense changes that have taken place in the Midwestern landscape, no transition-zone bird species have been eliminated from the region because of anthropogenic landscape changes. As a whole, transition-zone bird species have fared relatively well in the highly fragmented Midwestern landscape, and many are currently among the most numerous bird species in the region. Data from the United States Fish and Wildlife Service's North American Breeding Bird Survey suggest that 13 of the 25 most abundant breeding bird species in the Midwest are transition-zone species, including 4 of the 5 most abundant species (Table 1).

Although many transition-zone bird species have maintained sizable Midwestern populations, a few transition-zone species have populations that are presently much reduced from former times. Ten species of transition-zone birds are considered to be either endangered or threatened in at least one Midwestern state (Table 2). Four of these species, the Bachman's sparrow, Bewick's wren, loggerhead shrike, and Swainson's hawk, are considered to be either endangered or threatened in at least half of the Midwestern states in which they occur (Table 2) and may have regionally imperiled populations.

ACKNOWLEDGMENTS

I am grateful to Scott K. Robinson who helped me in categorizing the habitat associations for some birds included in this analysis.

LITERATURE CITED

Anderson. R. C. 1983 The eastern prairie-forest transition - an overview. In: R. Brewer, ed. Proceedings of the eighth North American Prairie Conference. Western Michigan University, Kalamazoo. P. 86-92.

Bohlen, H. D. 1989. The Birds of Illinois. Indiana Press. Bloomington, In. 221 p.

Brewer, R., G. A. McPeek and R. J. Adams, Jr. 1991. The Atlas Of Breeding Birds Of Michigan. Michigan State University Press, East Lansing.

Forbs, S. A. 1908. The mid-summer bird life of Illinois: A statistical study. American Naturalist 42:505-519.

• and A. O. Gross. 1922. The numbers and local distribution in summer of Illinois land birds of the open country. Illinois Natural History Survey Bulletin 14:187-218.

Green, J. C. and R. B. Janssen. 1975. Minnesota Birds: Where, When And How Many. University Minnesota Press, Minneapolis.

Kent, T. H. and C. J. Bendorf. 1991. Official checklist of Iowa birds. Iowa Bird Life 61:101-109.

Mumford, R. E. and C. E. Keller. 1984. The Birds Of Indiana. Indiana University Press, Bloomington.

Nuzzo, V. A. 1986. Extent and status of Midwest oak savanna: presettlement and 1985. Natural Areas Journal 6:6-36.

Peterjohn, B. G. 1989. The Birds Of Ohio. 352 pp.

Ridgway, R. 1873. The prairie birds of southern Illinois. American Naturalist 7:197-203.

• 1889. The Ornithology Of Illinois. Volume 1. Illinois State Laboratory of Natural History.

Robbins, M. B. and D. A. Easterla. 1992. Birds Of Missouri: Their Distribution And Abundance. University of Missouri Press, Columbia.

Robbins, S. D., Jr. 1991. Wisconsin Birdlife. University of Wisconsin Press, Madison.

TABLE 1. The twenty-five most abundant breeding birds in the Midwestern states of Iowa, Indiana, Illinois, Minnesota, Missouri, Michigan, Wisconsin, and Ohio based on data from the United State Fish and Wildlife Service's Breeding Bird Survey (BBS). Abundance represents the average number of birds recorded on BBS routes. Number of Routes is the number of BBS routes on which each species has been encountered (1966-1991). An asterisk indicates a bird that breeds in the transition-zone between Midwestern prairies and deciduous forests.

TABLE 2. Transition-zone breeding bird species that are considered to be either endangered or threatened in at least one Midwestern state.

¹ IL = Illinois; IN = Indiana; IA = Iowa; MO = Missouri; MN, Minnesota; MI = Michigan; OH = Ohio; WS = Wisconsin. State status is shown with superscripts ^E = Endangered or ^T = Threatened.

APPENDIX 1. Breeding birds of the transition-zone between Midwestern prairie and deciduous forest. An asterisk indicates species that are approximately as numerous in transition-zone and deciduous forest habitats.

Swainson's hawk, American kestrel, merlin, northern bobwhite, American woodcock, mourning dove, black-billed cuckoo*, yellow-billed cuckoo*, greater roadrunner, eastern screech-owl, great horned owl*, long-eared owl*, Chuck-will's-widow*, whip-poor-will*, ruby-throated hummingbird*, red-headed woodpecker*, downy woodpecker*, hairy woodpecker*, northern flicker, eastern wood-pewee*, alder flycatcher, willow flycatcher, least flycatcher*, eastern phoebe*, Say's phoebe, great crested flycatcher*, western kingbird, eastern kingbird, scissor-tailed flycatcher, purple martin, blue jay*, black-billed magpie, American crow*, common raven*, black-capped chickadee*, Carolina chickadee*, tufted titmouse*, rock wren, Carolina wren*, Bewick's wren, house wren*, blue-gray gnatcatcher*, eastern bluebird, American robin*, gray catbird, northern mockingbird, brown thrasher, cedar waxwing, loggerhead shrike, white-eyed vireo, Bell's vireo, solitary vireo*, yellow-throated vireo*, warbling vireo, philadelphia vireo*, blue-winged warbler, golden-winged warbler, nashville warbler, yellow warbler, chestnut-sided warbler, prairie warbler, mourning warbler, common yellowthroat, yellow-breasted chat, summer tanager*, scarlet tanager*, northern cardinal*, blue grosbeak, indigo bunting, rufous-sided towhee, Bachman's sparrow, chipping sparrow, clay-colored sparrow, field sparrow, lark sparrow, song sparrow, Lincoln's sparrow, white-throated sparrow, Brewer's blackbird, great-tailed grackle, common grackle, orchard oriole, American goldfinch.