Grassland Birds: An Overview of Threats and Recommended ...

Grassland Birds: An Overview of Threats and Recommended Management Strategies Peter D. Vickery James R. Herkert Fritz L. Knopf Janet Ruth Cherry E. Keller

Abstract—Grassland ecosystems are dependent on periodic disturbance for habitat maintenance. Historically, grazing by native herbivores and prairie fires were the agents principally responsible for maintaining grassland areas. However, elimination of native herbivores, widespread fire suppression, and conversion for agriculture have greatly altered grasslands in the United States and Canada. Because of these landscape changes, many grassland birds are increasingly dependent on land managers for habitat creation, maintenance, and health. Grazing, prescribed burning, and mowing/haying are the most frequently used, and versatile, grassland management techniques. Grassland birds prefer a wide range of grass heights and densities, with some species preferring short sparse vegetation, and others preferring taller, more dense vegetation. Due to differences in species habitat preferences and regional differences in soils and floristics, the responses of individual grassland species to specific grassland management practices can be variable and often are regionally dependent. As a result, management of grassland areas is best directed toward the creation of a mosaic of grassland habitat types. This habitat mosaic is probably best maintained through some type of rotational management system in which sections of large grassland areas receive management on a regular schedule. Such a rotational system would provide a variety of habitat types in every year, would ensure the availability of suitable habitat for birds at either end of the grassland management spectrum, and also would provide habitat for birds whose preferences lie between these extremes.

Grasslands are ecosystems that have evolved with frequent disturbances. Historically, the agents principally responsible for maintaining grassland habitats were drought, grazing by native herbivores, and fire. Generally, a west-toeast disturbance continuum exists in North America; grazing has been and continues to be the primary ecological force

on western shortgrass areas, whereas fire was the prominent disturbance factor to the east. Grassland habitats are occupied by a small number of uniquely adapted bird species. Most species select a particular suite of habitat features. Mountain Plovers (Charadrius montanus) and Horned Larks (Eremophila alpestris), for example, require short, sparse vegetation, whereas Henslow’s Sparrows (Ammodramus henslowii) and Sedge Wrens (Cistothorus platensis) require taller, more dense vegetation. Some grassland species are more abundant on recently burned or grazed grasslands, whereas others are more abundant on undisturbed or idle grasslands. Also, habitat preferences can vary throughout the range of a species. Because of these differences in habitat preferences, and because of regional differences in soils and floristics, the response of a particular species to a specific grassland management prescription may be variable. During the past quarter century, grassland birds have experienced steeper, more consistent, and more widespread population declines than any other avian guild in North America. While some grassland species are Neotropical migrants, most are short-distance migrants that winter primarily in the southern U.S. and northern Mexico. Thus, opportunities for conservation exist on both breeding and wintering grounds. The winter ecology of most grassland birds is poorly known; winter survivorship could be a critically important factor in the long-term declines that some species have experienced. Therefore, grassland bird conservation programs within North America need to address both breeding and wintering ecology. This discussion is focused on threats to grasslands east of the Rocky Mountains; grasslands farther west (e.g., California grasslands, palouse prairie) are beyond the scope of this presentation.

Historical Perspectives ___________ In: Bonney, Rick; Pashley, David N.; Cooper, Robert J.; Niles, Larry, eds. 2000. Strategies for bird conservation: The Partners in Flight planning process; Proceedings of the 3rd Partners in Flight Workshop; 1995 October 1-5; Cape May, NJ. Proceedings RMRS-P-16. Ogden, UT: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station. Peter D. Vickery, Center for Biological Conservation, Massachusetts Audubon Society, Lincoln, MA 01773. James R. Herkert, Illinois Endangered Species Protection Board, Springfield, IL 62701. Fritz L. Knopf and Janet Ruth, U.S. Geological Survey, Fort Collins, CO 80525. Cherry E. Keller, U.S. Geological Survey, Annapolis, MD 21401.

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Because most grassland ecosystems have been altered profoundly within the past two centuries, many are now among North America’s most endangered ecosystems. Effective grassland bird conservation and management must recognize the historical dynamics under which these habitats have evolved and, where feasible, incorporate the ecological processes that have generated and maintained these distinctive grassland biotas.

USDA Forest Service Proceedings RMRS-P-16. 2000

Western Shortgrass Prairie Western prairies are characterized by short (100 ha). Avoid further loss and fragmentation of existing grassland habitats. The protection and proper management of these habitats, especially those used by areasensitive, rare, or declining species, is the most effective means of conserving grassland bird populations. • Actively manage grasslands to control woody encroachment through the use of fire, grazing, and mowing.

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Shortgrass Prairie Knopf, F. L. 1994. Avian assemblages on altered grasslands. Studies in Avian Biology, No. 15. Samson, F. B. and F. L. Knopf. 1994. Prairie conservation in North America. Bioscience 44:418-421. Samson, F. B. and F. L. Knopf. 1996. Prairie conservation: Preserving North America’s most endangered ecosystem. Island Press, Covelo, CA.

USDA Forest Service Proceedings RMRS-P-16. 2000

Tallgrass Prairie Askins, R. A. 1993. Population trends in grassland, shrubland, and forest birds in eastern North America. Current Ornithology 11:1-34. Bock, C. E. and J. H. Bock. 1988. Grassland birds in southeastern Arizona: Impacts of fire, grazing, and alien vegetation. Pages 43-58 in Goriup, P. D. (ed.), Ecology and conservation of grassland birds. Tech. Publ. No. 7. International Council For Bird Preservation. Bollinger, E. K. 1991. Conservation of grassland birds in agricultural areas. Pages 279-287 in Decker, D. J., M. E. Krasny, G. R. Goff, C. R. Smith, and D. W. Gross (eds.), Challenges in the conservation of biological resources: A practitioner’s guide. Westview Press, Boulder, CO. Dobkin, D. S. 1992. Neotropical migrant landbirds in the Northern Rockies and Great Plains: A handbook for conservation and management. Publ. No. R1-93-34. USDA Forest Service, Missoula, MT. Herkert, J. R. 1994. The influence of habitat fragmentation on Midwestern grassland bird communities. Ecological Applications 4:461-471. Herkert, J. R., R. E. Szafoni, V. M. Kleen, and J. E. Schwegman. 1993. Habitat establishment, enhancement, and management for forest and grassland birds in Illinois. Tech. Publ. No. 1. Illinois Department of Conservation, Natural Heritage. 20 pp. Hunter, W. C. 1990. Handbook for nongame bird management and monitoring in the southeast region. U.S. Fish and Wildlife Service, Atlanta, GA. 198 pp.

USDA Forest Service Proceedings RMRS-P-16. 2000

Skinner, R. M., T. S. Baskett, and M. D. Blenden. 1984. Bird habitat on Missouri prairies. Terrestrial Series No. 14. Missouri Department of Conservation, Jefferson City. 42 pp.

Eastern Grasslands Askins R. A. 1996. History and conservation of grassland birds in the northeastern United States. In Vickery, P. D., P. Dunwiddie, and C. Griffin, (eds.), The ecology and conservation of grasslands and heathlands in the northeastern United States. Massachusetts Audubon Society, Lincoln. Vickery, P. D. 1992. A regional analysis of endangered, threatened, and special concern birds in the northeastern United States. Pages 1-10 in DeGraff, R. M. (ed.), Transactions of the Northeast section of the Wildlife Society 48. Amherst, MA. Vickery, P. D., M. L. Hunter, Jr., and S. M. Melvin. 1994. Effects of habitat area on the distribution of grassland birds in Maine. Conservation Biology 8:1087-1097. Vickery, P. D. and J. R. Herkert (eds.) 1999. Ecology and conservation of grassland birds of the Western Hemisphere; proceedings of a conference; 1995 October; Tulsa, OK. Studies in Avian Biology No. 19. Cooper Ornithological Society, c/o Western Foundation of Vertebrate Zoology, Camarillo, CA. 299 pp.

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