Investigation of grassland/shrubland migrants on the Lower Delmarva Peninsula

B. J. Paxton, The Center for Conservation Biology
B D. Watts, The Center for Conservation Biology


Intro and Objectives: Concerns about declines in many North American bird populations have recently increased within both the scientific community and the general populous. To a large degree, this concern has been focused on neotropical migrants. In particular, neotropical migrant passerines that breed within forested habitats have received a great deal of attention from research and conservation organizations. However, results from the annual U.S. Fish and Wildlife Service’s breeding bird survey suggest that species associated with grasslands and or shrublands have experienced annual population declines that in many cases are greater than those experienced by forest-dwelling birds (Robbins et al. 1986 Askins 1993). Declines of grassland species are particularly evident in northeastern North America where habitat loss due to secondary succession and urbanization has been dramatic. Results from two long-term studies have shown that several species that depend on early successional habitats have experienced marked declines over the past two decades (Hagan et al. 1992). Many of these declining species migrate either to the tropics or to the southeastern U.S. and depend on open habitats for rest and refueling. Open farmlands have declined by nearly 80% within the mid-Atlantic region since the 1940’s (U.S. Dept. of Commerce 1981). Dramatic changes in land use practices over this same time period have left remaining open habitat less suitable for use by grassland species (Millenbath et al. 1996). Each autumn large numbers migrant landbirds, reluctant to cross the Chesapeake Bay, are concentrated on the lower Delmarva Peninsula. To date, most of the research devoted to passerine migration on the lower Delmarva Peninsula has focused on neotropical migrants that depend on forested habitats (Watts and Mabey 1993, 1994). Relatively little attention has been given to species that require open habitats. The Eastern Shore of Virginia National Wildlife Refuge contains some of the most significant stopover habitat for open-habitat migrants within the mid-Atlantic region. Information is needed on the stopover ecology and habitat requirements of these species so that they may be incorporated into existing and developing management plans for the refuge and other landholders. The objectives of this study were to investigate the use of grassland/shrubland habitats during the late period of fall migration. Information gathered will be used to determine the abundance and time of movement for open-habitat migrants on the lower Delmarva Peninsula.