EARLY SUCCESSIONAL: Background

Prominent grassland habitats within the mid-Atlantic Coastal Plain are primarily derived from agricultural fields and pasturelands. Some of the most productive grassland habitats within the region are fallow agricultural fields in the early stages of oldfield succession. Without regular maintenance to set back succession, these fields will proceed from a mixed stand of grasses and forbs with no woody vegetation to a shrubland dominated by woody shrubs and saplings and eventually to forest. The specific form of these early successional grasslands is influenced by agricultural history, moisture, and soils. In addition to oldfields, active farm operations may provide significant breeding habitat for open habitat species particularly when agricultural practices include habitat buffers or rotations with idle fields. Grain and hay crops may provide breeding habitat directly when harvest intervals do not disrupt nesting. Other managed grasslands within the physiographic region include pasturelands, airports, golf courses, military training areas, parks, and recreational fields.

The current status, distribution, and importance of grasslands and their relationship to the conservation of open-habitat bird populations must be viewed in the appropriate historical context. Prior to European settlement, open grassland habitats were uncommon within the mid-Atlantic Coastal Plain. Such habitats were maintained as relatively small patches within a forested landscape by populations of native Americans. In the years following European settlement, open lands likely increased with the expansion of land development for agricultural use. However, throughout the nineteenth century, broad-scale clearing of forested lands occurred throughout northeastern North America that resulted in a significant wave of open lands. Subsequently, the

availability of open lands has declined dramatically throughout the twentieth century. This decline was due initially to secondary succession on lands cleared during the previous century and more recently due to the conversion of remaining farm lands to other human uses.

The suite of species that currently occupies open habitats within the mid-Atlantic Coastal Plain appears to be an assemblage that has formed in response to the wave of habitat availability that followed broad-scale land clearing. Many of these species were historically exclusive to other physiographic regions but underwent large range expansions into the northeast during the mid to late 1800's. Populations of other species that were components of the Coastal Plain avifauna historically, are suggested to have increased during this same time period. As availability of open habitats has waned in the twentieth century, these species have retreated back toward the core of their ranges or have experienced population declines and are now considered among the most threatened species within the physiographic region. The Bachman's Sparrow, Loggerhead Shrike, and White-eyed Vireo have all undergone documented range expansions and contractions within the northeast in response to shifts in landuse over the past 150 years. Populations of Henslow's Sparrow, Bobolinks, Eastern Towhees, Barn Owls, and Grasshopper Sparrows have all been suggested to have experienced expansions in response to land clearing followed by declines within the region.