BARRIER BAY ISLANDS: Population/Habitat Objectives

The common characteristic that attracts nesting birds to both barrier and bay islands is isolation from human disturbance and mammalian predators. The expansion of the human population within the region has resulted in a dramatic increase in the visitation of both island types. Visitation may result in site abandonment or a reduction in productivity. Objectives should focus on maintaining the availability of island habitats and providing bird populations with disturbance and predator free locations for nesting.

Birds that depend on barrier and bay islands for breeding have been the focus of targeted surveys since the 1970's. For this reason, regional population estimates are comparatively good. However, the underlying reasons for observed population declines remain poorly understood. Research is needed that focuses on demographic patterns and the mechanisms that have resulted in population declines.

Objective 1) To achieve and maintain a population of 300 pairs of Piping Plovers with 50% in Virginia/Maryland and 50% in Delaware/New Jersey.

Justification: The population of Piping Plovers along the Atlantic Coast is federally threatened. For this reason, there exists a recovery plan that includes the mid-Atlantic Coastal Plain. The known breeding population within the planning unit has increased from approximately 227 pairs in 1986 to 256 pairs in 1994. It is unlikely that the population would have stabilized within the region without specific plans to reduce the loss of breeding habitat, control human disturbance, and to reduce the impact of predation on productivity. Without continued active management the population would likely experience a dramatic decline. Even though the population has stabilized, it still represents only about 50% of the recovery goal of nearly 500 breeding pairs set for the region (value extrapolated from U.S Fish and Wildlife Service 1995). However, it is debatable whether or not this recovery goal is attainable within the lower portion of the planning unit where carrying capacity appears to be lower than projections.

Assumptions: It is assumed that maintenance of beach habitat to support the Piping Plover population will ensure adequate habitat to support stable populations of the Wilson's Plover, American Oystercatcher, Least Tern and associated beach-nesting species. However, it is acknowledged that while the Piping Plover population has been stable to increasing in recent years, the populations of some of the other beach-nesting species have been in decline. Success with the Piping Plover population has, at least in part, been due to specific management techniques that have increased productivity by reducing losses to disturbance and predation. Similar techniques may be required for the other beach-nesting species in order to stabilize and restore populations.

Objective 2) Restore the Gull-billed Tern population to >1,000 breeding pairs (pre-1980 levels).

Justification: The planning unit represents the northern fringe of the breeding distribution of the Gull-billed Tern. The breeding population within the region has declined dramatically since the 1970's. Along the Virginia barrier islands (the historic core of the breeding population within the planning unit) counts have declined steadily from more than 2,200 adults in the late 1970's to 51 adults in 1998 (Williams et al. survey). Deliberate action is needed to maintain a breeding population within the planning unit.

Assumptions: It is assumed that maintenance of nesting habitat to restore and maintain the Gull-billed Tern population will ensure adequate habitat to support stable populations of Black Skimmers, Least Terns and other beach-nesting, colonial species. However, it is acknowledged that Gull-billed Terns and the other species forage on distinctly different resources and so may be subject to different limiting factors.