Dependence of waterbirds and shorebirds on shallow-water habitats in the Mid-Atlantic coastal region: An ecological profile and management recommendations
Waterbirds (waterfowl, colonially nesting wading and seabirds, ospreys [ Pandion haliaetus ], and bald eagles [ Haliaeetus leucocephalus ]) and shorebirds (sandpipers, plovers, and relatives) may constitute a large fraction of the toplevel carnivore trophic component in many shallow-water areas of the mid-Atlantic region. The large biomass of many species (>1 kg body mass for the two raptors and some waterfowl) and enormous populations (e.g.,>1 million shorebirds in late May in parts of Delaware Bay) reveal the importance of waterbirds as consumers and as linkages in nutrient flux in many shallow-water habitats. Salt and brackish marsh shallow-water habitats, including marsh pannes and tidal pools and creeks as well as constructed impoundments, are used intensively during most months of the year; in fall and winter, mostly by dabbling ducks, in spring and summer by migrant shorebirds and breeding colonial wading birds and seabirds. In adjacent estuaries, the intertidal flats and littoral zones of shallow embayments are heavily used by shorebirds, raptors, and colonial waterbirds in the May to September periods, with use by duck and geese heaviest from October to March. With the regional degradation of estuarine habitats and population declines of many species of waterbirds in the past 20 yr, some management recommedations relevant to shallow waters include: better protection, enhancement, and creation of small bay islands (small and isolated to preclude most mammalian predators) for nesting and brooding birds, especially colonial species; establishment of sanctuaries from human disturbance (e.g., boating, hunting) both in open water (waterfowl) and on land; better allocation of sandy dredged materials to augment islands or stabilize eroding islands; improvement in water management of existing impoundments to ensure good feeding, resting, and nesting opportunities for all the waterbirds; support for policies to preclude point and nonpoint source runoff of chemicals and nutrients to enable submerged aquatic vegetation to recover in many coastal bays; and improvement in environmental education concerning disturbance to wildlife for boaters and recreationists using the coastal zone.