Post by Hunter on Feb 4, 2005 17:44:12 GMT -5
The birds that inhabit the Chesapeake Bay and its woodland and shoreline habitats constitute some of the region’s most beautiful and vulnerable species. Ospreys and bald eagles, great blue herons, laughing gulls, wood ducks, Canada geese and American oystercatchers are a few of the most visible resident and migratory birds, but their habitat requirements and behaviors are distinct. All are intricately entwined with the Bay’s ecosystem and each performs a different ecological function.
Birds roam; they are not tied as intimately to their habitats as benthic species such as blue crabs or oysters. But they require similarly protective nesting and nursery grounds. Shoreline development, toxic and nutrient pollution and natural stressors such as drought or saturating storms can damage these habitats and increasingly influence the life cycles of all Bay birds.
The great blue heron is one of six species of colonial nesting waterbirds that inhabit the Bay region. Along with its cousins the great egret, the snowy egret, the little blue heron, the green-backed heron and the night heron, the great blue hunts in the shallows, feeding mainly on small fish, amphibians and arthropods. These lanky birds (the great blue reaches a height of four feet and has a wing span of more than six feet, but reaches a mature weight of only six pounds) spend their days wading and patrolling the shorelines for food. They breed in the Bay area, using tall trees or forested areas for nesting habitat, but tend to migrate south in winter. Some night herons and great blue herons remain in the region year-round.
Bald eagles and ospreys are the Bay’s most familiar raptors, or birds of prey. The osprey builds its nests along the Bay shoreline and on navigation markers, utility poles or dead trees near the water, and performs spectacular dives for its main food source, finfish. Between the 1950s and the 1970s, pesticides such as DDT contaminated the ospreys’ food supply. The birds laid eggs with thin shells that often broke before hatching, which caused a serious decline in the osprey population. Since the DDT ban in the early 1970s, however, the population has steadily increased. It’s estimated that more than 500 nesting pairs make their home in the Bay area. Although the majestic eagle is our nation’s living symbol, the bald eagle is no friend to the osprey, from which it occasionally filches food. The bald eagle, in fact, is as likely to eat carrion as it is to hunt for live prey. These predator-scavengers nest in trees, often loblolly pines, close to a food and water source.
Dozens of species of waterfowl–ducks and geese, from the familiar mallard and the Canada goose to the wood duck and red-breasted merganser–also live in the Chesapeake Bay region, or at least stop here briefly during their migration between Canada and southern habitats. The shy wood duck, with its gorgeous plumage, lives in the Bay region in all but the coldest winter months and nests in the watershed’s forested wetlands, while the dabbling black duck nests on uninhabited islands in the Bay and in isolated coastal marshes and remains here all year. Both feed on wetland and shoreline vegetation.
Many other species inhabit the Bay region, including other "aerial gleaners" that consume fish or insects, such as gulls, terns, barn swallows, brown pelicans and the low-flying cormorants. Other wading birds include the sandpiper, sanderling, willet, black-bellied plover, ruddy turnstone, dowitcher and glossy ibis. The non-native, resident mute swan competes with the migratory tundra swan for food and habitat. The belted kingfisher patrols the territory along freshwater lakes, marshes and estuarine shorelines for small fish.
Loss of habitat along waterways poses the biggest threat to most bird species in the Bay watershed. Deforestation, shoreline development and shoreline erosion disrupt nesting activities, and chemical contaminants in the water damage the food source of many Bay birds.