Chesapeake Bay Program - Critter of the month

<body> <p><strong>Background</strong></p> <p>The black-crowned night heron, <em>Nyctirocorax nycticorax </em>, is a small to medium-sized wading bird whose range extends from Canada to South America. It has a stout body, a short neck and a sharp, downturned, heavy bill, which it uses to feed on small fish, amphibians, insects and vegetation. Its Latin name derives from the Greek, <em>nykitikorax</em>, which means <em>night raven </em>- referring both to the bird's nocturnal feeding habits and to its abrasive, crow-like call. These traits have also earned this bird the nickname <em>quark bird </em> because it makes this sound during its night flights. This species is one of seven extant species of night herons, worldwide.</p> <p><strong>Appearance and Detailed Morphology </strong><br> Adult night herons of both sexes share a similar appearance and have the following characteristics: <strong></strong></p> <ul> <li> Height of 20 inches, and a wingspan of 44 inches </li> <li>Short necks and stocky bodies </li> <li> Red eyes </li> <li> White breast, underside, face and throat </li> <li> Black bill, crown and neck </li> <li> Blue-gray wings </li> <li> An unusual pair of long, filamentary plumes that extend from the back of the bird's head </li> </ul> <table width="200" border="0" align="right"> <tr> <td><img src="../images/nightheron.jpg" width="217" height="194"></td> </tr> <tr> <td> <em><font size="2">Photo courtesy of Mike Land </font></em></td> </tr> </table> <p>Young night herons' plumage is generally duller in color than adults'; their upper bodies are brown, with some white streaking on chest and underside; darker brown crown and wings; the eyes are pale yellow or amber. Juveniles generally achieve adult plumage after the second year, although their crowns and backs are still dark brown, not black. </p> <p><strong>Life Cycle, Habitat and Feeding </strong></p> <p>In the Chesapeake Bay region, the black-crowned night heron may begin breeding in February, but eggs generally appear in the middle of March. Nesting activities usually follow these common traits: </p> <ul> <li> Nests are normally established among various bird and heron species in colonies that roost in many different kinds of trees, including pines, oaks, sassafras and alders, and in shrubs, undergrowth and near cattails in coastal marshes. </li> <li> Male night herons select the nesting site and gather materials for it; females build the nest. </li> <li> Nests are complex; the females construct their foundations of rough materials such as twigs and reeds, then use delicate materials (feathers, leaves, grasses) for upper layers, in which their clutches of 3 to 5 blue-green eggs will be laid </li> <li> Females and males alternate sitting on the eggs, for about 26 days </li> </ul> <p>Night herons, like other, non-nocturnal heron species, fish while remaining very still at the edges of streams, rivers and marshes, waiting for signs of prey. This is an adaptive, omnivorous species, and the birds will consume whatever food is most plentiful, including plants and algae. </p> <p>A night heron may appear transfixed for long periods in the shallows, or wait on pilings and docks, then catch its prey with one swift thrust of its bill. In the Bay, it feeds on shad, herring and eels, among other species, but it also consumes amphibians, aquatic insects, and crayfish or mussels in freshwater ponds. </p> <p><strong>Status in the Chesapeake Bay and Beyond </strong></p> <p><em>Nyctirocorax nycticorax </em> is one of the most common species of herons worldwide. Where threats exist to its populations, they are usual similar in type: loss of habitat or profusion of pesticides used to control mosquitos, which can result in mortality of young. </p> <p>In 1998, scientists from U.S. Fish and Wildlife, the U.S. Geological Survey and the New York State Department of Health conducted <a href="http://www.fws.gov/chesapeakebay/niteheron.htm" target="_blank">a study focusing on organochlorine contaminants </a> (e.g., DDT, Chlordane, dieldrin and toxaphene) in Baltimore Harbor and their potential impact on the reproduction of black-crowned night herons nesting there. The study's initial results showed that of 48 heron egg samples that had been collected and tested for concentrations of PCBs, 24 samples “…had levels greater than 5 ppm [parts per million], 20 samples were between 5 and 10 ppm and 4 samples had levels greater than 10 ppm.” Combining information from the samples with information on the locations of affected nesting colonies, scientists concluded that the occurrence of lesions in black-crowned night herons and other colonial nesting waterbirds could be more widespread than previously thought. </p> <p>Citing the fact that between 1985 and 1995, breeding colonies of the black-crowned night heron declined, in the Maryland portion of the Chesapeake Bay, by about 50 percent, scientists suspect that factor/s in addition to organochlorines and habitat loss may be responsible. </p> </body>