Please use this identifier to cite or link to this item:
|Title:||Colonial waterbird habitats and nesting populations in North Carolina estuaries : 1983 survey|
|Authors:||University of North Carolina at Wilmington.|
Point Reyes Bird Observatory.
United States. Army. Corps of Engineers. Wilmington District.
Dredging Operations Technical Support Program (U.S.)
Parnell, James F.
DuMond, David M.
McCrimmon, Donald A. (Donald Alan), 1944-
Dredged material islands
|Publisher:||Environmental Laboratory (U.S.)|
Engineer Research and Development Center (U.S.)
Abstract: As part of the Dredged Material Research Program, a research project conducted in 1975 demonstrated that colonial waterbirds were using dredged material islands in North Carolina estuaries as nesting sites. At that time, most dredged material islands were not diked. Subsequent research in 1976 and 1977 demonstrated further that most colonial waterbirds nesting in North Carolina were utilizing dredged material islands as nesting sites. Research during that same time period demonstrated that the practice of diking dredged material islands, a practice just coming into regular use in North Carolina, created islands quite different from undiked islands. That study compared community succession and bird utilization on diked and undiked dredged material islands. It showed that diking drastically changed plant succession during the first few years and implied that some species of ground nesting colonial birds such as royal terns may have difficulty in successfully utilizing diked islands as nesting sites. Most nesting islands in 1977 were, however, still undiked, and most diked islands were only a few years old. Thus, in 1983 nesting colonial waterbirds were censused throughout the North Carolina estuaries to determine whether or not the pattern and degree of use of undiked and diked islands had changed. Vegetation was also sampled on several islands where plant succession had proceeded for an additional 6 or 7 years since the earlier study. The 1983 research indicated that plant succession on diked islands had continued to occur at an accelerated rate compared with undiked islands. The pattern of succession, as indicated by species present, also continued to differ on the two island types. Undiked islands normally undergo a successional pattern similar to that on barrier islands, while diked sites have greater species diversity and vegetate more quickly. It appears that most seres will differ considerably. The utilization of diked sites by nesting colonial waterbirds has increased. It appears that, when appropriate habitat is present, most species will nest behind dikes. Royal terns may, however, be an exception, with most colonies remaining on undiked sites. It is also likely that diked sites will be available for shorter periods of time to those species requiring bare or nearly bare substrates. Whether or not reproductive success is different on diked and undiked sites is still not known. The study also indicated that overall nesting populations of colonial waterbirds have increased since 1977, and populations have dramatically increased on dredged material islands. Laughing gulls, royal terns, brown pelicans, and white ibises showed rather large increases, while gull-billed terns, Forster's terns, least terns, black skimmers, tri-colored herons, snowy egrets, and glossy ibises declined. Increases in bird populations from 1977 to 1983 were 33 percent on undiked and 82 percent on diked islands for ground nesting species, and 16 percent on undiked and 82 percent on diked islands for tree nesting species. A total of 77 percent of all colonial nesting species were nesting on dredged material; 139 colonies (60 percent) were on dredged material islands. The number of nesting sites being utilized declined, and colony size generally increased. A total of 87 island sites were utilized in 1983, compared with 97 island sites in 1977, a 10-percent decline. These are disturbing signs since they indicate that fewer suitable sites may be available to colonial waterbirds in North Carolina estuaries.
|Appears in Collections:||Technical Report|