EXECUTIVE SUMMARY 



This report describes colony distribution, species abundance, historical 

 trends, nesting chronology, and census techniques for 28 species of seabirds 

 and wading birds from Cape Elizabeth, Maine to the Virginia-North Carolina 

 border. A parallel report has been prepared for the rocky, island bound 

 coastal region of Nlaine north of Cape Elizabeth (Korschgen 1979). The loca- 

 tion and composition of all colony sites in 1977 are depicted in an atlas 

 (Ervn'n and Korschgen 1979). 



From May to July, 1976 and 1977, surveys of nesting colonies were 

 conducted by a number of teams of well-qualified field biologists. Fixed- and 

 rotary-wing aircraft were used extensively to locate, photograph, and 

 inventory colonies. In addition, surface (foot, boat) censuses of nests 

 and/or adults were rT;ade at many colonies and compared with aerial estimates. 

 Standardized data forms with census instructions were provided to all 

 participants. 



A total of 240,982 pairs of waterbirds was recorded at 512 colonies in 

 1977. Herring (75,709 pairs) and laughing gulls (64,662) and common terns 

 (26,905), respectively, were the 3 most abundant of the 17 seabird species. 

 The least abundant species were those at the limits of their breeding ranges 

 (the nearctic black guillemots and common eiders, and southern sandwich and 

 Caspian terns). The most abundant of the 11 wading bird species were snowy 

 egrets (10,148 pairs), black-crowned night herons (9,009), and cattle egrets 

 (6,515). Green herons and white ibises were the most rare. 



For the 10 coastal States, Virginia (54,423 pairs), New Jersey (53,389), 

 and Niassachusetts (42,488) harbored the greatest numbers of nesting birds, 

 respectively, while Connecticut (5,467) and New Hampshire (465) had the 

 fewest. Relative abundance of waterbirds is positively correlated with 

 wetland area, a crude measure of both feeding and nesting habitat. Most 

 nesting colonies are located on barrier, marsh, or coastal islands. In the 

 highly-developed coastal areas of New Jersey, Delaware, and Long Island, New 

 York, a number of beach- and dune-nesting seabird species (herring gulls, 

 terns, black skimmers) have shifted from their traditional beach habitat to 

 marsh or dredged niaterial islands in adjacent embayments. 



Analysis of census techniques indicated that, in general, aerial methods 

 are best for locating colonies, photography, and, under some conditions for 

 estimating adults. Helicopters are considered to be more useful than 

 fixed-wing aircraft because of their slow speed and ability to hover and land 

 in small open areas. Cost factors, however, must be balanced with efficiency. 

 A total nest count is the most accurate method of assessing populations, but 

 may be disruptive to colonies and costly in terrris of time and personnel. As 

 an alternative, nest counts can be taken at a number of sample colonies and 

 used to generate conversion factors to be applied to aerial estimates from 

 other colonies. Regression analysis of adult estimates versus nest counts 

 indicated both marked variation among species and among censuses for a given 

 species. This variation is attributable mainly to colony differences in 

 vegetation density, adult attendance (due to time, tidal and climatic 

 influences), and observer. In general, aerial counts often underestimate 

 gulls and wading birds. 



IV 



