species. They were presumably scarce prior to 1930, after which they have 

 increased markedly (figure 14-2). 



Common terns increased from a low of around 1000 pairs in 1900 to nearly 9000 

 pairs in 1930. Arctic terns, on the other hand, remained fairly stable 

 throughout the period (figure 14-2). Since the 1950s numbers of both common 

 and arctic terns have decreased, presumably as a result of increases in 

 numbers of herring and black-backed gulls which prey on eggs and chicks and 

 also steal food from adult birds that are on their way to feed nestlings. 

 Roseate terns, laughing gulls, puffins, and razorbills are also frequent 

 victims of gull predation (Nettleship 1972) . Gulls also may take over 

 preferred nesting sites. Puffin and razorbill populations are currently 

 stable, but all three species of terns and the laughing gulls are declining in 

 Maine . 



Although numbers of Leach's petrels seemed to be unaffected by exploitation in 

 the last century, their numbers have declined since 1900 because of habitat 

 disturbance on their nesting islands (e.g., construction, logging, and 

 grazing) . 



Present Status of Seabirds 



Breeding species. Fourteen species of seabirds breed along the Maine 

 coast (table 14-5) . The common loon breeds on inland lakes and least terns 

 nest on sand beaches on the mainland. All other species nest in colonies on 

 offshore islands. The characterization area has a total of 321 nesting 

 colonies of seabirds and supports the largest breeding populations of arctic 

 terns, double-crested cormorants, Leach's storm petrels, common eiders, 

 razorbills, common puffins, and black guillemots in eastern U.S. waters. 



Region 4 has the most seabird colonies (117), followed in decreasing order by 

 regions 3 (60); 1 (50); 5 (39); 6 (34); and 2 (21). A complete list of 

 nesting colonies and their locations are presented in the appendix table 1. 

 The most important nesting islands are shown on atlas map 4. 



The common eider is the most abundant nesting seabird along the Maine coast 

 (table 14-6). Over 22,000 pairs nest on 240 islands. Eiders nest in all 6 

 regions of the characterization area but 41% are found in region 4. Leach's 

 storm petrels are nearly as abundant as the common eider but are much more 

 localized in distribution. Petrels nest in 17 colonies in regions 3 to 6 but 

 nearly 95% of the population breeds in only 4 colonies in region 5 (table 14- 

 6). 



The herring gull ranks third in abundance (16,695 pairs). It breeds in all 6 

 regions but is most abundant (36%) in region 4. The double-crested cormorant 

 (14,549 pairs), great black-backed gull (6575 pairs), and black guillemot 

 ( 2665 pairs) are also found in all six regions, and like the herring gull and 

 common eider are most abundant in region 4 (table 14-6) . 



Of the large-bodied terns, the common and arctic terns are about equally 

 abundant (1393 and 1640 pairs respectively), whereas the roseate tern is much 

 less abundant (55 pairs). These terns nest on 29 coastal islands in either 

 mixed species (3 islands) or single-species colonies (26 islands). More than 

 one-half of the breeding population of arctic terns south of Labrador nests on 



14-10 



