58 



Birds — Our Llviiiii Rtwonrct.s 



by 

 Brian A. Harrington 



Manomet 



Observatory for Conservation 



Sciences 



with iheii" long-distance, nonstop tlights to the 

 next site (Monison and Harrington 1979: 

 Senner and Howe 1984; Harrington et al. 1991). 

 Growing evidence (Schneider and Hanington 

 1981 ) indicates that staging areas are unusually 

 productive sites with highly predictable but sea- 

 sonally ephemeral "blooms" of invertebrates, 

 which shorebirds use for fattening. In some 

 cases, especially for "obligate" coastal species, 

 specific sites are traditionally used; even other 

 species sites may shift between years. Because 

 of this, conservationists believe some species 

 are at risk through loss of strategic migration 

 sites (Myers et al. 1987). Other species are 

 threatened by the loss of breeding and wintering 

 habitats (Page et al. 1991; Haig and Plis.sner 

 1993; B. Leachman and B. Osmundson. U.S. 

 Fish and Wildlife Service, unpublished data). 



The predicted consequences of global warm- 

 ing, such as sea-level change, will also strongly 

 affect the intertidal marine habitats, which 

 many species of shorebirds depend upon. Some 

 of the strongest warming effects will be at high 

 latitudes, including those where many shore- 

 birds migrate to breed, as well as south temper- 

 ate latitudes, where many of them winter. 



Population Trend Data 



Information on population trends in North 

 American shorebirds comes largely from stud- 

 ies designed for other purposes, except in the 

 case of a few species that breed within latitudes 

 covered by the Breeding Bird Survey (BBS) and 

 one game species, the American woodcock 

 (Scolopa.x minor). We divide these studies into 

 two types, those based on surveys during breed- 

 ing and nonbreeding seasons. 



Population trend data from breeding seasons 

 come mostly from studies of declining or 

 threatened species such as piping plovers 

 (Charadrius melodus; Haig and Plissner 1993), 

 mountain plovers (C. montamis: Graul and 

 Webster 1976; F.L. Knopf. U.S. Fish and 

 Wildlife Service, unpublished data), and snowy 

 plovers (C alexandrimis: Page et al. 1991). 

 Additional data come from the BBS and from 

 special survey efforts on game species such as 

 American woodcock (Sauer and Bortner 1991 ). 



Nonbreeding season data come mostly from 

 aerial surveys of migrants on Delaware Bay 

 during spring (Clark et al. 1993). of migrants by 

 the International Shorebird Surveys (ISS) dur- 

 ing spring and fall (Hairington et al. 1989). and 

 by the Maritimes Shorebird Surveys (MSS) in 

 eastern Canada during fall (Moirison et al. 

 1994). Although none of these projects was 

 designed principally to gather data for popula- 

 tion trend monitoring, they are the only data 

 bases on migrant species that have been sys- 

 tematically compiled through a period of years. 



The Christmas Bird Counts are an exception; 

 they are conducted when most shorebirds are 

 south of the United States. 



Largely voluntary efforts of the ISS of 

 Manomet Observatory, the MSS of the 

 Canadian Wildlife Service, the BBS of the 

 National Biological Service, and surveys on 

 Delaware Bay (DELBAY) coordinated by New 

 Jersey and Delaware state wildlife agencies 

 have produced rough data useful for trend 

 analysis. Because the BBS is conducted during 

 the breeding season and is based on roadside 

 surveys, its value is greatest in analyzing popu- 

 lation change of broadly distributed shorebirds 

 common in temperate latitudes where survey 

 effort is greatest. The ISS. MSS. and DELBAY 

 projects have focused on migration season 

 counts and. therefore, are the best (though not 

 ideal) available resources for monitoring north- 

 em-breeding shorebirds. which include most 

 species in North America. 



Plovers 



Three of the eight species of plover that reg- 

 ularly occur east of the l()3th meridian (snowy 

 plover, piping plover, and mountain plover) are 

 species of concern (endangered, threatened, or 

 candidate species); killdeer (C vociferus) and 

 perhaps black-bellied plover {Pliivialis 

 sqiiatarolu) are in decline (Table). In North 

 America, all of these except the black-bellied 

 plover are distributed principally in temperate 

 latitudes; snowy, piping, and mountain plovers 

 breed in special, localized habitats (principally 

 sandy beaches, salt lakes, and salt flats for 

 snowy and piping plovers, short-grass prairie 

 for mountain plovers). There has been no evalu- 

 ation of trends for Wilson's plover (Charadrius 

 wihonia). typically a beach-nesting species in 

 southern North America. There are no statisti- 

 cally significant population changes in 

 American golden- (P. dominica) and semi- 

 palmated plovers (C semipalmatus). 



Oystercatchers, Avocets, and Stilts 



No significant population changes have been 

 detected in the three species of these groups east 

 of the lO.Sth meridian (Table). 



Sandpipers 



This is the largest family of shorebirds. Five 

 species of this family listed in the Table — willet 

 (Catoptrophorus semipalmatus). upland sand- 

 piper (Bartramia lougicauda), long-billed 

 curlew {Numeuius americanus). marbled god- 

 wit (Limosafedoa). and American woodcock — 

 commonly breed in the contiguous 48 United 

 States. Two others, the long-billed curlew, 

 which nest principally in short-grass prairie, 

 and the Ameilcan woodcock found in second- 



