Pecos, and scarce to rare elsewhere. Most are present between late October and 

 May, with extreme dates of occurrence of 21 October and 16 June. Summer strag- 

 glers are occasionally recorded both inland and along the coast. Oberholser 

 (1974) indicated that most Common Mergansers occur on fresh water, and only a 

 few are seen on brackish inlets and bays. 



SYNOPSIS OF PRESENT DISTRIBUTION AND ABUNDANCE 



Breeding In North America, most Common Mergansers breed from southern Al- 

 aska east across Canada to James Bay and across the Labrador Peninsula to New- 

 foundland, south in the western mountains to California and Colorado, and east 

 to the Great Lakes States and New England (AOU 1957, Palmer 1976b). They oc- 

 casionally breed south of this range; some records attributed to the more marine 

 Red-breasted Merganser may apply to this species. 



Bellrose (1976) estimated that the summer population of Common Mergansers 

 in North America may be as high as 641,000 birds. Johnsgard (1978) cautioned 

 that these estimates are based on uncertain assumptions, and suggested that this 

 figure may be an overestimate. Palmer (1976b) believed that the total popula- 

 tion in North America was small compared to populations of other ducks and prob- 

 ably consisted of no more than several hundred thousand birds. The principal 

 breeding grounds are apparently in the closed boreal forest from Alberta to Lab- 

 rador (Bellrose 1976). Breeding populations are much smaller in Europe and are 

 poorly known elsewhere. Some of the larger breeding populations reported by 

 Cramp et al. (1977) are as follows: 500-1,000 pairs in Great Britain, ca. 4,000 

 pairs in Finland, 1,300-1,400 pairs in the Baltic area of the U.S.S.R. , and 

 1,500 pairs in Estonia. 



Winter Most North American Common Mergansers winter from open waters 

 within the breeding range south to a line extending eastward from southern Cal- 

 ifornia through northern Texas to southern South Carolina (Bellrose 1976). Old 

 World populations from some areas (Iceland, Great Britain) largely winter with- 

 in the breeding range; other populations are more strongly migratory and occur 

 south to the northern Mediterranean, the Caspian Sea area and the Persian Gulf, 

 northern India, southeastern China, and Japan. 



Bellrose (1976) estimated that the wintering population of the North Amer- 

 ican Common Merganser was about 165,000 birds, the majority wintering in the 

 interior of the continent. He indicated that the largest wintering populations 

 were in Oklahoma (30,000 birds), Illinois (ca. 20,000), Ohio (12,000), eastern 

 New Mexico (12,000), Kansas (10,000), Nebraska (9,000), and upstate New York 

 (ca. 6,000). The status of the Common Merganser in the coastal waters of the 

 southeastern United States is inadequately known because of difficulties in 

 distinguishing it from the similar and more numerous Red-breasted Merganser. 

 Bellrose (1976) indicated that Common Mergansers are generally uncommon in the 

 southeast; only a few hundred are found along the Atlantic coast between Vir- 

 ginia and Florida, and less than a thousand winter south of Tennessee and Mis- 

 souri. 



Cramp et al. (1977) listed estimates for wintering populations of Common 

 Mergansers in northwestern Europe: 75,000 in the Europe/Black Sea/Mediterranean 



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