PALAEARCTIC ELEMENT IX NEW WORLD AVIFAUNA 423 



on this continent in the sense that there is no known breeding 

 population, but which occur here from time to time as so-called 

 accidentals or casuals. It is here we encounter some of the "unsolved 

 problems" appropriate to mention in a symposium with the general 

 title, "Some Unsolved Problems in Biology, 1957." 



In discussing the so-called accidentals, particular attention will 

 be paid to the Transatlantic species. Fewer Transpacific crossings 

 can be expected for obvious geographic reasons, and a stray Asiatic 

 bird might easily be overlooked along the Pacific Coast of North 

 America, which is much less closely scrutinized by bird-watchers 

 than is the Atlantic Coast. 



It is widely known that American birds occur in western Europe, 

 particularly the British Isles, far more often than European birds 

 appear in eastern North America. Peterson, Mountfort, and Hollom 

 (1954) list 41 American species or subspecies of non-pelagic, non- 

 introduced birds as accidental in western Europe. The American 

 Ornithologists' Union Check-list of North American Birds (1957), 

 hereafter referred to as "A.O.U. Check-list," lists 24 such species 

 or subspecies from Europe as accidental in eastern North America. 

 And even the comparative figure 41 versus 24 is misleading, since 

 the actual number of individual occurrences of accidental birds is 

 much higher in Europe than in North America. Alexander and 

 Fitter (1955) listed 260 authenticated records of North American 

 herons, cranes, rails, and waders alone in western Europe, and an 

 additional 126 records of land birds. The figures for European 

 accidentals in North America would be far fewer, particularly since a 

 substantial number of these are among the ducks, gulls, and other 

 families not included in the figures given by Alexander and Fitter. 



There is no great mystery here, as the prevailing winds across the 

 North Atlantic are predominantly from west to east. The unsolved 

 problem in this case lies with the species that do manage to get 

 across to the western side of the Atlantic with some frequency. 

 Six species of palaearctic water birds occur along our Atlantic 

 seaboard with such regularity that a large percentage of the bird- 

 watchers of Long Island and New England are familiar with them, 

 and keep an eye out for them every year. Two are ducks, the 

 European Green-winged Teal {Anas crecca) and the European 

 Widgeon {A . penelope) ; two are sandpipers, the Curlew Sandpiper 



