Pelagic Wandering 



Many of the pelagic birds observed off our coasts or at sea appear to 

 be nomadic when they are not breeding. These movements are not 

 necessarily at random because there is usually a seasonal shift in the 

 population, often for great distances and in specific directions, away 

 from the breeding area after completion of the nesting cycle. Also the 

 return from the sea to nesting areas is at a definite time of year. This 

 may not be true migration in the classical sense (Thomson 1964), 

 although it is similar in most respects. 



Because of the extensive and often inhospitable habitat of pelagic 

 birds (to human observers at least), observations on their movements 

 are difficult at best and accurate records are few. We do know some of 

 these species have regular routes (e.g., Arctic terns) and specific 

 patterns of migration (e.g., the loop in the short-tailed shearwater). 

 As more knowledge is accumulated on the "nomadic" species, we may 

 actually find they too have regular migration routes based on 

 biological needs. 



Movements of some of the tubenoses (Order Procellariiformes, that 

 includes albatrosses, fulmars, shearwaters, and petrels) have been 

 correlated with ocean currents, prevailing winds, temperatures, and 

 general water fertility (Kuroda 1957; Shuntov 1968; Fisher and 

 Fisher 1972). Commercial fishermen have long known ocean 

 currents are very important factors in the supply of nutrients, 

 plankton, and forage fish for larger fish. These same foodstuffs often 

 attract pelagic birds as evidenced by the tremendous concentrations 

 that occur off the Peruvian coasts where the upwelling of cold 

 nutrient-bearing water is evident. Kuroda (1957) found some fine 

 correlations between the route of the short-tailed shearwater and 

 ocean currents. Likewise Shuntov (1968) found the migratory routes 

 of albatrosses were over temperate marine waters of high biological 

 productivity. The Laysan albatross was correlated with cold 

 currents, while the black-footed albatross occurred over warm 

 currents. Many Southern Hemisphere pelagic species have been 

 extremely successful in exploiting rich northern waters during 

 the summer; the group is probably the most abundant and 

 widespread in the world (Bourne 1956). 



Leap-frogging 



When two or more races of the same species occupy different 

 breeding ranges on the same axis as migratory flight, the races 

 breeding the farthest north often winter the farthest south. Thus, a 

 northern race "leap-frogs" over the breeding and wintering range of 

 the southern populations. This has been well documented in the fox 

 sparrow discussed previously (Fig. 10) and is exhibited by races of 

 Canada geese breeding in central Canada as well. One of the smaller 

 races of this goose breeds along the Arctic coast of the Northwest 

 Territories and winters on the Gulf coast of Texas and northeastern 

 Mexico, while a much larger race breeds in the central United States 

 and Canada but winters in the central part of the United States. This 



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