Leap-Frog and Other Migration Patterns of Waders: A Critique of the Alerstam and Hogstedt Hypothesis, and Some Alternatives

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Abstract
Alerstam and Hogstedt (1980) proposed an explanation for leap-frog migration: the wintering of northern-breeding populations of some species in areas further south than those from more southerly breeding area. They suggested that there is strong selection on birds breeding in areas with marked between-year variation in onset of spring to remain during winter in the same climatic region so that they can respond quickly to favorable conditions; and that this is not possible for artic-breeding birds, which obtain no extra advantage in wintering in the northernmost parts of the possible non-breeding range. They unnecessarily complicated their argument by claiming that the onset of spring is generally less variable between years in arctic than in temperate regions: other studies cast doubt on this. Alerstam and Hogstedt''s hypothsis is challenged, particularly in respect to waders on which it is based on several grounds; namely the following assumptions: that there is a premium on birds in all areas starting to breed as early as possible in spring; that birds wintering in the same climatic region as the breeding area detect suitable conditions before migrating, and adjust their time of departure accordingly; and that longer migrations add little to the cost of migration. Alerstam and Hoegsedt''s reinterpretation of Pienkowski and Dick''s (1975) study of dunlin migration is unsound and problems in several of the other examples cited in support of their hypothesis are noted. Other factors which could lead to the observed migration patterns of shorebirds in western Palearctic and adjacent areas are discussed. [Birds studied were Calidris alpina, Pluvialis apricaria, Charadrius hiaticula, Tringa totanus, Calidris canutus, Philomachus pugnax, Limosa limosa.].