MIGRATIONS OF WATERFOWL 



tied to a single period of the annual life cycle. More than this, breeding be- 

 havior is divided into certain divisions of the reproductive cycle; as spring 

 advances, there is a sequence of sexual appetites. Some of these may be 

 given in chronological order: the urge to take a mate, consummated when 

 the pair is formed ; the appetite for home range and territory, satisfied when 

 the home marsh is reached; the need to incubate, appeased when the clutch 

 is completed. Normally the sexual behavior progresses step by step in an or- 

 derly fashion until nesting is finished and the young reared. Sowls (1949) 

 showed, however, that if one link in this chain is broken, the duck may 

 revert to an earlier stage in the cycle. When the nest is destroyed, for in- 

 stance, the female often returns to egg-laying; if her mate has by then 

 departed, she may go back still another step and seek another drake as her 

 partner. 



For migratory waterfowl the appetites of the sexual cycle arise on the 

 wintering waters at a time when the breeding marshes are still in the grip 

 of frost. The first reproductive goal, taking the mate, may be attained in 

 early winter or, sometimes in the Mallard, during autumn. Later, drake 

 and hen migrate together. Her appetites now are for acts that can be con- 

 summated only at a special place, the familiar home range. He hungers for 

 behavior which is to be activated only after his mate has settled down on 

 her home range, part of which becomes his defended territory. In some fe- 

 males the appetite for the breeding place may be aroused before she selects 

 her mate, and she migrates unmated, although usually attended by several 

 suitors. 



Eagle Clarke ( 1912 ) , aware of the sexual nature of homing migration, 

 suggested that "the periodic physiological changes in progress at the ap- 

 proach of spring in the shape of the development of the reproductive organs, 

 with their corollary, the reviving instinct of procreation, must prove an over- 

 powering incentive to seek accustomed breeding haunts." The pioneering 

 experiments of Rowan (1926, 1929a, 1931) demonstrated the intimate relation 

 between sexual awakening and homing migration. Inner stimuli of a sexual 

 nature awaken the appetite for the home, which may be attained only by 

 migration.* Fundamentally this drive-to-goal pattern of homing migration 

 differs from other appetitive behavior in the sexual cycle only in terms of 

 time and space. The distance from loafing bar to nest may be only a few 

 minutes and yards ; the distance between wintering waters and home marsh 



• Since Rowan's original studies there has developed some confusion concerning the exact 

 endocrine seat of these stimuli; but it is not denied that the migrational homing of spring is a 

 sexual act. See Farner (1950) for a careful review and bibliography. 



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