MIGRATIONS OF WATERFOWL 



to fire, when agriculture has drained sloughs and potholes, or when the 

 water is gone owing to drought — she must move elsewhere. This happens 

 sometimes on a grand scale. In 1949 a large portion of the mixed prairie 

 country of southern Saskatchewan dried out, and thousands of ducks re- 

 turned to find their breeding grounds untenantable. They evidently settled 

 elsewhere, and Lynch ( 1949 ) says that "it is quite apparent that some ducks 

 moved northward out of the dry grasslands and nested in the wetter Aspen 

 Parklands." Hawkins (1949) detected a late spring influx into Manitoba's 

 pothole country that same year and attributed these delayed arrivals to the 

 Saskatchewan dry-out. Prairie ducks are extremely mobile when compelled 

 to seek new breeding localities, but Hawkins believes that they do not re- 

 produce so successfully after forced moves as when they breed on their 

 home range. It is quite possible that some ducks simply refuse to breed 

 when conditions prove unsuitable, and Kalmbach (letter) suspected this to 

 be the case with the Canvasbacks he studied in the Prince Albert region of 

 Saskatchewan when the nesting grounds were shrunken during the dry year 

 of 1935. 



As in the fall, homeward migration moves on a wide front, and when 

 waterfowl pass over Delta we are aware, by word of cooperators, that similar 

 passages are taking place over other marshes. Merrill Hammond and I 

 noted, for example, that in 1949 the first major waterfowl flight of the year 

 reached Delta, Manitoba, and Upham, North Dakota (150 miles to the 

 southwest), on April 8. Weather may cause regional variations, however, 

 and, as there is a tendency for spring to arrive earlier on the western plains, 

 ducks are sometimes well established in southern Alberta before they have 

 reached this same latitude in Manitoba. 



Each migrant travels homeward with urgency; whatever the barriers 

 of storm, time, or distance, the bird must bring itself to the homeland for 

 which it hungers. Its whole being has an appetite for the range where repro- 

 duction will take place; as the salmon drives relentlessly to the headwaters 

 of the mother stream, so, with its sexual awakening, a duck or goose must 

 satisfy its need for the home marsh. This requirement for a special place or 

 situation falls into the pattern of appetitive behavior (Craig, 1918); "in- 

 ternal factors, sometimes together with external stimuli, activate a 'drive' 

 or an 'urge' in an animal" (Tinbergen, 1952:2), this giving rise to behavior 

 directed toward the attainment of a biological goal.* 



For a further discussion of goals, "consummatory acts," or "consummatory stimuli," see 

 Tinbergen (1951) and Bastock et al. (1953). 



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