AWARENESS OF TIME AND SPACE 



known the wind to start the morning birds before the break of light, but 

 a noon wind usually sends the fowl to the fields earlier than they choose to 

 go on calm days. The afternoon flight continues longer, always lasting more 

 than an hour and frequently consuming several hours. After the first ducks 

 appear, there is a steady passage, so that on a heavily used flight line the 

 supply of birds sometimes seems inexhaustible from early afternoon until 

 sunset. 



I suspect that the timing of the afternoon flight is related to metabolism. 

 Assuming that a Mallard takes its meal at the same time each morning, it 

 is reasonable to believe that hunger must be felt at about the same time 

 each afternoon. The ducks do not return to the fields while breakfast is still 

 heavy in their gizzards; but once digestion has progressed to the point of 

 hunger, this stimulus urges them to the prairies for a second meal. The wide 

 spread of the afternoon movement is further evidence, I believe, of the role 

 of hunger. In the dawn flight, all are pressed at about the same time by this 

 common urge. Once on their way, however, they are not equally successful 

 in taking their meal. Some find a close, safe, and abundant food supply, 

 then return quickly to the lake. Others are disturbed by hunters or by farm- 

 ing activity, and they must fly to a second or a third farm. All do not travel 

 the same distance to feed. It is plain that each band does not breakfast at 

 the same time ; hence, although the first are returning to their loafing bars 

 before sunup, others, not so fortunate, drift back to the lake all through the 

 forenoon. So it seems that these morning variations must cause the differ- 

 ences in the timing of the afternoon flights. Birds that come back from the 

 fields early are probably the first to go out in the afternoon. 



The second passage moves in the full light of day. When the shooting 

 season arrives, however, ducks feeding in areas heavily hunted sometimes 

 delay their meal until dusk. South of the village of Delta, where there is 

 much gunning, I have found ducks waiting until sunset before venturing 

 to stubble. Several miles farther west, where the hunting pressure is less 

 severe, the birds feed earlier and return to the lake before sundown. The 

 Delta Mallards apparently shift from "gizzard" time to sun time. 



I have spoken only of the Mallard, but of course the Pintail and a small 

 number of Black Ducks, mixed with the Mallards, make regular flights to 

 the stubble, following a schedule like that described for the "greenheads." 



It seems clear that the timing of stubble flights follows two types of 

 cues : the metabolic cue and the solar cue. The former is measured by the 

 interval between the filling of the bird's crop and the first hunger. If food 



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