SEASONAL FLIGHT OF DUCKS 183 



had nested elsewhere. It is a well-known fact that 

 drakes in most of our species of ducks desert their 

 mates shortly after incubation of the eggs is begun. 

 These males, particularly in some of the surface- 

 feeding ducks, congregate at once in large flocks, 

 and may at this time migrate to favorable localities 

 where they pass the remainder of the summer. At 

 the mouth of Bear River male pintails and mallards 

 begin to congregate in these post-breeding bands 

 at the end of the first week in June, and continue 

 to gather from that time until autumn. By the end 

 of June it was not unusual to find two thousand 

 pintails or more in one flock, and their number in- 

 creased regularly with the advance of the season. 

 A careful canvass of the vicinity in May showed an 

 average local breeding stock of only one hundred 

 pairs of this species, so that the majority of these 

 recreant benedicts had come from other regions, 

 how far distant we may not say. It is interesting 

 to note that observers in central and northern 

 Canada and in Alaska have commented on summer 

 flocking in this species with subsequent disappear- 

 ance of a part, so that some of the Bear River birds 

 may have come from a long distance. This, how- 

 ever, for the present is purely speculation. 



Summering bands of males moult at once into 

 dull summer or eclipse plumage, and then shed the 

 flight feathers, becoming flightless for a period, 



