ocT.,]'JOO.] INTRODUCTION. 49 



cut, the duck uiarshcs of North Dakota, or even the balsam thickets 

 of northern New England, the Yukon Valley seems wanting in ])ird 

 life^ — not the center of abundance of its avifauna, but rather a deposit 

 for the overflow from more favored regions. There are exceptions to 

 this rule, notably wandering flocks of crossbills, the colonies of bank 

 swallows of Fifty -Mile and Thirty -Mile rivers and the Yukon proper, 

 the spotted sandpipers that continually flitted across our bow, the 

 intermediate sparrows and j uncos that seldom failed to greet us as we 

 stepped ashore, and the Alma thrushes, whose songs sounded all night, 

 wherever we happened to camp. Bird life is fairly abundant, too, in 

 certain favored places such as Log Cabin, Caribou Crossing, the 

 swampy shores of Lake Marsh, and the ponds and level country at 

 the lower end of Lake Lebarge. Near Miles Canyon I noticed 23 

 species on July 11, but individuals of each, with the exception of bank 

 swallows, were few. In the entire Upper Yukon Valley breeding 

 colonies of shore and water birds were conspicuously absent. The 

 precipitous shores of the lakes, the comparative absence of islands, the 

 swift current of the Yukon, and its high banks cut by narrow, wooded 

 vallej^s, are a sufficient explanation of this; and I can not believe that 

 either geese, ducks, or shore birds ever bred abundantly in most of 

 the region visited, though their number has doubtless been reduced in 

 recent 3'ears. 



In the Yukon flats the condition changes, and no doubt many of 

 these birds find a summer home in the ponds a few miles back from 

 the river, as they do at the foot of Lake Lebarge; but these we had 

 no opportunity of visiting. Our study of the bird life of the Yukon 

 was chiefly confined to what could be seen or heard from our boat or 

 on the banks in the immediate vicinity of camping places. From the 

 lakes to the Alaska boundary snow-capped peaks were absent, and 

 no species were found that did not also occur upon the banks of the 

 river, although we climbed hills, visited deep woods, and ascended 

 small streams for some distance. As we proceeded north, however, 

 several birds were found at lower altitudes than those at which they 

 had been already noted. Away from the river, birds were rarer than 

 immediately upon its banks. 



We learned little regarding the Upper Yukon as a migratory high- 

 way for species breeding farther north, though we heard that thou- 

 sands of geese and ducks passed Lower Lebarge in the spring. It was 

 too late for the spring migration, and the southward movement of 

 ducks and geese had hardly begun on August 20, when we left Circle. 

 The fall migration of the Limicolfe should have been well under way 

 at this date, but very few of these birds were observed. If they 

 do pass in large numbers they must frequent the ponds back from 

 the river. Several times at Circle, I walked a long distance over 

 the sand flats left bare by the falling Yukon without seeing any 

 4494— No. 19 4 



