BIRDS. 



480 



white-tailed ptarmigan, reaching east into Minnesota and Iowa. It is 

 mottled above and white below, and on either side of the neck is a blue 

 air-sac, which is called into play in making their strange, booming, deep 

 bass note, sounded in the breeding season. When the cry is uttered, the 

 birds, male and female, gather in some favorable spot, and then begins the 

 ' dance.' One author describes it as a regular ' walk around ' as ludicrous 



Fig. 412. — Willow-ptarmigan (Lagojms albus) , in summer plumage. 



to the disinterested observer as some of the performances on the comic 

 stage. The males strut around with the wings spread, the feathers all 

 erect, the tail straight in the air, the head nearly resting on the ground, 

 and the vocal sacs inflated and displayed to the utmost. And so the affair 

 goes on, with its display, its strutting, and its occasional battles, until all 

 the birds are mated. 



When this affair is over, nest-building is in order ; and such care as 

 they exhibit to conceal their home is seldom excelled. It is artfully 



