204 CALIFORNIA ACADEMY OF SCIENCES. 



frequently exposed, and when it alights quickly the tail 

 is frequently thrown forward as if the bird had lost its 

 equilibrium for the instant, thus showing this patch of 

 contrasted color. It is without doubt an instance of a 

 recognition character which would be of great use as a 

 directive mark to birds living in the dense underbrush. 



The white patch on the wing of the shiny-crested Ay- 

 csitcher (l^li a i nope plu nitens) is concealed when the bird 

 is at rest, but very conspicuous in contrast to the black 

 of the body when the bird is in motion. The wing 

 band of Townsend's solitaire (Myndesies toumseivJii) is 

 concealed when the bird is at rest, but conspicuous in 

 motion. In many species the white outer tail feathers 

 are folded out of sight while the bird remains passive, 

 but are noticeable the moment the bird starts to fly. 

 Such, for instance, is the case with Junco, Anthus, etc. 

 The subterminal or terminal spots or bars on the tail are 

 always more conspicuous when the bird is in motion 

 than when at rest. 



The grouse, pigeons and hawks, present so many in- 

 teresting modifications of recognition markings upon 

 the tail that it may be worth while to consider them in 

 a little more detail. In the genus Dendragapus the tail 

 is black, tipi^ed with a distinct band of ash gray in the 

 dusky grouse {D. (jbscarvs)^ and with a narrower band in 

 the sooty grouse {D. nhscurus faliginostis)^ which is 

 almost entirely wanting in Richardson's grouse {D. oh- 

 scii I'UN ■richiirilsoiiii). In the Canada grouse (D. canaden- 

 sis) the tail is tipped with ochraceous rufous, while in 

 Franklin's grouse {D. frwnldinli) it is black to the tip. 

 The black tail is doubtless a directive recognition mark, 

 but the modification in the terminal bar is in all proba- 

 bility a character belonging to the class of (2) discrimi- 

 native marks. When, from differences in climate, food, 

 or selective influences two forms occupying adjacent 



