a4 THE Sl'ECIES ITS TAXONOMY, RANGE, BIOLUGY, & ECONOMIC IMPORTANCE 



appears that this is the only period during the course of the year when an actual moult oc- 

 curs which is not followed ininiediatel) h\ feather replacement. Dwight refers to this as the 



post-nuptial moult. 



Most feathers which droj) at this time are not renewed until f;di. Il seems logical to assume 

 that su<h sloughing of feathers adjacent to the spaces serves to assist in regulating body 

 temperature, since grouse as well as other birds lack the ability to perspire. Penned birds 

 are commonly observed during the warm sunnncr nmntlis panting nun ii like a dog. with 

 wings and body feathers distended, making it possible for air to circulate more freely over 

 the body. 



The reverse mav be equally true during the winter months, uiicii the feathers about these 

 areas are more abundant and arc held more tightly together to insulate the body and conserve 

 heat. 



Ace Identification Based on Feather Development 



Many are the times researchers and sportsmen alike have desired to know within reason- 

 able limits the age of young birds collected or found dead in the field. Ofttimes, too, the 

 question arises whether the bird is one hatched during the present year or is over a year old. 



Regarding the latter, there are two well known methods of determining whether a specimen 

 is a bird of the year or older. The first of these, which requires dissection, is based on the 

 presence or absence of the bursa Fabricii* and therefore is outside of the province of this 

 study. The other and more readily available method (although less positive) is based on 

 examination of the first two primaries or flight feathers. 



As will be shown later, these two feathers develop in the form of juveniles and are not 

 moulted until the year following hatching. The other primaries in the adult |ilumage have 

 rounded tips while the tips of the two mentioned are pointed, conforming in character to 

 the other juvenile remiges previously moulted. 





\V\ V 



\ 





V 



«.J>^ 







With respect to tiic rclalioM>iii|i nf pluniagc dcvclopinciU to the age of tiic ( iiick dining 

 the brood period, an attempt has been made to describe the principal features to be looked 

 for each week from hatching until the bird may be considered adult. Figures P. and ') cor- 

 respond to the age intervals reiognized and show graphically the develoiunenl ol ihc lliiihl 

 feathers which, owing to their regularity of n-placcnicnl. fiirnisli the most conxcniciit iiiilcx 

 for this purpose. 



* Set- diBcuBsioii ul Analoiiiy, p. 739. 



