54 The Ruffed Grouse 



tion (as contrasted to the cases where the hen is killed away from the 

 nest) have all been in the early stages of incubation or before egg- 

 laying was completed. It is rarely possible conclusively to prove 

 willful desertion since it is usually conceivable that the hen may 

 have been killed and her remains not located. It is true, however, 

 that the will to stay with a nest is weakest at the beginning and 

 strengthens rapidly. It never is absolutely complete. If the setting 

 bird is disturbed enough she may desert at any time. In oiu experi- 

 ence in trapping and marking setting females about a week before 

 hatching time about one bud in twenty would not return to the nest 

 after release. 



Renesting is the building of a new nest and laying of a second 

 clutch of eggs after the first nest has been destroyed. If the nest is 

 broken up before two weeks of incubation the probability of renest- 

 ing is fairly good. If the nest is broken up after two weeks of incu- 

 bation, and most destroyed nests are, there is practically no possi- 

 bility of a second nest. This is due to the loss of the urge to breed 

 so late, by both sexes. Explamed in terms of the sex rhythm, the 

 probability of both hen and cock reaching the mating stage of the 

 sexual cycle together after about the third week of May is almost 

 none. Second nests that are made following early season nest losses 

 are always in a new location, have fewer eggs than first nests and a 

 higher proportion of infertility. In most cases the later the second 

 nesting, the smaller will be the clutch, and the higher the number 

 of infertile eggs. 



Dust Bathing. Dust bathing by the brood has already been dis- 

 cussed. This practice is just as necessary for the adults as it is for the 

 chicks, for it seems to be a requisite for proper maintenance of the 

 feather coat as well as for normal feather growth. Grouse grown or 

 held in captivity without benefit of dusting facilities usually develop 

 a ragged coat. Dusting is done mostly from spring to fall with the 

 greatest activity in the summer. Little dusting is done in the winter 

 for lack of opportunity, but if the ground allows them to do so they 

 will dust all year round. The increase in dust bathing in the summer 

 lends weight to the supplementary theory of need for elimination of 

 ectoparasites, although whether this is a primary reason for dusting 

 is doubtful. The same bath is used repeatedly although one bird may 

 have several in different places. 



