98 U. S. NATIONAL MUSEUM BULLETIN 217 



Robins have been observed nesting at Umiat on the Colville River 

 (Karplus, 1952) . We have found them conmion in the Killik Valley 

 in summer, and I have seen them in migration in the upper Noatak 

 Valley and at Howard Pass. The conspicuous flocks seen about Sum- 

 mit in early September best indicate the large numbers of robins 

 which have summered in the arctic mountains and among the larger 

 willows of some of the more northern valleys. Because their range 

 of terrain is limited, the total arctic tundra population of robins is 

 locally conspicuous but not comparable with the numbers of the com- 

 monest birds. 



While searching for the races of Ball's sheep high among the moun- 

 tains along the Macmillan River in Yukon Territory, Sheldon (1911, 

 p. 127) remarked upon the numerous passing flocks of migrating 

 robins and noted that the last was seen on September 19. 



In early summer, robins take poses nearly as conspicuously statu- 

 esque as are those of the golden plover. They sing cheerily, but to my 

 mind much more weakly in the northeastern States, where, however, I 

 heard them with younger ears. Tliey appear vigorous and interested 

 in their arctic environment but unhurried by anxiety for the short- 

 ness of the summer and the remoteness of their winter quarters, con- 

 cerns which are in the usual thoughts of human strangers although not 

 apparent in normal arctic residents. 



Combative against other robins intruding upon their nesting terri- 

 tory in the early part of the season they later become increasingly 

 noisy toward any potentially dangerous enemy to their young. As the 

 young grow larger, other pairs from adjacent regions join in these 

 disturbances with as much singleness of purpose as if nothing but the 

 commotion among robins were important. Their excited calling and 

 generally conspicuous parental solicitude draws attention to the pres- 

 ence of the young birds, whose answering youthful calls precisely lo- 

 cate their position. Whether these parental demonstrations are, on 

 the whole, effective in protection of the young I cannot say. To me 

 they illustrate such an exaggeration of parental solicitude as would 

 attract a predator. Sometimes the social demonstrations of robins 

 are joined by birds of other species, but a pair of robins can seriously 

 trouble a marauding shrike so that his only safe tactic is to seize a 

 nestling victim in a stealthy dash and hope to get out of range intact. 

 In judging the interaction of animals we must recall that feeble birds 

 sometimes pursue and obviously discomfit large predators, and that 

 unexpected occurrences often disturb large mammals to flight. A hu- 

 man hunter can be much alarmed by strange sounds heard in dark- 

 ness when there is insufficient sensory information available for rea- 

 soned calmness. Animals must often be mentally unstable in the dark- 

 ness of their unreasonins: minds. 



