DIPPER 111 



and young. Since they build tlieir nests on the ground they are endangered by 

 more predators than are the tree nesters. 



Natural selection has developed a remarkable protection for the female 

 Dipper and her brood. During the nesting period and while the young remain 

 dependent, they give no body odor. As most ground-traveling predatory animals 

 depend primarily upon their keen sense of smell, they are in this way effectively 

 disarmed. The survival struggle has made the Dipper's enemies expert hunters, 

 and they acquire an uncanny knowledge of the birds' habits ; thus, though pro- 

 tected in this way, destruction is an ever present menace. 



The pollution of the streams by refuse from mills and by drainage 

 is doubtless destroying some of the dipper's food supply, and driving 

 them farther and farther back into the mountains. Some are driven 

 out by too congested settlements, and many hundreds of them are shot 

 at fish hatcheries. They are too much beloved, as cheerful companies 

 along the lonely brooks, to be molested by the trappers and the appre- 

 ciative anglers. 



Fall. — Fred M. Packard tells me that, in Estes Park, Colo., "the 

 adults and fledglings remain at the higher altitudes until September ; 

 then most of them begin to descend into the lower zones for winter. 

 Stragglers migrate as the upper waters freeze, and some will winter 

 in the park, if the larger streams remain partly free of ice." 



Winter. — The dipper is a hardy mountaineer, indifferent to cold and 

 impervious to it. His thick, downy underwear and his coat of dense 

 feathers keep the cold out and the heat in. He lives all winter as far 

 north, or as high up in the mountains, as he can find any open water. 

 And he sings as freely perched on a cake of ice, or in an icy cavern along 

 the shore, as he does from a rock in his summer haunts. Dr. Nelson 

 (1887) had several brought to him "in midwinter from the head of 

 Norton Sound, during a cold period when the thermometer registered 

 as low as —50° at Saint Michaels, and they must frequently endure a 

 temperature of —60°, or even lower, since in the interior the cold is 

 almost invariably much more severe than along the coast. On the 

 Upper Yukon it is also a resident, whence the fur traders brought me 

 wintering specimens." 



Farther south the dippers are forced to retire from the higher parts 

 of the mountains, as the streams freeze and are covered with snow; 

 then they become more crowded on the lower reaches of the streams or 

 rivers, or resort to the shores of open lakes. At that season they often 

 wander even beyond the foothills. Frank L. Farley, of Camrose, 

 Alberta, tells me that he has "several records of its appearance on rapid 

 creeks in the ranching country west of Innisfail, at least 50 miles 

 distant from the Rockies." And Laurence B. Potter, of Eastend, 

 Saskatchewan, writes me that he has sight records of the dipper "on the 

 swift flowing creeks that form the headwaters of the Frenchman 

 River." 



