CANON WREN 553 



great an altitude, and whether they would have wintered there, were points 

 not determined. It is possible that here was a case of local wandering 

 after the close of the nesting period. 



The preferred habitat of the Caiion Wren consists of broken rock sur- 

 faces, such as abound in parts of the region ; yet fallen logs, old buildings, 

 and even inhabited houses come within the forage range of certain indi- 

 viduals. No satisfactory estimate of numbers can be given, because of 

 the irregularity in the occurrence of suitable surroundings. At Pleasant 

 Valley 6 individuals in different directions could be heard during a certain 

 10-minute walk ; in Yosemite Valley 2 singing males were sometimes within 

 hearing at one time ; elsewhere the birds are as a rule much more widely 

 scattered than indicated by the observations just cited. 



At El Portal a Canon Wren frequented the cabin in which our indoor 

 work at that station was done. The bird would come in at various hours 

 of the day and proceed to zigzag about the floor, pursuing flies and spiders. 

 It would poke bill and head into crevices and at times even crawl all 

 through the space between the inner and outer walls of the drafty build- 

 ing. At Pleasant Valley, in May, 1915, the station house was similarly 

 tenanted, and the agent there complained mildly that the birds, hopping 

 across the desk and tables, interfered with his work. 



Crevices and crannies in rock walls and caverns and openings between 

 talus rocks are explored to their limits by the birds. Like the Rock Wren, 

 the Canon Wren has acquired a special flatness of body structure, which 

 is an obvious adaptation to allow it passage through horizontal crevices. 

 This is a quite different adaptation from that in a rail, whose narrow 

 compressed body, thin from side to side, allows progress through the 

 vertical interstices among standing reeds. 



Were the Caiion Wren less active, its disruptive scheme of coloration 

 would be exceedingly effective in rendering it inconspicuous ; but its almost 

 incessant bobbing movements make the bird easy to see against almost 

 any tone of background. Even in the dark recesses of a deep cavern the 

 white throat patch is, because of this motion, surprisingly conspicuous. 



When foraging, the Caiion Wren travels apparently with equal facilitj'' 

 on rock, earth bank, and w^all of building; it moves by short hops of two 

 or three inches, and usually changes direction, or zigzags, with every few 

 of these 'hitches.' The bird's legs (tarsi) are short and are held at an 

 acute angle with the surface on which it is traveling, so that the body is 

 close to the substratum. At intervals of two to twelve seconds the hinder 

 parts are slowly raised and then instantaneously depressed. So quickly 

 and violently is this done that the whole body is drawn into the movement. 

 This is the characteristic bobbing referred to above. 



