Vol. XXIII Breninger, Changes in Habits of Birds. 36 1 



1905 J 



used, but after all, its the ' hole ' that is selected and not the tree, 

 be it mesquite, willow or a fence post. I have seen probably a 

 hundred instances of the nesting of this warbler. I find that the 

 majority were in natural cavities in dead parts of living trees 

 — woodpecker cavities in trees and fence posts. The next great- 

 est number place their nests behind pieces of loose bark. In later 

 years we find them appropriating old and abandoned nests of the 

 Verdin (Auriparus fiaviceps) and other species. In one instance I 

 saw a thrasher's nest used. The warbler had built its nest within 

 the cavity of the larger nest. In still another instance a warbler had 

 built its nest in a hole in a bank of earth. The height of surprise 

 was reached in an open nest built among the smaller limbs of a 

 mesquite tree. The material used in its construction was of mes- 

 quite leaves and stems lined with horse-hair, the same as is used 



in a cavity. 



These unusual nesting sites were mostly noted in the vicinity of 

 Tucson, Arizona, where the larger trees had been cut away, and 

 with them all the holes used in former years, and in consequence 

 thereof certain species of birds are forced to adopt other nesting 

 sites and methods of nest building. 



Another instance is that of the Ash-throated Flycatcher {Myiar- 

 chus mexicanus magister). Not capable of cutting its own nesting 

 cavity, it preempts those cut by other species, chiefly woodpeckers. 

 With the destruction of the larger trees, Myiarchus is forced to 

 look elsewhere for a location. Unusual among nesting sites of 

 this species is one in a tree yucca, the hair-lined nest being built 

 among the hanging leaves close to the trunk, where the sitting bird 

 could look out upon the world through the lattice work of dry leaves. 

 Another instance is where a pair made their home in a barn, the 

 eggs being deposited in a nest of hair built on a cross beam on the 

 side of the barn. Entrance was gained through a hole cut by a 

 Flicker. 



Every one is familiar with the swallow's nest beneath the eaves 

 of the house, both of Cliff Swallows (Petrochelidon lunifrons) and 

 Barn Swallows (Hirundo erythrogastra), and to-day few people can 

 tell of seeing nests of Barn Swallows in any other place than 

 under the protection of some of man's structures. In the case of 

 the Cliff Swallow, many colonies still cling to the primitive method 



