224 BULLETIN 195, UNITED STATES NATIONAL MUSEUM 



catchiiij,' tlKun In the nt^sts I am confident that they were made use of at such 

 times as shelters from the storm and probably also as roosting places. It would 

 also appear that several of the nests were repaired and used during the winter 

 by the same pair of wrens. 



Upon coming to the Pacific Coast I was immediately impressed with the differ- 

 ence in the nesting habits of the species as seen in Soufheru and Lower California, 

 and in the higher regions of New Mexico and Arizona. I am iinfortunately with- 

 out a series of measurements of the nests of the two regions, but am safe in saying 

 that the bird of the coast region builds a smaller nest, especially noticeable in its 

 nmch shorter covered opening, which in fine specimens from the interior (New 

 Mexico and Arizona) frequently measures from twelve to fourteen inches in length 

 and is supported by being built along a horizontal branch of cholla cactus or 

 tJiorny bush. California nests are seldom or never, as far as my experience goes, 

 found in colonies. Two or more nests are sometimes seen in the same thicket of 

 cactus, but in such case each nest is used by a pair of birds, there being no supple- 

 mentary nests to be used as lodging-houses, as would appear to be the case in the 

 interior, nor have I any evidence of the nests in mild coast region being rebuilt for 

 use in winter. 



Tlie last sentence illustrates the danger that lies in the drawing of 

 negative conclusions, even by the most competent observers. Certainly 

 those inferences are not true in all southwestern California, and in view 

 of the general use of nests as night roosts by other species of this genus, 

 even in tropical latitudes, as described by Alexander F. Skutch (1940) , 

 it seems unlikely that there would be local deviations from this habit. 

 The more scattered distribution of the California nests may be in part, 

 at least, a matter of suitable sites. 



In constructing the framework of the nest, the bottom is first laid, 

 then the vaulted upper part is fashioned, and finally the entrance 

 tunnel is added. It is often impossible to determine exactly which 

 direction the entrance will face until the exterior of the nest is almost 

 finished, as the tunnel may be either straight or rather sharply curved 

 to one side. This tunnel, whose inner end is about even with the ceiling 

 of the nesting cavity, may be nearly horizontal, but usually it slopes 

 more or less steeply down into the interior of the nest. In the many- 

 branched "chollas" the tunnels are often so cleverly placed that the 

 branches form an encircling support and a convenient doorstep. The 

 building proceeds rapidly and would be completed in a short time were 

 it not that the work is conducted rather spasmodically, with long 

 intervals of apparent neglect. The lining of the nest is a more tedious 

 process and doubtless entails extended search for suitable materials, of 

 which feathers seem to be most favored, though kapok or cotton will be 

 used if found. Many abortive attempts at nest-building are made, the 

 nests being abandoned at various stages of construction when the birds 

 apparently decide to choose another location. 



Despite the accessibility of most cactus wrens' nests, a study of their 

 family affairs is not easy. The contents of the nest are seldom visible 

 through the entrance tunnel, which is directed toward the upper part 

 of the nesting cavity and is often curved or bent at a right angle, while 



