376 BULLETIN UNITED STATES GEOLOGICAL SURVEY. [Voir. 



that bird), and the geographical distribution of the various species south 

 of our border is as yet unknown. 



I mention the different forms of the same genus found on our southern 

 border to show how distinct are those of the Lower Eio Grande from 

 those of the Upper Eio Grande and Colorado Valleys ; the one nowhere 

 intruding upon the habitat of another, unless it may be in the case of 

 the Yellow-headed Tit, A. flavicevs. ISov are the lines of geographical dis- 

 tribution less noticeable in other families of birds, the Thrushes varying 

 quite as distinctly in different localities along the border. 



During this trip I saw more of the Black- crested Tit than on the 

 former one, owing to my being more favorably situated to study it in its 

 haunts. On arriving at Lomita, one of the first familiar birds to greet 

 me was this Titmouse. It was one of the very few birds of those found 

 in numbers on the former trip, whose eggs I did not obtain, being suc- 

 cessful only in discovering a nest with young. It was essential to find its 

 nests without delay on account of its commencing to breed earlier than 

 any other species found in the locality. Orders were given to shoot none 

 of this species, but to search diligently the trunks and stubs of trees 

 for nests. In a few days, several nests were found, all containing 

 young. It was a great pleasure to me, therefore, when, on April 20, 

 my assistant, Mr. Sanford, placed upon my table a nest, five young, 

 and a perfect egg of this species, together with the parent bird caught 

 on the nest. The chicks I preserved in spirits ,• the Qgg, being infertile, 

 was easily prepared ; and both, together with the nest and bird, are in 

 my collection. This, I believe, is the first thoroughly identified egg of 

 this bird brought to scientific notice. The bird taken on the nest was a 

 male, and other males were shot having bare and wrinkled bellies, show- 

 ing that both sexes share in the incubation and care of the young. The 

 nest was situated some six feet from the ground, in a hollow limb of a 

 half-dead willow, which was leaning on some brush, and was discovered 

 by the bird's flying into its opening. It lay some ten or twelve inches 

 from the opening, and is composed chiefly of wool intermixed with 

 strips of soft inner bark, and now and then bits of snake-skins ; the 

 whole being much firmer and thicker than is usual with nests that are 

 built in hollow stubs. All the other nests found with young were 

 situated higher, with one exception ; the distance varying from four to 

 twelve feet from the ground. I found them to occupy usually the 

 abandoned holes of the Texas Woodpecker, Picns sealaris ; but split 

 forks of trees were sometimes put in use. They prefer living, trees to 

 dead ones, and in every case in my exj)erience the opening had to be 

 enlarged, sometimes with diflElculty, before examination of the nest could 

 be made. The localities mostly selected for nesting are groves or open 

 timber free from undergrowth, whether in old lagoon beds, which re- 

 ceive the overflow from the river, or on the driest knolls. They do not 

 avoid human habitations, as two nests were found on the ranch in 

 ebony- trees, near buildings much frequented. The parents guard their 



