100 PROCEEDINGS OF THE ACADEMY OF [1892. 



species on new territory has become permanent. In seeking a cause 

 for this I am led to the belief that it is due chiefly to the introduc- 

 tion of cattle. When we remember that the growth of dense 

 mesquite chaparral, which now forms such a marked feature in the 

 landscape of southeastern Texas, and is steadily encroaching upon 

 the tithe of open prairie yet remaining, is directly due to the graz- 

 ing of immense herds of cattle which have, in their search for sub- 

 sistence, robbed the prairie fire of its fuel and at the same time dis- 

 tributed the seeds of mesquite and other arborescent shrubs, this 

 statement may not appear as paradoxical as it seems. The com- 

 paratively sudden conversion of many square miles of debatable 

 ornithological ground from prairie to brush-land in this manner, 

 would aflbrd just such inducements to arboreal birds in the further 

 extension of their winter range from the north and their summer 

 range from the south as now exist. On the other hand, as the true 

 prairie lands diminish, the more strictly plain-haunting species 

 must disappear. A comparison of the relative abundance of the 

 species noted by Beckham as compared with the same observed this 

 year by Mr. Chapman and myself tends to prove this. Even in 

 1887, the date of Beckham's observations. Dr. Havard reports the 

 mesquite as " shrubby " and Beckham characterizes it as " a dreary 

 waste of cactus," etc. The growth of mesquite in the surrounding 

 country, even since then, will tally well with the faunal changes re- 

 corded, for it must be borne in mind that until, say seven years ago, 

 the overstocking of pasture with cattle and the consequent efiect 

 upon a previously superabundant pasturage did not aflTect the 

 country far from city limits ; so that beyond a comparatively small 

 area surrounding the city, the virgin prairie retained its original 

 features. For this reason birds were scarce, not so much because 

 of drouth, but for lack of shelter and food suited to those of arbo- 

 real habits. Many insectivorous birds are found breeding in locali- 

 ties where water is unobtainable save in the form of dew, and, owing 

 to the juicy nature of their food, they can most likely enjoy life indefi- 

 nitely without the luxury of a drink. It seems therefore probable 

 that the late increase of passerine birds in this part of Texas is due, 

 not to an excess of rainfall, or to the absence of droughts in late 

 years, but to the vast extension of tree-covered areas into the 

 prairie and the increase of insect and vegetable food resulting from 

 this cause ; and these conditions apply not only to the increase of 



