48 



NORTH AMERICAN FAUNA. 



forms just named. Some specimens of insularis are much nearer 

 typical aglaice in color than albiventris. Females of insularis are more 

 distinct from those of aglaice than the males, owing to their generally 

 grayer backs, but even this is not a constant character. The only 

 character of insularis that is fairly constant is the smaller bill; a curi- 

 ous development, since there is a general tendency to an increase in 

 size of bill among Tres Marias birds. 



Measurement? of Platypsaris aglaice and its races in Mexico. 



Tyrannus melancholicus couchi (Baird.) Couch's Kingbird. 



On Maria Madre Island ten or a dozen of these birds were seen and 

 appeared to be resident. Two or three were noted on Maria Magdalena, 

 and others on Maria Cleofa, where they were most numerous. They 

 were always found near the seashore. The specimens obtained seem 

 to be identical with those from the adjacent mainland. Asa rule birds 

 from northeastern Mexico, the type locality, are lighter than those from 

 western Mexico, but this difference is not constant. 



Myiarchus mexicaiius magister Ridgway. Arizona Crested Flycatcher. 



Although resident on all the islands, birds from the Tres Marias are 

 almost identical with those from the mainland, and nothing distinctive 

 was noted in their habits. They frequent the thinner parts of the 

 scrubby forests which cover most of the slopes, but were most numer- 

 ous within a mile or two of the sea. They kept among the low trees, 

 usually perching on tops of bushes or on branches within 10 or 15 feet 

 of the ground, where they watched for passing insects. 



Myiarchus lawrencei olivascens Ridgway. Olivaceous Flycatcher. 



This was much more abundant than the preceding species, and one 

 of the commonest and most generally distributed resident birds on the 

 islands. Like the preceding, it was most numerous in the scrubby 



