90 TYRANNIDA. 
‘Manual of North-American Birds,’ recognized two forms which he called MM. mexicanus 
and M. m. magister—the former a smaller bird, ranging from the lower Rio Grande 
valley through Eastern and Southern Mexico to Guatemala and Salvador; the latter a 
larger bird, ranging from Southern Arizona through Western Mexico to Tehuantepec. 
As the character of size completely fails to distinguish every individual, and it is the 
only one he relies upon to discriminate his races, we have no alternative but to treat 
them all as one species. The fifty-two specinfens before us seem fully to justify this 
view. Mr. Sclater places these forms under the name of J. mexicanus, and he 
includes with them two birds from Southern Mexico which we hesitate to associate 
with the rest; their general dimensions do not differ materially from the more northern 
bird, but the bills are obviously very much smaller. These two birds undoubtedly 
belong to the true IZ. mexicanus of Kaup—not only do they agree with the description, 
but they have been compared with the type with which they correspond; they are 
again mentioned under the account of the next species. ‘The larger-billed bird is the 
Tyrannula cooperi of Kaup (nec Nuttall), as long ago recognized by Baird ; and it would 
have saved much perplexity if Baird’s suggestion for the employment of this name 
had been followed by subsequent writers. The fact of Muscicapa coopert of Nuttall 
being a synonym of Contopus borealis has caused its rejection in the present case. As 
we now unite the birds of Eastern and Western Mexico, Mr. Ridgway’s name for the 
western bird becomes available. MM. magister is not easily differentiated from the 
South-American I/. tyrannulus; but the northern seems to be the larger bird, rather 
lighter on the back, and with the rump rather more rufescent. These differences, 
however, are very trivial, and were the range of the two birds continuous we should 
hardly hesitate to unite them; but there is a wide tract of country lying between 
Colombia and Honduras unoccupied by this form, thus rendering slight differences of 
more importance. 
M. magister is common in the valley of the Rio Grande and also in Yucatan and the 
islands off the north and east coasts of that promontory. It is much rarer in Guate- 
mala, where we never met with it ourselves, though a specimen from one of Skinner’s 
collections must certainly be referred to it. 
Merrill found it breeding abundantly in the Lower Rio Grande valley, the nests 
being composed of felted locks of wool and hair, and placed not far from the 
ground, either in old holes of Woodpeckers or in natural hollows in decayed trees or 
stumps. 
Mr. W. E. D. Scott speaks of I. m. magister* as common in spring and summer 
about Tucson and other places in Arizona, including the foot-hills of the Catalina 
Mountains up to an altitude of about 4500 feet. A nest found in a deserted Wood- 
pecker’s hole in a dead stump of a sycamore was quite like that of MW. crinitus. The 
eggs also are similar to those of that species but a little larger. 
* ¢ Auk, 1887, p. 17. 
