54 SYLVIID^. 



The bird, a male, was found in scrubby wood near the roadside. The following year 

 Mr. Owen obtained a female bird with its nest and eggs in the same locality. The 

 nest, a very neat compact structure, was composed outwardly of dried stalks of grass 

 and roots, with a coating of cobweb and other adhesive materials. The lining consisted 

 of the feathery parts of seeds, horsehair, and fine grass ; the whole structure measured 

 If inch across the inside and 1-| inch in depth. This nest was situated in low 

 brushwood, almost under the eaves of one of the ranches. The eggs are white, spotted 

 with red, principally of two shades, the spots increasing in number towards the obtuse 

 end; they measure — axis 0-6, diam. 0"45 in. 



Besides these typical birds, the male of which has the lores white, but no white 

 supercilium, though a few white feathers are to be seen in this region in the type 

 specimen, we have seen similar ones from the Isthmus of Tehuantepec, where Prof. 

 Sumichrast observed them in May and December, 



Having thus given some account of the three forms of black-headed PolioptilcB found 

 in Central America (P. nigriceps with the lores wholly black, P. alhiloris with the lores 

 white, and P. Mlineata with both lores and superciliaries white), it remains to consider 

 the position of certain specimens which seem to have intermediate characters connecting 

 two or all of these forms together. These birds were obtained, with a female of the 

 true P. Mlineata, near La Union in San Salvador, and have the lores black, with a 

 few white feathers intermingled. They were once attributed by us to P. huffoni — that 

 is, the Colombian bird we now consider to be the same as P. nigriceps ; and they are 

 undoubtedly as closely allied as possible to that bird ; Prof. Baird, however, preferred 

 to call some of them P. albiloris. Putting P. alhiloris aside, and observing the ditribu- 

 tion of P. nigriceps and P. Mlineata, we find the curious fact that the ranges of these 

 two forms actually cross one another, and that the area where P. Mlineata comes into 

 contact with the northern section of P. nigriceps corresponds more or less to that occupied 

 by P. alUloris, at once suggesting the supposition that P. albiloris is not a true species 

 at all, but due to the intermingling of P. Mlineata with P. nigriceps, and, further, that 

 technically these last-named birds are not true species either. The way the present 

 state of afiairs has come about may have been as follows : — Formerly P. nigriceps was 

 the only form which was found from Colombia to Mazatlan. The form of Western 

 Ecuador, P. Mlineata, then began to spread, pushed out or more probably absorbed 

 P. nigriceps in Panama and Costa Pica, where now only pure-blooded P. Mlineata are 

 found. In San Salvador and Central and Western Guatemala to the Isthmus of Tehu- 

 antepec the process of absorption is still incomplete ; and hence the presence of the 

 intermediate forms represented by P. alMloris. But P. Mlineata has done more than 

 this ; for in Vera Paz we find pure-blooded birds, showing that it has established itself 

 beyond the influence of P. nigriceps. The range of this last form has thus been com- 

 pletely severed, one part remaining in Colombia and the other in Western Mexico. 



