526 NOTES ON COSTA EICAN BIRDS CHERKIE. 



Geothlypis caninucha icterotis. 



With twenty examples, all from the vicinity of San Jose, Costa Rica, 

 representing- specimens taken in the months from April to December, 

 and the types of G. poUocephala, G. caninucha, G. caninucha icterotis, and 

 G.'palpebralis^ all before me, I thought for some time that 1 could select 

 from the series of Costa Eican birds specimens that would exactly match 

 any one of the four types ; at the same time the gradation from one to 

 the other in the series seemed so gradual as to make them inseparable. 

 I felt convinced that Mr. Sharpe was correct when he placed caninucha 

 as a synonym of poUocephala (Cat. Birds Brit. Mus., Vol. x, }). 359), 

 but not as had already been point ed out by Mr. Ridgway (Manual of 

 Korth American Birds, p. 526), that the two forms represent seasonal 

 differences, because in my Costa Rican series, that which Mr. Sharpe 

 would call the winter ijlumage is to be found in birds from May to Au- 

 gust as well as December. The color differences are in my opinion due 

 entirely to individual variation. And, on the other hand, to be con- 

 vinced that relative measurements have little taxonomic value one has 

 only to glance through the accompanying table of measurements taken 

 from the series of Costa Rican birds. 



The above were my hastily* formed conclusions, part of which had to 

 be changed on more careful examination of the material, as follows : 

 The type of poUocephahi is a trifle paler on the belly and anal regionj 

 than the greater i^art of the specimens, but it is matched in this respect 

 by at least four examples. The back is, however, a dusky olive-green,^ 

 with very little indication of the brownish shading so conspicuous in 

 the majority of Costa Rica specimens; and while in many Costa Rican ^ 

 birds there is some white on the eyelids, it does not extend around the 

 eye as in poUocephala. 



Mr. Ridgway separated the Costa Rican bird as G. caninucha icterotis 

 (Proceedings TJ. S. National Museum, Yol. xi, p. 539), believing it to 

 have olive-yellow or yellowish-olive auriculars, distinguishing it from 

 the Guatamalau specimens. The series of Costa Rican examples pre- 

 sents much variation in the color of auriculars varying from an olive- 

 gray (almost as dark as seen in the type of caninucha) to a yellowish 

 olive, similar to the type of caninucha icterotis).* 



The specimens on which poUocephala, palpehraUs, caninucha, and 

 caninucha icterotis were based are, with the exception of the last, in 

 very old, worn, and poor plumage, and I believe a good series from 

 different localities would connect all as races of a single species. 



G. caninucha icterotis is a common resident bird in the fields about 

 San Jose, where it breeds abundantly. Its habits are similar^ to those 

 of the Maryland Yellow-throat {G. trichas). It is quite shy and difficult 

 to approach. Specimens are in best plumage from October to March. 



* I would here observe the type of caninucha icterotis seems to me to bo one with 

 uuuaually brij^jht auriculars, wliile the tyjie of caninuclia, ou the other haud, seema 

 to have very dark auriculars. lu otlier words, the birds chosen as tj'pes Avould seem 

 to repreaeut the extremes of color iu the two foruis. 



