NATURAL SCIENCES OF PHILADELPHIA- 69 



[Note. Just as these sheets are passing through the press, I find several 

 eka'mpVs of this species in a collection made hy Mr. C. Wood, at Belize, Hon- 

 duras, where it is said to be quite common. They are rather smaller than 

 iny Arizona specimens, but otherwise quite identical. It is somewhat re- 

 markable that the species has never been detected in the regions lying be- 

 tween these two countries.] 



89. Dendrosca nigrescens (Towns. 1 ) Baird. 



Common ; chiefly spring and autumn migrant ; but a few breed. Arrives 

 about Apr. 20, remains until late in September. Chiefiv pinicoline, and in 

 -other habits as well as in voice is exceedingly similar to D. GrdcicB. 



This species is by no means so peculiarly a Pacific one as has generally 

 been supposed. 



DO. Dexdrceca occidentalis (Towns. ) Baird. 



Very rare. Summer resident. A single specimen of this little known 

 species, taken early in September in thick scrub oak bushes. It measured 

 4-9 X 7*7. In this immature state the dusky olivaceous extends over the 

 whole upper parts, deeply tinging the pure ash of the rump of the adults with 

 a somewhat lighter" shade of the olivaceous of the back, and extending for- 

 ward on the crown nearly to the front, where it gradually lightens by becom- 

 ing more and more mixed with yellow. The sides of the head are clear yellow, 

 only slightly soiled by olivaceous, and the chin and throat are the same, fad- 

 ing insensibly on the breast into the dull greyish white of the under parts 

 generally. The sides show indications of streaks, very obsolete, however, and 

 have a slight wash of grayish olivaceous. There is no black whatever about 

 the head or throat, and the back is only very obsoletely streaked with that 

 color. The greater and median coverts are conspicuously tipped with white. 



A suite of specimens illustrating all the changes of plumage of this species, 

 so closely allied to virens, chrysopareia, etc., is still a great desideratum. 



91. Dendececa Auddbonii (Towns.) Baird. 



Exceedingly abundant ; spring and autumn migrant. A few possibly breed. 

 Some remain all winter. "Numerous at Fort Mojave in winter," (C>oper.) 

 Very numerous from Apr. 20th to May 10th, and during the month of Octo- 

 ber, in which seasons the cotton-woods and willows of the creek bottoms are 

 filled with the birds, which are also found in every other situation more or 

 less abundantly. 



Specimens in very high spring plumage have the black of the breast quite 

 pure, and unmixed with slate in any portion of its extent, contrasting sharply 

 with the whole width of the posterior edge of the yellow throat. The streaks 

 on the sides and flanks are very narrow and distinctly defined. The intersca- 

 pulare is very thickly streaked with black. The greater wing coverts are so 

 broadly edged with white as to leave only a small space on their inner webs 

 dusky. The yellow crown is intense in color, small and sharply defined, and 

 there is much black on the front and lores. For so small a bird, the species 

 varies much in size. Seasonal and sexual changes of plumage are quite ho- 

 mologous with those of D. coronata. 



92. Dendrozca ^estiva (Gm.) Baird. 



Abundant. Summer resident, from April 25th to second week in September. 

 Most numerous in the willow and cotton-wood copses. 



93. Geotiilypis trichas (L.) Cob. 



Trichas ddafieldiil Heerman, P. R. R. Surv. x. 1859, p. 40. 



Rare; summer resident. Arrives^early in April; remains until October. 

 Less common than the succeeding species. 



Dr. Heerman is mistaken in supposing he saw Trichas delqfieldii Audubon, 

 in Arizona. This is a syuomym of Geothlypis cequinoctialis, from South 

 America. 



1866.] 



