bkewster: birds of the gape region, lower galifornia. 209 



Polioptila caerulea obscura Ridgw. 



Western Gnatcatcher. 



Polioptila caerulea (not Motacilla caerulea Linnaeus) Baird, Rev. Amer. Birds, 

 pt. I. 1864, 74, 75, part (crit. ; Cape St. Lucas). Belding, Proc. U. S. Nat. 

 Mus., V. 1883, 534 (Cape Region) ; VI. 1883, 346, 347 (crit.; Victoria Mts.). 

 Bryant, Proc. Calif. Acad. Sci., 2d ser., II. 1889, 318 (Cape Region; Vic- 

 toria Mts.). 



P.[olioptila] caerulea obscura Ridgwat, Proc. U. S. Nat. Mus., V. 1883, 534, 536 

 (provis. name based on specimens from San Jose', Lower California, Cali- 

 fornia, Arizona, etc. ; measurements of bird from San Jose, etc.). 



Although, the characters which distinguish the Western Gnatcatcher from 

 P. caerulea are rather slight, they are well maintained in the series of over 

 thirty specimens before me. The most constant difference is that relating to 

 the extent of the white on the outer tail feathers, P. c. obscura having the 

 white much more restricted than P. caerulea. 



The Western Gnatcatcher is a rather common resident of the Cape Eegion, 

 where it appears to be indifferent to conditions of mean temperature or environ- 

 ment, for it occurs nearly everywhere from the seacoast (La Paz and San Jose 

 del Cabo) to the summits of the highest mountains (Sierra de la Laguna). 

 Mr. Frazar found it breeding at San Jose del Rancho in July. His first nest, 

 discovered on the 7th, contained four eggs on the point of hatching, and was 

 not disturbed. Two others, taken respectively on the 14th and 19th of the 

 month, had full sets of four eggs each, all freshly laid. One of these nests, 

 built in the fork of a bush at a height of about five feet, measures as fol- 

 lows : Greatest external diameter, 2.25; greatest external depth, 2.00; in- 

 ternal diameter at top, 1.30; internal depth, 1.10 ; greatest thickness of walls, 

 .50. The exterior is composed of gray, hemp-like, vegetable fiber and narrow 

 strips of reddish brown bark, and is decorated with a very few lichens, all these 

 materials being over- wrapped and kept in place by a nearly invisible tissue of 

 spider-web. The interior is lined with fragments of silky cocoons and a few 

 featliers. The other nest, which was placed in the fork of a small tree about 

 ten feet above the ground, and which is essentially similar to the specimen 

 just described, save that it has no lichens whatever, measures externally 2.15 

 in diameter by 2.10 in depth; internally, 1.40 in diameter by 1.50 in depth. 

 Both nests are smaller and more compact than any of the nests of P. caerulea 

 in my collection. The eggs of one set are ovate in shape, and measure respec- 

 tively : .69 X .44, .59 X .45, .60 X .45 and .60 by .44. The ground-color is 

 greenish white ; the markings, which are generally distributed, but most numer- 

 ous and crowded about the larger ends, are reddish browm, purplish, and laven- 

 der. The eggs of the other set are blunt ovate, and measure respectively : 

 .56 X .43, .56 X .44, .56 X .43 and .57 by .45. The ground-color is like 

 that of the eggs just described, but almost all the spots are bright reddish brown. 



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