CASSIN'S VIREO 313 



mores along the bottom of the larger canyons, and in the valley areas 

 occur only in migration." 



Nesting. — Thomas D. Burleigh (1930) reports five nests fomid near 

 Tacoma, Wash. The first "was twelve feet from the ground at the 

 outer end of a limb of a small scrub oak in a stretch of open fir 

 woods, and was built of grasses and usnea moss, lined with fine grasses 

 and bright red moss rootlets, and well ornamented on the outside with 

 white spiders' egg cases and bits of dead leaves. * * * Within 

 the next month four other nests were found, and two of them were 

 in small oaks and two in alder saplings, varying in height from five to 

 ten feet from the ground." 



Mr. Rathbun has sent me the foUov/ing description of two nests 

 of the Cassin's vireo, found in that same region : "The nest is a cup- 

 shaped affair and is attached by its upper edges to the horizontal 

 fork of a limb, geiierally at no great height. It is neatly made, reflect- 

 ing skill in its construction. The material used for the outer part of 

 one consisted of pieces of dead leaves of various dull colors, some 

 bits of heavy gray paper, dry gray grasses and a small quantity of 

 greenish-gray moss, these materials being interwoven and bound firmly 

 by tough plant fibers. The lining was entirely of fine, dry grasses. 

 The general color effect of this nest was a composite one, formed of 

 many rieutral tints, harmonizing with tlie lichen-covered limbs of a 

 small oak, in which it was built. The outside of the nest was deco- 

 rated with pieces of white cocoon." 



Of the other, he says : "This nest was attached, pendantly, to a V- 

 shapecl fork near the extremity of a low-er limb of a young fir, at a 

 height of about 15 feet, the top of the nest being screened from view 

 by a small twig overarching it. The material used consisted of many 

 small pieces of thin, soft, dead leaves, long dry grasses, with a few 

 horsehairs interwoven to help bind them and give strength; the nest 

 was firmly bound to its support by strips of dry moss and vegetable 

 fibers. The lining was of fine fibers, small stems of leaves, and a few 

 horsehairs ; the outside of the nest was decorated with a few pieces of 

 white cocoons. On the twigs to which it was attached grew a few 

 lichens, and a few of these w^ere scattered about the upper part of the 

 nest. Diameter outside, 3i/t inches; height, 2i/4 inches; diameter in- 

 side, 214 inches ; depth, 1% inches." 



Dawson and Bowles (1909) say that some nests are placed as much 

 as 30 feet above the ground, and Mr. Bowles adds: "They are the 

 quickest as well as the slowest birds in completing their nests that have 

 come under my notice. One pair built a handsome nest and laid four 

 eggs in precisely ten days; while another pair were more than three 

 weeks from the time the nest was started until the eggs were laid. They 

 are the only Vireos that I have ever known to nest in communities. 



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