He gives an interesting account of his attempts to locate another nest in "a short-leaf pine whose branches were weighted down with masses of twigs and cones." He worked from ten in the morning until three in the afternoon, following the birds about, climbing the suspected tree several times and cutting off many twigs, before he finally found the nest. "The tree was not a very large one and I had shaken every branch and jarred them with my foot, but until I practically toucht the nest she had stayed on." While I was in Arizona with Willard he collected for me on May 30 a beautiful nest of the olive warbler, with four fresh eggs. It was taken at an altitude of 8,500 feet on the Huachuca Mountains and was built in a clump of mistletoe near the tip of a branch of a sugar pine about 20 feet out from the trunk and 55 feet from the ground. Its construction was similar to those described previously (pl. 23). The loftiest nest that he ever found was 70 feet from the ground in a pine. The nest built by the Arizona olive warbler is beautiful, and quite different from that of any other species of its group. A typical nest (in the Thayer collection in Cambridge) is made mainly of a brown lichen or moss mixed with other lichens and mosses, bud scales, flower scales, and some plant down, reinforced with fine yellowish rootlets. All these are compactly worked into and supported by the living needles of the yellow pine in which the nest was built. The lining consists of plant down and finer strands of the same yellowish rootlets. It measures 3-1/2 by 3 inches in outside diameter and 2-1/2 in height; the inner cavity is about 2 inches in diameter and 1-1/4 inches in depth. _Eggs._--Three or four distinctive eggs seem to constitute the full set for the northern olive warbler. These are ovate to short ovate and have a very slight lustre. They are grayish or bluish white, or even very pale blue, liberally speckled, spotted and blotched with "dark olive-gray," "dark grayish olive," "drab," "olive-brown," or "dark brownish drab." These are interspersed with undertones of "mouse gray," "deep mouse gray," or "Quaker drab." On some eggs the spots are sharp and distinct, while on others the olive, brown, and drab markings are clouded into the undertones. The spottings are usually well scattered over the entire surface, but tend to become heavier at the large end. The measurements of 28 eggs average 17.1 by 12.8 millimeters; the eggs showing the four extremes measure =19.0= by =16.0=, =16.0= by 12.2, and 18.1 by =12.0= millimeters (Harris). _Young._--Information is lacking on incubation and care of the young.