_Eggs._--Audubon's warbler lays from 3 to 5 eggs, almost always 4. They are ovate, tending toward short ovate, and are slightly glossy. They are grayish or creamy white, spotted and blotched with "raw umber," "Brussels brown," "argus brown," and sometimes "auburn," with underlying spots of "pale brownish drab," "light brownish drab," or "light mouse gray." The markings are often confined to the large end, and frequently the drab undertones are in the majority, sometimes running together to form a cap, and this is relieved with a few superimposed spots or blotches of dark "argus brown," or scattered small scrawls so dark as to appear almost black. The eggs generally are sparsely but rather boldly marked. The measurements of 50 eggs average 17.6 by 13.5 millimeters; the eggs showing the four extremes measure =19.4= by 14.0, 19.1 by =14.5=, and =15.4= by _12.3_ millimeters (Harris). _Young._--The period of incubation is probably between 12 and 13 days, as with the Myrtle warbler. Mrs. Wheelock (1904) writes: In the brood whose incubation was closely watched, I found that twelve days elapsed between the laying of the last egg and the advent of the young. The female did most of the brooding; the male was found on the nest only once, but was usually perched on a neighboring tree warbling his enthusiastic little song, "cheree-cheree-cheree-cheree." After the young were feathered enough to leave the nest, which occurred when they were two weeks old, the male forgot to sing and became a veritable family drudge with the brood ever at his heels clamoring for food. * * * The pair whose young had hatched so early were very friendly, feeding them without much fear while I sat within three or four feet of the nest and on a level with it. They usually came with nothing to be seen in their beaks, but the insect food they had gleaned and carried in their own throats was regurgitated into the throats of the young. When the latter were five days old the mother bird, for the first time, brought an insect large enough to be seen, and crammed it into the open bill of one of the nestlings, and from that time on most of the food brought was eaten by the young while fresh. The general opinion seems to be that two broods are often, perhaps usually, raised in a season. The young birds are the first to leave their mountain resorts, probably driven out by their parents, and are the first to appear in the lowlands. _Plumages._--The plumages and molts of Audubon's warbler are similar in sequence to those of the myrtle warbler; in juvenal and first fall plumages the two species are almost indistinguishable, though there is always more white in the tail feathers of the western bird, in which the white spot usually reaches the fourth feather even in young birds. In any plumage the white areas in the tail of Audubon's warbler occupy two more feathers on each side of the tail than in the myrtle warbler.