May, x9o6 I THE CALAVERAS WARBLER IN WESTERN WASHINGTON 69 is to be found as a rule only on the dryest prairies. Here the birds frequent the scattered clumps of young oaks and fir trees that have reached a height of some three or four feet, and which border the large tracts of dense fir timber. It is a noteworthy fact that, while these birds are not often to be found more than a hun- dred yards outside of the forests, they are seldom or never seen inside of the divid- ing line where the heavy timber meets the prairie. Also they do not encroach upon the hillside territory of the lutescent Warbler, which bird in turn does not appear on the prairies but confines itself to the brush-covered uplands. The nest, besides being rare, is exceedingly difficult to locate, so much so that nine seasons of field work have yielded us only five sets o[ eggs. The male never sings anywhere in the vicinity of the nest, and the female covers her eggs until forced from the nest by the intruder. The site chosen is usually at the base of a v. ery young oak, or fir, tho on one occasion we found one built under some blackberry vines at the base of a large fir stub. The nests are sunk well into the ground or moss, and are so well concealed as to defy discovery unless one flushes the bird. They are well made, being c?m- posed of a quantity of fine strips of bark and fine dead grass, the lining consisting of very fine dead grass, horse-hair and an occasional feather. '['he external di- mensions of a typical nest are three inches wide by two inches deep; in- ternal dimensions one and three-fourths inches wide by one and one-fourth inches deep. In appearance, as might be expected, they are almost counterparts of nests of the Nashville warbler, taken by us in eastern Massachusetts. The number of eggs to a set is almost invariably four, one set of three fresh eggs being taken which was probably incomplete. This seems at variance with the sets taken in California, where the majority appear to consist of five eggs. There are two distinct types of markings. In one the ground color is a dull white heavily sprinkle3 all over with five dots of reddish-brown, distributed rather more thickly around the larger end. The other type has the same ground color, but is much more sparingly dotted and has large blotches such as are some- times termed "flowers" of reddish-brown. These two types are practically in- distinguishable from sets of the Nashville warbler in our collection. In shape they vary from rounded oval to ovate oval. There is a slight varia- tion in size, the eggs of the largest set in our collection are .65x.5 o, .67x.5o, .65x.49 and .65x.49 inches, and the eggs of the smallest set measure .62x.49, .62x.5o, and .62x.49 inches. It seems almost certain that two sets of eggs are laid in a season, altho few of the birds in the northwest appear to have any fixed time for nesting. The earliest date on which we have taken eggs was May 25, when incubation was about a third advanced. The latest was June 24, on which date a nest containing fresh eggs was taken. When flushed from the nest the female instantly disappears, and only returns after a considerable interval of time. Then she approaches with the greatest caution, ready to dart away again at the first movement of the intruder. In this connection the male has a very curious and amusing habit. If he sees her after she leaves the nest, instead of joining her and consoling her in her misfortune, he promptly gives chase in the most furious manner, driving her from bush to bush as if she had wilfully deserted their treasures. Tacoma, Washington.
