Plates 18, 19
HABITS
Dr. J. G. Cooper discovered this tiny and inconspicuous warbler at Fort Mojave, on the Arizona side of the Colorado River, in the spring of 1861, and named it in honor of Miss Lucy Baird, daughter of Prof. Spencer F. Baird. It might well have been named the mesquite warbler, as its distribution coincides very closely with that of this tree, which seems to furnish its favorite home, most of its nesting sites, and much of its foraging area.
Harry S. Swarth (1905) wrote of conditions then existing:
South of Tucson, Arizona, along the banks of the Santa Cruz River, lies a region offering the greatest inducements to the ornithologist. The river, running underground for most of its course, rises to the surface at this point, and the bottom lands on either side are covered, miles in extent, with a thick growth of giant mesquite trees, literally giants, for a person accustomed to the scrubby bush that grows everywhere in the desert regions of the southwest, can hardly believe that these fine trees, many of them sixty feet high and over, really belong to the same species. This magnificent grove is included in the Papago Indian Reservation, which is the only reason for the trees surviving as long as they have, since elsewhere every mesquite large enough to be used as firewood has been ruthlessly cut down, to grow up again as a scraggly bush.
But this magnificent forest did not long remain in its pristine glory. When I was in Arizona with Frank Willard in 1922, we had looked forward with keen anticipation to visiting the mesquite forest, where he had told me that we should find a thick stand of big trees covering a large area, and some wonderful bird life. We were disappointed in the forest, for the Papago Indians had been cutting down the larger trees unmercifully and had made a network of cart roads all through it for hauling out the firewood. There were only a few large trees left, more or less scattered, and between them many open spaces in which were thickets of small mesquites and thorn or patches of medium-sized mesquites and hackberries. But we were not disappointed in the bird life, for here and in other parts of Pima County, wherever there were mesquites, we found Lucy’s warblers really abundant and breeding. The forest fairly teemed with bird life, from the graceful Mexican goshawks soaring overhead to the Gambel’s quails whistling on the ground. The constant cooing of the white-winged doves was almost too monotonous, but the rich song of the Arizona cardinal, mingled with the voices of the orioles, towhees, wrens, and vireos made a delightful chorus, among which the sweet song of Lucy’s warbler was prominent.
Dr. Joseph Grinnell (1914) writes, referring to the Colorado Valley: “On the California side, both at Riverside Mountain and above Blythe, Lucy warblers were numerous, and very closely confined to the narrow belt of mesquite. The singing males, each representing the forage area and nesting site of a pair, were spaced out very uniformly, so that an estimated strip of about 200 yards in length belonged to each. The birds foraged out to a limited extent from the mesquites towards the river into the arrowweed and willows, and away from the river at the mouths of washes into the ironwoods and palo verdes. But the metropolis was always most emphatically the mesquites.”
Nesting.—M. French Gilman (1909) had considerable experience with the nesting habits of Lucy’s warbler along the Gila River in Arizona, of which he says:
Four general types of nesting sites were noticed, in the following order of frequency: in natural cavities, under loose bark, in woodpecker holes, and in deserted Verdins’ nests. Of 23 nests observed, 12 were in natural cavities, 4 under loose bark, 4 in woodpecker holes, and three in Verdins’ nests. Natural cavities were of various kinds. Some were where a limb had been broken off; others in the crack made by a large branch splitting from the trunk; and again a decayed spot furnisht a sufficient hollow to conceal the nest. In all cases the site was in a sheltered or protected position; that is, the trunk leaned enough to shade the entrance from above. A mesquite tree was usually selected, tho others were taken. Of the nests observed, 15 were in mesquites, 5 in palo verde, 2 in ironwood, and one in catsclaw. * * *