Part 39

On November 3, 1923, I collected one of these birds at Todos Santos, on the Pacific Ocean side of the peninsula of Lower California, some forty miles north of Cape San Lucas. * * * On February 5, 1924, I saw another of these little warblers, within a few feet of me; but my gun was not at hand, so I had to be content with a sight record. The locality was inland, at El Oro, on the east side of the Victoria Mountains, about thirty miles from Todos Santos. The next occurrence, like the first, was at Todos Santos, where, on July 23, 1924, I secured an adult female which is now in my collection at the Los Angeles County Museum, Los Angeles. The taking of these two birds, in the winter and summer of two successive years, would indicate that the species is of more or less regular occurrence in the Cape Region of Lower California. The capture of a specimen in July suggests the possibility of breeding at the point of record.

Nothing more seems to have been heard of the species since. And we know nothing of its habits.

DISTRIBUTION

Range.--Socorro Island and the Cape region of Baja California.

Breeding range.--The Socorro warbler is known to breed only on Socorro Island, where it is resident. It has been found in the breeding season near Todos Santos, Baja California.

This warbler has been found in winter in two localities (Todos Santos and El Oro) in Baja California, and appears to be resident in small numbers.

PEUCEDRAMUS TAENIATUS ARIZONAE Miller and Griscom

NORTHERN OLIVE WARBLER

PLATE 23

HABITS

The olive warbler was long classed as a species of Dendroica, with Peucedramus regarded as a subgenus, but it is now properly placed in a genus by itself, for as Dr. Chapman (1907) points out it differs from Dendroica chiefly "in its slenderer, more rounded bill, proportionately longer wings (about 1.00 inch longer than the tail) and decidedly forked tail, the central tail feathers being more than .25 inches shorter than the other ones. In general color and pattern of coloration Peucedramus is markedly unlike Dendroica, from all the species of which the male differs in requiring two years to acquire adult plumage."

For a still longer time it was supposed to be a homogeneous species, until Miller and Griscom (1925) made a study of it and divided the species into five subspecies, mostly Mexican and Central American. In giving this bird the name P. t. arizonae, they state that it is entirely different in coloration from the type race; "upperparts plain mouse-gray, in spring plumage almost never tinged with olivaceous, even on the upper tail-coverts, appearing lighter and grayer than typical olivaceus; collar on hind neck not so complete, usually invading the occiput; primaries rarely if ever edged with olive-green in spring plumage; head and throat plain ochraceous, duller than in typical olivaceus; underparts lighter, the center of the belly purer white, more contrasted with the flanks, which are less olivaceous, more grayish brown; size as in typical olivaceus. Throat and side of neck of adult female and immature pale lemon-yellow." They give as its range "mountains of southern and central Arizona south at least to Chihuahua and perhaps east to western Tamaulipas (Miquihuana)."

The species had long been known in Mexico and had been erroneously reported in Texas, but it remained for Henry W. Henshaw (1875) to record it definitely as a North American bird by capturing three specimens on Mount Graham, Ariz., in September, 1874. Since then it has been noted by numerous observers on several other mountain ranges in southern Arizona, where it is now known to be fairly common in summer and where a few remain in winter.

It is a bird of the open pine forests on or near the summits of the mountains. In the Huachucas we found it breeding at about 9,000 feet elevation in the open forests of yellow pine, sugar pine, and fir. As Swarth (1904) says: "I found them only in the pine forests of the highest parts of the mountains, even in cold weather none being seen below 8,500 feet; and more were secured above 9,000 feet than below it."

In the Chiricahuas, Frank Stephens collected a fine series of these warblers for William Brewster (1882a) in March, 1880, in the pine woods at elevations from 10,000 to 12,000 feet. And it was here that W. W. Price (1895) found the first nest in 1894; "the region was a dry open park, thinly set with young pine (Pinus jeffreyi), at between nine and ten thousand feet above the sea."

The olive warbler is not always confined to the pines at all seasons, for Dr. Walter P. Taylor tells me that he obtained a single specimen from an oak tree in the Santa Rita Mountains at 5,000 feet on February 4, 1923. It was in the same general locality with bridled titmice and ruby-crowned kinglets, and was alone, perhaps a winter wanderer, foraging nervously through the foliage of the oak.

Spring.--According to Swarth (1904), migrating olive warblers reach the Huachuca Mountains, from their winter resorts in northern Mexico, about the first of April. "In 1903 they became fairly abundant, particularly in April, when many small flocks of five or six birds each, were seen. * * * They were seldom in company with other warblers, but when not alone, associated with nuthatches and creepers." Frank C. Willard (1910) says that "the first few days are spent, as it were, in staking out their claims anew. The males at this time are quite pugnacious toward one another, and, tho apparently already mated, they promptly drive any wanderer of the same sex from their selected bit of forest. I believe they return each year to the same locality in which they made their home of the previous year, as I have found them in the same patch of trees year after year while other places near by, with the same apparent advantages, never seem to be chosen." Dr. Taylor (MS.) saw a pair of olive warblers, 20 to 30 feet up in some yellow pines in the Santa Catalina Mountains on May 13, 1928. They kept giving a whistled call with descending inflection. "The two birds were courting apparently, flying about, often facing each other at short range, 6 to 18 inches, calling at very frequent intervals."

Nesting.--To William W. Price (1895) belongs the honor of finding the first nest of the Arizona olive warbler. On June 15, 1894, on the Chiricahua Mountains, he--

saw a female, closely followed by a male, fly from a bush of spirea (Spirea discolor) to the top of a small pine, and busy itself on a small horizontal limb partially concealed by pine needles. She soon returned to the spirea, followed by the male, which did not enter the bush but perched on a pine branch near by. The female again flew with a dry flower-stem in her bill, from the bush directly to the pine, where a nest was in process of construction. * * * A few days after, a forest fire drove me from my camp, and it was not until July 1 that I was able to visit the nest. The female was sitting, and when frightened from the nest, kept hovering about, but made no sound. The male did not appear at all. The nest was compactly built and placed on a small horizontal branch, about forty feet from the ground, and about six feet from the top of the tree. The eggs, four in number, were in an advanced state of incubation. * * * The body and walls of the nest are composed of rootlets and flower stalks of Spirea discolor, and the inner lining consists of fine rootlets and a very small quantity of vegetable down. It is a compactly built structure, measuring about 4 inches in outer diameter by 1-3/4 inches in depth; the inner cup measures 2 inches in width by 1-1/8 inches in depth.

A few years later, O. W. Howard (1899) reported finding four nests in the Huachuca Mountains; one was about 30 feet up in the fork of a large limb of a red fir; another was in a sugar pine near the extremity of a limb and about 30 feet from the ground; a third was near the end of a long slender limb of a yellow pine, about 50 feet up, and well concealed among the long pine needles; the fourth was on a branch of a red fir, not far from the trunk, and over 60 feet from the ground.

F. C. Willard (1910), collecting in the Huachucas, says that "short-leaf pines, long-leaf pines and firs are chosen for the nesting sites." One female that he watched building her nest "was gathering rootlets at the time and seemed very particular about them, picking up and dropping several before selecting one which she thought satisfactory. This she carried into a dense growth at the tip of a branch of a large fir about one hundred yards away. The male was singing and feeding in a tree close by. After a few trips with material the female would fly into the tree where he was and let him feed her. This is the only time I have observed nest building going on and the male not following the female in her flights." In his description of the nest, he says: "It is supported by ten small live twigs from the size of a pencil down, all growing from a branch about five eighths of an inch in diameter. It is composed outwardly of moss and pine bud hulls with plant down scattered thruout. The proportion of this latter increases until the the lining is reacht where it forms a felt like a hummingbird's nest. This lining is supplemented with a few very fine rootlets."

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.

Plumages.--The plumages and molts of the olive warbler are as distinctive as its nest and eggs. The sexes are not quite alike in juvenal plumage. Ridgway (1902) describes the young male as "pileum, hindneck, back, scapulars, rump, and upper tail-coverts plain dull olive or brownish olive; supra-auricular region and sides of neck dull yellowish buffy, the latter tinged with olive; chin, throat, and chest dull yellowish buffy; otherwise like adult female." And of the young female, "similar to the young male but paler and grayer above; supra-auricular and post-auricular regions pale brownish buffy; chin, throat, and chest still paler buffy, the chin and upper throat dull buffy whitish." The white tips of the greater wing coverts are tinged with yellowish.

I have not been able to trace the postjuvenal molt in the series I have examined but it apparently occurs in July and produces very little change, young birds of both sexes in their first winter plumage closely resembling the adult female at that season, though the crown and nape are grayer and the throat and breast are paler. I can find no evidence of a prenuptial molt. Young males evidently breed in this plumage and do not acquire the fully adult plumage until their second fall, or perhaps later. In Brewster's series, collected in March, three males are in this condition, of which he (1882) says that "two of them, although in unworn dress, are absolutely undistinguishable from adults of the opposite sex; the third (No. 77), however, has the throat appreciably tinged with the brownish-saffron of the adult male." This last may be a bird that is one year older, for Ridgway (1902) describes the "second year" male as "identical in coloration with the adult female." Judging from the series that I have examined, including all of Brewster's birds, I am inclined to think that the adult winter plumage is acquired at the first postnuptial molt, or when the bird is a little over one year old.