Part 20

_Food._--We have no definite information about the food of Sennett's warbler, but Clarence F. Smith has sent me the following note: "The only laboratory report available on the food of the species pertains specifically to a South American subspecies of the _pitiayumi_ group. The stomach contents were reported to consist of remains of hymenopterous insects and two-winged flies (Zotta, 1932)."

* * *

Nothing further seems to have appeared in print regarding the habits of this warbler. It is much like the well-known parula warbler in appearance and behavior, but can be recognized in the field by the conspicuous black lores and cheeks and by the complete absence of any pectoral band.

DISTRIBUTION

_Range._--The species ranges from southern Texas to northern Argentina and Uruguay. The race occurring in the United States is found in southern Texas and northeastern Mexico.

_Breeding range._--Sennett's olive-backed warbler breeds =north= to northeastern Coahuila (Sabinas); and southern Texas (Hidalgo, Harlingen, and Point Isabel). =East= to southern Texas (Point Isabel and Brownsville); and southeastern Tamaulipas (Altamira and Tampico). =South= to southern Tamaulipas (Tampico); and southern San Luis Potosí (Valles). =West= to eastern San Luis Potosí (Valles); and eastern Coahuila (Cerro de la Silla and Sabinas).

_Winter range._--While probably not a sedentary form, its winter range very nearly coincides with its breeding range. It has been found in winter from Brownsville, Tex., to northern Hidalgo (Jacala).

_Egg dates._--Texas: 6 records, April 28 to May 30; 4 records, May 2 to 12, indicating the height of the season.

Mexico: 2 records, May 27 and July 5.

PARULA GRAYSONI Ridgway

SOCORRO WARBLER

HABITS

The Socorro warbler is closely related to Sennett's warbler and other races of _pitiayumi_ but is accepted as a distinct species. It differs from _nigrilora_ in having gray, instead of black, lores and cheeks, and in having much less white on the inner webs of the outer rectrices. It was supposed to be confined to Socorro Island, one of the Revillagigedo group, about 250 miles southwest of the southern tip of Baja California. It was added to our fauna by Chester C. Lamb (1925), who states:

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.

There can be no doubt, however, that young males breed in this immature plumage, for Price (1895) secured a pair that were feeding a brood of young, and the "male was not in fully adult plumage and was very similar in coloration to the female." Swarth (1904) writes: "The male bird breeds in the immature plumage, for on June 21, 1902, I assisted O. W. Howard in securing a nest, containing four eggs, the parents of which were indistinguishable in color and markings. * * * I was surprised at the large proportion of birds in this immature plumage that were seen. At a very liberal estimate I should say that the males in adult plumage comprised barely a third of the birds seen in the spring."

Adults have a complete postnuptial molt, mainly in July; all June birds that I have seen are in worn plumage, and August and September birds are in new, fresh feathers. The fall plumage of the male is similar to that of the spring male, but the colors of the head, neck, and chest are duller, more clay color, the back is more olive and the sides are browner. In the female at this season the crown is tipped with grayish and the throat and breast with buffy, while the sides are browner than in the spring; the white tips of the greater wing coverts are tinged with yellowish. The nuptial plumage is acquired mainly, if not entirely, by wear, the edgings wearing away and the colors becoming brighter.

_Food._--Nothing definite seems to have been recorded on the food of the olive warbler, but its habit of creeping over the branches and twigs of the pines, much after the manner of the pine warbler, would seem to indicate that it was foraging for the many small insects that infest these trees. It is evidently one of the protectors of the pine forests. Brewster (1882b) says: "In their actions these Warblers reminded Mr. Stephens of _Dendroeca occidentalis_. They spent much of their time at the extremities of the pine branches where they searched among the bunches of needles for insects, with which their stomachs were usually well filled. Occasionally one was seen to pursue a falling insect to the ground, where it would alight for a moment before returning to the tree above."

_Behavior._--One of the members of Henshaw's (1875) party brought in a specimen of this warbler, on September 20, "which he stated he had shot from among a flock of Audubon's Warblers and Snowbirds, which he had started from the ground while walking the pine woods. With the rest, it had apparently been feeding upon the ground, and had flown up to a low branch of a pine, where it sat and began to give forth a very beautiful song, which he described as consisting of detached, melodious, whistling notes."

W. E. D. Scott (1885), writing of his field work in the Santa Catalina Mountains in late November, says:

Associated with flocks of the Mexican Bluebird (_Sialia, mexicana_), which was, by the way, the only kind of Bluebird observed, was always to be found one and sometimes two representatives of the Olive Warbler (_Peucedramus olivaceus_). The Bluebirds were generally feeding on some insects in the tall pines, in flocks of from six to ten individuals. The Olive Warblers were on the best of terms with their blue friends, and as the Bluebirds were shy and restless they made it difficult to obtain or observe very closely their smaller allies. I did not in these pine woods see the two species apart, and became at length so well aware of the intimacy that existed between them, that I would fire at any small bird passing high overhead in company with Bluebirds. They were chance shots, certainly, but the only two small birds obtained flying in this way with the Bluebirds were Olive Warblers. * * * Generally they preferred the largest branches of the pines when they alighted, though I took one not more than three feet from the ground in a small bush. Their movements while feeding or searching for food are very deliberate, though I noticed now and again certain motions when at the extremity of a bough that reminded me of a Kinglet or a Titmouse.

Swarth (1940) says: "Though frequenting the tree tops to a great extent, they seem singularly tame and unsuspicious, and several times I have had one feeding in some of the lower branches, within arm's reach of me, without its showing the least sign of fear."

_Voice._--The olive warbler has a rather loud, attractive, and distinctive note, but few observers have referred to it as a song. The "beautiful song" mentioned above consisted of "detached, melodious, whistling notes."

One of its whistling notes sounds very much like the _peto_ note of the tufted titmouse and might easily deceive the listener. Scott (1885) observed that these warblers "had a call-note so like that of their associates [the bluebirds] as to be almost identical. It seemed to me only a clearer whistle of more silvery tone." Price (1895) saw a male alight on a twig near his mate, during nest-building, uttering "a liquid _quirt, quirt, quirt_, in a descending scale." Mr. Henshaw (1875) heard "a few strange Vireo-like notes coming" from an olive warbler. A bird that Dr. W. P. Taylor (MS.) watched in apparent courtship gave "a whistled call with descending inflection."

_Field marks._--In general appearance and behavior the olive warbler suggests the pine warbler, especially as it creeps over the pines. The orange-brown head, neck, and breast of the adult male, with the conspicuous black band through the eye, is distinctive; these colors are much paler and more yellowish in the female, and the band through the eye is grayish. Both adults have two white wing bars, a white area at the base of the primaries and much white in the tail, the white areas being more restricted in the female. Young birds are much like the female (see descriptions of plumages).

_Winter._--The olive warbler, as a species, is probably permanently resident throughout most of its Mexican and Central American range. But the northern olive warbler is evidently partially migratory, though some individuals, perhaps many, remain in Arizona during part, or all, of the winter. All of the 15 specimens taken by Stephens for William Brewster (1882b) were collected in March, probably too early to be migrants, and he says that Stephens had previously taken one in February 1880, evidently a wintering bird. Mr. Swarth (1904) writes: "I have not found this species very abundant in the Huachucas at any time, but it is probably resident to some extent, for I secured an adult male on February 21 when the snow was deep on the ground. During March I saw several more, all adult males and single birds, usually with a troop of Pygmy Nuthatches; but it was not until the first of April, when the other warblers were arriving, that they became at all abundant." Scott (1885) found them on the Catalinas under winter conditions, with snow on the ground, and says: "I think there can be little if any doubt that they are residents all the year." And Dr. W. P. Taylor (MS.) took one in the Santa Ritas on February 4, 1923. Just how far south go the birds that migrate away from Arizona does not seem to be known, but apparently they have not been detected beyond Chihuahua and Tamaulipas. Perhaps they do not migrate at all.

DISTRIBUTION

_Range._--Southwestern United States to northern Nicaragua.