Abert’s Towhee

Published by the Smithsonian Institution between the 1920s and the 1950s, the Bent life history series of monographs provide an often colorful description of the birds of North America. Arthur Cleveland Bent was the lead author for the series. The Bent series is a great resource and often includes quotes from early American Ornithologists, including Audubon, Townsend, Wilson, Sutton and many others.

Bent Life History for the Abert’s Towhee – the common name and sub-species reflect the nomenclature in use at the time the description was written.

The Abert’s towhee comprises two subspecies, the ecology and the behavior of which appear similar, and both forms are treated in this account. They are abundant residents in the vicinity of water courses, either permanent or intermittent, in parts of the deserts of southwestern United States, and they actively penetrate the thickest parts of the riparian vegetation with which they are characteristically associated (E. Coues, 1866; C. B. R. Kennerly, 1859; W. Brewster, 1882a; W. W. Price, 1899; and John Davis, 1951). However, they will exploit edge vegetation, and I was successful in trapping birds of the subspecies P. a. dumeticolus at the junction between riparian growth and what A. H. Miller (1951c) has termed “desert scrub” vegetation.

The plant associates of the two forms of the Abert’s towhee are generally similar. In New Mexico and Arizona, P. a. aberti has been recorded most frequently in mesquite (Prosopis sp.) (H. W. Henshaw, 1875; F. Stevens, 1878; W. Brewster, 1882a; H. K. Coale, 1894; G. F. Breninger, 1901; and H. S. Swarth, 1905a) and to a lesser extent in cottonwoods (Populus frernontii) and willow (Salix sp.). According to Davis (1951), the late A. J. van Rossem and L. H. Miller collected them in arrowweed (Pluchea .sericea) along the Bill Williams River in western Arizona. They have also been observed in Arizona about farms, citrus groves, and urban areas (F. M. Dille, 1935). The increased irrigation of desert lands in this state undoubtedly is increasing the amount of habitat suitable for Abert’s towhees.

Birds of the subspecies P. a. dumeticolus have been most frequently recorded in willow, mesquite, and arrowweed growth (W. W. Price, 1899; N. Hollister, 1908; van Rossem, 1911; Q. Bancroft, 1922; and W. R. Dawson, 1954), but J. Grinnell (1914b) concludes that they are most commonly associated along the Colorado River with quail brush (Atriplex lentijormis) and mesquite. In the Imperial Valley of California I have observed them occurring frequently in a reed (Phragrnites corn munis), and somewhat less commonly in a species of Baccharis and in an introduced tree, Tamarix gallica. I believe that a marked enlargement of habitat suitable for Abert’s towhees has occurred in southeastern California, as in Arizona, as a result of the enlargement of irrigation facilities there in the past few decades.

Nesting: Abert’s towhees of both subspecies nest most commonly in willows, and three quarters of the 80 nests of P. a. aberti C. E. Bendire (1890) found along Rillito Creek near Tucson, Pima County, Ariz., were in plants of this type, particularly stumps. Mesquite also appears to be regularly used as a nest site (Gilman, 1915; Bendire, 1890). P. a. aberti has also been recorded nesting in a Mexican elderberry shrub (Sambucus mexicana?) (Brandt, 1951); a species of ash (Frainus sp.) (Bendire, 1890); Suaeda torreyana, umbrella tree (Melia azedaracA), and Zizyphus (M. F. Gilman, 1915); cottonwood (F. C. Willard, 1923), and a mistletoe clump (Phoradendron sp.) in a cottonwood (F. Stevens, 1878). P. a. dumeticolu.s is known to nest in willows and mesquite and has also been recorded nesting in arrowweed and mistletoe clumps (Phorade’ndron sp.) probably located in mesquite (van Rossem, 1911), and in such introduced plants as pepper trees (Schinus molle) and orange trees near Palm Springs, Riverside County, Calif. (M. F. Giman, 1903).

The nest of the Abert’s towhee is rather bulky and loosely constructed (H. Brandt, 1951;H. Brown, 1903; and F.M. Bailey, 1928). W. L. Dawson (1923) describes a typical one as follows:

“A typical nest of this towhee is a bulky assemblage of weed-stems, dead vines, bark-strips, green leaves; and, interiorly, coiled bark, dried grasses, and horsehair. Bark is a favorite material, and I have seen nests which contained nothing else. Occasionally, the taste inclines to green grass, and the superstructure may be composed of green, or recently dried, grass or leaves of a single sort. * * ~ Bendire (1890) reported the dimensions of one nest to be: outer diameter, 5.5 inches; overall depth, 4 inches; inner diameter, 3 inches; inside depth, 2.5 inches. Brown’s (1903) and Brewster’s (1882a) measurements of other nests of this species are comparable.

The nests are placed off the ground usually in low bushes. There are several records of them placed in trees. Bendire (1890) found one such along Rihito Creek in an ash fully 25 feet above the ground, and Stevens (1878) found another apparently along the Gila River in a clump of mistletoe about 30 feet above the ground. Perhaps the most unusual nest site on record was a cavity near the top of a rotten cottonwood stump 12 feet above the ground (F. C. Willard, 1923).

Eggs: The clutch size for birds of both subspecies ranges from two to four (C. K. Avenill, 1933; F. M. Bailey, 1928; Bendire, 1890; van Rossem, 1911; and M. F. Gilman, 1903), with the usual number three. There is a single record of a clutch of five eggs, apparently for P. a. dumeticolus (H. Brown, 1903).

The eggs are generally ovate, though elliptical or elongate-ovate examples are found occasionally. Characteristically their ground color is a plae clay blue, and Bendire (1890) thought it to be paler than that of the eggs of either Pipilo Juscus cHssalis (senicula?) or P. J. aThigula. The markings of the eggs of Abert’s towhees are sparse but well defined. They are usually heaviest about the larger end, and are dark brown in color. Eggs with almost black markings occur occasionally. Some have been described with brown markings bordered by vinaceous and rufous. Infrequently the markings, whatever their color, are connected by fine pigmented lines. Paler shell markings of lavender or purple have been described in some eggs.

Measurements of 83 eggs of P. a. aberti yielded the following datamean dimensions, 0.94 by 0.70 inches (23.8 by 17.8 millimeters); largest egg in the series, 1.08 by 0.70 inches (27.4 by 17.8 millimeters); and smallest egg in the series, 0.82 by 0.69 inches (20.8 by 17.5 millimeters). Brewster’s (1882a) measurements of three eggs fall within these ranges.

W. G. F. Harris writes: “The Abert’s towhee usually lays three or four slightly glossy eggs, sometimes only two and less frequently five. They are ovate or short-ovate and practically indistinguishable from those of the canon towhee. The ground may be very pale greenish or creamy white with scattered spots and scrawls of black and very dark browns such as ‘chestnut brown,’ ‘Carob brown,’ or ‘mummy brown,’ with undermarkings of ‘light neutral gray,’ or ‘dark purplish gray.’ The eggs generally are rather sparingly marked, and mostly toward the large end. Often a loose wreath is formed of small black scribblings interspersed with a few gray spots. The measurements of 50 eggs average 24.1 by 17.8 millimeters; the eggs showing the four extremes measure 27.7 by 17.3, 23.4 by 1.9.3, 20.8 by 17.5, and 25.4 by 16.3 millimeters. The measurements of 17 western Abert’s towhee eggs average 24.8 by 18.2 millimeters; the eggs showing the four extremes measure 27.3 by 19.9, 23.3 by 18.2, and 25.1 by 17.3 millimeters.”

Plumages: The following information on the molts and plumages of all the brown towhees (Pipilo Juscus, Pipilo albicollis, and Pipilo aberti) is taken directly from John Davis (1951):

The molt pattern of the brown towhees has been determined through the study of fall-taken specimens, the ages of which were ascertained by the degree of ~kul1 ossification. The only molt of real significance in the brown towhees is the fall molt. At this time adults undergo complete feather replacement. Birds undergoing the postiuvenal (first fall) molt retain the primaries and secondaries, and usually the rectrices. This molt pattern offers plumage characters that may be used to separate first-year birds from second-year or oldcr birds. In fresh fall plumage the primaries of the first-year (=~ immature) birds are dull brown and the margins of these feathers are finely erose because of wear. The primaries of second-year and older (=adults) at this time are glossy and nearly black and the margins of these feathers are entire. The rectrices of immature birds have pointed tips * * * and show signs of wear. The rectrices of adults are obtuse at the tip * * * and are glossy and unworn. Since rectrices are often replaced in the postjuvenal molt, the amount of wear on the primaries offers the most reliable criterion for judging age. * * *

Juveniles are at once distinguished from immatures and adults by the extensive streaking and spotting of the underparts and by the very soft and lacy texture of the head and body plumage.

Coues (1866) considered the molt of the Abert’s towhee to occur from July well into October. ilenshaw (1875) found all of the six specimens he obtained along the Gila River in mid-September to be molting. I did not observe towhees in this condition in the Imperial Valley of California until late August.

The Abert’s towhee has a grayish brown pileum and a slightly paler and grayer dorsum. Its breast, sides, and flanks are pinkish gray. The chin is black and the throat is grayish pink streaked with black. The under tail coverts are dull cinnamon, and the primaries are dark grayish brown with the rectrices blackish brown. P. a. aberti, originally described by S. F. Baird (1852), differs from P. a. dumeticolus, originally described by van Rossem (1946a), in having a darker, grayer pileum and dorsum, and grayer underparts with a pinkish rather than a cinnamon tinge. The bill in both forms is horn colored and contrasts strongly with the black face patch. Immatures and adults show no consistent differences in coloration (Davis, 1951).

Food: No comprehensive study of the food habits of Abert’s towbees has been published, but presumably the general nature of their diet approximates those of the brown and the spotted towhees (P. Juscus and P. erytltrophtalmu.s) analyzed in California by F. E. L. Beal (1910): animal material constituted 14 percent of the total food taken by the former and 24 percent of that by the latter. I have observed Abert’s towhees foraging extensively around quail brush, apparently obtaining the fallen seeds of this plant, and I have trapped these birds successfully using millet seed as bait. Like most other passerines, they will readily eat meal worms (Tenebrio larvae) in captivity. Their utilization of insects in nature is suggested by Stevens’s (1878) and Stephens’s (in Brewster, 1882a) observations of their hunting in the bark of large trees like wrens or nuthatches.

Behavior: The wariness of Abert’s towbees has impressed many ornithologists, and Bendire (1890) rated them among the shyest birds of his acquaintance. They are generally difficult to approach and to observe, because of the denseness of the riparian growth which they frequent much of the time. However, it is usually easy to detect their presence in an area owing to their habit of calling frequently under most conditions. As indicated above, they are not strictly confined to riparian vegetation, but will venture forth a few yards into adjacent, more open situations to forage and dust bathe. When disturbed, they usually retreat directly back into riparian growth, even though closer shelter may be available.

Abert’s towhees live in areas marked by very hot summers; environmental temperatures above 400 C. and intense solar radiation are common. During hot weather these birds generally confine their activity to the cooler parts of the day: the early morning and late afternoon. In the hottest part of the day, between approximately 11:00 a.m. and 3:30 p.m., they apparently take shelter in the densest part of their riparian habitat and remain inactive. Along the Alamo River, Imperial County, Calif., I (1954) never found them in open areas during mid-day in hot weather. This pattern of behavior, which minimizes their metabolic heat production in the coolest surroundings available, appears to be of critical importance in their coping with heat stress. Activity of Abert’s towhees declined to a much smaller degree during the middle of the day in cooler weather, when birds were observed frequently in the more open parts of their habitat.

Various opinions have been expressed concerning the social tendencies of these birds. Bendire (1890), on the basis of experience with P. a. aberti, considered them to be less social than brown towhees (P. J. mesoleucus), whereas Coues (1860), on the basis of experience with the same form, thought them to be more gregarious than other members of the genus Pipilo. Coues, according to Baird, Brewer, and Ridgway (1874b), observed small flocks of this form in September. llenshaw (1875) also observed them to be gregarious in this month. Coues (1866) noted Abert’s towhees to associate occasionally with brown towhees along Rillito Creek in Arizona. I have always considered Abert’s towhees to be rather gregarious during the nonbreeding season, and this is consistent with the observations of Brown (1903), who repeatedly saw them in rather large flocks in the early winter months along the Colorado and lower Gila rivers “scratching in the earth and sunning themselves like a lot of quail.”

In the vicinity of Tucson, Arizona, P. a. aberti and P. fuscue mesoleucus occur together in the same mesquite river-bottom woodlands. J. T. Marshall (1960) considers that they are in direct competition with each other there, though he found little indication of antagonism between the two species.

Voice: The call of the Abert’s towhee is reminiscent of that of the brown towhee, but it seems to me to be less metallic and to have a more whistlelike quality. It has been variously described as “sharp, high pitched” (F. M. Bailey, 1928); a “loud, clear, sharp chirp”

(Coues, 1866); a “loud chuck” (Coale, 1894); a “huit, huit” (Bendire, 1890); and a “sharp chirp” (Brewster, 1S82a). The Abert’s towhee will occasionally produce a succession of notes which progressively increase in frequency, characterized by Baird, Brewer, and Ridgway (1874b) as “chip, chip, chee-chee-ehee.”

Marshall (1960) provides the most comprehensive account of the voice of this species. He characterizes the call note as a “sharp peep,” the male song as an “accelerating series of its ordinary call note, peep, often terminating in coarse phrases like the song of a Tolmie Warbler,” the locative note as a quavering “seee,” the alarm note near a nest with young as a “tic,” and the pair reinforcement call as a “squeai-cha-cha-c ha.”

Field marks: Abert’s towbecs are light brown birds about 9 inches in total length and weighing approximately 45 grams. The most conspicuous field mark is the black face patch which contrasts sharply with the light-colored conical bill.

Enemies: Abert’s towhees of both subspecies are occasionally parasitized by cowbirds (Molothrus ater obscurws). Brown (1903) found nests with cowbird eggs in them along the Colorado and lower Gila rivers, A. B. Howell found a nest containing a cowbird egg near Gadsden, Yuma County, Ariz. (Friedmann, 1929), and H. Friedmann (1931) records several others near Mesa, Maricopa County, Ariz.

A number of predators appear to prey on Abert’s towhees at all stages in their life history, and Bendire (1890) suggests that snakes, jays, squirrels, hawks, and owls all take a toll of eggs, young, and, in some cases, adults. Gilman (1915) recorded discovering an empty nest with a blacksnake coiled around it near Sacaton, Pinal County, Ariz.; a pair of adult towhees obviously agitated by its presence remained nearby. Roadrunners (Geococcyx califor’nicus) may prey on young birds, because one H. C. Bryant (1916) collected at Palo Verde, Imperial County, Calif., contained a nestling Abert’s towhee. However, the possibility that the roadrunner bad obtained it dead could not be discounted.

Two helminth parasites have been found in Abert’s towhees of the subspecies dumeticolus, collected in the Imperial Valley of California. One of these was a tape worm, Anonchotaenia ion giovata (M. Voge and B. S. Davis, 1953); the other, a nemotode crop worm for which the identification is not at this time available (W. R. Dawson, notes).

DISTRIBUTION
Range: The eastern Abert’s towhee (P. a. aberti) is resident along the Gila River and its tributaries in southern Arizona and southwestern New Mexico (Cliff, Redrock). The western Abert’s towhee (P. a. dumeticolu.s) is resident in the valleys of the Virgin and lower Colorado rivers from southwestern Utah (St. George) to northeastern Baja California and northwestern Sonora, and in the Salton Sea Basin of southeastern California (west to Whitewater).

Egg dates: Arizona: 92 records, February 28 to September 4; 46 records, April 1 to May 31.