Toxostoma Curvirostre Research Articles

PHYLOGEOGRAPHY AND PATTERNS OF DIFFERENTIATION IN THE CURVE-BILLED THRASHER

Abstract Recent mitochondrial DNA (mtDNA) and morphological studies suggest that the Curve-billed Thrasher (Toxostoma curvirostre) consists of three historical groups, corresponding to the subspecies curvirostre and palmeri and a new taxon distributed in Oaxaca and Puebla. Previous mtDNA analysis did not include the subspecies T. c. insularum found on Tiburon Island (Sonora, Mexico). We collected new samples to address the distinctiveness of the three groups, to explore possible contact between the curvirostre and southern clades, to clarify the status of T. c. insularum, and to explore population histories of the major clades. Our mtDNA results confirm the existence of three major haplotype clades, which represent either two or three species depending on the species concept used. We interpret the occurrence of two mismatched haplotypes in Puebla and Oaxaca as recent gene flow. Haplotypes from Tiburon Island were intermixed within the palmeri clade, thereby failing to support the subspecies T. c. insularu...

Geographic Variation of the Curve-Billed Thrasher (Toxostoma Curvirostre) Complex

Abstract Geographic patterns of variation in morphological characters in the Curve-billed Thrasher (Toxostoma curvirostre) have been recognized by the description of seven subspecies. Twelve standard measurements, as well as three colorimetric characters and two color pattern characters, were analyzed to test whether subspecies limits predict patterns of variation. Measurement error was addressed by measuring each character three times and calculating the mean. A total of 821 male study skins were used, representing 29 locations. A variety of analysis revealed two major groups, an eastern and western group, divided by the Sierra Madre Occidental. Those two groups had previously been recognized as the curvirostre and palmeri groups, respectively. Those groups were also recovered by analysis of mtDNA. The two groups fulfill the requirements for species. The Tiburón Island (T. c. insularis) sample was distinct for several characters; however, small sample size precludes formal taxonomic recommendation. Within the two major groups, most characters showed incongruent clinal patterns of variation that did not match subspecies limits.

GEOGRAPHIC VARIATION OF THE CURVE-BILLED THRASHER (TOXOSTOMA CURVIROSTRE) COMPLEX

Abstract Geographic patterns of variation in morphological characters in the Curve-billed Thrasher (Toxostoma curvirostre) have been recognized by the description of seven subspecies. Twelve standard measurements, as well as three colorimetric characters and two color pattern characters, were analyzed to test whether subspecies limits predict patterns of variation. Measurement error was addressed by measuring each character three times and calculating the mean. A total of 821 male study skins were used, representing 29 locations. A variety of analysis revealed two major groups, an eastern and western group, divided by the Sierra Madre Occidental. Those two groups had previously been recognized as the curvirostre and palmeri groups, respectively. Those groups were also recovered by analysis of mtDNA. The two groups fulfill the requirements for species. The Tiburon Island (T. c. insularis) sample was distinct for several characters; however, small sample size precludes formal taxonomic recommendation. Withi...

Comparative Phylogeography of Some Aridland Bird Species

AbstractWe compared mitochondrial DNA sequences for six species distributed across the aridlands of North America to document phylogeographic patterns and assess levels of congruence. The Curve-billed Thrasher (Toxostoma curvirostre) and Canyon Towhee (Pipilo fuscus) show genetic divisions between the Sonoran and Chihuahuan Deserts, whereas the Cactus Wren (Campylorhynchus brunneicapillus), Black-tailed Gnatcatcher (Polioptila melanura), and Verdin (Auriparus flaviceps) do not. Most likely, species without phylogeographic structure only recently colonized their entire current range. Therefore, although these species are today part of a widespread avifauna, species' distributions were historically different from today. In Baja California, the Cactus Wren and the Verdin show phylogeographic breaks at 28°–30°N, consistent with a division previously described in the LeConte's Thrasher (Toxostoma lecontei) and in some members of the herpetofauna. These genetic divisions were likely caused by isolation resulting from a mid-peninsular seaway that existed one million years ago. Hence, these species appear to have been broadly sympatric for at least one million years. In contrast, the California Gnatcatcher (Polioptila californica) lacks such a phylogeographic division, and apparently only recently expanded into the northern part of its current range. Thus, not all species in Baja California have had similar histories, although further sampling might reveal a general pattern. Comparative phylogeography therefore provides an indirect method of evaluating the long-term stability of faunas via assessment of levels of phylogeographic congruence, and can show whether particular species are likely to have had a long period of co-association.

COMPARATIVE PHYLOGEOGRAPHY OF SOME ARIDLAND BIRD SPECIES1

We compared mitochondrial DNA sequences for six species distributed across the aridlands of North America to document phylogeographic patterns and assess levels of congruence. The Curve-billed Thrasher (Toxostoma curvirostre) and Canyon Towhee (Pipilo fuscus) show genetic divisions between the Sonoran and Chihuahuan Deserts, whereas the Cactus Wren (Campylorhynchus brunneicapillus), Black-tailed Gnatcatcher (Polioptila melanura), and Verdin (Auriparus flaviceps) do not. Most likely, species without phylogeographic structure only recently colonized their entire current range. Therefore, although these species are today part of a widespread avifauna, species' distributions were historically different from today. In Baja California, the Cactus Wren and the Verdin show phylogeographic breaks at 28°–30°N, consistent with a division previously described in the LeConte's Thrasher (Toxostoma lecontei) and in some members of the herpetofauna. These genetic divisions were likely caused by isolation resulting from a mid-peninsular seaway that existed one million years ago. Hence, these species appear to have been broadly sympatric for at least one million years. In contrast, the California Gnatcatcher (Polioptila californica) lacks such a phylogeographic division, and apparently only recently expanded into the northern part of its current range. Thus, not all species in Baja California have had similar histories, although further sampling might reveal a general pattern. Comparative phylogeography therefore provides an indirect method of evaluating the long-term stability of faunas via assessment of levels of phylogeographic congruence, and can show whether particular species are likely to have had a long period of co-association.

Species Limits and Recent Population History in the Curve-Billed Thrasher

AbstractWe surveyed 1,115 base pairs of mitochondrial DNA sequence from three gene regions in 66 Curve-billed Thrashers (Toxostoma curvirostre) taken from throughout their range. We found that populations sorted unambiguously into three groups. Two of these groups, the Curvirostre and Palmeri groups, have been known for many years because of their distinctive phenotypic characteristics, and their status was recently confirmed with an intensive morphometric analysis. The third (southern) group consists of populations in Puebla and Oaxaca, Mexico. The strong morphological and mtDNA distinctiveness of the Curvirostre and Palmeri groups suggests that they warrant species status. We recommend that more specimens of the southern group be obtained prior to formal taxonomic recognition of this form. Coalescence analyses suggest that the Curvirostre group has undergone a recent population increase, whereas the Palmeri group seems to have been more stable in its Sonoran Desert range.

SPECIES LIMITS AND RECENT POPULATION HISTORY IN THE CURVE-BILLED THRASHER

Abstract We surveyed 1,115 base pairs of mitochondrial DNA sequence from three gene regions in 66 Curve-billed Thrashers (Toxostoma curvirostre) taken from throughout their range. We found that populations sorted unambiguously into three groups. Two of these groups, the Curvirostre and Palmeri groups, have been known for many years because of their distinctive phenotypic characteristics, and their status was recently confirmed with an intensive morphometric analysis. The third (southern) group consists of populations in Puebla and Oaxaca, Mexico. The strong morphological and mtDNA distinctiveness of the Curvirostre and Palmeri groups suggests that they warrant species status. We recommend that more specimens of the southern group be obtained prior to formal taxonomic recognition of this form. Coalescence analyses suggest that the Curvirostre group has undergone a recent population increase, whereas the Palmeri group seems to have been more stable in its Sonoran Desert range.

Curve-billed thrasher winters in St. Claude, Manitoba

Curve-billed thrasher winters in St. Claude, Manitoba

Seasonal changes of the adrenocortical response to stress in birds of the Sonoran Desert.

Many avian species of the North American Sonoran desert, e.g., the black-throated sparrow, Amphispiza bilineata, cactus wren, Campylorhynchus brunneicapillus, and curve-billed thrasher, Toxostoma curvirostre, can potentially breed from March/April to August. It is possible that, at least in summer, intense heat and aridity may have inhibitory effects on breeding by precipitating a stress response. Stress typically results in a rise in secretion of adrenocorticosteroid hormones that then inhibit reproduction by suppressing release of gonadal hormones. However, we found that plasma levels of corticosterone were not higher during summer, compared with winter, even in 1989 when summer temperatures were higher than normal. In June 1990, temperatures were also above normal and soared to the highest level recorded in Arizona (50 degrees C). Plasma levels of corticosterone during June were high in black-throated sparrows, but less so in two other species (Abert's towhee, Pipilo aberti, and Inca dove, Scardafella inca) found in more shady riparian and suburban habitat with constant access to water. The adrenocortical response to stress (as measured by the rate of corticosterone increase following capture) was reduced in the hottest summer months in black-throated sparrows, cactus wrens, and curve-billed thrashers, but less so in Abert's towhee an Inca dove. These data suggest that at least some birds breeding in the open desert with restricted access to water are able to suppress the classical adrenocortical response to stress. The response is then reactivated in winter after breeding has ceased. It is possible that this stress modulation may allow breeding to continue despite severe heat. Analysis of plasma from these species indicated that the apparent modulation of the adrenocortical response to stress was not an artifact of reduced affinity or capacity of corticosterone binding proteins.

Bird Visitation to Agave salmiana: Comparisons among Hummingbirds and Perching Birds

We studied bird visits to the flowers of Agave salmiana at two sites on the Mexican Plateau. At one site the main visitors were four species of perching birds (Northern Flicker, Colaptes auratus; Curve-billed Thrasher, Toxostoma curvirostre; Scott's Oriole, Icterus parisorum; and Northern Oriole, Icterus galbula abeillei) and one hummingbird, the Magnificent Hummingbird (Eugenesfulgens). At a second site, plants were visited by five species of hummingbirds (E. fulgens; White-eared Hummingbird, Hylocharis leucotis; Berylline Hummingbird, Amazilia beryllina; Violet-crowned Hummingbird, Amazilia violiceps; and Blue-throated Hummingbird, Lampornis clemenciae), and the Cinnamon-bellied Flowerpiercer, Diglossa baritula. At both sites, male E. fulgens defended inflorescences against other hummingbirds but not against perching birds. At one site, E. Julgens males defended inflorescences only in places with sparse vegetation; inflorescences located in areas with dense vegetation were visited by highly mobile nonterritorial hummingbirds. At both sites the numbers of birds in each inflorescence were a linear function of number of nectarproducing flowers. Arrival rates were also linearly related to flower numbers. For inflorescences with equal numbers of flowers, arrival rates were higher for hummingbirds than for perching birds. This resulted from the shorter residence times of the hummingbirds in the inflorescences. Different species of birds tended to use different parts of inflorescences.

Partitioning of Foraging Space and Nest Sites in a Desert Shrubland Bird Community

Partitioning of foraging space and nesting substrates by birds was examined in a desert community in southern Arizona. The study site was dominated by low shrubs, with scattered thorn trees and stem succulents. Chi-square analysis demonstrated the importance of plant height, growth form, and patch location within the habitat in selection by birds of foraging and nesting substrates and, ultimately, in determination of bird community composition. Phainopeplas, ash-throated flycatchers, verdins, black-tailed gnatcatchers and gila woodpeckers favored thorn trees for feeding substrates, which they subdivided according to height, plant part and habitat patch. Most of these birds, as well as the common ground feeding species (cactus wrens, curve-billed thrashers, black-throated sparrows and Gambel's quail), also used thorn trees and succulents for nesting sites. The presence of thorn trees and stem succulents apparently enhances avian diversity in complex desert shrublands by providing protected nest sites and a structural framework that facilitates subdivision of foraging space. INTRODUCTION Most ecologists agree that vegetation exerts a major influence on the assemblage of breeding birds that occurs within a habitat. In addition to providing the architectural framework within which birds exist, vegetation affects the supply of both plant and animal foods, nest sites and song perches. MacArthur and MacArthur (1961) inspired a wealth of research into bird community structure when they found a predictive linear relationship between vegetation complexity and bird species diversity in forested habitats of the eastern U.S. Scholars subsequently studied bird communities in various temperate and tropical habitats in efforts to substantiate and refine MacArthur's predictive model (e.g, MacArthur et al., 1962; MacArthur et al., 1966; Recher, 1969; Karr, 1971). The arid portions of the southwestern U.S. are well-represented in this body of literature, with studies done by Tomoff (1974) and others (Austin, 1970; Carothers et al., 1974; Stamp, 1978). In keeping with the ecological attitudes of their day, most scholars studying desert bird communities during the 1970s were concerned with communities as units, which they often summarized with diversity indices. Little attention was paid to variation within communities, such as the use of different vegetation components by individual bird species. Indeed, Tomoff (1974) was one of the few students of arid lands of this era who sought underlying functional links between vegetation structure and birds by examining feeding and nesting habits of the community overall. More recently ecologists have probed beneath the superficial community generalizations that were an outgrowth of MacArthur's time to analyze both species interactions and spatial and temporal variation in community composition. Examples include recent studies of desert bird communities by Rosenberg et al. (1982) and Meents et al. (1983). Both studies are in-depth examinations of habitat characteristics and patterns of species occurrence, but, unlike Tomoffs work, do not attempt analysis of nesting patterns. The intent of this study is to examine patterns of vegetation use for feeding and nesting by common species breeding in a desert shrub habitat in southern Arizona. This analysis addresses two questions: (1) What plant cover characteristics separate the common bird species? (2) To what extent does partitioning of nest sites augment subdivision of foraging substrates in the determination of avian community composition in desert habitats?

The Parasitic Behavior of the Bronzed Cowbird in South Texas

Aspects of the breeding ecology of the Bronzed Cowbird (Molothrus aeneus) were studied from early April to mid-July or August 1980 to 1982 at the Santa Ana National Wildlife Refuge in southern Texas. Female Bronzed Cowbirds, similar to Brown-headed (M. ater) and Shiny (M. bonariensis) cowbirds, are generalists in their egg laying. Of five common host species on the refuge, all were equally and usually repeatedly parasitized. Of these, only the Green Jay (Cyanocorax yncas) and Longbilled Thrasher (Toxostoma longirostre) are larger than the cowbirds in body size and are better host choices based on their relative success as fosterers. Experimental parasitism of Couch's Kingbirds (Tyrannus melancholicus), Curve-billed Thrashers (Toxostoma curvirostre), and Great-tailed Grackles (Quiscalus mexicanus) showed that they eject cowbird eggs from the nest. Female Bronzed Cowbirds, like Shiny Cowbirds, pierce both host eggs and previously laid cowbird eggs. Approximately twice as many host eggs were pierced compared to cowbird eggs. In some parasitized nests, more than one cowbird laid eggs and final host clutch size was greatly reduced. The vocal reaction of host species to cowbird intrusion probably provided clues on nest location to nest-searching female cowbirds who were drawn to such stimuli. Like the other four parasitic cowbird species, Bronzed Cowbird nestlings possess no apparent special adaptation for brood parasitism. Their vocal nature, however, appears to give them a competitive edge against less vocal host nestmates.

Wintering Ecology of Thrashers in Southern Texas

Three sympatric thrashers, the Brown, the Long-billed, and the Curve-billed (Toxostoma spp.), were studied during the winters of 1977 and 1978 in San Patricio County, Texas. The species avoided competition primarily by occupying different habitats. Brown Thrashers wintered abundantly within riparian woodlands, Long-billed Thrashers stayed mostly within shrub cover of chaparral, and Curve-billed Thrashers inhabited the more open portions of the chaparral. All three species foraged mostly on the ground and were omnivorous. The foraging behavior of Brown and Long-billed thrashers was similar (sweeping debris aside with bill) and both fed only within cover. Curve-billed Thrashers differed from the other thrashers in foraging techniques (reliance upon digging), diet, and in feeding frequently outside of shrub/tree cover. Brown and Long-billed thrashers maintained intra- and inter-specific winter territories. Both were highly philopatric, with 27% of the color-marked Brown Thrashers and 48% of the color-marked Long-billed Thrashers returning in 1978 to their 1977 winter territories. Brown Thrashers apparently were superior competitors, mostly excluding Long-billed Thrashers from arthropod/gastropod-rich riparian habitats.

Miscellaneous Summer Records of Birds from Southwestern Kansas

Two summers (1978 and 1979) of field research on nongame wildlife in southwestern Kansas have established several new records for both breeding and migratory species of birds. New breeding records were established for the ferruginous hawk (Buteo regalis), lesser prairie chicken (Tympanuchus pallidicinctus), great-tailed grackle (Quiscalus mexicanus), and the field sparrow (Spizella pusilla) from Morton County; the American avocet (Recurvirostra americana) from Seward and Kearny counties; and the Cassin's sparrow (Aimophila cassinii) from Meade County. Species showing increased summer movements and breeding activities include the curvebilled thrasher (Toxostoma curvirostre), great-tailed grackle, and the Brewers sparrow (Spizella breweri) from Morton County. Sightings of rare species include the ladder-backed woodpecker (Dendrocopos scalaris), northern parula warbler (Parula americana), Blackburnian warbler (Dendroica fusca), and the chestnut-sided warbler (Dendroica pensylvanica) from Morton County; and the rose-breasted grosbeak (Pheucticus ludovicianus) from Grant County. While some species show distributional increases (e.g. great-tailed grackle) others have shown a decline in this region (e.g. ladder-backed woodpecker). Still not enough is known about other species (e.g. rose-breasted grosbeak, field sparrow) to understand their distributional patterns in southwestern Kansas. Several studies describe the status and distribution of summer birds in southwestern Kansas (Rising, 1974; Ely and Thompson, 1971; Graber and Graber, 1951). Recent fieldwork in this region has nevertheless resulted in several new breeding and distributional records. During the summers of 1978 and 1979, while employed by the Kansas Fish and Game Commission, I conducted a nongame research project to 1 Present address: 2924 Lakeside Drive, Oklahoma City, Oklahoma 73120. This content downloaded from 157.55.39.22 on Sat, 16 Jul 2016 05:08:02 UTC All use subject to http://about.jstor.org/terms 110 TRANSACTIONS OF THE KANSAS ACADEMY OF SCIENCES determine the status and distribution of some rare and peripheral species of birds in southwestern Kansas. This resulted in new breeding records for the curve-billed thrasher, great-tailed grackle, Brewers sparrow, ferruginous hawk, lesser prairie chicken, and American avocet. Other records for species such as the rose-breasted grosbeak, Cassin's sparrow, and the field sparrow serve to help understand their distributions in this region. Included here are records for such species as the ladder-backed woodpecker, northern parula warbler, Blackburnian warbler, and chestnut-sided warbler which are considered rare in southwestern Kansas. The following species deserve close attention by field ornithologists in the future. Ferruginous Hawk. This hawk is an uncommon summer resident in western Kansas with most of the breeding records coming from counties north of the Arkansas River (Johnston, 1964). On 4 June 1979 a nest with two half grown nestlings was discovered in Morton County in far southwestern Kansas. The nest was 10 ft. up in a small stand of trees (Morus) surrounded by Sand sagebrush (Artemisia filifolia)-grasslands. This constitutes the first breeding record of this hawk for Morton County. Lesser Prairie Chicken. This species is reported to be fairly common in the southwestern counties of Morton, Meade, and Ford but actual breeding records from this region are few (Rising, 1974). Two nests of this species were found 2/2 mi. SE of Wilburton, Morton County, in an area of sandhills covered with sagebrush, forbs, and sparse grasses. One nest, discovered on 18 May 1979, was placed beneath a sagebrush on the ground concealed by tufts of new grass. It held 12 eggs. On 1 June 1979 this nest held 12 recently hatched nestlings no more than a few hours old. A nest discovered on 26 May 1979 contained 13 eggs and was placed only 200 yards from the first

Breeding Biology of Curve-Billed Thrashers and Long-Billed Thrashers in Southern Texas

Curve-billed Thrashers and Long-billed Thrashers were studied in Live Oak County, Texas, during the summers of 1977 and 1978. Curve-billed Thrashers nested and foraged mostly within open habitats, although they also nested in dense chaparral if clearings were nearby. Long-billed Thrashers nested and foraged exclusively within dense chaparral. Curve-billed Thrashers often nested in exposed sites whereas Long-billed Thrashers always nested in shelter. Curve-billed Thrashers constructed deeper nests, incubated their eggs for less time each day, and brooded their young for many more days than did Long-billed Thrashers. Curve-billed Thrashers had greater reproductive success (37%) than did Long-billed Thrashers (26%). This difference was attributed to the frequent use of Yucca for nest support by Curve-billed Thrashers. Nest success was not significantly affected by nest height, brood size, or the date when the nest was initiated. Snakes were the primary predators of thrasher eggs and nestlings. The roles of the sexes of Curve-billed Thrashers were examined during the breeding cycle. Females incubated and fed the nestlings significantly more often than males. Only females brooded the young. Male participation varied greatly among pairs and between nesting attempts.

Host and distributional records for the tick Amblyomma inornatum (Banks) (Acarina: Ixodidae), with descriptions of the immature stages.

New host and locality records for adult Amblyomma inornatum are given and published records reviewed. The previously unknown larval and nymphal stages are described. Immature ticks of this species were recovered in Cameron County, Texas, during the period of May 1960 to August 1964 from the Hispid Cotton Rat, Sigmodon hispidus ; Mexican Ground Squirrel, Spermophilus mexicanus ; Roadrunnner, Geococcyx californianus ; Curve-billed Thrasher, Toxostoma curvirostre ; and Ninebanded Armadillo, Dasypus Novemcinctus . Breeding occurred throughout the year.

New Breeding Records of Toxostoma curvirostre and T. bendirei in New Mexico

Journal Article Audubon’s Shearwater, Hudsonian Godwit, and Long-Tailed Jaeger in Oaxaca, Mexico Get access Laurence C. Binford Laurence C. Binford California Academy of Sciences Golden Gate Park San Francisco, California 941186 Search for other works by this author on: Oxford Academic Google Scholar The Condor, Volume 72, Issue 3, 1 July 1970, Pages 366–367, https://doi.org/10.2307/1366020 Published: 01 July 1970 Article history Accepted: 27 May 1969 Published: 01 July 1970

Brood Reduction in the Curve-Billed Thrasher

Lack (1954; 40-41) has pointed out that in species of birds which have asynchronous hatching, brood size may be adjusted to temporal fluctuations in food availability. Parents generally feed the most active of their brood, that is, the largest (oldest) and the strongest. When such nestlings are replete, they become inactive and food is then passed on to the smaller members of the brood. When food availability is high, the parents are capable of satisfying all of the brood; when low, only the largest or first hatched are satisfied and the others starve to death. Thus, because of size differences due to asynchronous hatching, the parents are able to distinguish their young and can distribute limited food resources to the best advantage. If differentiation were not possible, food would be distributed randomly with each nestling having equal probability of being fed. During a poor year, all of the young would be underfed, a condition presumably less advantageous than having fewer well-fed young. Brood reduction is generally thought of as being prevalent in the hawks and owls and in some sea birds. It is the purpose of this paper to demonstrate the phenomenon in a passerine, the Curve-billed Thrasher (Toxostoma curvirostre). Up to a point, the parent can increase its rate of food delivery to the young by increasing its own effort. When food availability is low, it presumably takes a greater effort to deliver food at a given rate than during a more favorable period. It is convenient to think of the rate as being constant for any given level of food availability. Although probably unrealistic, this assumption is not impractical if we consider that regardless of the food availability there is an optimum effort which the parent can devote to gathering food. For different resource levels, this optimum effort will yield different rates of food delivery to the young. The energy requirement for the growth of the nestling increases with age up to a certain point after which it decreases (fig. 1). Thus, the parents are increasingly taxed not only with the addition of more young to the brood, but also with time. In a good year, the parents are able to keep up with the increasing demands and can deliver food at the maximum rate required by a full brood of nestlings. In a poor year, the requirement of the entire brood may exceed the delivery capacity of the parents long before the peak requirement is reached. When this happens, the smallest receives no food and dies. If, several days later, the requirement of the reduced brood again exceeds the delivery capacity of the parents, the smallest of the remaining birds has already been starved to death. It is theoretically possible that not one nestling would end up well fed in extremely hard times, but the birds would not be likely to breed under such conditions.

Observations on the Inca Dove at Tucson, Arizona

For the past ten years the Inca Dove (Scardafella inca) has nested on or near our acre lot in the Rillito Valley, six miles northeast of Tucson, Arizona. The following summary of our observations is intended to fill in a few of the gaps in the life history of this somewhat neglected species. Inca Doves moved into our neighborhood about thirteen years ago when the first house was built. At that time the ten-acre block was covered chiefly with creosote bush and cholla cactus. A thin line of mesquites and catclaw fringed an abandoned irrigation ditch which traversed the area. Gradually homes were built on six of the acres. Small chicken houses with enclosed yards and gardens were added. Much of the original vegetation was left undisturbed. A few ornamental trees such as tamarix, pepper, and china berry, which were planted early, grew rapidly to large size. Brief notes are available on 28 nesting attempts in this area. Although we have found nests in introduced ornamental trees in other parts of Tucson, all the nests in our neighborhood were placed in native shrubs. We found one in a catclaw bush (Acacia greggii), and all the others in chollas (Opuntia spinosior). Two other species of cholla which grew to suitable size were not selected for nest sites. Of these, Opuntia versicolor may have been unsuitable because of its smaller twigs and fewer horizontal branches. Opuntia fulgida was probably avoided because of the presence of nests of the Curvebilled Thrasher (Toxostoma curvirostre) and Cactus Wren (Campylorhynchus brunneicapillus), although two of the dove nests were built on old weathered remnants of Cactus Wren nests. Nest heights varied from three to six feet above the ground. There was no apparent attempt at concealment. Although the scanty nest platform was often difficult to make out, the incubating bird always sat in plain view and could readily be seen from some distance away. Its dull, gray-brown coloration in such a situation had little protective value. With the exception of one nest at 125 feet, all were placed within 50 feet of occupied buildings. Occasionally automobile traffic would pass as close as 15 feet from a nest.