Myiarchus Cinerascens Research Articles

Ash-Throated Flycatchers (Myiarchus cinerascens) Raise Mountain Bluebird (Sialia currucoides) Young

Ash-throated Flycatchers (Myiarchus cinerascens) and Mountain Bluebirds (Sialia currucoides) are secondary cavity-nesters that are sympatric in juniper woodlands of northern Nevada. While conducting a study of Mountain Bluebird reproductive strategies during the 1988-1989 breeding seasons, we observed two instances of Ash-throated Flycatchers raising bluebird nestlings in addition to their own young. Our study area is located in partially burned juniper woodlands north of Reno, Nevada, and contains 68 nestboxes. These boxes have been used since 1985 by Mountain Bluebirds and are also used occasionally by Ash-throated Flycatchers. In the first incident, a nestbox which contained two bluebird eggs on 30 May 1989 was taken over by Ashthroated Flycatchers. The adult bluebirds were unbanded, so we are not sure what happened to them after losing the nestbox; they did not use the nestbox again that season. The female flycatcher did little additional nestbuilding (flycatchers in this area use clumps of fur for nest material whereas bluebirds mainly use strips of bark), but laid her clutch of five eggs alongside the two bluebird eggs by 6 June. She incubated the mixed clutch, and all seven eggs hatched on approximately 19 June. In the four times we checked the nest between hatching and 3 July, the rate of nestling development appeared to be equal for both species. Only flycatchers were seen feeding the young. All nestlings presumably fledged on 11 July, except for one almost completely feathered bluebird nestling found mummified in the nestbox on 12 July (cause of death unknown). Despite repeated searches, we did not see the young after fledging. In the second incident, an Ash-throated Flycatcher laid two eggs by 22 June 1989 in a nestbox in which a bluebird pair had previously fledged a clutch of four young. On 5 July there was one Mountain Bluebird egg in the nest, along with two additional Ash-throated Flycatcher eggs. The flycatcher incubated all five eggs. On 12 July, we found one bluebird and two flycatcher young along with a dead flycatcher nestling and an unhatched egg. The young were approximately two days old. Again, only flycatchers were seen caring for the young. On 15 July (five days after hatching), the nest contained only two dead young (one flycatcher and one bluebird). The other nestling and the unhatched egg were missing. The adults were not in the area and were not seen again. Since predation is a major cause of bluebird egg and nestling mortality in our study area (unpubl. data), we assume this was the cause of nest failure, though nest abandonment cannot be completely ruled out. To our knowledge, this is the first report of Ashthroated Flycatchers raising the young of any other species. These two cases are qualitatively different, and we consider two possible explanations for them: 1. competition for suitable nest sites, and 2. facultative brood parasitism. Nest site competition. Two lines of evidence suggest that Mountain Bluebirds and Ash-throated Flycatchers compete for suitable nest sites in this study area. First, we know of four takeovers of bluebird nests by flycatchers since 1985 (two in 1986, one in 1987, one in 1989). There have been no reciprocal takeovers by bluebirds, presumably because flycatchers are much ' Received 15 October 1990. Final acceptance 7 December 1990. SHORT COMMUNICATIONS 461

Energetics of Growth and Maturation in Sympatric Passerines That Fledge at Different Ages

We studied the energetics of growth and maturation of sympatric Western Bluebird (Sialia mexicana) and Ash-throated Flycatcher (Myiarchus cinerascens) nestlings in the San Jacinto Mountains, Riverside County, California. Both species fledge at a body mass of 27-28 g, but the flycatcher leaves the nest 4-5 days earlier than the bluebird. The growth curves of these two species become asymptotic by 14 days of age. Energy budgets, derived from estimates of CO2 production and energy accumulation in tissues, demonstrate that the average daily total metabolizable energy requirement of the nestling flycatcher is approxi- mately 22% (range: 16-32%) higher than the nestling bluebird. Most of this difference is due to a significantly higher field metabolic rate throughout the nestling period of the flycatcher. We attribute this higher energy expenditure to a greater daily allocation of energy to the metabolic processes and activity associated with maturation, which allows the flycatcher to fledge at a younger age than the bluebird. Because of the nestling flycatcher's higher daily energy requirements, adult flycatchers must gather up to 20 g more food each day than bluebird parents with the same number of young. Nestling mortality indicates that Ash- throated Flycatchers may be more susceptible to nest failure than Western Bluebirds during periods of poor food availability. Received 7 October 1988, accepted 7 July 1990. THE ENERGY requirements of young in rela- tion to the parents' ability to provide sufficient food to meet those requirements is an intrinsic relationship that affects the reproductive strat- egies of birds. Many factors influence the en- ergy requirements of growing birds. Differ- ences in body size, growth pattern, and the thermal environment of the nest site can affect the peak energy demands of a brood (Fiala and Congdon 1983, Ricklefs and White 1981, Mer- tens 1969, O'Connor 1975, Bryant and Gardiner 1979, Drent and Daan 1980). Our purpose was to compare the energy ex- penditure of sympatric nestling Western Blue- birds (Sialia mexicana) and Ash-throated Fly- catchers (Myiarchus cinerascens). The adult mass of both species is similar (range: 25-30 g), and nestlings fledge at a body mass ca. 27-28 g. The age at fledging differs by 4-5 days (bluebird: 20-21 days; flycatcher: 16-17 days). These two species have very similar breeding ecologies. The species share the same habitat, both are cavity nesters, and both are insectivorous dur- ing the breeding season. Because the breeding

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?

Ash-Throated Flycatcher Takes Sagebrush Lizard

Ash-Throated Flycatcher Takes Sagebrush Lizard

Nasal Mites of the Subfamily Speleognathinae (Ereynetidae) from Birds in Texas

Nasal mites of the subfamily Speleognathinae were recovered from several species of birds in Texas. New host records include Ophthalmophagus striatus (Crossley) 1952 from Columbigallina passerina, Boydaia clarki Fain 1963 from Callipepla squamata, Boydaia falconis Fain 1956 from Falco sparverius, and Boydaia tyrannus Ford 1959 from Myiarchus cinerascens. Also recovered was Astrida coccyzae Pence 1972 from Coccyzus americanus. Boydaia pheucticola sp. n. from Pheucticus melanocephalus is described. It differs from similar species in the adult female by having the coxal setae formula 2-1-2-0, sensillae clavate but not globose or subglobose, and interior seta on coxa I reduced in size but not vestigial. The larva is differentiated by the modified legs II with one long recurved hooklike claw and a shorter curved claw.

Ash-Throated Flycatcher in Illinois: Summary of Records East of the Mississippi River

Ash-Throated Flycatcher in Illinois: Summary of Records East of the Mississippi River

Interspecific Aggression of Ash-Throated Flycatchers on Cassin's Sparrows

During the course of field studies in 1970 on the Santa Rita Experimental Range, Pima County, Arizona, we observed eight instances of interspecific aggression by Ash-throated Flycatchers (Myiarchus cinerascens) on Cassin's Sparrows (Aimophila cassinii). The former is a medium-sized tyrannid which nests in abandoned woodpecker holes in much of the southwestern United States and into M6xico. It forages mainly by hawking for insects from the upper limbs of trees. The sparrow is a ground-foraging species, feeding on seeds in winter and ground-inhabiting insects during the summer. Nests are placed near the ground in low vegetation. Its song is delivered in an upward arching flight from upper limbs of trees. The pattern of singing flights closely resembles the hawking maneuvers of the flycatcher. It was during the flight song that the sparrows were attacked by the flycatcher. The latter flew straight at the sparrow and usually knocked it to the ground. Apparently, the flycatcher was responding to a behavioral image which approximates its own foraging maneuvers. Selection against such behavior is probably weak since Cassin's Sparrow is rather restricted in its distribution and then only occurs in grasslands. On the other hand, strong selection pressures may operate to maintain this type of behavior in the flycatcher since it overlaps several potential competitors (Myiarchus spp., Tyrannus spp.). One other observation adds strength to the above suggestion. A Cactus Wren (Campylorhynchus brunneicapillus), flying about 3 m above the ground, suddenly made an upward jog in its straight line flight. This deviation was similar in form to a flycatcher foraging maneuver. Immediately, an Ashthroated Flycatcher, which was perched about 4 m away, flew at the wren and knocked it to the ground. These data were obtained during research supported by the US/IBP Desert Biome program under grant no. GB 15886 from the National Science Foundation.

Hematozoa from Colorado Birds. III. Passeriformes

Hematozoa are reported from 1,361 members of the Passeriformes representing 101 species and 22 families, all from Colorado. Some parasitemia was observed in 693 birds (51%). The parasites and their incidences were: Plasmodium (all species), 43 (3%); Haemoproteus, 229 (17%); Leucocytozoon, 273 (20%); Trypanosoma, 401 (29%); Haemogregarines sensu lato (Hepatozoon and Lankesterella), 40 (2.9%); microfilaria, 174 (13%). Seventy-one new host-parasite associations were encountered. Two papers on the hematozoa of Colorado birds have been published by Stabler and Holt (1963, 1965). This third in the series deals with 1,361 members of the Passeriformes, representing 101 species and 22 families. MATERIALS AND METHODS All birds were from Colorado, the majority being from east of the Continental Divide. The period of collection extended from 1948 to 1969. Blood from those captured alive was obtained from a snipped toenail and from the body cavity of those which were shot. Following staining with Giemsa, the blood films were first scanned under low dry magnification (150 X ) and then searched under oil immersion (1,455 X) until we felt that all hematozoan types had probably been detected. The femoral marrow from many of the dead birds was examined in physiological saline for trypanosomes. RESULTS The results are summarized in Table I. Of the 1,361 birds examined, 693 (51%) showed some parasitemia. The parasites and their incidences were: Plasmodium (all species), 43 Received for publication 22 July 1969. (3%); Haemoproteus, 229 (17%); Leucocytozoon, 273 (20%); Trypanosoma, 401 (29%); Haemogregarines sensu lato (Hepatozoon and Lankesterella), 40 (2.9%); microfilaria, 174 (13%). Of the 401 infections with Trypanosoma, only 91 had the organism in the circulating blood. Seventy-one new host-parasite associations were encountered. The common redpoll appears to have been examined parasitologically for the first time. DISCUSSION The complete hematological picture of some of the 1,361 passeriforms has already been published (Stabler, 1961). These birds constitute less than 10% of the total, are all magpies, and are included here for the sake of completeness. Table I bears a column headed "Hg sensu lato" (Haemogregarines sensu lato). It includes parasites similar to those described by Wood and Herman (1943) and Clark and Swinehart (1966) as Hepatozoon (32 cliff swallows, 1 plain titmouse, and 1 western blueTABLE I. Hematozoa from Colorado Passeriformes. Hg sensu Bird Total No.+ Pr Pc Pr-c Pp Pv Pn Ph H L T lato M Tyrannidae Eastern kingbird 10 4 2 2 1 Tyrannus tyrannus Western kingbird 16 9 1* 1' 2 7* Tyrannus verticalis Ash-throated flycatcher 2 1 1* Myiarchus cinerascens Say's phoebe 10 2 1* 1 Sayornis saya Western flycatcher 4 4 2* 4 Empidonax difficilis Western wood pewee 9 5 4 1* Contopus sordidulus Vermillion flycatcher 1 0 Pyrocephalus rubinus Genera and species names are listed according to the fifth (1957) edition of the AOU Check-list. Abbreviations: Pr, Plasmodium relictum; Pc, P. cathemerium; Pr-c, P. relictum-cathemerium; Pp, P. polare; Pv, P. vaughani; Pn, P. nucleophilum; Ph, P. hexamerium; H. Haemoproteus; L, Leucocytozoon; T, Trypanosoma; Hg sensu lato, Haemogregarines sensu lato; M, Microfilaria; *, New host-parasite records. 12 This content downloaded from 207.46.13.71 on Sat, 22 Oct 2016 06:17:57 UTC All use subject to http://about.jstor.org/terms STABLER AND KITZMILLER-HEMATOZOA FROM COLORADO PASSERIFORMES 13

Ash-Throated Flycatcher in Rhode Island

Ash-Throated Flycatcher in Rhode Island

Ash-throated Flycatcher in British Columbia

Ash-throated Flycatcher in British Columbia

The Occurrence of Myiarchus cinerascens inquietus in Lower California

The Occurrence of Myiarchus cinerascens inquietus in Lower California