Pheucticus Melanocephalus Research Articles

Demographic responses to climate-driven variation in habitat quality across the annual cycle of a migratory bird species.

The demography and dynamics of migratory bird populations depend on patterns of movement and habitat quality across the annual cycle. We leveraged archival GPS‐tagging data, climate data, remote‐sensed vegetation data, and bird‐banding data to better understand the dynamics of black‐headed grosbeak (Pheucticus melanocephalus) populations in two breeding regions, the coast and Central Valley of California (Coastal California) and the Sierra Nevada mountain range (Sierra Nevada), over 28 years (1992–2019). Drought conditions across the annual cycle and rainfall timing on the molting grounds influenced seasonal habitat characteristics, including vegetation greenness and phenology (maturity dates). We developed a novel integrated population model with population state informed by adult capture data, recruitment rates informed by age‐specific capture data and climate covariates, and survival rates informed by adult capture–mark–recapture data and climate covariates. Population size was relatively variable among years for Coastal California, where numbers of recruits and survivors were positively correlated, and years of population increase were largely driven by recruitment. In the Sierra Nevada, population size was more consistent and showed stronger evidence of population regulation (numbers of recruits and survivors negatively correlated). Neither region showed evidence of long‐term population trend. We found only weak support for most climate–demographic rate relationships. However, recruitment rates for the Coastal California region were higher when rainfall was relatively early on the molting grounds and when wintering grounds were relatively cool and wet. We suggest that our approach of integrating movement, climate, and demographic data within a novel modeling framework can provide a useful method for better understanding the dynamics of broadly distributed migratory species.

First Documented Breeding of the Black-headed Grosbeak in Alaska

First Documented Breeding of the Black-headed Grosbeak in Alaska

Spatial variation in songbird demographic trends from a regional network of banding stations in the Pacific Northwest

ABSTRACT Many North American landbird populations have declined in recent decades, including those that occupy Western forest habitats. Long-term monitoring of abundance and vital rates allows us to detect species and habitats of concern, and to identify potential management actions. Here, we analyze capture data from a regional network of 10 banding sites in the Klamath-Siskiyou Bioregion, USA, to examine demographic trends for 12 Western forest bird species from 2002 to 2013. Adult abundance declined significantly in some breeding populations of Audubon's Yellow-rumped Warbler (Setophaga coronata auduboni) and Purple Finch (Haemorhous purpureus), and near-significantly in Oregon Dark-eyed Junco (Junco hyemalis oreganus). We observed significant declines in productivity of the Purple Finch and Spotted Towhee (Pipilo maculatus). Black-headed Grosbeaks (Pheucticus melanocephalus) and Yellow-breasted Chats (Icteria virens) increased significantly in adult abundance, but with variation among sites. Productiv...

GPS-tracking reveals non-breeding locations and apparent molt migration of a Black-headed Grosbeak

Black-headed Grosbeaks (Pheucticus melanocephalus) have been observed to undergo prebasic molt during fall in the North American Monsoon region of the southwestern United States and northwestern Mexico, but it is unknown whether molt migration is pervasive across populations of the species. During the 2014 breeding season, we GPS-tagged (where GPS is global positioning system) nine adult Black-headed Grosbeaks in Yosemite National Park with archival GPS tags to determine specific locations where grosbeaks breeding in Yosemite spent portions of the non-breeding season, and to assess whether those locations were consistent with molt migration. On 2 June 2015, one of these birds, a male GPS-tagged on 19 June 2014, was recaptured with its GPS unit still attached. Data downloaded from the unit revealed that, by 20 August 2014, the bird had moved 1300 km from Yosemite National Park to Sonora, Mexico, where it remained until at least 15 October 2014. By 24 November 2014, the grosbeak had moved >1300 m from Sonora to the Michoacan-Jalisco border region, where it remained until the last GPS-determined location was obtained on 24 March 2015. The seasonal timing of these movements and the length of stay in Sonora are consistent with the expected behavior of a molt-migrating bird. Remote-sensed enhanced vegetation index (EVI) data indicated that the grosbeak arrived in the monsoon region near the area's annual peak in EVI, and then, as the index was declining sharply, departed for the Michoacan-Jalisco region, where the index also declined during the same period, but substantially less so than in Sonora. Climate change in the coming decades is expected to delay the annual onset of the monsoon while also accelerating the initiation of arid, summer-like conditions throughout much of western North America, possibly yielding a temporal mismatch between fall migration and the monsoon-driven conditions that may be critical for molt-migrating birds.

A systematic review of the subfamily Syringophilinae (Acari: Syringophilidae) of the Nearctic region. Part 1: quill mites associated with passerines (Aves: Passeriformes).

Quill mites belonging to the subfamily Syringophilinae Lavoipierre, 1953 associated with the Nearctic passeriform birds are revised. All of the 49 known species, which are grouped in seven genera, are recorded. Among them, four new species are described: Syringophiloidus audubioni sp. nov. from Spizella breweri (Cassini) (Emberizidae), Syringophilopsis catesbyi sp. nov. from Vireo olivaceus (Linnaeus) (Vireonidae), S. wilsoni sp. nov. from Pheucticus melanocephalus (Swainson) (Cardinalidae), and S. bartrami sp. nov. from Spizella passerina (Bechstein) (Emberizidae). The species Syringophilopsis hylocichlae Clark, 1964 syn. nov. is synonymized with Syringophilopsis turdus (Fritsch, 1958), and Syringophiloidus zonotrichia syn. nov. is synonymized with Betasyringophiloidus seiuri (Clark, 1964) comb. nov. Six species are recorded from the Nearctic region for the first time: Syringophiloidus delichonum Bochkov, 2001, S. glandarii (Fritsch, 1958), S. weiszii Skoracki et al., 2001, S. bombycillae Skoracki, 2002, Syringophilopsis mimidus Sikora et al., 2011, and Torotrogla merulae Skoracki et al., 2000. Data on Nearctic syringophiline species, their hosts and distribution are summarized and the keys to all species are constructed.

Synergistic effects of spring temperatures and land cover on nest survival of urban birds

ABSTRACT Climate change has the potential to influence avian population dynamics through nest-fate sensitivity to temperatures during the breeding season. Nest fate also varies across spatially heterogeneous habitat, and changing land uses may independently introduce stressors on reproductive outcome. Identifying the individual and synergistic effects of climate change and land-use change is necessary for understanding the impact of global change on native species. We studied the nest fate of 3 sympatric species breeding in urban habitat in an arid region of the western United States. We monitored nests (n = 371) of American Robin (Turdus migratorius), Mourning Dove (Zenaida macroura), and Black-headed Grosbeak (Pheucticus melanocephalus) over 4 yr on an urban-to-rural gradient and analyzed nest fate in relation to temperatures at the time of egg laying and after eggs hatched. Habitat measurements included nest height and the amounts of canopy cover and impervious surfaces at 3 spatial scales of 20-m, 100...

Extensive gene flow characterizes the phylogeography of a North American migrant bird: Black-headed Grosbeak (Pheucticus melanocephalus)

We describe range-wide phylogeographic variation in the Black-headed Grosbeak (Pheucticus melanocephalus), a songbird that is widely distributed across North American scrublands and forests. Phylogenetic analysis of mitochondrial DNA (mtDNA, n=424) revealed three geographically structured clades. One widespread clade occurs throughout the Rocky Mountains, Great Basin, and Mexican Plateau, a second clade is found on the Pacific coast and in coastal ranges; and, a third in the Sierra Madre del Sur of Oaxaca and Guerrero. Some geographical structuring occurs in Mexican Plateau and Sierra Madre Oriental mtDNA clade, presumably because these populations have been more stable over time than northern populations. Multiple mitochondrial groups are found sympatrically in the Okanogan River Valley in Washington, the eastern Sierra Nevada, and the Transvolcanic Belt across central Mexico, indicating that there is a potential for introgression. Analyses of 12 nuclear loci did not recover the same geographically structured clades. Population analyses show high levels of gene flow in nucDNA from the Interior into the Sierra Madre del Sur and Pacific population groups, possibly indicating expansion of the Interior population at the expense of peripheral populations.

Early seral hardwood vegetation increases adult and fledgling bird abundance in Douglas-fir plantations of the Oregon Coast Range, USA

Recent evidence suggests that population declines of bird species associated with early-successional forest conditions may be associated with reduced quality of breeding habitat. Increasing intensity of forest management on private lands and decreased harvest rates on federal lands in the Pacific Northwest, USA, have resulted in a loss of diverse young forest stands, typically called early seral forest. Previous studies suggest that the amount of early seral broadleaf cover within conifer forests is linked to the composition of foliage-gleaning bird communities. However, information regarding productivity and juvenile use of post-breeding habitat in highly modified plantation habitat is lacking. We examined the relationship between vegetation structure resulting from intensive forest management practices and the abundance of five species of leaf-gleaning, neotropical migrants: orange-crowned warbler ( Oreothlypis celata (Say, 1823)), Wilson’s warbler ( Wilsonia pusilla (A. Wilson, 1811)), MacGillivray’s warbler ( Oporornis tolmiei (J.K. Townsend, 1839)), Swainson’s thrush ( Catharus ustulatus (Nuttall, 1840)), and black-headed grosbeak ( Pheucticus melanocephalus (Swainson, 1827)). All species, except MacGillivray’s warbler, showed positive associations with the amount of early seral hardwood cover as fledglings, breeding adults, or both. However, the relative magnitude of these associations varied, suggesting that other factors may also have influenced avian responses. Abundances of breeding pairs and young are likely to show positive responses to management practices that increase early seral hardwood cover in regenerating stands. If adopted at landscape and regional scales, such practices may positively influence population trends of several declining bird species.

Effects of fuel reduction on bird density and reproductive success in riparian areas of mixed-conifer forest in southwest Oregon

Studies in southwest Oregon suggest that riparian areas within mixed-conifer forests historically burned with frequencies and intensities similar to upland areas and that fire played an important role in maintaining both of these ecosystems. Currently, most fuel reduction projects do not include riparian, due to the perception that these riparian areas are negatively affected by anthropogenic disturbance. However, there is very little information on the ecological consequences of including riparian areas in fuel reduction projects. We compared the effects of non-commercial thin and handpile treatments followed by prescribed burns in riparian areas of intermittent and perennial streams that were treated to the streamside (unbuffered), to the typical prescription in which sites were treated only in the adjacent upland (buffered). Unbuffered fuel reduction treatments have the potential to affect bird density and reproductive success differently than buffered treatments by altering (1) available nest habitat, (2) predator and nest parasite abundance, and (3) food availability in riparian areas. This study assessed whether unbuffered fuel reduction treatments yielded similar bird response as buffered treatments by quantifying differences in density and reproductive success of five bird species, vegetation structure, the frequency of occurrence of predators and a nest parasite, and arthropod biomass. Density was greater for the shrub and tree-nesting Pacific-slope Flycatcher in buffered streams post treatment. Reproductive success showed a minimal, near-term effect for the shrub-nesting Black-headed Grosbeak. For potential causal factors, we found differences between buffered and unbuffered streams only for available nest habitat in the upper-ground strata and frequency of occurrence of raptors. Overall, results suggest that fuel reduction in riparian areas as compared with typical upland treatments with buffers had a small effect on bird density and a near-term effect on reproductive success. Additional study of fuel reduction in riparian areas is warranted because of its effectiveness in reducing the risk of unnaturally severe wildfire and, correspondingly, the potential benefit to bird communities over the long-term.

Occasional Mimicry and Night-time Singing by the Western Curve-billed Thrasher (Toxostoma curvirostre palmeri)

The first instance of vocal mimicry is reported for the western subspecies of Curve-billed Thrasher (Toxostoma curvirostre palmeri). A Curve-billed Thrasher engaged in countersinging with a migrating Black-headed Grosbeak (Pheucticus melanocephalus) near Tucson, Arizona. Night-time singing by Curve-billed Thrasher is also documented for the first time. At least three responding Curve-billed Thrashers engaged in spontaneous song near Tucson, Arizona. Additional night-time singing was elicited by playback recordings

A hybrid zone revisited: molecular and morphological analysis of the maintenance, movement, and evolution of a Great Plains avian (Cardinalidae: Pheucticus) hybrid zone

Black-headed grosbeaks (Pheucticus melanocephalus) and rose-breasted grosbeaks (Pheucticus ludovicianus) are passerine bird species known to hybridize in the Great Plains of North America. Both extrinsic (environmental) and intrinsic factors (pre- and postzygotic reproductive isolation) have been credited for the generation and maintenance of the grosbeak hybrid zone, but little is known about the genetic characteristics of this hybrid zone. To investigate the stability and extent of the grosbeak hybrid zone, we constructed clines from both molecular sequence data (mtDNA, three autosomal intron loci, and one Z-linked locus) and morphological data (morphometric analyses and hybrid index scores) to determined zone centre and width. Hybrid zone centre and width were also determined for samples collected across the zone 40 years ago from morphological data. The present and past clines were compared and provided support for stability in hybrid zone location and width, and the evolutionary implications of this are discussed. Three models of hybrid zone maintenance were investigated to consider the influence of intrinsic and extrinsic factors on this zone. Our results suggest low hybrid frequencies, a stable zone location and narrow width, and reduced hybrid fitness over the past 40 years best categorize the grosbeak hybrid zone as a tension zone.

Associations Among Breeding Birds and Gambel Oak in Southwestern Ponderosa Pine Forests

Abstract: Ponderosa pine (Pinus ponderosa) forests with Gambel oak (Quercus gambelii) are associated with higher bird abundance and diversity than are ponderosa pine forests lacking Gambel oak. Little is known, however, about specific structural characteristics of Gambel oak trees, clumps, and stands that may be important to birds in ponderosa pine‐Gambel oak (hereafter pine‐oak) forests. We examined associations among breeding birds and structural characteristics of Gambel oak at a scale similar in size to individual bird territories in pine‐oak forests in northern Arizona and western New Mexico, USA. Avian species richness and occurrence of some bird species were associated with specific growth forms of Gambel oak. Estimated probability of Virginia's warblers (Vermivora virginiae), black‐headed grosbeaks (Pheucticus melanocephalus), and red‐faced warblers (Cardellina rubrifrons) occurring at points increased with increasing density of pole‐sized Gambel oak 7–15 cm in diameter at breast height. We also found evidence that large Gambel oak trees (≥23 cm dbh) were associated with increased occurrence of yellow‐rumped warblers (Dendroica coronata) at points. Some avian associations with oak were influenced by characteristics of ponderosa pines. For example, bird species richness was positively associated with the abundance of large Gambel oak when density of large pine trees ≥23 cm in diameter at breast height was low. Because large oak trees are rare and their numbers are thought to be declining, efforts should be made to retain and promote growth of additional oaks in this size class. Forest management practices that maintain forest openings, such as prescribed burning, could promote growth of pole‐sized Gambel oak, which appears important to some bird species in pine‐oak forests.

SITE-SPECIFIC SURVIVAL OF BLACK-HEADED GROSBEAKS AND SPOTTED TOWHEES AT FOUR SITES WITHIN THE SACRAMENTO VALLEY, CALIFORNIA

We estimated apparent annual survival and recapture probabilities for adult Black-headed Grosbeaks (Pheucticus melanocephalus) and Spotted Towhees (Pipilo maculatus) at four sites along the Sacramento River, California. To calculate our estimates, we used capture-recapture mist-net data collected over two time periods at four study sites: from 1993 to 1995 at Flynn, Ohm, and Sul Norte, and from 1995 to 2000 at Ohm and Phelan Island. Our primary objective was to determine whether there were site-specific differences in adult survival and recapture probabilities for each species. Such differences are rarely investigated, yet, if present, suggest site-specific differences in habitat quality, with important implications for source/sink dynamics. We found site-specific variation in Black-headed Grosbeak survival within both the 1993–1995 dataset (Flynn = 0.797 ± 0.496, Ohm = 0.158 ± 0.191, Sul Norte = 0.773 ± 0.131) and the 1995–2000 dataset (Ohm = 0.088 ± 0.090, Phelan Island = 0.664 ± 0.111). For Spotted Towhees (1993–1995 data), the most supported model assumed constant survival across sites (0.602 ± 0.240), but there was some support for site variation in survival, as well (Flynn = 0.653 ± 0.365, Ohm = 0.214 ± 0.253, Sul Norte = 0.632 ± 0.258). These results clearly suggest site variation for Black-headed Grosbeaks, and weak evidence of site variation for Spotted Towhees. For both species, the general pattern was low survival at Ohm, suggesting low-quality habitat there and/or reduced site fidelity. The magnitude of site-to-site variation in survival observed in the Black-headed Grosbeak, and suggested for Spotted Towhee, has strong implications for determining source versus sink population status. To determine source versus sink status, we conclude that investigators must not only take into account site variation in reproductive success, but also consider site-specific estimation of adult survival.

COMPARISON OF BLACK-HEADED GROSBEAKS NESTING IN RIPARIAN AND GAMBEL OAK PASTURES IN SOUTHWESTERN COLORADO

From mid-May through July, 1992 to 1998, we searched for black-headed grosbeak (Pheucticus melanocephalus) nests in riparian and Gambel oak (Quercus gambelii) pastures in La Plata County, Colorado. Twenty-six nests (63%) were successful in fledging at least 1 young, and 15 nests (37%) failed because of predation. The mean number of grosbeaks hatched and fledged per nest did not differ between riparian pastures and oak pastures. The proportion of nests depredated in riparian pastures (10/25, 40%) and oak pastures (5/17, 29%) did not differ significantly. Mortality rates did not differ between habitats during the incubation stage (riparian: 0.056 nests/day; oak: 0.046 nests/day) or during the nestling stage (riparian: 0.011 nests/day; oak: 0.0 nests/day). Mean nest height did not differ between depredated nests and successful nests in either riparian pastures or oak pastures.

Testis Mass and Subadult Plumage in Black-Headed Grosbeaks

Like males of approximately 30 other species of North American passerines, male Black-headed Grosbeaks (Pheucticus melanocephalus) do not attain complete definitive alternate plumage until their second breeding season. I collected yearling and adult male Black-headed Grosbeaks in the Rio Grande valley in central New Mexico to test the hypothesis that delayed plumage maturation in Black-headed Grosbeaks is one manifestation of a general, hormonally-mediated developmental pattern. I compared the mass of testes to the degree of plumage maturation in eleven yearling males and found a significant positive correlation. Moreover, the mean testis mass of yearling males was significantly lower than the mean testis mass of older males. In contrast, I found no significant relationship between plumage brightness and testis mass among seven adult males in definitive alternate plumage. These observations support the idea that delayed plumage maturation in Black-headed Grosbeaks is part of a general delay in investment in first-year reproduction.

Late spring arrival and dull nuptial plumage: aggression avoidance by yearling males?

The hypothesis that a late spring arrival and a dull nuptial plumage can aid yearling male passerines in avoiding aggression from territorial adult males was tested. Adult male black-headed grosbeaks, Pheucticus melanocephalus, were presented with three types of conspecific models: (1) adult male, (2) yearling male with bright plumage, and (3) yearling male with dull plumage. Models were associated with a song playback and were presented at (1) the time of adult male arrival and territory establishment, and (2) 2 weeks later at the time of yearling arrival and settlement. Test males were more aggressive toward all model types during early presentations than during late presentations. In addition, adult models elicited more aggression from territorial males than bright yearling models, which elicited more aggression than dull yearling models. The hypothesis that a late spring arrival may be due to energetic constraints imposed on the winter grounds was also addressed by comparing the arrival chronology of yearling males at two sites 25 km apart and separated by 550 m of elevation. Yearling male grosbeaks arrived at the high elevation site 8 days later than they arrived at the lowland site. It seems unlikely that the 8-day delay was caused by insufficient energy to travel only 25 km. These observations support the hypothesis that both a dull nuptial plumage and a late spring arrival aid yearling males in avoiding adult aggression. They are not in accord with the hypothesis that late spring arrival is due to constraints on the wintering grounds that prevent yearling males from migrating as early as adult males.

Age, Plumage Brightness, Territory Quality, and Reproductive Success in the Black-Headed Grosbeak

Age, Plumage Brightness, Territory Quality, and Reproductive Success in the Black-Headed Grosbeak

The Function of Delayed Plumage Maturation in Male Black-Headed Grosbeaks

Abstract I used data from two breeding populations of Black-headed Grosbeaks (Pheucticus melanocephalus) in central New Mexico to test alternative hypotheses regarding the function of delayed plumage maturation in male passerines. Yearling male grosbeaks displayed a wide range of subadult plumage types, but most individuals were intermediate in appearance between adult males and females. Subadult male grosbeaks arrived on the study sites about 2 weeks after adult males, with no tendency for individuals with brighter or duller plumage to arrive first. Only a few of the most brightly plumaged subadult males defended territories and attracted females; most were nonterritorial floaters. All territories of subadult males were positioned outside clusters of adult male territories with few total neighbors. When I removed adult males from their territories, the territories remained empty. These results are not consistent with predictions of the female-mimicry hypothesis, but they are in accord with those of the cryptic hypothesis.

FORAGING DYNAMICS OF BIRD PREDATORS ON OVERWINTERING MONARCH BUTTERFLIES IN MEXICO.

By suspending nets within and adjacent to a 2.25 hectare overwintering colony of monarch butterflies in Mexico, we estimated that black-backed orioles and black-headed grosbeaks killed 4,550 to 34,300 and an average of 15,067 butterflies per day. A conservative calculation of mortality through the 135 day overwintering season was 2.034 million butterflies, or about 9% of the colony. The birds preyed selectively upon male butterflies, possibly because of a difference in fat content, or possibly because females contain higher concentrations and larger amounts of cardenolide or other defensive chemicals. The risk to individual monarchs of being killed was much greater on the colony periphery and in thinned areas of the forest. Bird predation thus is sufficient to have played a major role in shaping the evolution of the monarch's overwintering and aggregation behavior. Substantial daily variation in predation intensity occurred, 26% of which was attributable to the birds eating more butterflies on colder days, and 30% of which was attributable to a 7.85 day predation cycle. The hypothesis is put forward that the birds feed cyclically because they build up toxic levels of cardenolides or other defensive chemicals contained in the butterflies. The cyclic predation may reduce total predation on the colony by as much as 50%. Such chemical-based group protection is interpreted as a fortuitous by-product of the evolution of unpalatability through selective processes acting on other phases of the monarch's life history.

Hummingbirds Feeding from Exudates on Diseased Scrub Oak

971) suggested that this represented a use of song selected to acquire male nest defense. In this case, as in the Black-headed Grosbeak, such deceptive behavior would be adaptive since both parties would ultimately benefit by the female's singing and the male's reaction to it, i.e., the bluebird nest is defended against a possible predator and the eggs or young of the grosbeak are not left unprotected when the female leaves the nest. I thank Keith L. Dixon for his assistance in this study. I also thank Susan Smith and an anonymous reviewer for helpful suggestions on the manuscript. This study was supported by grants from The Frank M. Chapman Memorial Fund of The American Museum of Natural History and from Sigma Xi.