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Thursday, 7 July 2016

The Wilson Journal of Ornithology June 2016 : Volume 128 Issue 2

The Wilson Journal of Ornithology
Published by: The Wilson Ornithological Society

Table of Contents
June 2016 : Volume 128 Issue 2



Notes on the natural history, taxonomy, and conservation of the endemic avifauna of the Samoan Archipelago
H. Douglas Pratt and John C. Mittermeier

The Samoan Archipelago is an important area of avian diversity and endemism within the tropical Pacific. Here, we summarize observations on the natural history and vocalizations of Samoan birds based on fieldwork conducted over the course of five visits to Samoa and American Samoa from 1977 to 2006 with particular emphasis on the Manu’a Islands and the highlands of Savai’i. We interpret our findings in light of modern understanding of the biological species concept to identify seven Samoan forms as previously unrecognized endemic species: Samoan Wood Pigeon Columba [vitiensis] castaneiceps, Peale’s Kingfisher Todiramphus [chloris] pealei + manuae, Manu’a Shrikebill Clytorhynchus [vitiensis] powelli, Samoan Myzomela Myzomela [cardinalis] nigriventris, Samoan Robin Petroica [multicolor] pusilla, Manu’a Starling Aplonis [tabuensis] manuae, and Samoan Thrush Turdus [poliocephalus] samoensis. The number of endemic species in the archipelago thus increases from 10 to 17. Field surveys on Savai’i reveal significant differences between highland and lowland bird communities, with several lowland species reaching their upper elevational limit at 1,200 m. We conclude that the critically endangered Samoan Woodhen Gallinula pacifica has been extinct for over a century, and suggest that recent reports are based on misidentifications. We found the Tooth-billed Pigeon Didunculus strigirostris to be Critically Endangered and in urgent need of conservation action.

An ornithological survey of Gunung Mulu National Park, Sarawak, Malaysian Borneo
Ryan C. Burner, Vivien L. Chua, Matthew L. Brady, Paul van Els, Philip O. M. Steinhoff, Mustafa Abdul Rahman and Frederick H. Sheldon

Mount Mulu, an isolated 2,376 m peak in eastern Sarawak, Malaysian Borneo, has not been thoroughly surveyed for bird species since shortly after the creation of Mount Mulu National Park in 1974. The Park is of particular interest for its isolation, spectacular limestone structures, bat flights, and extensive primary forest that ranges from near sea level to the mountain’s peak. We spent 2.5 months surveying, observing, and mist-netting birds in the Park and recorded 244 species across its elevational gradient from 50–1,850 m, including 32 species new to the 1979–82 Mt. Mulu checklists. Here, we report the elevational range of each species we observed, compare our list with these earlier Mt. Mulu checklists compiled 25 years ago, and comment on unique observations.

Long-term changes in composition of bird communities at an “undisturbed” site in eastern Ecuador
John G. Blake and Bette A. Loiselle

Bird populations vary both spatially and temporally with consequences for patterns of species richness and community composition. Many species of birds have declined in abundance over the last 14 years at a site in lowland Ecuador. Here, we examine impacts of those declines on composition of bird assemblages on two 100-ha plots in lowland forest at Tiputini Biodiversity Station, eastern Ecuador. Birds were sampled with mist nets (2001–2014) and by direct observations (2003–2006, 2009, 2010, 2013, and 2014). Species accumulation curves were similar on both plots but varied among years; rates of accumulation were particularly low in 2013, following declines in abundance of many species. Community composition differed between the two study plots based on species and guild composition; annual changes at the community level reflected changes in abundance of many species, particularly insectivores. Overall, assemblages of birds at this site in lowland Ecuador showed substantial variation over time and, to a lesser degree, between plots. If bird populations eventually return to levels seen in the early years of this study, we might expect community composition to resemble that of earlier years as well. Results demonstrate the value of long-term (>10 years) studies on replicate plots to help understand dynamics of bird communities in lowland tropical forests.

Occurrence and taxonomy of Arctic Warblers (Phylloscopus borealis) sensu lato in North America
Jack J. Withrow, Daniel D. Gibson, Yuri Gerasimov, Nickolay Gerasimov, Alexander Shestopalov and Kevin Winker

We reviewed the taxonomic status of Arctic Warblers (Phylloscopus borealis) sensu lato occurring in North America following the splitting of the complex into three species by the American Ornithologists’ Union (Chesser et al. 2014). We used phenotypic and genetic markers to assess the status of this species complex in North America and identified Arctic-type warblers occurring in the Aleutian Islands as Kamchatka Leaf Warblers (P. examinandus). This species occurs at least occasionally through the Bering Sea, to the Alaska mainland, and as far east as arctic Canada. Measurements of Arctic and Kamchatka Leaf warblers were found to differ by only a small degree, offering no simple diagnostic characteristics. In addition, we recommend maintaining the long-recognized Alaska subspecies P. b. kennicotti as a synonym of P. b. borealis.

Grassland bird response to recent loss and degradation of native prairie in central and western South Dakota
Mitchell J. Greer, Kristel K. Bakker and Charles D. Dieter

Central and western South Dakota contain some of the largest intact blocks of mixed-grass prairie in North America, but conversion to row crops has accelerated sharply in recent years and existing grasslands have been further degraded by introduced plant species and the presence of anthropogenic woodlands. Our objective was to simultaneously investigate the effects of relatively recent habitat loss and degradation on grassland bird communities at the local, patch, and landscape scales. Specifically, to determine how 1) local- (vegetation structure, introduced plant coverage), 2) patch- (patch size, shape, and tree edge) and 3) landscape- (proportion of grassland surrounding surveyed sites) level habitat characteristics affect occurrence and density of six grassland bird species. We surveyed birds on 288 native grassland sites in 29 counties throughout central and western South Dakota. We calculated multiple metrics of habitat degradation and loss at the local, patch, and landscape scales and used logistic and zero-inflated negative binomial regression to model occurrence and density of six grassland bird species. All six species responded negatively to habitat degradation resulting from increased introduced plant coverage and/or percent wooded patch edge. Chestnut-collared Longspurs, Lark Buntings and Western Meadowlarks were negatively affected by degradation of native grasslands related to the increase of introduced plant species. Chestnut-collared Longspurs, Grasshopper Sparrows, Savannah Sparrows, and Western Meadowlarks were impacted negatively by increasing amounts of wooded edge surrounding a grassland patch. Contrary to studies conducted in more fragmented habitats, no species was associated with area of grassland patch, but three species were affected negatively by measures of loss of grassland habitat in the surrounding landscape. Our results indicate the need for conservation and management of grasslands at multiple scales. Habitat degradation resulting from invasion by exotic species and the inclusion of woody vegetation appear to be as detrimental to some grassland birds as habitat loss. Our results suggest there is an urgency to preserve large, intact native grasslands before habitat loss reaches levels that cause grassland bird species to shift from landscape scale associations to patch area measures of habitat, as significant population declines would likely accompany the habitat loss leading to such a shift.

Wintering grassland bird responses to vegetation structure, exotic invasive plant composition, and disturbance regime in coastal prairies of Texas
David T. Saalfeld, Sarah T. Saalfeld, Warren C. Conway and Kevin M. Hartke

Many migratory grassland passerines complete their annual life cycle within the United States and investigations into wintering ecology of these species are scarce, particularly in ecoregions where habitat quality is considered to be compromised, such as the coastal prairie of Texas. During 2008–2010, we investigated wintering grassland bird ecology as related to coastal prairie composition and management practices on the mid-upper Texas coast. To quantify grassland bird composition and density among management regimes, we performed 260 transect surveys on 40 different study site pastures deployed among 7 different management regimes, varying in plant community composition as well as frequency (or occurrence) of burning, grazing, and mowing from 29 October 2008–7 April 2009 and 17 November 2009–17 March 2010. A total of 79 bird species (48 species in 2008–2009 and 66 species in 2009–2010) were recorded during this study. Sites that were recently (<2 years prior) grazed, burned, or mowed tended to have the greatest species richness of obligate grassland bird species. Management regime and the resulting habitat characteristics also appeared to influence densities of Le Conte’s Sparrow (Ammodramus leconteii), Sedge Wren (Cistothorus platensis), and Sprague’s Pipit (Anthus spragueii), with the former two species selecting areas that had not been recently burned, grazed, or mowed and were characterized by greater vertical vegetation density and litter depth, respectively. Conversely, Sprague’s Pipit selected recently burned, grazed, or mowed prairies, characterized by less litter depth and percentage of shrubs nearby. More cosmopolitan species, such as Eastern Meadowlark (Sturnella magna) and Savannah Sparrow (Passerculus sandwichensis) occurred equally among management regimes. Despite similar species richness in floristically disturbed sites, nonnative vegetation appeared to negatively influence species with specific habitat requirements such as Sprague’s Pipit, Sedge Wren, and Le Conte’s Sparrow. In order to increase wintering avian diversity, coastal prairie habitat conservation and management in Texas should focus on restoring management regimes (i.e., burning, mowing, and grazing) that create heterogeneous environments, while maintaining native vegetation communities.

Role of landscape elements on recent distributional expansion of European Starlings (Sturnus vulgaris) in agroecosystems of the Pampas, Argentina
Emmanuel Zufiaurre, Agustin Abba, David Bilenca and Mariano Codesido

Previous studies of European Starlings in Argentina have focused on identifying biological aspects correlated with establishment of new populations in urban and suburban areas. Starlings have recently invaded rural areas in the Pampas. To understand the factors involved in the recent expansion of European Starlings into these rural habitats, we investigated how expansion patterns were associated with season, proportion of crop fields, distance to woodlots, and distance to small and big urban centers in agroecoystems of the Pampas. We surveyed 392 fields during 2011–2013 to collect data on presence of starlings and landscape features. We found that the range of European Starlings has expanded by a total area of ~65,000 km2 since 2005, at a linear range expansion rate of 22.2 km per year. Generalized linear mixed model analysis revealed that presence of European Starlings was significantly related with reduced distances to nearest small urban area. Our findings indicate that range expansion of European Starlings into rural areas of Argentina may follow a neighborhood diffusion pattern, by which well-established populations act as sources of individuals that disperse short distances into nearby favorable areas. In absence of human control, this species is expected to continue its spread and population increase.

Nesting ecology of early-successional birds in restored longleaf and loblolly pine stands
Leah D. Novak, Christopher E. Comer, Warren C. Conway, Daniel G. Scognamillo and Richard D. Gay

After historic declines in acreage and function, longleaf pine (Pinus palustris) savannah is considered one of the most important ecological communities in need of protection and restoration along the Atlantic and Gulf Coastal Plains. Numerous state and federal programs are available to encourage restoration on private lands; however, the success of these programs in producing quality habitat for longleaf pine savannah specialist species is largely unknown. To assess quality of restored longleaf pine forests in east Texas, we compared nest success, nest survival, and nest site selection of Prairie Warblers (Setophaga discolor), Yellow-breasted Chats (Icteria virens), Indigo Buntings (Passerina cyanea), and Northern Cardinals (Cardinalis cardinalis), in young (0–5 years) and mid-aged (5–10 years) stands of longleaf pines to these same parameters in young, managed stands of loblolly pines (P. taeda). We monitored 65 nests for all four species combined, where 28 (43%) occurred in longleaf stands, and 37 (58%) occurred in loblolly stands. Of these, cardinals accounted for 35% of all nests, and this was the only species in which we monitored more nests in habitats of longleaf than loblolly. For all focal species, Mayfield nest success estimates were low (4–17%) in stands of both longleaf and loblolly pines, except the values for Prairie Warblers (54%). The primary reason for nest failures was predation (43% of all active nests), where each stand was comprised of mostly (~80%) edge habitat. Restored young longleaf stands did not appear to provide differential nesting habitat or greater nesting success for our focal species compared to loblolly stands of comparable age.

Effects of diet on plumage coloration and carotenoid deposition in red and yellow domestic canaries (Serinus canaria)
Rebecca E. Koch, Kevin J. McGraw and Geoffrey E. Hill

Atlantic Canaries (Serinus canaria) are the most commonly kept caged bird with extensive carotenoid-based plumage coloration. Domestic strains of canaries have been bred for a variety of colors and patterns, making them a valuable model for studies of the genetic bases for feather pigmentation. However, no detailed account has been published on feather pigments of the various strains of this species, particularly in relation to dietary pigments available during molt. Moreover, in the twentieth century, aviculturists created a red canary by crossing Atlantic Canaries with Red Siskins (Carduelis cucullata). This “red-factor” canary is reputed to metabolically transform yellow dietary pigments into red ketocarotenoids, but such metabolic capacity has yet to be documented in controlled experiments. We fed molting yellow and red-factor canaries seed diets supplemented with either β-carotene, lutein/zeaxanthin, or β-cryptoxanthin/β-carotene and measured the coloration and carotenoid content of newly grown feathers. On all diets, yellow canaries grew yellow feathers and red canaries grew orange or red feathers. Yellow canaries deposited dietary pigments and metabolically derived canary xanthophylls into feathers. Red-factor canaries deposited the same plumage carotenoids as yellow canaries, but also deposited red ketocarotenoids. Red-factor canaries deposited higher total amounts of carotenoids than yellow canaries, but otherwise there was little effect of dietary supplementation on feather carotenoid content, hue, or chroma. These observations indicate that canaries can use a variety of dietary precursors to produce plumage coloration and that red canaries can metabolically convert yellow dietary carotenoids into red ketocarotenoids.

Reduced ultraviolet reflectance does not affect egg rejection by Northern Cardinals (Cardinalis cardinalis)
Virginia E. Abernathy and Brian D. Peer

With the discovery that the ultraviolet (UV) spectrum is visible to birds, studies have shown how this parameter can affect the ability of hosts of brood parasites to recognize eggs. However, the role UV reflectance plays in egg recognition has not been well studied in hosts of Brown-headed Cowbirds (Molothrus ater). Northern Cardinals (Cardinalis cardinalis) are common hosts that usually accept cowbird eggs, but evidence suggests that cardinals reject nonmimetic eggs more frequently. The purpose of this study was to determine if a reduction in UV reflectance of cowbird eggs would elicit a rejection response from the cardinal. Four treatments were used: (1) cowbird eggs covered with UV-block; (2) cowbird eggs covered with a control coating; (3) uncoated cowbird eggs used as a control, and (4) cardinal eggs covered with UV-block. Cowbird and cardinal eggs with UV-block were not more likely to be rejected than eggs in either of the control treatments. Cowbird and cardinal eggs are similar in both appearance and occasionally size, and high intraclutch variation has been found within cardinal clutches, all of which may be a constraint in evolving fine-tuned egg recognition. Furthermore, cowbird parasitism does not impose significant costs for cardinals, and therefore, selection pressures to evolve an ability to distinguish between cowbird and cardinal eggs are likely minimal.

Does white tail patch size indicate quality in male Cerulean Warblers (Setophaga cerulea)?
Elisabeth F. Purves, Mark A. Conboy, Raleigh J. Robertson and Paul R. Martin

Within species of birds, variation in plumage may allow potential mates or competitive rivals to quickly assess the quality of an individual. Little is known about the role of white tail feather patches (“tail white”) in male Cerulean Warblers (Setophaga cerulea) and whether variation in patch size could serve as a signal. We hypothesized that the size of tail white patches in males acts as an honest signal of quality, with larger white patches indicating high quality males. We measured and compared the area of tail white to four estimates of quality (age, structural size, body mass, and blood parasite load) in 71 male Cerulean Warblers at the Queen’s University Biological Station in eastern Ontario. We found that males 2 years old or older had significantly larger tail white patches than 1 year old males, and that structurally larger males (estimated by wing length) had significantly larger tail white patches than smaller males. Our best-performing statistical model suggested that heavier individuals had larger areas of tail white, but this relationship depended on wing length: white positively covaried with body mass in smaller individuals (shorter wings), but not in larger individuals. Our findings suggest that size of tail white patches may provide information on some, but not all, aspects of quality of male Cerulean Warblers; however, we do not know if this information is perceived and used by other Cerulean Warblers in nature.

Variation in bird-window collision mortality and scavenging rates within an urban landscape
Annie M. Bracey, Matthew A. Etterson, Gerald J. Niemi and Richard F. Green

Avian mortality from collisions with windows and buildings is one of the top sources of anthropogenic mortality of birds. Each year in the United States, an estimated 100 million to one billion birds die from window collisions. Many studies of bird-window collision mortality have aimed to identify architectural, landscape, and species-specific factors that may influence collision rates, but little research has assessed the potential for spatiotemporal variation in collision mortality. We studied window collision mortality at 42 residential houses located within an urban landscape, along the shores of Lake Superior in Duluth MN, USA from 2006–2009 to quantify window-related fatalities during migration. The rate of window collision mortality was modeled as a function of house location and season using Poisson regression. We also conducted carcass distribution trials to estimate scavenging and detection rates, and analyzed the resulting data using a multistate Markov model. We used hierarchical models of scavenging probability to compare the relationship between scavenging rates and six measured covariates. Models for collision mortality and scavenging were evaluated using Akaike’s Information Criterion (AIC). The adjusted number of birds killed (Nk) over the full course of monitoring was estimated using the Horvitz-Thompson estimator. A total of 40 species and 108 individual birds were recorded as window kills. Fatalities increased with distance from the city center, were higher at houses on the lake side of the study site, and on windows facing Lake Superior. Scavenging rates also increased with distance from the city center, with small carcasses being removed more quickly than large carcasses, and removal rates decreasing over time for all carcass sizes. Because of the low detection probability of homeowners, combined detection by both homeowners and researchers was <20%. Although mortality and scavenging rates were not uniformly distributed, we estimated an adjusted mortality rate of ~11–16 birds per house during the study period. Mortality estimates for all residential houses on Minnesota Point (n  =  520) during the study period (n  =  211 days) was 5,819–8,382 birds, ~1,421 birds per season. Results suggest spatiotemporal variation in both mortality and scavenging rates within our study area, both of which increased with distance from the city center. Houses with highest collision mortality also had the highest scavenging rates. Our results are consistent with other studies that have observed heterogeneity in mortality and scavenging rates associated with local structural and landscape level variables. Documenting patterns associated with increased collision mortality will be important in identifying locations that may pose a greater risk to birds.

Foraging ontogeny in a suburban population of Black Phoebes (Sayornis nigricans)
Jessica Baker and Elise D. Ferree

The ability to forage successfully is intimately tied to survivorship of juveniles in many avian species, yet may take varying amounts of time to develop in young birds. We examined the development of foraging skills in juvenile Black Phoebes (Sayornis nigricans). Black Phoebes are insectivorous and forage by scanning for and then pursuing potential prey while in flight. We hypothesized that before they disperse, ~2 months after fledging, phoebes should forage as successfully and with the same mechanics as adults. Because foraging proficiency should affect time allocation, we also compared how juveniles and adults divided their time among foraging and other activities. We found that by 7 weeks of age, phoebes foraged as successfully as the adults; however, they spent more time flying and less time perched. In line with their gained efficiency, by around 6 weeks of age, scanning rates and foraging flight durations of juveniles were similar to adults. Overall, these results confirm that the complex foraging behaviors of Black Phoebes develop in juveniles in a relatively short time period. The development of proficient foraging abilities, however, appears to precede effective time allocation, which must occur sometime after independence or dispersal.

Using foraging ecology to elucidate the role of species interactions in two contrasting mixed-species flock systems in northeastern Peru 
Ari E. Martínez and Scott K. Robinson

Mixed-species flocks are formed on the basis of both positive and negative species interactions. We use foraging behavior in two different flock types to interpret the extent to which core species minimize niche overlap to reflect negative interactions. We also use the foraging behavior of alarm-calling species to infer whether their behavior is consistent with predictions for species that accrue benefits by associating with other flocking species. The foraging patterns of core species in tierra firme flocks show large differences with respect to foraging maneuvers and substrates, a finding that is consistent with niche theory. In igapó (a blackwater seasonally inundated forest), only the alarm-calling species show differences in foraging patterns among core flock members. We also show that alarm-calling species in different sites show different patterns of association with other flocking species: one species, Thamnomanes saturninus, shows no strong tendency to associate with any other species in the flock and the other, Thamnomanes schistogynus, perches close to and immediately below other species in the flock. These observations are consistent with the hypothesis that alarm-callers benefit from insects flushed from other flock members in igapó forest but not in tierra firme forest. In northeastern Peru, subtle variation in the foraging behaviors among alarm-calling species in tierra firme and igapó flocks may reflect differences in species interactions among key flock members.

Trophic ecology of two raptors, Barn Owl (Tyto alba) and White-tailed Kite (Elanus leucurus), and possible implications for biological control of Hantavirus reservoir in Chile
Andrés Muñoz-Pedreros, Claudia Gil, José Yáñez, Jaime R. Rau and Patricia Möller

Raptors are important predators of various species of small mammals, which renders them of economic importance since their prey may be either disease vectors or reservoirs which represent health problems, or economically important through the damage they cause to crops and stocks. The long-tailed rice rat Oligoryzomys longicaudatus is a reservoir and vector of Hantavirus, a disease of increasing importance in various Latin American countries. The nocturnal Barn Owl (Tyto alba) and the diurnal White-tailed Kite (Elanus leucurus) appear to be the most significant predators of this species. Here, we characterize the diet of these two raptors and analyze their trophic specialization and dietary selectivity using published information, pellet analysis, and field abundances of small mammals. Both raptor species positively selected O. longicaudatus in their diets to suggest that they could be potential controllers of the Hantavirus reservoir in Chile, both in natural and agricultural ecosystems. Predation on O. longicaudatus by these two raptors is interesting because they have complementary activity periods, a condition which enables them to share the same prey without having strong interference.

Potential effects of Brown-headed Cowbirds (Molothrus ater) on host postfledging dispersal and survival
Julianna M. A. Jenkins and John Faaborg

Nest parasitism by Brown-headed Cowbirds (Molothrus ater) negatively affects nest production and nest success of the majority of their hosts. However, it is unclear what effects cowbird fledglings have on host broods during the postfledging period. We monitored 65 nests of Ovenbirds (Seiurus aurocapilla) from 2012–2014 in central Missouri, 49% of which were parasitized by Brown-headed Cowbirds. We used radio-telemetry to track daily movements, survival, and parental care for 13 Ovenbird fledglings from parasitized nests that fledged cowbirds and 21 Ovenbird fledglings from non-parasitized nests. Clutch size and nest productivity were lower in parasitized nests, but mean nestling mass at fledging and total brood size (host and parasite young) did not differ between parasitized and non-parasitized nests. All mortalities occurred within the first 10 days after fledging. Estimated postfledging cumulative survival and observed adult care were similar between parasitism groups. There was no difference in movement patterns of Ovenbirds during the first 2 weeks postfledging; however, Ovenbirds from non-parasitized nests moved farther from the nest after 14 days compared to Ovenbirds from nests that fledged a cowbird. Our observations do not support the hypothesis that negative effects of nest parasitism by Brown-headed Cowbirds extend into the postfledging period for Ovenbirds.

Nashville Warblers (Oreothlypis ruficapilla) use a single song type in southwestern Oregon with widely distributed song variants 
Stewart W. Janes and Lee Ryker

We investigated local and regional singing patterns of Nashville Warblers (Oreothlypis ruficapilla) in southern Oregon. Each male employed a single song, but within local populations individuals sang diverse and distinct variants with a mean of 13.5 ± 1.5 (±SD) variants among 20 males sampled at each of 10 sites. Forty-one variants were recorded among the 200 males, and 17 variants were shared among two or more sites separated from 2–92 km. The mean number of variants shared between pairs of sites was high (7.9 ± 1.6) and did not vary with distance separating them. Neighboring individuals showed no tendency to sing the same variant. The resulting pattern at each site was a mosaic of diverse variants drawn from a restricted pool of variants. Several of the variants recorded in southern Oregon were also recorded >400 km north in incidental sampling, indicating a broad distribution of the variants. High local song diversity implies that an important function of song is to proclaim the identity of the individual. Possible mechanisms for maintenance of high local song diversity are discussed.


First Documented Migration of Individual White-Crested Elaenias (Elaenia albiceps chilensis) in South America
Jaime E. Jiménez, Alex E. Jahn, Ricardo Rozzi and Nathaniel E. Seavy

Few details are available on the migration (rates, routes, dates) of Neotropical austral migrant birds, which breed and migrate wholly within South America. Only one long-distance austral migrant breeds in the South American temperate forest biome: the White-crested Elaenia (Elaenia albiceps chilensis). However, the migratory dates, routes, and wintering locations are poorly known. During the austral summers of 2011–2013, we attached light level geolocators to breeding White-crested Elaenias at the world’s southernmost forests, on Navarino Island, Chile. The duration of fall migration of three Elaenias to the Amazonian wintering grounds was 64–96 days, while spring migration was 45–60 days. The average distance between breeding and wintering grounds was 5,932 km, which constitutes the longest migration of a Neotropical austral migrant studied to date. A better understanding of the annual cycle of Elaenias could offer new opportunities to examine the evolution of migration and population regulation of one of Patagonia’s most common birds.

Assessing Nest Success of Black-Capped Chickadees (Poecile atricapillus) in an Urban Landscape Using Artificial Cavities
John Bender, Mason Fidino, Kelvin Limbrick and Seth Magle

Native bird diversity is compromised in urban areas partially because of the lack of available habitat for some species. As urbanization continues to increase, it is important to understand the behavioral dynamics of bird species located in cities. The Black-capped Chickadee (Poecile atricapillus), as a generalist species, offers an opportunity to investigate how common native birds use urban areas that lack natural habitat features while additionally competing with non-native, invasive species (e.g., House Sparrows, Passer domesticus). Our objectives were to determine nest box use and nesting success rate of Black-capped Chickadees and House Sparrows using artificial nest boxes in natural habitats located in an urban area, specifically a recently restored 5.66- ha area of pond sedge surrounded by oak (Quercus spp.) savannah located south of Lincoln Park Zoo in Chicago, Illinois, USA. Artificial nest cavities with 3 cm diameter entrance holes, intended to exclude House Sparrows, were installed on trees around the study site and monitored for activity. We found that Black-capped Chickadees will readily use artificial cavities; seven of the 20 boxes were excavated and four produced nests. The artificial nesting cavities successfully excluded House Sparrows from nest building and raising young.

Prevalence of Disjunct Roosting in Nesting Bank Swallows (Riparia riparia)
C. Myles Falconer, Greg W. Mitchell, Philip D. Taylor and Douglas C. Tozer

Bank Swallows (Riparia riparia) congregate in large nocturnal roosts during the non-breeding season. Scant evidence suggests that Bank Swallows may also congregate regularly in nocturnal roosts during the breeding period. To help clarify the issue, we used automated radio-telemetry to document the roosting behavior of 11 males and 11 females that were tending nests with young at two nesting colonies. Nineteen of the 22 birds (86%) spent at least one night roosting away from the colony, and 13 of the 22 birds (59%) spent at least one night roosting likely within a large marsh located ~30 km away from the colonies. Females tended to roost overnight at the colony more than males. The proportion of nights birds spent roosting away from the colony was highly variable between individuals. Minimum flight speeds to an evening roost site (~30 km distant) were significantly greater than return flights back to the colony in the morning. Our study confirms that breeding Bank Swallows do in fact regularly roost away from the colony during the nestling period. Our study also highlights some new and intriguing questions regarding how Bank Swallows use the landscape during the breeding season, and the potential importance of wetland roost sites in the proximity of breeding colonies.

Migratory Status, Winter Subspecies Interactions, and Habitat Segregation of Atlantic Song Sparrows (Melospiza melodia atlantica) 
Raymond M. Danner, Brian J. Olsen and David Luther

We performed the first winter surveys of the Atlantic Song Sparrow (Melospiza melodia atlantica), a poorly known subspecies that is endemic to sand dunes of the mid-Atlantic coast. Novel findings include that the Atlantic Song Sparrow is a year-round resident or partial migrant, primarily flocks with the same subspecies despite occurring in sympatry with the eastern Song Sparrow (M. m. melodia) in winter, and exhibits age-specific habitat use in winter, with immatures greatly outnumbering adults in adjacent saltmarshes. These results are important for conservation planning and understanding the ecology and evolution of this unique subspecies across the annual cycle.

A Test of the Nestling Discrimination Hypothesis for Parasitism of Red-Winged Blackbirds (Agelaius phoeniceus) by Brown-headed Cowbirds (Molothrus ater)
Ken Yasukawa, Hazel K. Berrios and Anthony W. Johannes

We tested the nestling discrimination hypothesis by observing responses of female Red-winged Blackbirds (Agelaius phoeniceus) to playback of begging calls by conspecifics or Brown-headed Cowbirds (Molothrus ater). Female redwings departed the nest to forage and returned with food significantly faster in response to redwing playback than to cowbird playback. We also observed feeding rates at redwing nests before and after we removed either a redwing or cowbird nestling. Female redwing feeding rates changed significantly with these manipulations, but there was no difference in response to redwing versus cowbird nestling removal. Although the removal experiment shows that parasitized and unparasitized broods receive equal care from their hosts, the playback results are consistent with the hypothesis that female Red-winged Blackbirds detect a difference between begging calls of conspecifics and parasites.

Flocking Behavior of Shiny Cowbirds (Molothrus bonariensis) At Feeding Areas During the Daily Cycle
Gustavo H. Kattan, Anamaría Posada, Diego Fernando Arenas, José Luis Moreno and Ángela Barrera

The social systems and space use of birds depend on the distribution and abundance of resources. Brood-parasitic cowbirds (Molothrus spp.) exhibit a unique pattern of changing social behavior on a daily cycle. Female Brown-headed Cowbirds (M. ater) in North America spend the morning accompanied by males searching for host nests, and in the afternoon both sexes join feeding flocks. We studied flocking patterns of Shiny Cowbirds (M. bonariensis) in open-habitat animal exhibits at a zoo in Colombia. Flock sizes of both males and females were low in the morning but increased towards noon. Male abundance remained high during the afternoon, but female abundance was very variable. Numbers of juveniles did not change throughout the day. This is consistent with the idea that cowbirds are spread out during the morning in the breeding areas and aggregate in the afternoon to feed. Cowbirds change their social behavior on a daily basis in response to the different pressures of their breeding and feeding ecologies.

Remarks on the Natural History of São Paulo Marsh Antwren (Formicivora paludicola)
Glaucia Del-Rio and Luís Fábio Silveira

The São Paulo Marsh Antwren (Formicivora paludicola) is a recently discovered species in the family Thamnophilidae that inhabits marshes in the vicinity of the São Paulo metropolitan region, which is the most populous area of South America and within the Brazilian Southeastern Atlantic Forest. This species should be considered “Critically Endangered” following IUCN criteria, as it has a total area of occupancy of only 1.42 km2, a sparse and fragmented distribution, low dispersal capacity, and has lost ~300 km2 of habitat in the last 200 years. F. paludicola was discovered on the verge of extinction, and virtually nothing is known about its natural history, breeding biology, and life history, hence compromising any conservation effort. By capturing and banding individuals from the three largest populations of São Paulo Marsh Antwrens, we provide the first assessment of the breeding period and molt cycles of F. paludicola. Our observations indicate breeding season is from October to February, and the species follows the Complex Basic molt strategy, with a partial pre-formative molt. F. paludicola also shows morphological sexual dimorphism, with males slightly larger than females.

Nest and Eggs of the Streamer-Tailed Tyrant (Gubernetes yetapa) from Brazil and Paraguay
Neander M. Heming, Daniel T. Gressler, Douglas G. D. Russell and Miguel Â. Marini

The breeding biology of approximately one third of all Fluvicolinae species is largely unknown and little is known about Streamer-tailed Tyrant (Gubernetes yetapa). Despite being locally fairly common, only a brief description of its nest has been published. For the species, Chubb (1910) described gonadal state, nest building, and young seen, but no additional details have been published. Here, we describe the nest and eggs of Streamer-tailed Tyrant from Brazil and Paraguay and review nesting activity based on fledgling records from Brazil. The nest was an open cup in the center of a clump of Saccharum sp. grass within a marshy area. The outer portion was lined with thick grass stems. The inner portion of the cup was lined with fine roots, grass stems, and shed snake skins (Colubridae and Viperidae). The nest contained three totally white and oval shaped eggs. Egg mass ranged from 6.84–9.02 g. The period of nesting activity apparently lasted at least from October through January, similar to several other Fluvicolinae species from southeastern Brazil.

Perch Usage by Hummingbirds in a Fragment of Atlantic Forest in Brazil
Lucas L. Lanna, Cristiano S. de Azevedo, Ricardo M. Claudino, Reisla Oliveira and Yasmine Antonini

We investigated if there are aspects of perches that are more attractive for hummingbirds, such as perch height, diameter, and distance from a food patch. The study was conducted in a fragment of Atlantic Forest of the Itacolomi State Park, in Minas Gerais, Brazil, with artificial feeders simulating a rich food patch. Characteristics of perches used by the recorded hummingbirds, such as height, diameter and distance from the food patch, were measured. From the six hummingbird species recorded visiting the artificial feeders, two preferentially used perches with certain characteristics: Thalurania glaucopis used more perches at a height of 0.51–1.0 m (intermediary high), and Leucochloris albicollis used more perches located 1.1–2.0 m distance from the food patch. T. glaucopis was territorial and defended the food patch; L. albicollis was subordinate and did not defend the food patch. The other species seemed to use perches randomly. Our results suggest that hummingbirds used perches according to their social status. Territorial species use perches primarily as platforms for defense and observation of the territory, as well as places of rest between feeding events; subordinate species use perches mainly as resting places during feeding bouts in the absence of the dominant species.

Freshwater Molluscs in Diet of Hooded Crow (Corvus cornix)
Bartłomiej Gołdyn, Zofia Książkiewicz-Parulska and Piotr Zduniak

The diet of nestling Hooded Crows (Corvus cornix) was investigated in Warta Mouth National Park (W Poland) in the breeding season of 2003. We analyzed 82 food samples of which 79% contained snails and bivalves. Hooded Crows prefer Viviparus spp. instead of smaller but more abundant molluscan species present in the studied area. We suspect that under conditions of the lowland flooded river valleys Viviparus spp., as a relatively large and meaty species, can be eaten without the shell and is a more valuable food source than smaller molluscs.

House Sparrows (Passer domesticus) Use Cars to Shelter
Laure Cauchard and Thomas Borderie

During winter 2015 in Montreal (Canada), we observed on two occasions a group of House Sparrows (Passer domesticus) hiding under the body of several cars, in the empty spaces between the wheels and the fender. On both occasions, it was either snowing or raining. This paper reports for the first time, to our knowledge, a description of birds using cars to shelter from rain or snow. Moreover, some individuals were engaged in continuous round trips between the car and bushes, seemingly to detect potential predators that would not be visible to the individuals under the car. Further study should examine the diversity of foraging and non-foraging innovations in different groups of birds, in order to better understand the evolution of behavioral flexibility and cognition in non-human animals.

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