Spizella Passerina Research Articles

16S rRNA gene sequencing of microbiota from the preen oil and cloaca of chipping sparrows (Spizella passerina).

We present the results of 16S rRNA gene amplicon sequencing of the microbiota from preen oil and the cloaca of chipping sparrows (Spizella passerina) collected near Mountain Lake Biological Station in Pembroke, VA.

Novel approaches for assessing acclimatization in birds reveal seasonal changes in peripheral heat exchange and thermoregulatory behaviors.

Using thermography and behavioral analyses, we found that heat exchange and thermoregulatory behaviors changed seasonally in chipping sparrows (Spizella passerina). Studies on seasonal acclimatization in birds have primarily involved metabolic measurements, few of which have investigated behaviors, and none have investigated changes in peripheral heat exchange. We captured chipping sparrows in the winter and summer of 2022 in Wilmington, North Carolina, USA, and we collected thermal images of these birds at 15.0, 27.5 and 40.0°C. We found that heat dissipation through the bill and legs changed seasonally, but surprisingly both were higher in winter than in summer. We found that heat dissipating behaviors were more common in winter, whereas heat conserving behaviors were more common in summer, and that behaviors associated with resource costs (e.g. panting) or predation risk (e.g. bill tucking) showed the most distinct differences between seasons. Meanwhile, low-cost and low-risk postural adjustments (e.g. feather adjustments and tarsus exposure) did not vary as strongly between seasons but followed similar trends. The seasonal adjustments to behaviors suggest that non-acclimatized birds must use costly thermoregulatory behaviors more frequently than acclimatized birds. The use of thermography resulted in the discovery of one completely novel behavior, and the first detection of a known behavior in a new species. Both novel behaviors aided in evaporative heat loss and occurred more commonly in winter, supporting the presence of seasonal acclimatization as evidenced by behavioral adjustments. These results provide novel insights into the process of acclimatization and suggest a role for behavioral adjustments in seasonal acclimatization.

Burrow webs: Clawing the surface of interactions with burrows excavated by American badgers.

Ecosystem engineers are organisms that influence their environment, which includes alterations leading to habitat provisioning for other species. Perhaps the most well‐examined guild of species provisioning habitat for other species is tree cavity excavators or woodpeckers (Picidae). Many studies have examined the suite of secondary cavity users that rely on woodpeckers, and how the ecological network of secondary users, collectively referred to as the nest web, changes across communities. Despite similar habitat provisioning processes, fewer studies have assessed the suite of species associated with burrowers providing access to subterranean habitat. Here, we begin to characterize the burrow web provisioned by American badgers (Taxidea taxus) and evaluate the diversity and frequency of species interactions we detected at abandoned badger burrows in Wyoming, USA. We deployed camera traps at 23 badger burrows and identified interactions with the burrow by birds, mammals, and reptiles. Overall, we discovered 31 other species utilizing badger burrows, consisting of 12 mammals, 18 birds, and 1 reptile. Mammals, other than American badgers themselves and other fossorial species such as ground squirrels (Urocitellus sp.), frequently using burrows included mice (Peromyscus sp.), long‐tailed weasel (Mustela frenata), pygmy rabbit (Brachylagus idahoensis), and desert cottontail (Sylvilagus audubonii). Of the 18 bird species detected, most accounted for <5% of overall detections, besides chipping sparrows (Spizella passerina) at 7.2%–11.5% of detections. The most common category of detection by bird species was foraging, contrary to mammals, which used the burrow frequently and were commonly observed entering and exiting the burrow. This work provides additional context on the ecological role of American badgers within their environment. More broadly, this work scratches the surface of many remaining questions to explore with the aim of advancing our understandings about burrow webs across the diversity of burrowing species and the communities in which they occur.

Climate variation drives dynamics and productivity of a subalpine breeding bird community

Abstract Effects of global climate change on local climate and dynamics of animal populations can be extreme at high latitudes and high elevation. Here, we investigated climate variation and its effects on the diversity and dynamics of a subalpine bird community in California’s Sierra Nevada over 32 years (1978–2009). For the first 16 years, we also assessed the effects of climate on fledging timing, fledging success, and fledgling numbers. We considered 4 climate variables: snowmelt timing, spring mean temperature, summer minimum temperature, and summer precipitation. Climate metrics were highly variable among years and exhibited evidence of temporal pattern. Cooler years with late-melting snowpack were less common in later years, and summer temperature increased, while summer precipitation tended to decrease, over the study period. Years of early snowmelt were associated with higher species richness, more breeding territories, population increases, earlier fledging, and fewer fledglings/successful breeding territory. After accounting for snowmelt timing, spring temperature was positively associated with population change and, although variable among species, negatively associated with fledging date and productivity metrics. Summers with higher minimum temperatures were associated with higher fledging success and (although variable among species) more fledglings. Three species showed evidence of population trend: Yellow-rumped Warbler (Setophaga coronata; increasing), Clark’s Nutcracker (Nucifraga columbiana; declining), and Chipping Sparrow (Spizella passerina; declining). We suggest that enhanced diversity and population growth in mild springs were driven primarily by the recruitment of young first-time breeders, which may also help explain lower productivity in those years. Spring and summer temperatures may have also affected productivity through effects on predator activity or on dynamics of moisture, vegetation, and food availability. Finally, summer precipitation was largely accumulated through summer storms, which were observed to cause occasional deaths to eggs and nestlings. Our results highlight the value of long-term single-site multispecies data in understanding population and community dynamics at an environmental extreme with high annual variability.

Geographically well-distributed citizen science data reveals range-wide variation in the chipping sparrow's simple song

Geographical variation has been widely studied in oscine songbirds, with particular attention paid to the interplay between variables associated with learned song and dispersal. While most field-based studies have focused on discrete dialects, analysing data from quickly growing citizen science libraries could uncover geographical patterns in species previously thought to exhibit random variation in song. Specifically, using citizen science birdsong databases, we test whether chipping sparrow, Spizella passerina, song is geographically structured on a continental scale. The chipping sparrow is a particularly well-suited species for this study, since individuals have a simple song of one repeated syllable, have only the beginning of their first breeding season to adjust their song before crystallization and have been shown to match their song to a nearby neighbour while establishing their first territory. If most chipping sparrows adopt a neighbour-matching strategy, we might expect local syllable similarity; in contrast, field studies have shown that local syllable diversity has been maintained over time. We analyse 820 individual recordings of the simple, yet diverse, song of chipping sparrows to assess whether long-range geographical patterns have formed despite this local song variation. We found significant correlations between song features and geographical distance, associated with longitude but not latitude: chipping sparrows in the eastern United States and Canada sing at a slower rate (fewer, longer syllables) than the western population. However, comparing individual syllable types between regions, we found diverse song types persist across this species’ range. To better contextualize our findings, we re-evaluate available genetic sequences of chipping sparrows to test for genetic differentiation between the eastern and western populations in which we found song differences. Our results suggest that there are two culturally distinct subpopulations of migratory chipping sparrows that are genetically indistinguishable using mitochondrial DNA, motivating future studies on migration patterns and additional sequencing of nuclear DNA.

Lee Conell

Lee Conell Lee Conell (bio) It was six-thirty in the morning, too early to be awake at a writing conference, and yet here I was, a lone fiction writer standing outside the Sewanee Inn for a bird walk with a group of poets. The [End Page 707] genre imbalance made sense to me. I'd long felt that it was only poets—only good poets—who could do justice to the beauty and the weirdness and the rhythm of birds. While I was looking forward to the walk, I was also a little anxious. After almost two weeks of attending readings and lectures, of nonstop close listening, I wasn't entirely sure I had it in me to listen to birds, too. As a kid, I'd been obsessed with birds. I'd gone bird-watching with the park rangers in New York City, learned to notice not just different types of pigeons, but the different types of hawks that ate the different types of pigeons. Then I'd entered middle school and become self-conscious about outright geekery. I put the binoculars away and tried to look like I wasn't noticing anything, not even my own existence. As a writer, too, I'd tried to avoid showcasing my interest in birds, worried they'd feel like easy narrative symbolism (freedom!), or like I was trying to be Jonathan Franzen (Freedom!). Yet somehow a bird-watching scene between two important characters had lingered, persistently, in my in-progress novel. I'd tried to get rid of it, watched Portlandia's "Put a Bird On it!" to help shame me into revising away all that potentially overwrought symbolism, the stupid emotional truths revealed via bird. But the scene—maybe because of the stupid emotional truths—proved pivotal to the book. And the bird walk I took that day in Sewanee also proved pivotal to the book, though not in a way I understood at first. Its importance had nothing to do with seeing the bluebird that was so blue it shocked me, or the birds we saw hidden in brush low to the ground, like feathered spies. It had almost nothing to do with hearing Mark Jarman and Sidney Wade, whose reading voices I loved, list off bird names in a cadence that reminded me of listening to them read their work. What wound up lingering with me wasn't the birds we saw or identified, but one of the first moments of the walk, when a bird sang especially loudly as we passed beneath its tree. The group grew [End Page 708] quiet. How strange it was—to see the faces of poets I'd just heard give readings stilled into a new, surprising hush. We'd been listening these last two weeks to craft talks and readings, listening intently to each other's work. That listening suddenly felt like it had trained me to be silent here. And of course that was what the stupid emotional truths in the bird-watching scene needed too. I was getting too worried about all that noise around symbolism, around beauty, around birds. I needed to be silent in some different way with that scene. If the stupid emotional truths were really stupid, at least I'd try to hear them, to identify them more clearly. Then someone guessed at the name of the singing bird. And someone else guessed too. There was a rush of naming, an energy that felt a little bit like writing. Later, we were emailed a list of the names of the birds we saw on the walk. I shared the list with my friends at home like the lilt of the names was something I'd composed myself. Rock Pigeon, Mourning Dove, Chimney Swift, Northern Flicker, Eastern Wood-Pewee, Eastern Phoebe, Blue Jay, American Crow, Tree Swallow, Barn Swallow, Carolina Chickadee, Tufted Titmouse, Eastern Bluebird, Gray Catbird, Brown Thrasher, European Starling, Chipping Sparrow, Song Sparrow, Eastern Towhee, Northern Cardinal, Brown-headed Cowbird, and House Finch. I woke up early the next morning. Too early for a writing conference. I went back to the stupid birding scene, and I listened. Lee Conell Lee Conell's debut...

Avian Semen Collection by Cloacal Massage and Isolation of DNA from Sperm.

Collection of semen may be useful for a wide range of applications including studies involving sperm quality, sperm telomere dynamics, and epigenetics. Birds are widely used subjects in biological research and are ideal for studies involving repeated sperm samples. However, few resources are currently available for those wishing to learn how to collect and extract DNA from avian sperm. Here we describe cloacal massage, a gentle, non-invasive manual technique for collecting avian sperm. Although this technique is established in the literature, it can be difficult to learn from the available descriptions. We also provide information for extracting DNA from avian semen using a commercial extraction kit with modifications. Cloacal massage can be easily used on any small- to medium-sized male bird in reproductive condition. Following collection, the semen can be used immediately for motility assays, or frozen for DNA extraction following the protocol described herein. This extraction protocol was refined for avian sperm and has been successfully used on samples collected from several passerine species (Passer domesticus, Spizella passerina, Haemorhous mexicanus, and Turdus migratorius) and one columbid (Columba livia).

Encounters With Adult Brood Parasitic Cowbirds At Nests, Not Costly Parasitic Eggs, Elicit Nest Desertion By Chipping Sparrows (Spizella passerina)

ABSTRACT Whereas most host species parasitized by Brown-headed Cowbirds (Molothrus ater) accept cowbird eggs in their nests, others reject the foreign eggs or desert parasitized clutches. Chipping Sparrows (Spizella passerina) are a nest deserting host of cowbirds, but many of their nests continue to be incubated with cowbird eggs suggesting that cowbird eggs per se do not necessarily trigger desertion. We demonstrate that encounters with an adult female brood parasitic cowbird rather than with a cowbird egg in the nest, elicit nest desertion. We observed that a total of 33 (67.3%) of 49 nests were naturally parasitized in Illinois. Parasitized nests fledged less than one third of the number of host young than unparasitized nests did, indicating that parasitism is extremely costly in this species and that an evolved response to parasitism would likely spread through the population over time.

Decade-long bird community response to the spatial pattern of variable retention harvesting in red pine (Pinus resinosa) forests

Structural complexity is widely recognized as an inherent characteristic of unmanaged forests critical to their function and resilience, but often reduced in their managed counterparts. Variable retention harvesting (VRH) has been proposed as a way to restore or enhance structural complexity in managed forests, and thereby sustain attendant biodiversity and ecosystem function. Here we examined the decade-long response of diurnal breeding birds to a VRH experiment that, for the first time, incorporated both overstory and shrub layer treatments in red pine (Pinus resinosa) dominated forests in Minnesota, USA. Overstory treatments included dispersed retention, aggregated retention achieved by cutting small (0.1ha) gaps, aggregated retention achieved by cutting large (0.3ha) gaps, and an uncut control. A shrub layer treatment of ambient or reduced shrub density was also implemented as a split-plot design in each harvest treatment. We found a consistent increase in bird species richness and abundance with all retention harvest treatments over time compared to the control; species richness was also significantly greater in the large gap-aggregated treatment compared to dispersed and small gap-aggregated retention harvests. Among guilds, foliage-gleaning and shrub- and tree-nesting birds exhibited the strongest positive response to retention harvesting. Species associated with early-successional habitat, forest edges, and shrubs responded most positively to VRH including Chestnut-sided Warbler (Setophaga pensylvanica) and American Restart (S. ruticilla), although late-successional species such as Blackburnian Warbler (S. fusca) and Black-throated Green Warbler (S. virens) also showed positive response. We found few differences due to shrub reduction, and only at the species level: Ovenbird (Seiurus aurocapilla) and American Redstart were more abundant in the ambient shrub treatment, whereas Brown Creeper (Certhia americana), Veery (Catharus fuscenscens), and Chipping Sparrow (Spizella passerina) were more abundant with a reduced density of shrubs. Results through the first 10years following harvest revealed differences in bird response to both VRH and shrub treatment, suggesting that management can result in forested landscapes with bird communities that are species rich, diverse, and abundant.

Bird consumption of sweet and tart cherries

Identifying species responsible for crop damage is an important fi rst step in developing management strategies. Previous studies have surveyed bird species fl ying through cherry orchards but have not documented which species were consuming cherries. We conducted traditional surveys and behavioral observations in orchards of sweet cherries (Prunus avium) and tart cherries (Prunus cerasus) in Michigan during 2010 to compare results from the 2 techniques. American robins (Turdus migratorius) were detected most frequently during sweet cherry surveys, while behavioral observations showed that cedar waxwings (Bombycilla cedrorum) consumed more sweet cherries than did robins. Chipping sparrows (Spizella passerina) were the most commonly detected species during tart cherry surveys, while observations showed that American robins and common grackles (Quiscalus quiscula) consumed the most tart cherries. Although observational work is more labor-intensive than surveys, observations are more likely to provide accurate information on the relative importance of fruit-consuming species.

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.

Dynamics of Vector-Host Interactions in Avian Communities in Four Eastern Equine Encephalitis Virus Foci in the Northeastern U.S.

BackgroundEastern equine encephalitis (EEE) virus (Togaviridae, Alphavirus) is a highly pathogenic mosquito-borne zoonosis that is responsible for occasional outbreaks of severe disease in humans and equines, resulting in high mortality and neurological impairment in most survivors. In the past, human disease outbreaks in the northeastern U.S. have occurred intermittently with no apparent pattern; however, during the last decade we have witnessed recurring annual emergence where EEE virus activity had been historically rare, and expansion into northern New England where the virus had been previously unknown. In the northeastern U.S., EEE virus is maintained in an enzootic cycle involving the ornithophagic mosquito, Culiseta melanura, and wild passerine (perching) birds in freshwater hardwood swamps. However, the identity of key avian species that serve as principal virus reservoir and amplification hosts has not been established. The efficiency with which pathogen transmission occurs within an avian community is largely determined by the relative reservoir competence of each species and by ecological factors that influence contact rates between these avian hosts and mosquito vectors.Methodology and principle findingsContacts between vector mosquitoes and potential avian hosts may be directly quantified by analyzing the blood meal contents of field-collected specimens. We used PCR-based molecular methods and direct sequencing of the mitochondrial cytochrome b gene for profiling of blood meals in Cs. melanura, in an effort to quantify its feeding behavior on specific vertebrate hosts, and to infer epidemiologic implications in four historic EEE virus foci in the northeastern U.S. Avian point count surveys were conducted to determine spatiotemporal host community composition. Of 1,127 blood meals successfully identified to species level, >99% of blood meals were from 65 avian hosts in 27 families and 11 orders, and only seven were from mammalian hosts representing three species. We developed an empirically informed mathematical model for EEE virus transmission using Cs. melanura abundance and preferred and non-preferred avian hosts. To our knowledge this is the first mathematical model for EEE virus, a pathogen with many potential hosts, in the northeastern U.S. We measured strong feeding preferences for a number of avian species based on the proportion of mosquito blood meals identified from these bird species in relation to their observed frequencies. These included: American Robin, Tufted Titmouse, Common Grackle, Wood Thrush, Chipping Sparrow, Black-capped Chickadee, Northern Cardinal, and Warbling Vireo. We found that these bird species, most notably Wood Thrush, play a dominant role in supporting EEE virus amplification. It is also noteworthy that the competence of some of the aforementioned avian species for EEE virus has not been established. Our findings indicate that heterogeneity induced by mosquito host preference, is a key mediator of the epizootic transmission of vector-borne pathogens.Conclusion and significanceDetailed knowledge of the vector-host interactions of mosquito populations in nature is essential for evaluating their vectorial capacity and for assessing the role of individual vertebrates as reservoir hosts involved in the maintenance and amplification of zoonotic agents of human diseases. Our study clarifies the host associations of Cs. melanura in four EEE virus foci in the northeastern U.S., identifies vector host preferences as the most important transmission parameter, and quantifies the contribution of preference-induced contact heterogeneity to enzootic transmission. Our study identifies Wood Thrush, American Robin and a few avian species that may serve as superspreaders of EEE virus. Our study elucidates spatiotemporal host species utilization by Cs. melanura in relation to avian host community. This research provides a basis to better understand the involvement of Cs. melanura and avian hosts in the transmission and ecology of EEE virus and the risk of human infection in virus foci.

Nesting Birds in Hawthorn-Savannah Habitats of Canaan Valley, Tucker County, West Virginia

Abstract A decline in the amount of North America's early-successional habitats has triggered a concern for birds that nest in these environments. In West Virginia and throughout the Northeast, sharp drops have been detected in the populations of early-successional birds. We monitored the nest success of birds in Crataegus (hawthorn)-dominated areas of grasslands in the Canaan Valley National Wildlife Refuge (herein called The Refuge) during the summers of 1999 and 2000. We found 30 nests of six species, including Bombycilla cedrorum (Cedar Waxwing), Turdus migratorius (American Robin), Pooecetes gramineus (Vesper Sparrow), Tyrannus tyrannus (Eastern Kingbird), Spizella passerina (Chipping Sparrow), and Geothlypis trichas (Common Yellowthroat). Hawthorn trees were the dominant plants used for nest placement. Overall, a similar number of nests fledged young (n = 17, 56.7%) as failed (n = 13, 43.3%) (P = 0.31). We attributed most nest failures to avian or mammalian predation, which may reflect an edge effec...

Avian Use of Black-Tailed Prairie Dog Colonies in Shortgrass Prairie

Downward trends in populations of many grassland bird species are of conservation concern. Declines in black-tailed prairie dog ( Cynomys ludovicianus ) populations result in loss of habitat for birds and other species associated with their colonies. We measured abundance, diversity, and species composition of avian communities on prairie dog colonies and noncolony sites in the Texas Panhandle. More resident species ( P &lt; 0.001) occurred on prairie dog colonies than on noncolony areas whereas, more nearctic-neoptropical migrants ( P = 0.003) and nearctic-temperate migrants ( P &lt; 0.001) occurred on noncolony sites. Total avian abundance was greater ( P &lt; 0.001) on noncolony sites than at prairie dog colonies, and differed by season ( P &lt; 0.001). Barn swallows ( Hirundo rustica ), red-winged blackbirds ( Agelaius phoeniceus ), horned larks ( Eremophila alpestris ), and chipping sparrows ( Spizella passerina ) were more abundant on noncolony sites than on prairie dog colonies. Burrowing owl ( Athene cunicularia ), Cassin’s sparrow ( Peucaea cassinnii ), and lark bunting ( Calamospiza melanocorys ) abundances were greater on prairie dog colonies. Vegetative alterations made by prairie dogs may not influence bird populations as much in these shortgrass prairies as has been reported in mixed-grass prairies.

A review of the zumpti species group of the genus Harpyrhynchoides (Acariformes: Harpirhynchidae)--ectoparasites of passerines.

The zumpti species group of the genus Harpyrhynchoides (Harpirhynchidae), parasites of passerines, is revised. A key to the species of this group is provided and data on host associations and geographic distribution of its constituent species are summarized. This group includes six previously recognized species: Harpyrhynchoides alaudinus Bochkov, 2000, H. brevis (Ewing, 1911) comb. nov., H. heatherae Bochkov and Galloway, 2013, H. rubeculinus (Cherny and Sixl, 1971), H. vulgaris Bochkov and Galloway, 2004, and H. zumpti (Fain, 1972). Three species from North American passerines are described as new: H. setophaga sp. nov. from Setophaga ruticilla (Parulidae), H. xanthocephalus sp. nov. from Xanthocephalus xanthocephalus (Icteridae), and H. spizella sp. nov. from Spizella passerina (Emberizidae). Additionally, H. brevis is redescribed based on samples from Coccothraustes vespertinus (type host) and Loxia curvirostra (Passeriformes: Fringillidae) from North America. Harpyrhynchoides kirgizorum Fain et al. 1999 syn. nov. is synonymized with H. zumpti.

Bird-window collisions in the summer breeding season.

Birds that reside in urban settings face numerous human-related threats to survival, including mortality from bird-window collisions (BWCs). Our current understanding of this issue has largely been driven by data collected during spring and fall migration, and patterns of collision mortality during the summer breeding season remain relatively unexplored. We assessed BWCs during four breeding seasons (2009–2012) at a site in northwestern Illinois, USA, by comparing the abundance, richness, migratory class, and age of the species living around buildings to species mortally wounded by window collisions. We also systematically assessed the daily timing of BWCs throughout the breeding season. We documented BWCs in 4 of 25 (16%) species and 7 of 21 (33%) species in 2009 and 2010, respectively. The relationship between BWCs and abundance depended on age. For adults, BWCs were highest in the least abundant species, e.g., Red-eyed Vireo (Vireo olivaceus), and lowest in species with high abundance values, e.g., Chipping Sparrow (Spizella passerina). For juveniles, mortality was greatest for the most abundant species, and the American Robin (Turdus migratorius) accounted for 62% of all juvenile carcasses. Early in the breeding season, collision mortality was restricted to adults of Long-distance Migrants, whereas juveniles of all three migratory guilds (Long-distance and Short-distance Migrants and Permanent Residents) died at windows from late June through early August. Daily mortality for all species was highest between sunrise–1600 h and lowest from 1600 h–sunrise the next day. Generally, the species observed as carcasses matched birds considered a ‘high risk’ for BWCs, e.g., Ruby-throated Hummingbird (Archilochus colubris), and those considered ‘low risk’ were not observed as carcasses, e.g., Blue-gray Gnatcatcher (Polioptila caerulea). Our results suggest that the number of BWCs during the breeding season does not necessarily increase with abundance, but rather appears related to variation among species and age classes, which may have important implications on the population health of affected species. The mechanisms driving these differences are unknown, but may be related reproductive behavior, flight speed, distance movements, and dispersal patterns.

Avian communities of managed and wilderness hemiboreal forests

We compared breeding bird communities of hemiboreal forests in multiple-use managed forests and relatively unmanaged wilderness forests in northern Minnesota. A total of 240 point-count locations, 120 in each of the managed and wilderness areas, were sampled three times across ten paired transects in 2010 and 2011. Transects were paired near lotic systems that cross each management type, with half of the points adjacent to (100m) or distant (400m) from the riparian corridor. Total number of individuals and species richness detected per count were higher within the unmanaged forest (F1,9=9.76, p=0.01; F1,9=11.17, p<0.01) and forest adjacent to the riparian corridor (F1,9=28.30, p<0.001; F1,9=42.12, p<0.001). These results were negatively correlated with increased area of regenerating forests (mainly from logging) within the managed forest and positively correlated with tree species richness and overstory height of forest stands within the wilderness forest. Of 35 species analyzed individually, Black-capped Chickadee (Poecile atricapillus), Brown Creeper (Certhia americana), Canada Warbler (Cardellina canadensis), Golden-crowned Kinglet (Regulus satrapa), Least Flycatcher (Empidonax minimus), Red-breasted Nuthatch (Sitta canadensis), Winter Wren (Troglodytes hiemalis), and Yellow-bellied Flycatcher (Empidonax flaviventris) were more common in the wilderness forest. Only the Mourning Warbler (Geothlypis philadelphia) and Chipping Sparrow (Spizella passerina) were more common in the managed forest. Species associated with mature or mixed forests tended to be found in the wilderness area at higher densities, but most species associated with early-successional habitats did not differ between the managed and wilderness landscapes. Results suggest that forests with natural disturbance and succession regimes provide habitat for a higher density and richness of bird species. Responses by breeding birds were similar in both management types regarding distance from riparian areas. To adequately provide for effective conservation of the avian community, forested regions should include wilderness forests.

Invasive plant erodes local song diversity in a migratory passerine

Exotic plant invasions threaten ecosystems globally, but we still know little about the specific consequences for animals. Invasive plants can alter the quality of breeding habitat for songbirds, thereby impacting important demographic traits such as dispersal, philopatry, and age structure. These demographic effects may in turn alter song-learning conditions to affect song structure and diversity. We studied Chipping Sparrows (Spizella passerina) breeding in six savannas that were either dominated by native vegetation or invaded by spotted knapweed (Centaurea stoebe), an exotic forb known to diminish food resources and reproductive success. Here, we report that the prevalence of older birds was relatively low in knapweed-invaded habitat, where recruitment of yearlings compensated for diminished site fidelity to sustain territory abundance. In both habitat types, yearling males tended to adopt songs similar to their neighbors and match the songs of older birds rather than introducing new song types, a pattern seen in many songbird species. As a consequence, in invaded habitat where age structure was skewed away from older birds serving as potential song models, yearlings converged on fewer song types. Similarity of songs among individuals was significantly higher and the overall number of song types averaged nearly 20% lower in invaded relative to native habitat. Degradation of habitat quality generally impacts site fidelity and age ratios in migratory songbirds and hence may commonly alter song-learning conditions. Associated shifts in song attributes known to influence reproductive success could in turn enforce demographic declines driven by habitat degradation. Local song structure may serve as an important indicator of habitat quality and population status for songbirds.

Team of rivals: alliance formation in territorial songbirds is predicted by vocal signal structure

Cooperation and conflict are regarded as diametric extremes of animal social behaviour, yet the two may intersect under rare circumstances. We here report that territorial competitors in a common North American songbird species, the chipping sparrow (Spizella passerina), sometimes form temporary coalitions in the presence of simulated territorial intruders. Moreover, analysis of birds' vocal mating signals (songs) reveals that coalitions occur nearly exclusively under specific triadic relationships, in which vocal performances of allies and simulated intruders exceed those of residents. Our results provide the first evidence that animals like chipping sparrows rely on precise assessments of mating signal features, as well as relative comparisons of signal properties among multiple animals in communication networks, when deciding when and with whom to form temporary alliances against a backdrop of competition and rivalry.

The Influence of Study Species Selection on Estimates of Pesticide Exposure in Free-Ranging Birds

Field studies of pesticide effects on birds often utilize indicator species with the purpose of extrapolating to other avian taxa. Little guidance exists for choosing indicator species to monitor the presence and/or effects of contaminants that are labile in the environment or body, but are acutely toxic, such as anticholinesterase (anti-ChE) insecticides. Use of an indicator species that does not represent maximum exposure and/or effects could lead to inaccurate risk estimates. Our objective was to test the relevance of a priori selection of indicator species for a study on pesticide exposure to birds inhabiting fruit orchards. We used total plasma ChE activity and ChE reactivation to describe the variability in anti-ChE pesticide exposure among avian species in two conventionally managed fruit orchards. Of seven species included in statistical analyses, the less common species, chipping sparrow (Spizella passerina), showed the greatest percentage of exposed individuals and the greatest ChE depression, whereas the two most common species, American robins (Turdus migratorius) and gray catbirds (Dumatella carolinensis), did not show significant exposure. Due to their lower abundance, chipping sparrows would have been an unlikely choice for study. Our results show that selection of indicator species using traditionally accepted criteria such as abundance and ease of collection may not identify species that are at greatest risk. Our efforts also demonstrate the usefulness of conducting multiple-species pilot studies prior to initiating detailed studies on pesticide effects. A study such as ours can help focus research and resources on study species that are most appropriate.