Cardinalis Cardinalis Research Articles

Heavy metal bioaccumulation in two passerines with differing migration strategies

Various anthropogenic activities have resulted in concentration of heavy metals and contamination of surrounding environments. Historically, heavy metal contamination at the Savannah River Site (SRS) in South Carolina has resulted from accidental releases of stored waste generated from nuclear weapon production in the early 1950s. Songbirds inhabiting and using resources from these areas have the potential to bioaccumulate metals but there is limited information on metal concentration levels in areas suspected of contamination as well as uncontaminated sites. Nonlethal tissues samples from avian blood and feathers provide a reliable approach for determining the bioavailability of these pollutants (As, Cd, Cr, Cu, Hg, Ni, Pb, Se, and Zn). The objectives of this study were to survey terrestrial heavy metal contamination at the SRS on potentially bioavailable contaminated (PBC) sites through blood and feather samples from resident Northern Cardinals (Cardinalis cardinalis) and migratory Great Crested Flycatchers (Myiarchus crinitus) and quantify sex-specific concentrations within species. Samples were collected in April to June of 2016. Cardinals had lower blood concentrations of Hg (β=−0.17, 85% CL=−0.26, −0.09) and Se (β=−0.33, 85% CL=−0.50, −0.16) than flycatchers. Cr feather concentrations were less in cardinals (β=−1.46, 85% CL=−2.44, −0.49) and all feathers of both species from reference locations had significantly less Zn (β=−67.92, 85% CL=−128.71, −7.14). Results indicate flycatchers were exposed to differing heavy metal levels during feather formation on their wintering grounds as compared to their recent exposure (through bloods samples) on their breeding grounds. Sex of individuals did not have a significant impact on bioaccumulation in either species. Overall, metal concentration levels in both species indicate minimal risk for acute toxicity; however, there is limited research on wild passerine populations with similar concentration levels. Therefore, further research on reproductive success of these birds should be explored.

Avian species diversity and transmission of West Nile virus in Atlanta, Georgia

BackgroundThe dilution effect is the reduction in vector-borne pathogen transmission associated with the presence of diverse potential host species, some of which are incompetent. It is popularized as the notion that increased biodiversity leads to decreased rates of disease. West Nile virus (WNV) is an endemic mosquito-borne virus in the United States that is maintained in a zoonotic cycle involving various avian host species. In Atlanta, Georgia, substantial WNV presence in the vector and host species has not translated into a high number of human cases.MethodsTo determine whether a dilution effect was contributing to this reduced transmission, we characterized the host species community composition and performed WNV surveillance of hosts and vectors in urban Atlanta between 2010 and 2011. We tested the relationship between host diversity and both host seroprevalence and vector infection rates using a negative binomial generalized linear mixed model.ResultsRegardless of how we measured host diversity or whether we considered host seroprevalence and vector infection rates as predictor variables or outcome variables, we did not detect a dilution effect. Rather, we detected an amplification effect, in which increased host diversity resulted in increased seroprevalence or infection rates; this is the first empirical evidence for this effect in a mosquito-borne system.ConclusionsWe suggest that this effect may be driven by an over-abundance of moderately- to poorly-competent host species, such as northern cardinals and members of the Mimid family, which cause optimal hosts to become rarer and present primarily in species-rich areas. Our results support the notion that dilution or amplification effects depend more on the identities of the species comprising the host community than on the absolute diversity of hosts.

Species-dependent effects of bird feeders on nest predators and nest survival of urban American Robins and Northern Cardinals

ABSTRACT The abundance of anthropogenic foods in urban areas offers an excellent opportunity to examine the effects of supplementary food on animal communities, but few studies have examined the consequences of these supplements on relationships between predators and prey. We used observational and experimental approaches to investigate how supplementary food (i.e. bird feeders) affected predator abundances and nest survival of American Robins (Turdus migratorius) and Northern Cardinals (Cardinalis cardinalis) in 7 neighborhoods of Columbus, Ohio, USA. From April to August of 2011–2014, we quantified supplementary foods, the relative abundance of 6 common nest predators, and the nest survival of 2 songbirds. In April–August of 2013 and 2014, we supplemented 3 neighborhoods with additional bird feeders, the supplementary food most frequently available to predators. The effects of bird feeders varied among predator and prey species. Bird feeders were positively associated with the relative abundance of Amer...

On Visiting Faulkner’s Grave, and: Before My Mother Moves South, and: Northern Cardinal in Winter, and: Mississippi Gambers after Dusk

On Visiting Faulkner’s Grave, and: Before My Mother Moves South, and: Northern Cardinal in Winter, and: Mississippi Gambers after Dusk Rob Shapiro (bio) On Visiting Faulkner’s Grave He said time is dead as long as it’s beingclicked off by little wheels; only whenthe clock stops does time come to life. i My stepbrother pinned a shotgun shell to his breast pocket when he got married, wore aviators even though dark pastures of clouds brushed above the delta and turned, suddenly, to rain. He planted his footprints deep in the black dirt to see how much the land could hold, how quickly it committed us to memory. And because this was Mississippi, he named his son for himself—the same way his father named him. ii Framed and gawking, the dead decorate my family’s walls— [End Page 64] local ghosts looking out, captured in crops of cotton, the white fields ripe as if blooming with snow. Always, a bloodshot sky just out of reach— always, they refuse to smile for the camera aimed like a pistol at their hearts, its aperture drawing in their sweat-drenched collars and rolled-up sleeves— their work-boots muddied in the same soil tilled year after year. iii When I visited Faulkner’s grave, grazed my hand on the granite stone lined with empty flasks and whiskey fifths, I could have walked the mile down to the house where my stepbrother was raised. And I’ve read of doom, the lord marching his angels out of Mississippi. I’ve read of generations held in the rough arms of countryside— the bluffs and fields and sky. iv He sends photographs to Carolina, prints taken with his father’s old Kodak. I imagine my stepbrother working [End Page 65] the darkroom until dawn: lightheaded from fixer fumes, his fingers uncoiling loose spools of film. Tin sink. Safelight. His son bursting into focus from the shallow darkness— already looking back. Before My Mother Moves South Another week of flurries and frozen rain.You let the sheltie out into the stiffwinter dawn, still thick with stars and fogwhile upstairs, my sister and I sleep—the three of us living togetherfor the last time. Snow-chained truckssand the street, rattle through the darkpast the For Sale sign buriedbeneath our bulldozed banks. Come spring, you’ll be kneelingin the flooded front yard, white statuetteof Saint Joseph held to your chest.Too superstitious not to try prayerto sell the house, you’ll break openthe half-thawed earth and pushthe figurine deep inside the tangled dirt,speaking to it, bargaining. Mother, I want to keep you in that housea little longer, standing by the window [End Page 66] watching the sheltie pace the yardand sink through the melting drifts.The radiator clinks its cast-iron heart;you stir your coffee, spoon rattling rim,and look out at the linden treescradling abandoned nests like palmscupping water—you wait there for the skyto brighten, to disappear behind the rushof snow that falls and clings to nothing. Northern Cardinal in Winter My father is not the feather nor the red crest,but the song sung from the canopies— the slender trill needling through frost and frozen light,woven through the hills outside my bedroom window. And you might think I mean my father is beautifulor far off, some small echo I can’t trace. Truth is, I find he follows like that flickering voice lifting over power linesand fresh snow, that bright fragment I’ve always known. [End Page 67] Mississippi Gamblers after Dusk Gathered on the lawn between the chicken coop and the pond, still high from spring’s thaw, we watch my stepbrother kneel on the jetty beside the thicket of cattails loading tube-launched fireworks. Across the water, rows of barbed wire border the pastures, fence us in as gunpowder cracks like a sheet of ice, sends a Mississippi Gambler streaking across the swath of summer sky until it bursts into light, familiar constellations that drift down, disappear. We grip cans of beer and call to each other...

Avian thermoregulation in the heat: resting metabolism, evaporative cooling, and heat tolerance in Sonoran Desert songbirds

We examined thermoregulatory performance in seven Sonoran Desert passerine bird species varying in body mass from 10 to 70 g - lesser goldfinch, house finch, pyrrhuloxia, cactus wren, northern cardinal, Abert's towhee and curve-billed thrasher. Using flow-through respirometry, we measured daytime resting metabolism, evaporative water loss and body temperature at air temperatures (Tair) between 30 and 52°C. We found marked increases in resting metabolism above the upper critical temperature (Tuc), which for six of the seven species fell within a relatively narrow range (36.2-39.7°C), but which was considerably higher in the largest species, the curve-billed thrasher (42.6°C). Resting metabolism and evaporative water loss were minimal below the Tuc and increased with Tair and body mass to maximum values among species of 0.38-1.62 W and 0.87-4.02 g H2O h-1, respectively. Body temperature reached maximum values ranging from 43.5 to 45.3°C. Evaporative cooling capacity, the ratio of evaporative heat loss to metabolic heat production, reached maximum values ranging from 1.39 to 2.06, consistent with known values for passeriforms and much lower than values in taxa such as columbiforms and caprimulgiforms. These maximum values occurred at heat tolerance limits that did not scale with body mass among species, but were ∼50°C for all species except the pyrrhuloxia and Abert's towhee (48°C). High metabolic costs associated with respiratory evaporation appeared to drive the limited heat tolerance in these desert passeriforms, compared with larger desert columbiforms and galliforms that use metabolically more efficient mechanisms of evaporative heat loss.

Melanin ornament brightness and aggression at the nest in female Northern Cardinals (Cardinalis cardinalis)

ABSTRACT Research is increasingly addressing the evolution and use of sexually selected traits in females. One strong area of interest is the display of intrasexual aggression and how female ornaments are used in intrasexual competition. One particular type of ornament focused on for its use in intrasexual aggression in both sexes is the melanin pigmented ornaments. Over the course of 2 breeding seasons in a southeastern Mississippi population of cardinals, we assessed brightness of the melanin face mask plumage ornament in female Northern Cardinals (Cardinalis cardinalis) and compared it to behavioral responses during intraspecific simulated nest intrusions (SNIs). All females responded to the SNI, but face mask brightness did not co-vary with the level of aggression shown. Our findings do not support earlier work suggesting that the face mask in female Northern Cardinals is an indicator of aggression at the nest. Potentially, differences in behavior and environmental variables between populations of car...

Research Article: Physiological profiles of free-living birds with antibodies to West Nile virus

Abstract Studies of West Nile virus (WNV) are prevalent in avian, equine, and human health literature over the past 15 years. What remain poorly understood are immune and physiological mechanisms that promote survival of WNV infection in natural populations. We captured downy woodpeckers, house finches, and northern cardinals before, during, and after a local WNV outbreak to determine seroprevalence of immunoglobulin M (IgM) antibodies to WNV in the local bird population. Variation in physiological traits associated with a history of WNV infection was assessed in these free-living avian hosts. The presence of WNV antibodies differed among the three species. The findings also reveal phenotypic qualities of birds that survived the virus, and potential costs associated with carrying the virus. Body condition, innate immune function, and antioxidant capacity differed significantly among birds with and without antibodies to WNV. Northern cardinals with WNV IgM were in significantly better body condition. Indiv...

Vacant lots as a habitat resource: nesting success and body condition of songbirds

AbstractVacant lots are a common feature throughout many cities and may provide necessary habitat resources for urban bird populations. We evaluated the quality of vacant lots throughout Baltimore, Maryland, by determining how differences in vacant lot properties related to songbirds' nesting success and body condition. We observed 130 nests from American robins (Turdus migratorius), gray catbirds (Dumetella carolinensis), and northern cardinals (Cardinalis cardinalis) across the city and assessed body condition of 19 adult robins. Nesting success for all three species was greatest within areas of vacant lots with high shrub densities. The robins' body condition index did not vary extensively and was not related to any vacant lot site‐ or landscape‐level variables. Even so, we found vacant lots to be actively used by 60 bird species for a variety of resources, with those containing more shrubs to be the most beneficial for bird species' nesting attempts. Vacant lots should no longer be discarded and underestimated; instead, they should be valued for the opportunities they provide for generalist bird species through small‐effort habitat management practices.

Distribution and Prevalence of Haemosporidian Parasites in the Northern Cardinal (Cardinalis cardinalis).

Avian haemosporidian parasites provide a model system for understanding ecological and evolutionary host-parasite interactions. The diversity and distribution of these parasites remains incomplete, and, here, we provide the first range-wide assessment of avian haemosporidians in a continentally distributed host, the Northern Cardinal ( Cardinalis cardinalis ). Based on molecular techniques, we show geographical differences in prevalence and lineage diversity between host subspecies and identify several novel lineages. We use phylogenetic reconstruction to show where these lineages fit into the expanding evolutionary tree of avian haemosporidian lineages. All except 1 subspecies of Northern Cardinal are highly parasitized by a wide diversity of Plasmodium and Parahaemoproteus. Compared to published studies that used microscopy to determine prevalence in this host, we find a much higher number of infected individuals (67.4% vs. 45% or less). Consistent with previous studies, Parahaemoproteus from the Northern Cardinal was found to be highly host specific and geographically structured, whereas Plasmodium was less host specific and geographically unstructured.

Do Birds Alter Levels of Parental Investment Based on Nest‐Site Habitat Features?

AbstractMany habitats have undergone rapid changes over the past century as a result of anthropogenic activities. Organisms can respond to changes in their environment in many ways, including how much they invest in a given reproductive bout. Optimality theory and life history theory together have provided a framework for understanding how individuals make decisions about the risks and rewards of investing high levels of resources into their offspring within the context of current vs. future reproduction. Shrubland birds in the United States often breed in habitat that has been impacted by humans to varying degrees and provide an ideal system for examining whether organisms alter their levels of parental investment based on the habitat around the nest site. In this study, we assessed levels of nest‐defense behavior during a simulated nest predation event in four shrubland birds: American robins (Turdus migratorius), gray catbirds (Dumetella carolinensis), brown thrashers (Toxostoma rufum), and northern cardinals (Cardinalis cardinalis). We found that thrashers and catbirds exhibited significantly higher levels of nest defense compared to robins and cardinals and that birds with larger broods acted more aggressively in defending them. We also found that thrashers acted less aggressively as the proportion of shrubland around the nest increased and as the proportion of developed land around the nest decreased and that cardinals acted less aggressively as the proportion of developed land around the nest increased. These patterns suggest that nest‐defense behavior can covary with features of the landscape surrounding the nest, but that the factors shaping that behavior can differ by species.

Predictors of flight behavior in rural and urban songbirds

ABSTRACT The urban environment poses novel anthropogenic challenges to wildlife. Some species have been noted for changes in their behavior in response to humans and urban-associated activities. Understanding the anthropogenic factors which influence these behavioral changes would contribute significantly to avian conservation in an increasingly urbanized world. We investigated the flight initiation distances (FIDs) and alert distances (ADs) of wild Song Sparrows (Melospiza melodia) and Northern Cardinals (Cardinalis cardinalis) in urban and rural habitats of southwestern Virginia to determine if wild songbirds' tolerances for human approaches differed by species or habitat type (urban or rural). We found Song Sparrows to be more tolerant than Northern Cardinals of human approaches, and urban birds of both species tended to tolerate closer approaches than did rural birds. We then investigated whether cues such as gaze direction or human figure explain differences in Song Sparrows' approach response behavi...

Supersuppression: Reservoir Competency and Timing of Mosquito Host Shifts Combine to Reduce Spillover of West Nile Virus.

In the eastern United States, human cases of West Nile virus (WNV) result from spillover from urban epizootic transmission between passerine birds and Culex mosquitoes. In Atlanta, GA, substantial WNV presence in hosts and vectors has not resulted in the human disease burden observed in cities with similar infection pressure. Our study goal was to investigate extrinsic ecological conditions that potentially contribute to these reduced transmission rates. We conducted WNV surveillance among hosts and vectors in urban Atlanta and recorded an overall avian seroprevalence of nearly 30%, which was significantly higher among northern cardinals, blue jays, and members of the mimid family, and notably low among American robins. Examination of temporal Culex feeding patterns showed a marked feeding shift from American robins in the early season to northern cardinals in the late season. We therefore rule out American robins as superspreaders in the Atlanta area and suggest instead that northern cardinals and mimids act as WNV "supersuppressor" species, which slow WNV transmission by drawing many infectious bites during the critical virus amplification period, yet failing to amplify transmission due to low host competencies. Of particular interest, urban forest patches provide spillover protection by increasing the WNV amplification fraction on supersuppressor species.

Reduced ultraviolet reflectance does not affect egg rejection by Northern Cardinals (Cardinalis cardinalis)

ABSTRACT 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 a...

Nesting ecology of early-successional birds in restored longleaf and loblolly pine stands

ABSTRACT 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, an...

Sources of variation in plasma corticosterone and dehydroepiandrosterone in the male northern cardinal (Cardinalis cardinalis): I. Seasonal patterns and effects of stress and adrenocorticotropic hormone

The secretion of steroids from the adrenal gland is a classic endocrine response to perturbations that can affect homeostasis. During an acute stress response, glucocorticoids (GC), such as corticosterone (CORT), prepare the metabolic physiology and cognitive abilities of an animal in a manner that promotes survival during changing conditions. Although GC functions during stress are well established, much less is understood concerning how adrenal androgens, namely dehydroepiandrosterone (DHEA) are influenced by stress. I conducted three field studies (one experimental and two descriptive) aimed at identifying how both CORT and DHEA secretion in free-living male northern cardinals (Cardinalis cardinalis), vary during acute stress; across different circulations (brachial vs. jugular); in response to ACTH challenge; and during the annual cycle. As predicted, restraint stress increased plasma CORT, but unexpectedly DHEA levels decreased, but the latter effect was only seen for blood sampled from the jugular vein, and not the brachial. The difference in DHEA between circulations may result from increased neural uptake of DHEA during stress. Injection with exogenous adrenocorticotropic hormone (ACTH) increased CORT concentrations, but failed to alter DHEA levels, thus suggesting ACTH is not a direct regulator of DHEA. Monthly field sampling revealed distinct seasonal patterns to both initial and restraint stress CORT and DHEA levels with distinct differences in the steroid milieu between breeding and non-breeding seasons. These data suggest that the CORT response to stress remains relatively consistent, but DHEA secretion is largely independent of the response by CORT. Although CORT functions have been well-studied in wild animals, little research exists for the role of DHEA and their variable relationship sets the stage for future experimental research addressing steroid stress responses.

Sources of variation in plasma corticosterone and dehydroepiandrosterone in the male northern cardinal (Cardinalis cardinalis): II. Effects of urbanization, food supplementation and social stress

Perturbations in an organism’s environment can induce significant shifts in hormone secretory patterns. In this context, the glucocorticoid (GC) steroids secreted by the adrenal cortex have received much attention from ecologists and behaviorists due to their role in the vertebrate stress response. Adrenal GCs, such as corticosterone (CORT), are highly responsive to instability in environmental and social conditions. However, little is understood about how adrenal dehydroepiandrosterone (DHEA) is influenced by changing conditions. We conducted field experiments to determine how circulating CORT and DHEA vary during restraint stress in the male northern cardinals (Cardinalis cardinalis). Specifically, we examined how four different changes in the physical (urbanization and food availability) and social (territorial conflict, distress of a mate) environment affect CORT and DHEA levels. The majority of cardinals responded to restraint stress by increasing and decreasing CORT and DHEA, respectively, however this depended on sampling context. Cardinals sampled from urban habitats had both lower initial and restraint stress CORT concentrations, but a comparable DHEA pattern to those sampled from a forest. Supplementing food to territorial males did not alter circulating initial DHEA or CORT concentrations nor did it change the response to restraint stress when compared to unsupplemented controls. Exposing cardinals to varying durations of song playback, which mimics a territorial intrusion, did not affect CORT levels, but did attenuate the DHEA response to restraint stress. Examining a larger dataset of males captured before, after or at the same time as their female mate, allowed us to address how the stress of a captured mate affected the male’s CORT and DHEA response. Males showed elevated initial and restraint CORT and DHEA when their female mate was captured first. Taken together, these data demonstrate that both CORT and DHEA secretion patterns depends on environmental, and particularly current social conditions.

When the birds go unheard: highway noise disrupts information transfer between bird species.

Highway infrastructure and accompanying vehicle noise is associated with decreased wildlife populations in adjacent habitats. Noise masking of animal communication is an oft-cited potential mechanism underlying species loss in sound-polluted habitats. This study documents the disruption of between-species information transfer by anthropogenic noise. Titmice and chickadees broadcast specific calls to alert kin of predator threats, and sympatric vertebrates eavesdrop on these alarm calls to avoid predators. We tested if tufted titmouse alarm call eavesdropping by northern cardinals is disrupted by road noise. We broadcast recorded alarm calls to cardinals in natural areas near and far from highways. Cardinals reliably produced predator avoidance responses in quiet trials, but all birds in noisy areas failed to respond, demonstrating that highway noise is loud enough to disrupt this type of survival-related information via masking or cognitive distraction. Birds in family Paridae are abundant, highly social and vocal residents of woodlands across the Holarctic whose alarm calls are used by many species to mediate predation risks. Our work suggests that communication network disruption is likely to be widespread, and could help explain the pattern of reduced biodiversity near roadways.

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.

Urban-associated drivers of song variation along a rural–urban gradient

Most studies demonstrating associations between avian song and urbanization have tested noise as the primary driver, but alternative explanations remain largely unexplored. In particular, urban-associated changes in vegetation, density of conspecifics, and morphology also may promote changes in song. In this study, we 1) identified relationships between urbanization and song characteristics and 2) evaluated the extent to which altered song was explained by variation in noise level, vegetation, social context, and morphology of individual birds. We monitored the territories and recorded songs of northern cardinals (Cardinalis cardinalis) within forest stands in central Ohio that varied with surrounding urbanization. As landscapes surrounding forests urbanized, songs were longer, sung at faster rates, and comprised of higher-frequency notes. Noise best predicted minimum song frequency, with individuals singing at higher frequencies in environments with higher levels of background noise. However, temporal attributes of song (e.g., syllable rate, length) were best explained by conspecific densities, which are substantially greater in urban than rural landscapes. Morphology and vegetation did not predict any song attributes tested. These findings show that although anthropogenic noise may shape urban-associated changes in song, other features of the urban environment may be more important contributors to patterns in song variation.

New Records of Ixodes affinis (Acari: Ixodidae) Parasitizing Avian Hosts in Southeastern Virginia.

Ixodes affinis Neumann (Acari: Ixodidae) is a hard-bodied tick species distributed throughout much of the southeastern United States. Although I. affinis does not parasitize humans, it is a competent vector of Borrelia burgdorferi sensu stricto, the causative-agent of Lyme disease, and thus contributes to the enzootic maintenance of this pathogen. This study presents evidence of I. affinis parasitizing five new host passerine species. During 2012-2014, 1,888 birds were captured and examined for ticks, and 18 immature I. affinis were collected from 12 birds-six Carolina Wrens (Thyrothorus ludovicianus); two Brown Thrashers (Toxostoma rufum); and one American Robin (Turdus migratorius), Eastern Towhee (Pipilo erythrophthalmus), Northern Cardinal (Cardinalis cardinalis), and White-throated Sparrow (Zonotrichia albicollis). Of 15 larvae and 3 nymphs collected, one nymph tested positive for B. burgdorferi DNA. I. affinis was found co-feeding on birds with immature Amblyomma americanum (L.), Ixodes brunneus Koch, Ixodes dentatus Marx, Ixodes scapularis Say, and Haemaphysalis leporispalustris Packard. The results of this research provide a better understanding of I. affinis hosts and identify avian taxa that may play a role in the maintenance and dispersal of this tick species.