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do songbirds in wetlands show higher mercury bioaccumulation relative to conspecifics in non-wetland habitats?environmental conditions in wetlands facilitate favorable biogeochemical conditions for the conversion of inorganic mercury into methylmercury. for this reason, wetlands are increasingly classified as mercury hotspots, places where biota exhibit elevated mercury concentrations. while it is clear that wetlands play an important role in methylmercury production, factors such as geographic variation in mercury deposition, wetland type, and trophic dynamics can cause variation in mercury dynamics an ...202031942663
expanding our view of bartonella and its hosts: bartonella in nest ectoparasites and their migratory avian hosts.bartonella is a genus of gram-negative facultative intracellular alphaproteobacteria of public health importance. although they are known to mainly infect mammalian hosts with some blood-feeding arthropods having been confirmed as vectors, there is some evidence of bartonella association with non-mammalian hosts including birds.202031924262
host tolerance and resistance to parasitic nest flies differs between two wild bird species.hosts have developed and evolved defense strategies to limit parasite damage. hosts can reduce the damage that parasites cause by decreasing parasite fitness (resistance) or without affecting parasite fitness (tolerance). because a parasite species can infect multiple host species, determining the effect of the parasite on these hosts and identifying host defense strategies can have important implications for multi-host-parasite dynamics.over 2 years, we experimentally manipulated parasitic flie ...201931832149
reproductive success of eastern bluebirds (sialia sialis) varies with the timing and severity of drought.drought affects avian communities in complex ways. we used our own and citizen science-generated reproductive data acquired through the cornell lab of ornithology's nestwatch program, combined with drought and vegetation indices obtained from governmental agencies, to determine drought effects on eastern bluebird (sialia sialis l.) reproduction across their north american breeding range for the years 2006-2013. our results demonstrate that some aspects of bluebird reproductive success vary with ...201931398191
necrotizing enteritis in nesting adult eastern bluebirds (sialia sialis) in new york state, usa.increased mortalities of adult eastern bluebirds, sialia sialis, breeding in artificial nesting boxes were recorded in new york state, us. a total of 46 dead bluebirds were reported from 23 sites between early april and mid-august 2017. the maximum distance between sites was over 600 km. a total of 27 carcasses were available for postmortem examination. the most common cause of death was necrotizing enteritis, found in 56% (9/16) of birds that could be examined histopathologically. lesions consi ...201930856049
interactions of body temperature and nutritional status on hypothalamo-pituitary-adrenal axis activity in pre-thermoregulatory eastern bluebird chicks (sialia sialis).early life experiences can affect the function of the hypothalamo-pituitary-adrenal (hpa) axis of vertebrates, with potential fitness consequences later in life. in altricial species, for example, variation in parental behavior, e.g. brooding or feeding, can modify the activity of the hpa axis of the young by altering their exposure to noxious stimuli as the young develop in the nest. we have shown that a drop in the body temperature of eastern bluebird (sialia sialis) chicks, such as occurs whe ...201829908835
spatial extent of mercury contamination in birds and their prey on the floodplain of a contaminated river.mercury (hg) exposure has been extensively studied in aquatic and piscivorous wildlife, but, historically, less attention has been directed towards terrestrial species. however, it has become apparent that aquatic hg crosses ecosystem boundaries along with beneficial subsidies, thereby entering the terrestrial food chain. it is still not known how far from contaminated waterways hg exposure remains a risk. we examined the spatial extent of exposure in terrestrial songbirds breeding in the floodp ...201829554763
origin, paleoecology, and extirpation of bluebirds and crossbills in the bahamas across the last glacial-interglacial transition.on low islands or island groups such as the bahamas, surrounded by shallow oceans, quaternary glacial-interglacial changes in climate and sea level had major effects on terrestrial plant and animal communities. we examine the paleoecology of two species of songbirds (passeriformes) recorded as late pleistocene fossils on the bahamian island of abaco-the eastern bluebird (sialia sialis) and hispaniolan crossbill (loxia megaplaga). each species lives today only outside of the bahamian archipelago, ...201728847933
pre-gnrh and gnrh-induced testosterone levels do not vary across behavioral contexts: a role for individual variation.hormones can facilitate the expression of behavior, but relatively few studies have considered individual variation and repeatability in hormone-behavior relationships. repeated measures of hormones are valuable because repeatability in hormone levels might be a mechanism that drives repeatability in behavior ("personality"). testosterone is predicted to promote territorial aggression and suppress parental behaviors. in our population of eastern bluebirds (sialia sialis), parental care and nest ...201728322761
ecologically relevant cooling early in life alters prefledging adrenocortical response in free-living songbirds.in vertebrates, exposure to stressful stimuli early in development may alter the activity of the hypothalamo-pituitary-adrenal (hpa) axis, with the potential for fitness consequences later in life. for altricial species, whose young rely on their parents for food, warmth, and protection from predators, adult behavior can modify the impact of some stressors on their offspring after birth or hatching. we have shown that single bouts of cooling that normally occur when brooding females leave the ne ...201728051939
relationship between maternal environment and dna methylation patterns of estrogen receptor alpha in wild eastern bluebird (sialia sialis) nestlings: a pilot study.there is mounting evidence that, across taxa, females breeding in competitive environments tend to allocate more testosterone to their offspring prenatally and these offspring typically have more aggressive and faster-growing phenotypes. to date, no study has determined the mechanisms mediating this maternal effect's influence on offspring phenotype. however, levels of estrogen receptor alpha (er α) gene expression are linked to differences in early growth and aggression; thus, maternal hormones ...201627547309
baseline hormone levels are linked to reproductive success but not parental care behaviors.consistent behavioral differences among individuals, or personalities, have been hypothesized to arise as a result of consistent individual differences in hormone levels. individual variation in baseline hormone levels or hormonal similarity within a breeding pair may be related to reproductive success, as suggested by the corticosterone-fitness hypothesis and the hormonal similarity hypothesis, respectively. in a population of eastern bluebirds (sialia sialis) with repeatable behavioral express ...201626972151
plumage color and reproductive output of eastern bluebirds (sialia sialis) nesting near a mercury-contaminated river.despite the growing evidence of mercury's impact on ecosystems, few studies have looked at the environmental impact of mercury pollution on terrestrial songbirds and the complex ways through which mercury might influence their fitness. in 2007-2008 eastern bluebirds (sialia sialis) were monitored on mercury contaminated and reference sites for blood and feather mercury, reproductive success and plumage coloration. higher tissue mercury accumulation was associated with plumage that was overall br ...201526121017
eastern bluebirds alter their song in response to anthropogenic changes in the acoustic environment.vocal responses to anthropogenic noise have been documented in several species of songbird. however, only a few studies have investigated whether these adjustments are made in "real time" or are longer-term responses to particular soundscapes. furthermore, increased ambient noise often is accompanied by structural changes to the habitat, including the introduction of noisy roadways and the removal of native vegetation. to date, no studies have simultaneously investigated the impact of both acous ...201526116201
mercury concentrations in birds from two atmospherically contaminated sites in north texas, usa.mercury (hg) is a ubiquitous and highly toxic contaminant that can have negative effects on wildlife. only a few studies have measured hg concentrations in birds from the south central united states, and the potential threat of hg contamination to birds in this region is largely unknown. in the present study, we assess hg concentrations in blood and feathers from five bird species [eastern bluebird (sialis sialis), carolina wren (thryothorus ludovicianus), wood duck (aix sponsa), great egret (ar ...201526137900
occurrence of twin embryos in the eastern bluebird.we report the first record of presumed twinning in eastern bluebird (sialia sialis) and provide a review of previously reported twinning events in wild birds. a nest containing twin eastern bluebird nestlings was monitored in 2013 in central pennsylvania and reported to the cornell lab of ornithology's nestwatch program, a national program where volunteers submit data on wild nesting birds. a presumed double-yolked egg of a free-living eastern bluebird pair hatched successfully, and twin nestlin ...201424688852
parental behavior correlates to baseline corticosterone of mates and offspring in nesting eastern bluebirds (sialia sialis).raising nestlings in a biparental species involves a complex and dynamic interaction of physiology and behavior among a group of organisms. parents may be predicted to vary their behaviors based not only upon their own state, but also in relation to the states of both offspring and the other parent. in this study we explore the relationships between parental feeding behaviors and family member condition in eastern bluebirds, with a special emphasis on baseline corticosterone, a hormone associate ...201424681151
interspecific competition influences fitness benefits of assortative mating for territorial aggression in eastern bluebirds (sialia sialis).territorial aggression influences fitness and, in monogamous pairs, the behavior of both individuals could impact reproductive success. moreover, territorial aggression is particularly important in the context of interspecific competition. tree swallows and eastern bluebirds are highly aggressive, secondary cavity-nesting birds that compete for limited nesting sites. we studied eastern bluebirds at a field site in the southern appalachian mountains that has been recently colonized (<40 yr) by tr ...201424516672
island life shapes the physiology and life history of eastern bluebirds (sialia sialis).abstract island organisms face a range of extrinsic threats to their characteristically small populations. certain biological differences between island and continental organisms have the potential to exacerbate these threats. understanding how island birds differ from their continental relatives may provide insight into population viability and serve as a predictive tool for conservation efforts. we compared an eastern bluebird population in ohio with a threatened population in bermuda in terms ...201424457931
environmentally relevant bouts of cooling stimulate corticosterone secretion in free-living eastern bluebird (sialia sialis) nestlings: potential links between maternal behavior and corticosterone exposure in offspring.in vertebrates, exposure to stressful stimuli or to elevated glucocorticoids early in development can contribute to phenotypic variation that may have significant fitness consequences. in species with altricial young, offspring may be partially buffered from elevations in glucocorticoids by a period of low glucocorticoid responsiveness to stressors coupled with high levels of parental care. because altricial young depend heavily on their parents for warmth, parental brooding behavior could buffe ...201424275608
effect of prenatal and natal administration of testosterone on production of structurally based plumage coloration.testosterone has been implicated as a developmental mechanism involved in the organization and expression of sexually dimorphic traits, such as plumage coloration, in birds. although research findings relating testosterone levels to plumage expression is equivocal, few studies have investigated how testosterone may influence the expression of structurally based plumage coloration. here, we use experimental and correlational evidence to test the hypothesis that testosterone influences the develop ...201323629882
neonatal handling alters the development of the adrenocortical response to stress in a wild songbird (eastern bluebird, sialia sialis).neonatal handling of captive vertebrates can shape the development of their hypothalamo-pituitary-adrenal (hpa) axis and alter their ability to respond to stressful stimuli later in life. however, the long-term effects of such handling on this endocrine axis in free-living species are not well understood. we investigated the effects of age and neonatal handling on corticosterone secretion in response to restraint in eastern bluebird (sialia sialis) chicks. we found that unhandled ("naïve") and h ...201323524000
cryptic introductions and the interpretation of island biodiversity.species with cryptic origins (i.e. those that cannot be reliably classed as native or non-native) present a particular challenge to our understanding of the generation and maintenance of biodiversity. such species may be especially common on islands given that some islands have had a relatively recent history of human settlement. it is likely that select island species considered native might have achieved their current distributions via direct or indirect human actions. as an example, we explor ...201323432192
vector contact rates on eastern bluebird nestlings do not indicate west nile virus transmission in henrico county, virginia, usa.sensitive indicators of spatial and temporal variation in vector-host contact rates are critical to understanding the transmission and eventual prevention of arboviruses such as west nile virus (wnv). monitoring vector contact rates on particularly susceptible and perhaps more exposed avian nestlings may provide an advanced indication of local wnv amplification. to test this hypothesis we monitored wnv infection and vector contact rates among nestlings occupying nest boxes (primarily eastern blu ...201324287858
variable effects of yolk androgens on growth, survival, and immunity in eastern bluebird nestlings.female birds allocate androgens differentially within and among clutches, and it has been suggested that this is a strategy to maximize reproductive success. only a few studies, however, have examined the effects of yolk testosterone (t) on the growth and development of nestlings, and none have reported on the immunological effects of yolk t nor have they examined several different effects in the same nestlings. to examine the effects of yolk t on nestling eastern bluebirds, we administered two ...201315957111
anthropogenic noise is associated with reductions in the productivity of breeding eastern bluebirds (sialia sialis).although previous studies have related variations in environmental noise levels with alterations in communication behaviors of birds, little work has investigated the potential long-term implications of living or breeding in noisy habitats. however, noise has the potential to reduce fitness, both directly (because it is a physiological stressor) and indirectly (by masking important vocalizations and/or leading to behavioral changes). here, we quantified acoustic conditions in active breeding ter ...201223210314
invasive ants alter foraging and parental behaviors of a native bird.introduced species can exert outsized impacts on native biota through both direct (predation) and indirect (competition) effects. ants frequently become established in new areas after being transported by humans across traditional biological or geographical barriers, and a prime example of such establishment is the red imported fire ant (solenopsis invicta). introduced to north america in the 1930's, red imported fire ants are now firmly established throughout the southeastern united states. alt ...201222844172
structural coloration signals condition, parental investment, and circulating hormone levels in eastern bluebirds (sialia sialis).many of the brilliant plumage coloration displays of birds function as signals to conspecifics. one species in which the function of plumage ornaments has been assessed is the eastern bluebird (sialia sialis). studies of a population breeding in alabama (usa) have established that plumage ornaments signal quality, parental investment, and competitive ability in both sexes. here we tested the additional hypotheses that (1) eastern bluebird plumage ornamentation signals nest defense behavior in he ...201222622467
reproductive success of three passerine species exposed to dioxin-like compounds near midland, michigan, usa.nests of three passerine birds, house wren (howr), tree swallow (tres), and eastern bluebird (eabl) were monitored daily (2005-2007) at study areas (sas) downstream of midland, michigan where soil and sediment concentrations of polychlorinated dibenzofurans (pcdfs) were significantly greater than the regional background concentrations and upstream reference areas (ras). similarly, tres research conducted at sites contaminated with dioxin-like compounds indicated that concentrations of polychlori ...201222392542
the effects of brood size on growth and steroid hormone concentrations in nestling eastern bluebirds (sialia sialis).birds in multi-nestling broods often experience reduced growth and elevated nutritional and social stress as a result of competition for parental resources. while responses are often species-specific, experimentally increasing brood size has been shown to decrease growth and increase production of both testosterone and corticosterone in nestling passerines. to investigate the relationship between brood size, growth, and steroid hormone production in eastern bluebirds, we cross-fostered nestlings ...201121819987
invasive fire ants reduce reproductive success and alter the reproductive strategies of a native vertebrate insectivore.introduced organisms can alter ecosystems by disrupting natural ecological relationships. for example, red imported fire ants (solenopsis invicta) have disrupted native arthropod communities throughout much of their introduced range. by competing for many of the same food resources as insectivorous vertebrates, fire ants also have the potential to disrupt vertebrate communities.201121799904
multiple lines of evidence risk assessment of terrestrial passerines exposed to pcdfs and pcdds in the tittabawassee river floodplain, midland, michigan, usa.a site-specific multiple lines of evidence risk assessment was conducted for house wrens (troglodytes aedon) and eastern bluebirds (sialia sialis) along the tittabawassee river downstream of midland, michigan, where concentrations of polychlorinated dibenzofurans (pcdfs) and polychlorinated dibenzo-p-dioxins (pcdds) in flood-plain soils and sediments are greater compared to upstream areas and some of the greatest anywhere in the world. lines of evidence supporting the population-level assessment ...201121804755
dietary exposure of three passerine species to pcdd/dfs from the chippewa, tittabawassee, and saginaw river floodplains, midland, michigan, usa.dietary exposure of house wrens (troglodytes aedon), tree swallows (tachycineta bicolor), and eastern bluebirds (sialia sialis) to polychlorinated dibenzofurans (pcdfs) and polychlorinated dibenzo-p-dioxins (pcdds) near midland, michigan (usa) was evaluated based on site-specific data, including concentrations of residues in bolus samples and individual invertebrate orders and dietary compositions by study species. site-specific dietary compositions for the three species were similar to those re ...201120145996
passerine exposure to primarily pcdfs and pcdds in the river floodplains near midland, michigan, usa.house wren (troglodytes aedon), tree swallow (tachycineta bicolor), and eastern bluebird (sialia sialis) tissues collected in study areas (sas) downstream of midland, michigan (usa) contained concentrations of polychlorinated dibenzofurans (pcdfs) and polychlorinated dibenzo-p-dioxins (pcdds) greater than in upstream reference areas (ras) in the region. the sum of concentrations of pcdd/dfs (sigmapcdd/dfs) in eggs of house wrens and eastern bluebirds from sas were 4- to 22-fold greater compared ...201019894014
the effects of west nile virus on the reproductive success and overwinter survival of eastern bluebirds in alabama.we tested for negative effects of west nile virus (wnv) on a breeding population of eastern bluebirds in alabama by comparing fecundity and reproductive success in years before and after the arrival of wnv and by comparing fecundity, reproductive success, and overwinter survival of seropositive and seronegative individuals within the same population in the same years. we found that female bluebirds were more likely to be seropositive than male bluebirds. age and individual condition did not affe ...201019589058
sex-biased parental investment is correlated with mate ornamentation in eastern bluebirds.males typically have greater variance in reproductive success than females, so mothers should benefit by producing sons under favorable conditions. being paired with a better-than-average mate is one such favorable circumstance. high-quality fathers can improve conditions for their offspring by providing good genes, good resources, or both, so females paired to such males should invest preferentially in sons. ornamentation has been linked to male quality in many birds and, in support of differen ...201020514141
feeding decisions of eastern bluebirds are situationally influenced by fledgling plumage color.the relative amount of resources that avian parents provide to individual offspring within a brood represents a strategy that can have large effects on reproductive success. we tested whether parental feeding decisions of eastern bluebirds sialia sialis are influenced by offspring plumage color by presenting pairs of differently colored fledglings side by side and observing how they were provisioned by parents. after a control period, we manipulated blue plumage color so that one sibling in each ...201022476433
a single exposure to an acute stressor has lasting consequences for the hypothalamo-pituitary-adrenal response to stress in free-living birds.in vertebrates, activation of the hypothalamo-pituitary-adrenal (hpa) axis in response to unpredictable events results in elevated glucocorticoid secretion. repeated exposure to stressors alters subsequent glucocorticoid secretion, either by inducing chronic stress or as a result of habituation. however, most studies of repeated stress focus on the impacts of multiple and frequent exposures to acute stressors, and few have been carried out in free-living animals. we investigated whether a single ...201019682993
demography of reintroduced eastern bluebirds and brown-headed nuthatches.species reintroductions are used commonly as a tool for conservation, but rigorous, quantitative assessments of their outcome rarely occur. such assessments are critical for determining success of the reintroduction and for identifying management actions needed to ensure persistence of reintroduced populations. we collected 9 years of demographic data on populations of brown-headed nuthatches (sitta pusilla) and eastern bluebirds (sialia sialis) reintroduced via translocation into long pine key, ...200923538326
electron tomography, three-dimensional fourier analysis and colour prediction of a three-dimensional amorphous biophotonic nanostructure.organismal colour can be created by selective absorption of light by pigments or light scattering by photonic nanostructures. photonic nanostructures may vary in refractive index over one, two or three dimensions and may be periodic over large spatial scales or amorphous with short-range order. theoretical optical analysis of three-dimensional amorphous nanostructures has been challenging because these structures are difficult to describe accurately from conventional two-dimensional electron mic ...200919158016
feather growth influences blood mercury level of young songbirds.dynamics of mercury in feathers and blood of free-living songbirds is poorly understood. nestling eastern bluebirds (sialia sialis) living along the mercury-contaminated south river (virginia, usa) had blood mercury levels an order of magnitude lower than their parents (nestling: 0.09 +/- 0.06 mg/kg [mean +/- standard deviation], n = 156; adult: 1.21 +/- 0.57 mg/kg, n = 86). to test whether this low blood mercury was the result of mercury sequestration in rapidly growing feathers, we repeatedly ...200918937528
a field test of female mate preference for male plumage coloration in eastern bluebirds.a growing body of evidence shows that female birds use male plumage coloration as an important criterion in mate choice. in the field, however, males with brighter coloration may both compete better for high quality territories and be the object of female choice. positive associations between territory quality, male-male competitive ability, and female preferences can make it difficult to determine whether females actively choose the most ornamented males. male eastern bluebirds (sialia sialis) ...200927041746
do adult eastern bluebird sialia sialis males recognize juvenile-specific traits?juveniles of many avian species possess spotted or mottled plumage that is distinct from the plumage of adults. such plumage has typically been assumed to aid in camouflaging vulnerable immature birds. here, we propose that spotty plumage signals juvenile status, thereby decreasing aggression from territorial adults. we tested this hypothesis by measuring the aggressive responses of adult eastern bluebird males to different combinations of simultaneously presented taxidermic mounts. we found tha ...200920161226
assessing mosquito feeding patterns on nestling and brooding adult birds using microsatellite markers.the role that different age classes of birds play in the amplification of arthropod-borne viruses depends critically on the feeding choices made by mosquitoes. to determine if mosquitoes are more likely to feed on nestling or adult birds, we introduced culex quinquefasciatus mosquitoes into eastern bluebird sialia sialis nest boxes after dark and recaptured them the following morning. we collected blood from each nestling and brooding mother and used molecular genotyping methods to trace the blo ...200919706928
key amino acids in the aryl hydrocarbon receptor predict dioxin sensitivity in avian species.dioxin-like compounds are toxic to most vertebrates, but significant differences in sensitivity exist among species. a recent study suggests that the amino acid residues corresponding to ile324 and ser380 in the chicken aryl hydrocarbon receptor 1 (ahr1) are important determinants of differential biochemical responses to 2,3,7,8-tetrachlorodibenzo-p-dioxin (tcdd) in chickens and common terns. here, we investigate whether the identity of these amino acid residues can predict embryonic sensitivity ...200818939598
sex-specific costs of reproduction in eastern bluebirds sialia sialis.in species with bi-parental care, individuals must partition energy between parental effort and mating effort. typically, female songbirds invest more than males in reproductive activities such as egg-laying and incubation, but males invest more in secondary sexual traits used in attracting mates. animals that breed more than once within a season must also allocate time and energy between first and subsequent breeding attempts and between current and future breeding seasons. to investigate strat ...200819809582
development and cross-species testing of western bluebird (sialia mexicana) microsatellite primers.western and eastern bluebirds (sialia mexicana and s. sialis) are socially monogamous passerines that engage in extra-pair copulations. we obtained microsatellites from s. mexicana and optimized and characterized 15 microsatellite dna loci in 60 individuals of this species. primer pairs yielded an average of 13 alleles per locus in western bluebirds (range 3-35 alleles) with an average observed heterozygosity of 0.68 (range 0.27-0.88). all 15 loci also successfully amplified in s. sialis (n = 24 ...200821586042
reproductive success of passerines exposed to polychlorinated biphenyls through the terrestrial food web of the kalamazoo river.the eastern bluebird (sialia sialis) and the house wren (troglodytes aedon) were identified as ecological receptors of concern due to exposure and potential effects stemming from polychlorinated biphenyl (pcb) contamination in floodplain soils of the kalamazoo river superfund site, michigan, usa. measures of population health were compared at a contaminated and a less-contaminated reference location. during this 3-year study, productivity of bluebirds was significantly less at the downstream loc ...200716343620
the effect of rearing environment on blue structural coloration of eastern bluebirds (sialia sialis).we used a brood-size manipulation to test the effect of rearing environment on structural coloration of feathers grown by eastern bluebird (sialia sialis) nestlings. ultraviolet (uv)-blue structural coloration has been shown to be sexually selected in this species. our experimental design took advantage of the growth of uv-blue wing feathers in nestlings that are retained as part of the first nuptial plumage. we cross-fostered nestlings to create enlarged and reduced broods with the purpose of m ...200719655039
bacteria as an agent for change in structural plumage color: correlational and experimental evidence.recent studies have documented that a diverse assemblage of bacteria is present on the feathers of wild birds and that uropygial oil affects these bacteria in diverse ways. these findings suggest that birds may regulate the microbial flora on their feathers. birds may directly inhibit the growth of harmful microbes or promote the growth of other harmless microbes that competitively exclude them. if keratinolytic (i.e., feather-degrading) bacteria degrade colored feathers, then plumage coloration ...200719426087
accumulation of polychlorinated biphenyls from floodplain soils by passerine birds.eggs, nestlings, and adults of the eastern bluebird (sialia sialis) and house wren (troglodytes aedon) were collected at a polychlorinated biphenyl (pcb)-contaminated site and a reference location on the kalamazoo river (mi, usa). eggs and nestlings of eastern bluebirds at the more contaminated location contained concentrations of 8.3 and 1.3 mg/kg, respectively, of total pcbs and 77 and 6.3 ng/kg, respectively, of 2,3,7,8-tetrachlorodibenzo-p-dioxin equivalents (teqs). eggs, nestlings, and adul ...200616764468
external heart deformities in passerine birds exposed to environmental mixtures of polychlorinated biphenyls during development.necropsy-observable cardiac deformities were evaluated from 283 nestling passerines collected from one reference site and five polychlorinated biphenyl (pcb)-contaminated sites around bloomington and bedford, indiana, usa. hearts were weighed and assessed on relative scales in three dimensions (height, length, and width) and for externally visible deformities. heart weights normalized to body weight (heart somatic index) were decreased significantly at the more contaminated sites in both house w ...200616519318
site specific pcb-correlated interspecies differences in organ somatic indices.we correlated site specific differences in the organ somatic indices of nestlings of five passerine species (tree swallow, red-winged blackbird, house wren, carolina chickadee, and eastern bluebird) with the degree of polychlorinated biphenyls (pcb) exposure in ovo and post-hatching. the birds were exposed to pcbs at or downstream of four pcb-contaminated sites. of the organs evaluated for this paper, brain, bursa, heart, kidneys, lungs, pancreas, spleen, stomach, and thyroid varied significantl ...200616317482
mechanisms of evolutionary change in structural plumage coloration among bluebirds (sialia spp.).combinations of microstructural and pigmentary components of barbs create the colour displays of feathers. it follows that evolutionary changes in colour displays must reflect changes in the underlying production mechanisms, but rarely have the mechanisms of feather colour evolution been studied. among bluebirds in the genus sialia, male rump colour varies among species from dark blue to light blue while breast colour varies from blue to rusty. we use spectrometry, transmission electron microsco ...200616849249
thyroid function in nestling tree swallows and eastern bluebirds exposed to non-persistent pesticides and p, p'-dde in apple orchards of southern ontario, canada.this study examined the associated effects of pesticides and persistent residues of p,p'-dde on thyroid function in 16-day-old tree swallows (tachycineta bicolor) and 12-day-old eastern bluebirds (sialia sialis). apple orchards sprayed with pesticides in current use and reference sites were chosen for study in southern ontario, canada, during 2000-2001. we assessed thyroid hormone concentrations (plasma and muscle thyroxine [t4], and triiodothyronine [t3]) and the response to a challenge with th ...200515943111
variable effects of climate change on six species of north american birds.many recent studies have shown that birds are advancing their laying date in response to long-term increases in spring temperatures. these studies have been conducted primarily in europe and at local scales. if climate change is a large-scale phenomenon, then we should see responses at larger scales and in other regions. we examined the effects of long-term temperature change on the laying dates and clutch sizes of six ecologically diverse species of north american birds using 50 years of nest r ...200516096849
microbial diversity of wild bird feathers revealed through culture-based and culture-independent techniques.despite recent interest in the interactions between birds and environmental microbes, the identities of the bacteria that inhabit the feathers of wild birds remain largely unknown. we used culture-based and culture-independent surveys of the feathers of eastern bluebirds (sialis sialis) to examine bacterial flora. when used to analyze feathers taken from the same birds, the two survey techniques produced different results. species of the poorly defined genus pseudomonas were most common in the m ...200516132422
evidence for sexual selection on structural plumage coloration in female eastern bluebirds (sialia sialis).although the function of ornamental traits in males has been the focus of intensive research for decades, expression of such traits in females has received much less study. eastern bluebirds (sialia sialis) display structurally based ultraviolet/blue and melanin-based chestnut plumage, and in males this plumage coloration is related to both reproductive success and competitive ability. compared to males, female bluebirds show a subdued expression of blue and chestnut ornamental coloration, and w ...200516331840
male eastern bluebirds trade future ornamentation for current reproductive investment.life-history theory proposes that organisms must trade-off investment in current and future reproduction. production of ornamental display is an important component of reproductive effort that has rarely been considered in tests of allocation trade-offs. male eastern bluebirds (sialia sialis) display brilliant ultraviolet-blue plumage that is correlated with mate acquisition and male competitive ability. to investigate trade-offs between current reproductive effort and the future expression of a ...200517148168
stress and immune responses of nestling tree swallows (tachycineta bicolor) and eastern bluebirds (sialia sialis) exposed to nonpersistent pesticides and p,p'-dichlorodiphenyldichloroethylene in apple orchards of southern ontario, canada.to determine the relative effects of pesticides in current use and persistent residues of p,p'-dichlorodiphenyldichloroethylene (p,p'-dde), we examined endocrine and immune responses in tree swallow (tachycineta bicolor) and eastern bluebird (sialia sialis) chicks from pesticide-sprayed apple orchards and reference sites in southern ontario, canada, during 2000 to 2001. nests were exposed to as many as seven individual pesticide applications and up to five mixtures of pesticides during the egg-i ...200415648768
nanostructure predicts intraspecific variation in ultraviolet-blue plumage colour.evidence suggests that structural plumage colour can be an honest signal of individual quality, but the mechanisms responsible for the variation in expression of structural coloration within a species have not been identified. we used full-spectrum spectrometry and transmission electron microscopy to investigate the effect of variation in the nanostructure of the spongy layer on expression of structural ultraviolet (uv)-blue coloration in eastern bluebird (sialia sialis) feathers. fourier analys ...200312965009
burrowing fly larvae (philornis porteri) associated with mortality of eastern bluebirds in florida.we investigated mortality among nestling eastern bluebirds (sialia sialis) in polk and highlands counties, florida (usa) in 1999-2001. at least six species of maggots from three families of muscoid flies, calliphoridae, sarcophagidae, and muscidae were found associated with the nestlings. philornis porteri, the only species of obligate bird parasite collected, was found in the contents of two nests, in the ear canal and the musculature of the jaw of one nestling, and in the abdominal subcutis of ...200212528446
certainty of paternity and paternal investment in eastern bluebirds and tree swallows.extra-pair paternity is common in many socially monogamous passerine birds with biparental care. thus, males often invest in offspring to which they are not related. models of optimal parental investment predict that, under certain assumptions, males should lower their investment in response to reduced certainty of paternity. we attempted to reduce certainty of paternity experimentally in two species, the eastern bluebird, sialia sialis, and the tree swallow, tachycineta bicolor, by temporarily ...19989632472
age-dependent changes in plasma and brain cholinesterase activities of eastern bluebirds and european starlings.age-dependent changes in plasma and brain cholinesterase (che) activity were characterized in two altricial passerine species: eastern bluebirds (sialia sialis) and european starlings (sturnus vulgaris). plasma acetylcholinesterase (ache) activity declined rapidly immediately after hatching, while plasma butyrylcholinesterase (bche) activity increased throughout the nestling period. these patterns continued after birds fledged, since the bche: ache ratio was higher in adult birds than fledglings ...19938445767
sex ratios in the eastern bluebird. 198228568052
sternostoma sialiphilus n. sp. (acarina: rhinonyssidae) from the nasal cavities of the eastern bluebird. sialia sialis (linnaeus). 196113717155
vector-host interactions in avian nests: do mosquitoes prefer nestlings over adults?the hypothesis that nestlings are a significant driver of arbovirus transmission and amplification is based upon findings that suggest nestlings are highly susceptible to being fed upon by vector mosquitoes and to viral infection and replication. several previous studies have suggested that nestlings are preferentially fed upon relative to adults in the nest, and other studies have reported a preference for adults over nestlings. we directly tested the feeding preference of nestling and adult bi ...020682889
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