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1.
PLoS One ; 15(2): e0228982, 2020.
Artículo en Inglés | MEDLINE | ID: mdl-32045456

RESUMEN

Host-associated microbial communities can influence the overall health of their animal hosts, and many factors, including behavior and physiology, can impact the formation of these complex communities. Bacteria within these communities can be transmitted socially between individuals via indirect (e.g., shared environments) or direct (e.g., physical contact) pathways. Limited research has been done to investigate how social interactions that occur in the context of mating shape host-associated microbial communities. To gain a better understanding of these interactions and, more specifically, to assess how mating behavior shapes an animal's microbiome, we studied the cloacal bacterial communities of a socially monogamous yet genetically polygynous songbird, the North American tree swallow (Tachycineta bicolor). We address two questions: (1) do the cloacal bacterial communities differ between female and male tree swallows within a population? and (2) do pair-bonded social partners exhibit more similar cloacal bacterial communities than expected by chance? To answer these questions, we sampled the cloacal microbiome of adults during the breeding season and then used culture-independent, 16S rRNA gene amplicon sequencing to assess bacterial communities. Overall, we found that the cloacal bacterial communities of females and males were similar, and that the communities of pair-bonded social partners were not more similar than expected by chance. Our results suggest that social monogamy does not correlate with an increased similarity in cloacal bacterial community diversity or structure. As social partners were not assessed at the same time, it is possible that breeding stage differences masked social effects on bacterial community diversity and structure. Further, given that tree swallows exhibit high variation in rates of extra-pair activity, considering extra-pair activity when assessing cloacal microbial communities may be important for understanding how these bacterial communities are shaped. Further insight into how bacterial communities are shaped will ultimately shed light on potential tradeoffs associated with alternative behavioral strategies and socially-transmitted microbes.


Asunto(s)
Bacterias , Cloaca/microbiología , Microbiota , ARN Bacteriano/genética , ARN Ribosómico 16S/genética , Reproducción , Golondrinas/microbiología , Animales , Bacterias/clasificación , Bacterias/genética , Femenino , Masculino
2.
Oecologia ; 192(3): 713-722, 2020 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-32100152

RESUMEN

Population decline and the threat of extinction are realities currently facing many species. Yet, in most cases, the detailed demographic data necessary to identify causes of population decline are unavailable. Using 43 years (1975-2017) of data from a box-nesting population of tree swallows (Tachycineta bicolor), we identified reduced survival of offspring as a probable demographic cause of population decline. Poor fledging success was associated with increased predation and poor weather conditions during early nestling development. Low juvenile survival and subsequent recruitment was linked to poor weather conditions during the post-fledging period and may also be linked to conditions on the wintering grounds. Regional weather conditions during critical stages of breeding (early nestling and post-fledging) have become progressively worse over the 43-year study period. None of the other factors linked to offspring survival have similarly deteriorated. Overall, our results suggest tree swallows should be added to the growing list of species challenged by climate change, and that other species of aerial insect specialists may face similar impacts of climate change.


Asunto(s)
Golondrinas , Animales , Cruzamiento , Cambio Climático , Árboles , Tiempo (Meteorología)
3.
Sci Total Environ ; 709: 136195, 2020 Mar 20.
Artículo en Inglés | MEDLINE | ID: mdl-31887506

RESUMEN

Farmland bird populations have declined with increasing agricultural intensification possibly due to putative reductions in prey insects and effects of pesticide exposure. Presence of agriculture may be especially relevant for aerial insectivorous songbirds whose primary diet is flying insects. Here, we investigated the effects of agricultural land use on nestling body condition, an important determinant of post-fledging survival, for barn swallows (Hirundo rustica), an aerial insectivore breeding within an agro-ecosystem in southern Ontario, Canada. Our scale-of-effect analysis revealed that nestling and pre-fledging body condition varied most strongly with the proportion of row crop within 100 m of the natal barn. Unexpectedly, this correlation was positive for both nestling body condition (2016 only) and for pre-fledging condition (2016 and 2017). We found a weak positive effect of row crop on number of young fledged. We speculate that the positive effects of agricultural row-cropping on condition and number of young fledged was due to higher prey availability and/or more open foraging habitat around barns surrounded by row crops. Alternatively, higher nestling condition in high agriculture environments could reflect an insurance policy to increase survival during the post-fledging period. Our results suggest that, in our southern Ontario study area, the degree of agricultural conversion does not negatively influence individual nestling condition and number of young produced for barn swallows. We recommend future research on this species to examine reproductive success in more intense agricultural landscapes and possible effects of pesticide exposure.


Asunto(s)
Golondrinas , Agricultura , Animales , Ecosistema , Ontario , Pájaros Cantores
4.
PLoS One ; 14(12): e0226886, 2019.
Artículo en Inglés | MEDLINE | ID: mdl-31869383

RESUMEN

Animal groups often represent nonrandom subsets of individuals, and increasing evidence indicates that individuals may sort among groups based on their personalities. The size of a group can predict its personality composition in some species due to differential suitability of a personality for groups of certain sizes, and the group itself may function more effectively if particular personality types are present. We quantified cliff swallow (Petrochelidon pyrrhonota) behavioral measures using linear and generalized linear mixed models to identify whether they: (1) varied among individuals within colonies and among colonies, (2) were related to reproductive success, and (3) predicted levels of parental care. Significant among-individual and among-colony site variation in a cliff swallow's latency to enter its nest when presented with a novel stimulus was revealed. We also found significant among-individual variation in the number of attacks directed toward a novel stimulus at the nest and in the response to broadcast of a cliff swallow alarm call recording, but among site variation in these measures was not significant. We did not find evidence for behavioral syndromes linking the personalities measured. Differences among individuals in latency to enter the nest and the number of attacks were not significantly related to reproductive success or to the extent to which birds fed their nestlings. However, extent of nestling feeding was significantly predicted by the number of mist net captures. The limited evidence in general of systematic variation in the behavior we measured among cliff swallow colonies may reflect the different and sometimes opposing selection pressures on behavior in different social environments. Future work should perhaps examine variation in other behavioral traits, such as foraging, in cliff swallow colonies of different sizes.


Asunto(s)
Conducta Animal , Golondrinas/fisiología , Animales , Aglomeración , Reacción de Fuga , Conducta Exploratoria , Femenino , Masculino , Comportamiento de Nidificación , Densidad de Población , Reproducción , Conducta Social
5.
Zootaxa ; 4568(1): zootaxa.4568.1.1, 2019 Mar 19.
Artículo en Inglés | MEDLINE | ID: mdl-31715868

RESUMEN

Seven species of the feather mite genus Trouessartia Canestrini, 1899 (Astigmata: Trouessartiidae) have been recorded on swallows and martins (Passeriformes: Hirundinidae) in Manitoba (Canada). Of them, five are described as new species: Trouessartia ampulicaudata sp. n. and T. petrochelidon sp. n. from the American cliff swallow Petrochelidon pyrrhonota (Vieillot), T. bochkovi sp. n. from the tree swallow Tachycineta bicolor (Vieillot), and T. cryptocaudata sp. n. and T. progne sp. n. from the purple martin Progne subis (Linnaeus). A new species group stelgidopteryx, incorporating Trouessartia species living on hirundinids of the genera Progne, Tachycineta and Stelgidopteryx, is established. Renewed diagnoses of four Trouessartia species groups (appendiculata, crucifera, minutipes, and stelgidopteryx) restricted to hirundinids and a key to species recorded so far and potentially expected on swallows of North America are proposed. Host associations of Trouessartia species with swallows in North America are briefly discussed.


Asunto(s)
Enfermedades de las Aves , Infestaciones por Ácaros , Ácaros , Golondrinas , Animales , Canadá , Manitoba , América del Norte
6.
J Parasitol ; 105(5): 693-696, 2019 10.
Artículo en Inglés | MEDLINE | ID: mdl-31580788

RESUMEN

Barn swallows (Hirundo rustica) are the most widespread swallow species in the world. However, little is known about the coccidian parasites of H. rustica. Feces from a single H. rustica nesting in McCurtain County, Oklahoma, were collected in May 2018 and examined for coccidia; the swallow was found to be passing a new species of Eimeria. Oocysts of Eimeria hochatownensis n. sp. are ellipsoidal with a smooth bi-layered wall, measure (L × W) 25.5 × 15.2 µm, and have a length/width (L/W) ratio of 1.7; a micropyle and oocyst residuum are absent, but polar granule(s) are present. Sporocysts are ellipsoidal and measure 12.8 × 6.5 µm, L/W 2.0; a nipple-like Stieda body is present, but sub-Stieda bodies and para-Stieda bodies are absent. The sporocyst residuum is composed of a compact spheroid with a dense, irregular mass of finer granules lying between and dispersed among the sporozoites. This is the first eimerian reported from H. rustica and the family Hirundinidae, and only the fourth Eimeria spp. known from passerine birds of the New World.


Asunto(s)
Enfermedades de las Aves/parasitología , Coccidiosis/veterinaria , Eimeria/clasificación , Golondrinas/parasitología , Animales , Enfermedades de las Aves/epidemiología , Coccidiosis/epidemiología , Coccidiosis/parasitología , Eimeria/aislamiento & purificación , Eimeria/ultraestructura , Heces/parasitología , Femenino , Oklahoma/epidemiología , Oocistos/clasificación , Oocistos/aislamiento & purificación , Oocistos/ultraestructura
7.
Environ Toxicol Chem ; 38(12): 2797-2810, 2019 12.
Artículo en Inglés | MEDLINE | ID: mdl-31433524

RESUMEN

There is an acknowledged need in ecotoxicology for methods that integrate spatial analyses in risk assessment. This has resulted in the emergence of landscape ecotoxicology, a subdiscipline of ecotoxicology. However, landscape ecotoxicology has yet to become common practice in risk assessment due to the underdevelopment of techniques and a lack of standardized methods. In the present study, we demonstrate how geographic information systems (GISs) can serve as a standardized platform to integrate data, assess spatial patterns of ecotoxicological data for multiple species, and assess relationships between chemical mixture exposures and effects on biota for landscape ecotoxicological risks assessment. We use data collected under the Joint Oil Sands Monitoring Program in the Athabasca Oil Sands Region in Alberta, Canada. This dataset is composed of concentrations of contaminants including metals and polycyclic aromatic compounds, and health endpoints measured in 1100 biological samples, including tree swallows, amphibians, gull and tern eggs, plants, and mammals. We present 3 examples using a GIS as a platform and geospatial analysis to: 1) integrate data and assess spatial patterns of contaminant exposure in the region, 2) assess spatial patterns of exposures to complex mixtures, and 3) examine patterns of exposures and responses across the landscape. We summarize the methods used in the present study into a workflow for ease of use. The GIS methods allow researchers to identify hot spots of contamination, use georeferenced monitoring data to derive quantitative exposure-response relationships, and assess complex exposures with more realism. Environ Toxicol Chem 2019;38:2797-2810. © 2019 SETAC.


Asunto(s)
Monitoreo del Ambiente/métodos , Yacimiento de Petróleo y Gas/química , Animales , Canadá , Charadriiformes/crecimiento & desarrollo , Análisis por Conglomerados , Ecotoxicología , Contaminantes Ambientales/análisis , Sistemas de Información Geográfica , Mercurio/análisis , Óvulo/química , Óvulo/metabolismo , Plantas/química , Plantas/metabolismo , Golondrinas
8.
Mol Ecol ; 28(16): 3722-3737, 2019 08.
Artículo en Inglés | MEDLINE | ID: mdl-31330076

RESUMEN

Individuals often differ in their ability to cope with challenging environmental and social conditions. Evidence from model systems suggests that patterns of DNA methylation are associated with variation in coping ability. These associations could arise directly if methylation plays a role in controlling the physiological response to stressors by, among other things, regulating the release of glucocorticoids in response to challenges. Alternatively, the association could arise indirectly if methylation and resilience have a common cause, such as early-life conditions. In either case, methylation might act as a biomarker for coping ability. At present, however, relatively little is known about whether variation in methylation is associated with organismal performance and resilience under natural conditions. We studied genome-wide patterns of DNA methylation in free-living female tree swallows (Tachycineta bicolor) using methylated DNA immunoprecipitation (MeDIP) and a tree swallow genome that was assembled for this study. We identified areas of the genome that were differentially methylated with respect to social signal expression (breast brightness) and physiological traits (ability to terminate the glucocorticoid stress response through negative feedback). We also asked whether methylation predicted resilience to a subsequent experimentally imposed challenge. Individuals with brighter breast plumage and higher stress resilience had lower methylation at differentially methylated regions across the genome. Thus, widespread differences in methylation predicted both social signal expression and the response to future challenges under natural conditions. These results have implications for predicting individual differences in resilience, and for understanding the mechanistic basis of resilience and its environmental and social mediators.


Asunto(s)
Metilación de ADN , Plumas , Estrés Fisiológico , Golondrinas/genética , Golondrinas/fisiología , Animales , Femenino , Genoma , Pigmentación
9.
Integr Comp Biol ; 59(2): 251-263, 2019 08 01.
Artículo en Inglés | MEDLINE | ID: mdl-31168615

RESUMEN

Vertebrates respond to a diversity of stressors by rapidly elevating glucocorticoid (GC) levels. The changes in physiology and behavior triggered by this response can be crucial for surviving a variety of challenges. Yet the same process that is invaluable in coping with immediate threats can also impose substantial damage over time. In addition to the pathological effects of long-term exposure to stress hormones, even relatively brief elevations can impair the expression of a variety of behaviors and physiological processes central to fitness, including sexual behavior, parental behavior, and immune function. Therefore, the ability to rapidly and effectively terminate the short-term response to stress may be fundamental to surviving and reproducing in dynamic environments. Here we review the evidence that variation in the ability to terminate the stress response through negative feedback is an important component of stress coping capacity. We suggest that coping capacity may also be influenced by variation in the dynamic regulation of GCs-specifically, the ability to rapidly turn on and off the stress response. Most tests of the fitness effects of these traits to date have focused on organisms experiencing severe or prolonged stressors. Here we use data collected from a long-term study of tree swallows (Tachycineta bicolor) to test whether variation in negative feedback, or other measures of GC regulation, predict components of fitness in non-chronically stressed populations. We find relatively consistent, but generally weak relationships between different fitness components and the strength of negative feedback. Reproductive success was highest in individuals that both mounted a robust stress response and had strong negative feedback. We did not see consistent evidence of a relationship between negative feedback and adult or nestling survival: negative feedback was retained in the best supported models of nestling and adult survival, but in two of three survival-related analyses the intercept-only model received only slightly less support. Both negative feedback and stress-induced GC levels-but not baseline GCs-were individually repeatable. These measures of GC activity did not consistently covary across ages and life history stages, indicating that they are independently regulated. Overall, the patterns seen here are consistent with the predictions that negative feedback-and the dynamic regulation of GCs-are important components of stress coping capacity, but that the fitness benefits of having strong negative feedback during the reproductive period are likely to manifest primarily in individuals exposed to chronic or repeated stressors.


Asunto(s)
Glucocorticoides/metabolismo , Rasgos de la Historia de Vida , Estrés Fisiológico/fisiología , Golondrinas/fisiología , Animales , Vertebrados/fisiología
10.
Cytogenet Genome Res ; 158(2): 98-105, 2019.
Artículo en Inglés | MEDLINE | ID: mdl-31158838

RESUMEN

As in many other bird groups, data on karyotype organization and distribution of repetitive sequences are also lacking in species belonging to the family Hirundinidae. Thus, in the present study, we analyzed the karyotypes of 3 swallow species (Progne tapera, Progne chalybea, and Pygochelidon cyanoleuca) by Giemsa and AgNOR staining, C-banding, and FISH with 11 microsatellite sequences. The diploid chromosome number was 2n = 76 in all 3 species, and NORs were observed in 2 chromosome pairs each. The microsatellite distribution pattern was similar in both Progne species, whereas P. cyanoleuca presented a distinct organization. These repetitive DNA sequences were found in the centromeric, pericentromeric, and telomeric regions of the macrochromosomes, as well as in 2 interstitial blocks in the W chromosome. Most microchromosomes had mainly telomeric signals. The Z chromosome displayed 1 hybridization signal in P. tapera but none in the other species. In contrast, the W chromosome showed an accumulation of different microsatellite sequences. The swallow W chromosome is larger than that of most Passeriformes. The observed enlargement in chromosome size might be explained by these high amounts of repetitive sequences. In sum, our data highlight the significant role that microsatellite sequences may play in sex chromosome differentiation.


Asunto(s)
Análisis Citogenético/veterinaria , Cariotipo , Golondrinas/genética , Animales , Bandeo Cromosómico/veterinaria , Evolución Molecular , Femenino , Hibridación Fluorescente in Situ/veterinaria , Masculino , Repeticiones de Microsatélite
11.
Zoolog Sci ; 36(2): 154-158, 2019 04 01.
Artículo en Inglés | MEDLINE | ID: mdl-31120651

RESUMEN

Sperm competition can theoretically affect sperm morphology; however, it remains unclear whether and how sperm morphology tracks the intensity of sperm competition in each population. The barn swallow Hirundo rustica is a model species used in the study of sexual selection, and exhibits considerable variation in extra-pair paternity (percentage extra-pair young, ca. 3-30%) among populations. In the Joetsu population of the barn swallow, extra-pair paternity is virtually absent (< 3%), providing a rare opportunity to study sperm morphology under limited sperm competition, and to compare it with those reported in populations with frequent extra-pair paternity (>15%). We found that head, midpiece, and total sperm length were significantly shorter in the Joetsu population than in populations with frequent extra-pair paternity. Moreover, the variability in total sperm length, measured as the coefficient of variation in the Joetsu population, was twice as high as that of populations with frequent extra-pair paternity. These results are consistent with a positive, directional, and stabilizing effect of sperm competition on sperm morphology. Together with previous studies in populations with frequent extra-pair paternity, the current study provides one of few sets of evidence to show a link between the intensity of sperm competition and the mean and variance of sperm morphology within a wild bird species.


Asunto(s)
Espermatozoides/citología , Golondrinas , Animales , Japón , Masculino , Espermatozoides/fisiología
12.
Proc Biol Sci ; 286(1894): 20181916, 2019 01 16.
Artículo en Inglés | MEDLINE | ID: mdl-30963870

RESUMEN

Latitudinal differences in timing of breeding are well documented but how such differences carry over to influence timing of events in the annual cycle of migratory birds is not well understood. We examined geographical variation in timing of events throughout the year using light-level geolocator tracking data from 133 migratory tree swallows ( Tachycineta bicolor) originating from 12 North American breeding populations. A swallow's breeding latitude influenced timing of breeding, which then carried over to affect breeding ground departure. This resulted in subsequent effects on the arrival and departure schedules at autumn stopover locations and timing of arrival at non-breeding locations. This 'domino effect' between timing events was no longer apparent by the time individuals departed for spring migration. Our range-wide analysis demonstrates the lasting impact breeding latitude can have on migration schedules but also highlights how such timing relationships can reset when individuals reside at non-breeding sites for extended periods of time.


Asunto(s)
Distribución Animal , Migración Animal , Golondrinas/fisiología , Animales , Canadá , Geografía , Reproducción , Estaciones del Año , Estados Unidos
13.
Arch Environ Contam Toxicol ; 77(1): 1-13, 2019 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-30955057

RESUMEN

A site in northeastern Michigan, Oscoda Township, has some of the highest recorded exposure in birds to perfluorinated substances (PFASs) in the United States. Some egg and plasma concentrations at that location exceeded the lowest reproductive effect threshold established for two avian laboratory species. The objectives of this study were to determine whether there were reproductive effects or physiological responses in a model bird species, the tree swallow (Tachycineta bicolor), associated with this extremely high exposure to PFASs. The lack of exposure above background to other contaminants at this site allowed for an assessment of PFAS effects without the complication that responses may be caused by other contaminants. A secondary objective was to determine the distribution of PFASs in multiple tissue types to better understand and interpret residues in different tissues. This can best be done at highly exposed locations where tissue concentrations would be expected to be above detectable levels if they are present in that tissue. There were no demonstrable effects of PFAS exposure on reproduction nor on most physiological responses.


Asunto(s)
Contaminantes Ambientales/toxicidad , Fluorocarburos/toxicidad , Comportamiento de Nidificación/efectos de los fármacos , Golondrinas/fisiología , Animales , Monitoreo del Ambiente , Michigan , Reproducción/efectos de los fármacos
14.
Health Phys ; 117(3): 267-277, 2019 09.
Artículo en Inglés | MEDLINE | ID: mdl-30958805

RESUMEN

Discharge of groundwater contaminant plumes has created elevated concentrations of Sr in some aquatic sediments at Chalk River Laboratories. Tree swallows (Tachycenita bicolor) feed and supply their nestlings almost exclusively with airborne insects that developed as larvae in aquatic sediments. To monitor the uptake and test for potential detriment due to Sr in a terrestrial animal, we measured the gross beta concentrations in the bone of 12-d-old tree swallow nestlings in areas having sediments with elevated levels of gross beta (Sr and Y) and in several control areas where sediment gross beta was primarily due to naturally occurring K. Nesting behavior and reproductive success of the tree swallows were similar regardless of the gross beta concentrations in sediments near their nest boxes. Radiation can damage DNA and cause micronuclei to form in cells, so we examined the frequency of micronuclei in erythrocytes of nestlings. The formation of micronuclei in the erythrocytes of the nestlings was also similar wherever nestlings were analyzed. The results revealed no significant increases even near sediments with the highest gross beta levels. At Perch Lake, where Chalk River Laboratories has a large area of Sr-contaminated sediments, the bones of 12-d-old nestlings contained gross beta concentrations as high as 29 Bq g. This would produce a skeletal dose rate of 9 µGy h, which is one-fourth of the threshold dose rate of 40 µGy h, above which detriment could occur. Failing to find any indication of detriment in the field study, we irradiated wild eggs in the lab and returned them to their nest for natural incubation, hatching, and feeding by the parents. There was an increase in formation of micronuclei following a dose of 3.2 Gy, and the other results were consistent with existing literature.


Asunto(s)
Sedimentos Geológicos/análisis , Agua Subterránea/análisis , Óvulo/efectos de la radiación , Reproducción/efectos de la radiación , Radioisótopos de Estroncio/efectos adversos , Golondrinas/crecimiento & desarrollo , Contaminantes Químicos del Agua/efectos adversos , Animales , Ríos/química , Radioisótopos de Estroncio/análisis , Contaminantes Químicos del Agua/análisis
15.
Environ Sci Technol ; 53(9): 5396-5405, 2019 05 07.
Artículo en Inglés | MEDLINE | ID: mdl-30924331

RESUMEN

Methylmercury is a neurotoxin and endocrine disruptor and may impair avian reproduction directly through embryotoxicity or by altering parental care behaviors. We studied mercury exposure and incubation behavior of free-living tree swallows ( Tachycineta bicolor) nesting in artificial nest boxes. Using small temperature dataloggers, we measured incubation constancy (the proportion of each day the female spent incubating eggs), the number of incubation recesses taken per day, and the duration of incubation recesses. We also assessed maternal mercury exposure by measuring mercury concentrations in both blood and eggs. Females with higher mercury concentrations exhibited lower incubation constancy, took more frequent and shorter incubation recesses, and were more likely to take incubation recesses that caused nest temperature decreases that were likely to slow embryonic development. Overall, females that laid eggs with the highest observed mercury concentration (0.53 µg/g fww) spent an average of 12% less time incubating their eggs over the 14-day incubation period than females that laid eggs with the lowest mercury concentration (0.07 µg/g fww). Because less time spent incubating can lower egg temperatures, slow embryonic development, and potentially lengthen the incubation period, these results suggest that environmentally relevant mercury concentrations may negatively influence reproduction by altering parental nesting behaviors of wild songbirds.


Asunto(s)
Mercurio , Pájaros Cantores , Golondrinas , Animales , Femenino , Comportamiento de Nidificación , Reproducción
16.
Physiol Biochem Zool ; 92(3): 274-285, 2019.
Artículo en Inglés | MEDLINE | ID: mdl-30840539

RESUMEN

Organisms are frequently exposed to challenges during development, such as poor weather and food shortage. Such challenges can initiate the hormonal stress response, which involves secretion of glucocorticoids. Although the hormonal stress response helps organisms deal with challenges, long-term exposure to high levels of glucocorticoids can have morphological, behavioral, and physiological consequences, especially during development. Glucocorticoids are also associated with telomere shortening, and they have a complex relationship with survival. To investigate whether brief, acute exposures to glucocorticoids can also produce these phenotypic effects in free-living birds, we exposed wild tree swallow (Tachycineta bicolor) nestlings to a brief exogenous dose of corticosterone once per day for 5 d and then measured their morphology, baseline and stress-induced corticosterone levels, and telomere length. We also deployed radio tags on a subset of nestlings, which allowed us to determine the age at which tagged nestlings left the nest (fledged) and their pattern of presence and absence at the natal site during the postbreeding period. Corticosterone-treated nestlings had lower mass, higher baseline and stress-induced corticosterone, and reduced telomeres; other metrics of morphology were affected weakly or not at all. Our treatment resulted in no significant effect on survival to fledging, fledge age, or age at first departure from the natal site, and we found no negative effect of corticosterone on interannual return rate. These results show that brief acute corticosterone exposure during development can have measurable effects on phenotype in free-living tree swallows. Corticosterone may therefore mediate correlations between rearing environment and phenotype in developing organisms, even in the absence of prolonged stressors.


Asunto(s)
Distribución Animal/efectos de los fármacos , Corticosterona/farmacología , Glucocorticoides/farmacología , Actividad Motora/efectos de los fármacos , Estrés Fisiológico/efectos de los fármacos , Golondrinas/fisiología , Telómero/efectos de los fármacos , Animales , Corticosterona/administración & dosificación , Glucocorticoides/administración & dosificación , Golondrinas/anatomía & histología , Telómero/fisiología
17.
Proc Biol Sci ; 286(1898): 20190018, 2019 03 13.
Artículo en Inglés | MEDLINE | ID: mdl-30862285

RESUMEN

As species shift their ranges and phenology to cope with climate change, many are left without a ready supply of their preferred food source during critical life stages. Food shortages are often assumed to be driven by reduced total food abundance, but here we propose that climate change may cause short-term food shortages for foraging specialists without affecting overall food availability. We frame this hypothesis around the special case of birds that forage on flying insects for whom effects mediated by their shared food resource have been proposed to cause avian aerial insectivores' decline worldwide. Flying insects are inactive during cold, wet or windy conditions, effectively reducing food availability to zero even if insect abundance remains otherwise unchanged. Using long-term monitoring data from a declining population of tree swallows ( Tachycineta bicolor), we show that nestlings' body mass declined substantially from 1977 to 2017. In 2017, nestlings had lower body mass if it rained during the preceding 3 days, though females increased provisioning rates, potentially in an attempt to compensate. Adult body mass, particularly that of the males, has also declined over the long-term study. Mean rainfall during the nestling period has increased by 9.3 ± 0.3 mm decade-1, potentially explaining declining nestling body mass and population declines. Therefore, we suggest that reduced food availability, distinct from food abundance, may be an important and previously overlooked consequence of climate change, which could be affecting populations of species that specialize on foraging on flying insects.


Asunto(s)
Reproducción , Golondrinas/fisiología , Tiempo (Meteorología) , Animales , Femenino , Masculino , Ontario , Dinámica Poblacional , Lluvia , Estaciones del Año , Golondrinas/crecimiento & desarrollo
18.
Gen Comp Endocrinol ; 276: 14-21, 2019 05 15.
Artículo en Inglés | MEDLINE | ID: mdl-30796896

RESUMEN

Anthropogenic impacts, such as noise pollution from transportation networks, can serve as stressors to some wildlife species. For example, increased exposure to traffic noise has been found to alter baseline and stress-induced corticosterone levels, reduce body condition and reproductive success, and increase telomere attrition in free-living birds. However, it remains unknown if alterations in nestling phenotype are due to direct or indirect effects of noise exposure. For example, indirect (maternal) effects of noise may occur if altered baseline and stress-induced corticosterone in mothers results in differential deposition of yolk steroids or other components in eggs. Noise exposure may also alter nestling corticosterone levels directly, given that nestlings cannot escape the nest during development. Here, we examined maternal versus direct effects of traffic noise exposure on baseline and stress-induced corticosterone levels, and body condition (as measured by size-corrected mass) in nestling tree swallows (Tachycineta bicolor). We used a two-way factorial design and partially cross-fostered eggs between nests exposed to differing levels (i.e. amplitudes) of traffic noise. For nestlings that were not cross-fostered, we also investigated the effects of traffic noise on telomere dynamics. Our results show a positive relationship between nestling baseline and stress-induced corticosterone and nestling noise exposure, but not maternal noise exposure. While we did not find a relationship between noise and body condition in nestlings, nestling baseline corticosterone was negatively associated with body condition. We also found greater telomere attrition for nestlings from nests with greater traffic noise amplitudes. These results suggest that direct, rather than maternal, effects result in potentially long-lasting consequences of noise exposure. Reduced nestling body condition and increased telomere attrition have been shown to reduce post-fledging survival in this species. Given that human transportation networks continue to expand, strategies to mitigate noise exposure on wildlife during critical periods (i.e. breeding) may be needed to maintain local population health in free-living passerines, such as tree swallows.


Asunto(s)
Exposición a Riesgos Ambientales , Comportamiento de Nidificación/fisiología , Ruido , Golondrinas/fisiología , Telómero/metabolismo , Contaminación por Tráfico Vehicular , Animales , Corticosterona/sangre , Femenino , Modelos Teóricos , Estrés Fisiológico , Golondrinas/sangre , Homeostasis del Telómero
19.
Arch Environ Contam Toxicol ; 76(3): 414-424, 2019 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-30734087

RESUMEN

Selected elements were targeted in state Remedial Action Plans as one group of chemicals affecting the Beneficial Use Impairments of Great Lakes Areas of Concern (AOCs). Livers of nestling tree swallows, Tachycineta bicolor, were harvested from 76 sites in the Great Lakes, which included multiple sites at 27 AOCs and 12 reference sites from 2010 to 2015, and were analyzed for 21 elements. Mercury concentrations were at background levels at all sites. Elevated cadmium (Cd) concentrations were associated with industry. The highest Cd values were from the Black River, OH AOC and were associated with historic coke production but were not at toxic levels. Lead (Pb) concentrations were highest on the Rouge River, MI AOC-the oldest and most heavily populated and industrialized area in southeast Michigan. Individual Pb concentrations were elevated to a level associated with delta-aminolaevulinic acid dehydratase inhibition but not to a level considered toxic. In contrast, livers harvested from sites on the southwest shore of Lake Michigan had selenium (Se) concentrations elevated to levels associated with reduced avian reproduction. One likely source of the high Se concentrations was pollution from a local coal-fired power plant. Concentrations of the remaining elements were at background levels.


Asunto(s)
Monitoreo del Ambiente/métodos , Lagos/química , Metales Pesados/análisis , Golondrinas/crecimiento & desarrollo , Oligoelementos/análisis , Contaminantes Químicos del Agua/análisis , Animales , Canadá , Hígado/química , Ríos/química , Estados Unidos
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