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USGS2017

Comparison of acoustic recorders and field observers for monitoring tundra bird communities

Acoustic recorders can be useful for studying bird populations but their efficiency and accuracy should be assessed in pertinent ecological settings before use. We investigated the utility of an acoustic recorder for monitoring abundance of tundra‐breeding birds relative to point‐count surveys in northwestern Alaska, USA, during 2014. Our objectives were to 1) compare numbers of birds and species detected by a field observer with those detected simultaneously by an acoustic recorder; 2) evaluate how detection probabilities for the observer and acoustic recorder varied with distance of birds from the survey point; and 3) evaluate whether avian guild‐specific detection rates differed between field observers and acoustic recorders relative to habitat. Compared with the observer, the acoustic recorder detected fewer species (β Method = −0.39 ± 0.07) and fewer individuals (β Method = −0.56 ± 0.05) in total and for 6 avian guilds. Discrepancies were attributed primarily to differences in effective area surveyed (91% missed by device were >100 m), but also to nonvocal birds being missed by the recorder (55% missed <100 m were silent). The observer missed a few individuals and one species detected by the device. Models indicated that relative abundance of various avian guilds was associated primarily with maximum shrub height and less so with shrub cover and visual obstruction. The absence of a significant interaction between survey method (observer vs . acoustic recorder) and any habitat characteristic suggests that traditional point counts and acoustic recorders would yield similar inferences about ecological relationships in tundra ecosystems. Pairing of the 2 methods could increase survey efficiency and allow for validation and archival of survey results.

Alaska↗

USGS1995

Dicofol and DDT residues in lizard carcasses and bird eggs from Texas, Florida, and California

Dicofol is an organochlorine agricultural pesticide used to control mites. The principal commercial dicofol product is known as Kelthane TM. More than 70% of dicofol product (about 3 million Ib or 1.4 million kg) sold annually in the U.S. is applied in California, Arizona, Texas, and Florida. Florida citrus and California cotton receive more than half the total (Clark 1990). In laboratory studies, dicofol, which is structurally similar to DDT, had adverse impacts on reproduction in fish (deformed larvae, delayed hatching), birds (reduced eggshell thickness, reduced hatchability), and mammals (reduced insemination rate, reduced pregnancy rate, failure to produce young) (see Clark 1990 for review). Overall, the reproduction of birds seems less sensitive to dicofol than to DDE. However, in birds, dietary concentrations of dicofol between 1 and 10 µg/g (wet weight) fed to captive adult females caused such problems as eggshell thinning, reduced hatching success, or reduced fertility in American kestrels ( Falco sparverius ) (Fry et al. 1988, Clark et al. 1990) and eastern screech-owls ( Otus asio ) (Wiemeyer et al. 1989). In spite of these laboratory findings, there have been no intensive field investigations of possible reproductive effects of dicofol on wild birds. Such studies must wait until field residue data are sufficient to identify populations with high exposure. If dicofol accumulates in birds in the field and heavily exposed populations can be identified, then their reproduction can be studied. Residues have not been reported from reptiles. Analytical screening of wildlife tissue samples for organochlorine chemicals only rarely includes dicofol, and this may explain why the relative hazard of dicofol to wildlife populations is poorly known.

California, Florida, Texas↗

USGS1984

High PCB residues in birds from the Sheboygan River, Wisconsin

Organochlorine residues were measured in the carcasses and, in some cases, brains and stomach contents of four species of birds collected along the Sheboygan River, Wisconsin during the years 1976 to 1980. Polychlorinated biphenyls (PCBs) were high in all samples and were the contaminants of greatest concern. Carcass residues ranged from 23 to 218 ppm PCBs on a wet weight basis; these are levels associated with reproductive impairment in laboratory studies with some birds. Food items in the stomachs of collected birds contained from 12 to 58 ppm PCBs, indicating a heavy contamination of food sources. The brain of one bird contained 220 ppm PCBs, a level that is not in the lethal range but is very high. Birds feeding in the contaminated portions of the Sheboygan River may have been harmed by high PCB levels.

Wisconsin↗

USGS1984

Aroclor 1254 residues in birds: Lethal levels and loss rates

Lethal residues of polychlorinated biphenyls (PCBs) were determined experimentally in four species of wild birds given dietary dosage of 1,500 ppm of Aroclor 1254 ® until one-half had died, sacrificing the survivors, chemically analyzing the tissues, and comparing results in dead birds and survivors. For all species, residues of 310 ppm or higher in the brain showed increasing likelihood of death from PCB poisoning. Residues in dead birds did not differ among species except for starlings ( Sturnus vulgaris ), which averaged slightly lower than the others. However, the species differed in the length of time to 50% mortality and in the levels of PCBs in brains at sacrifice. Concentrations in bodies and livers were not diagnostic when expressed on a wet weight basis. On a lipid basis, however, concentrations of PCBs in bodies of dead birds were higher than in sacrificed birds, but in both groups residues increased with time, suggesting that overlapping values could be expected. Loss rates were followed in grackles ( Quiscalus quiscula ) fed 1,500 ppm PCBs for 8 days, then given untreated feed and sacrificed at intervals of 7, 28, 56, 112, and 224 days. PCB residues were lost from bodies at somewhat irregular rates; overall, the rate was estimated at 0.77% per day (half-life 89 days). Residues in brains generally were related to the percentage of body fat, but also showed a somewhat irregular pattern.

Archives of Environmental Contamination and Toxico↗

USGS1975

Studies on combined effects of organophosphates and heavy metals in birds. I. Plasma and brain cholinesterase in Coturnix quail fed methyl mercury and orally dosed with parathion

We found that mercury potentiated the toxicity and biochemical effects of parathion. Male Coturnix quail (Coturnix coturnix japonica) were fed a sublethal concentration of morsodren (4 ppm as methyl mercury) for 18 weeks. This resulted in an accumulation of 21.0 ppm of mercury in the liver and 8.4 ppm in the carcass. Birds fed clean feed and those fed morsodren-treated feed were orally dosed with 2, 4, 6, 8,and 10 mg/kg parathion, and their 48-h survival times compared. The computed LD50 was 5.86mg/kg in birds not fed morsodren and 4.24 in those fed the heavy metal. When challenged with a sublethal, oral dose of parathion (1.0 mg/kg), morsodren-fed birds exhibited significantly greater inhibition of plasma and brain cholinesterase activity than controls dosed with parathion. Brain cholinesterase activity was inhibited 41% in morsodren-fed birds and 26in clean-fed birds dosed with parathion, which suggested that the increase in parathion toxicity in the presence of morsodren was directly related to the inhibitation of brain cholinesterase.

Bulletin of Environmental Contamination and Toxico↗

USGS2001

Chlorinated hydrocarbons and biomarkers of exposure in wading birds and fish of the Lower Rio Grande Valley, Texas

During 1997 we evaluated reproductive success in colonial water birds nesting in the Lower Rio Grande Valley (LRGV), Texas, and correlated success with concentrations of contaminants in eggs. We also measured steroid hormones and gonadosomatic index (GSI) as biomarkers of endocrine effects in common carp (Cyprinus carpio). Nest and fledging success of green herons (Butorides virescens) and great egrets (Ardea alba) were similar to those found in other parts of North America; however, nesting success of black-crowned night-herons (Nycticorax nycticorax) was lower, very likely due to flooding of the nesting area. Except for DDE and toxaphene, all chlorinated pesticides in bird eggs were low and not of concern for negative effects on any of the three species. DDE was highest in green heron eggs and seemed to increase along a geographic gradient from west to east, with eggs from Falcon Reservoir containing low concentrations, and those at Los Indios containing the highest concentrations (approx. 11,000 ng/g WW), near or above the threshold for reproductive impairment. DDE levels in great egrets and black-crowned night-herons were below those that are associated with reproductive impairment. Mean DDE levels in carp at the JAS Farms site were above the threshold level suggested for predator protection. Toxaphene was detected in about 20% of the samples with high levels observed in green heron eggs from Los Indios (mean = 4,402 ng/g WW). These are the highest toxaphene levels reported in bird eggs in the LRGV. Toxaphene levels in fish ranged between 90 and 312 ng/g WW. In general, PCBs in bird eggs and fish tissue were low and at levels not of concern for reproductive effects. The greatest concentrations of testosterone and 11-ketotestosterone were detected in fish from the JAS Farms site, which also had the greatest concentrations of DDE. Increased androgen production and gonad development in fish at this site, relative to Pharr, could be possibly associated with endocrine disrupting effects of p,p???-DDE. DDE, toxaphene, PCBs, and hormones were highest in birds and fish from the eastern edge of the study area.

Archives of Environmental Contamination and Toxico↗

USGS2014

Mercury bioaccumulation in Southern Appalachian birds, assessed through feather concentrations

Mercury contamination in wildlife has rarely been studied in the Southern Appalachians despite high deposition rates in the region. From 2006 to 2008 we sampled feathers from 458 birds representing 32 species in the Southern Appalachians for total mercury and stable isotope δ 15 N. Mercury concentrations (mean ± SE) averaged 0.46 ± 0.02 μg g −1 (range 0.01–3.74 μg g −1 ). Twelve of 32 species had individuals (7 % of all birds sampled) with mercury concentrations higher than 1 μg g −1 . Mercury concentrations were 17 % higher in juveniles compared to adults ( n = 454). In adults, invertivores has higher mercury levels compared to omnivores. Mercury was highest at low-elevation sites near water, however mercury was detected in all birds, including those in the high elevations (1,000–2,000 m). Relative trophic position, calculated from δ 15 N, ranged from 2.13 to 4.87 across all birds. We fitted linear mixed-effects models to the data separately for juveniles and year-round resident adults. In adults, mercury concentrations were 2.4 times higher in invertivores compared to omnivores. Trophic position was the main effect explaining mercury levels in juveniles, with an estimated 0.18 ± 0.08 μg g −1 increase in feather mercury for each one unit rise in trophic position. Our research demonstrates that mercury is biomagnifying in birds within this terrestrial mountainous system, and further research is warranted for animals foraging at higher trophic levels, particularly those associated with aquatic environments downslope from montane areas receiving high mercury deposition.

Ecotoxicology↗

USGS2006

Dermal insecticide residues from birds inhabiting an orchard

The US Environmental Protection Agency conducts risk assessments of insecticide applications to wild birds using a model that is limited to the dietary route of exposure. However, free-flying birds are also exposed to insecticides via the inhalation and dermal routes. We measured azinphos-methyl residues on the skin plus feathers and the feet of brown-headed cowbirds ( Molothrus ater ) in order to quantify dermal exposure to songbirds that entered and inhabited an apple ( Malus x domestica ) orchard following an insecticide application. Exposure to azinphos-methyl was measured by sampling birds from an aviary that was built around an apple tree. Birds sampled at 36 h and 7-day post-application were placed in the aviary within 1 h after the application whereas birds exposed for 3 days were released into the aviary 4-day post-application. Residues on vegetation and soil were also measured. Azinphos-methyl residues were detected from the skin plus feathers and the feet from all exposure periods. Our results underscore the importance of incorporating dermal exposure into avian pesticide risk assessments.

Environmental Monitoring and Assessment↗

USGS2017

The future demographic niche of a declining grassland bird fails to shift poleward in response to climate change

Context Temperate grasslands and their dependent species are exposed to high variability in weather and climate due to the lack of natural buffers such as forests. Grassland birds are particularly vulnerable to this variability, yet have failed to shift poleward in response to recent climate change like other bird species in North America. However, there have been few studies examining the effect of weather on grassland bird demography and consequent influence of climate change on population persistence and distributional shifts. Objectives The goal of this study was to estimate the vulnerability of Henslow’s Sparrow ( Ammodramus henslowii ), an obligate grassland bird that has been declining throughout much of its range, to past and future climatic variability. Methods We conducted a demographic meta-analysis from published studies and quantified the relationship between nest success rates and variability in breeding season climate. We projected the climate-demography relationships spatially, throughout the breeding range, and temporally, from 1981 to 2050. These projections were used to evaluate population dynamics by implementing a spatially explicit population model. Results We uncovered a climate-demography linkage for Henslow’s Sparrow with summer precipitation, and to a lesser degree, temperature positively affecting nest success. We found that future climatic conditions—primarily changes in precipitation—will likely contribute to reduced population persistence and a southwestward range contraction. Conclusions Future distributional shifts in response to climate change may not always be poleward and assessing projected changes in precipitation is critical for grassland bird conservation and climate change adaptation.

Landscape Ecology↗

USGS2022

A critical review of bioaccumulation and biotransformation of organic chemicals in birds

A literature review of bioaccumulation and biotransformation of organic chemicals in birds was undertaken, aiming to support scoping and prioritization of future research. The objectives were to characterize available bioaccumulation/biotransformation data, identify knowledge gaps, determine how extant data can be used, and explore the strategy and steps forward. An intermediate approach balanced between expediency and rigor was taken given the vastness of the literature. Following a critical review of > 500 peer-reviewed studies, > 25,000 data entries and 2 million information bytes were compiled on > 700 organic compounds for ~ 320 wild species and 60 domestic breeds of birds. These data were organized into themed databases on bioaccumulation and biotransformation , field survey , microsomal enzyme activity , metabolic pathway , and bird taxonomy and diet . Significant data gaps were identified in all databases at multiple levels. Biotransformation characterization was largely fragmented over metabolite/pathway identification and characterization of enzyme activity or biotransformation kinetics. Limited biotransformation kinetic data constrained development of an avian biotransformation model. A substantial shortage of in vivo biotransformation kinetics has been observed as most reported rate constants were derived in vitro. No metric comprehensively captured all key contaminant classes or chemical groups to support broad-scope modeling of bioaccumulation or biotransformation. However, metrics such as biota-feed accumulation factor, maximum transfer factor, and total elimination rate constant were more readily usable for modeling or benchmarking than other reviewed parameters. Analysis demonstrated the lack of bioaccumulation/biotransformation characterization of shorebirds, seabirds, and raptors. In the study of bioaccumulation and biotransformation of organic chemicals in birds, this review revealed the need for greater chemical and avian species diversity, chemical measurements in environmental media, basic biometrics and exposure conditions, multiple tissues/matrices sampling, and further exploration on biotransformation. Limitations of classical bioaccumulation metrics and current research strategies used in bird studies were also discussed. Forward-looking research strategies were proposed: adopting a chemical roadmap for future investigations, integrating existing biomonitoring data, gap-filling with non-testing approaches, improving data reporting practices, expanding field sampling scopes, bridging existing models and theories, exploring biotransformation via avian genomics, and establishing an online data repository.

Reviews of Environmental Contamination and Toxicol↗

USGS2015

Avoidance of unconventional oil wells and roads exacerbates habitat loss for grassland birds in the North American great plains

Oil development in the Bakken shale region has increased rapidly as a result of new technologies and strong demand for fossil fuel. This region also supports a particularly high density and diversity of grassland bird species, which are declining across North America. We examined grassland bird response to unconventional oil extraction sites (i.e. developed with hydraulic fracturing and horizontal drilling techniques) and associated roads in North Dakota. Our goal was to quantify the amount of habitat that was indirectly degraded by oil development, as evidenced by patterns of avoidance by birds. Grassland birds avoided areas within 150 m of roads (95% CI: 87–214 m), 267 m of single-bore well pads (95% CI: 157–378 m), and 150 m of multi-bore well pads (95% CI: 67–233 m). Individual species demonstrated variable tolerance of well pads. Clay-colored sparrows ( Spizella pallida ) were tolerant of oil-related infrastructure, whereas Sprague's pipit ( Anthus spragueii ) avoided areas within 350 m (95% CI: 215–485 m) of single-bore well pads. Given these density patterns around oil wells, the potential footprint of any individual oil well, and oil development across the region, is greatly multiplied for sensitive species. Efforts to reduce new road construction, concentrate wells along developed corridors, combine numerous wells on multi-bore pads rather than build many single-bore wells, and to place well pads near existing roads will serve to minimize loss of suitable habitat for birds. Quantifying environmental degradation caused by oil development is a critical step in understanding how to better mitigate harm to wildlife populations.

Biological Conservation↗

USGS2025

Using GPS tracking data to validate the conservation value of bird migration counts

Effective conservation of migratory birds requires gathering of information about their population trends, often acquired using migratory bird counts. These schemes ideally operate at migratory bottlenecks, through which a significant portion of the counted migratory populations is funneled. Yet it is rare to validate the conservation value of the data from these counts. Here we perform this validation using GPS tracking data collected from two migratory species during their movement over two count schemes: the globally endangered steppe eagle counted in Eilat, Israel, and the black kite, counted in Batumi, Georgia. We use tracking data to answer two questions: which populations are counted and what affects the probability that a given individual will be counted. Our results illustrate variability in the effectiveness of these two migratory bird counting schemes. Considering the goal of estimating population trends, we show that Eilat does not represent a good location for understanding population trends of steppe eagles, while Batumi appears to provide better information on demographic trends of black kites. We further present differences in annual and individual variability, evidence regarding the breeding area origins of the counted populations and effects of environmental factors on the raptors' routes and, consequently, on the probabilities of being counted. Beyond the direct implications of our results, this study provides an example of using telemetry data to parameterize inference from bird counts. Further coupling of migratory bird count data and GPS data can improve our understanding of migration ecology and the conservation of migratory species.

Biological Conservation↗

USGS2014

Breeding bird community response to establishing intercropped switchgrass in intensively-managed pine stands

Intercropping switchgrass ( Panicum virgatum L.) between tree rows within young pine ( Pinus spp.) plantations is a potential method to generate lignocellulosic biofuel feedstocks within intensively managed forests. Intensively managed pine supports a diverse avian assemblage potentially affected by establishment and maintenance of an annual biomass feedstock via changes in plant communities, dead wood resources, and habitat structure. We sought to understand how establishing switchgrass on an operational scale affects bird communities within intercropped plantations as compared to typical intensively managed loblolly pine ( Pinus taeda L.) forest. We conducted breeding bird point counts using distance sampling for three years (2011–2013) following establishment of intercropped switchgrass stands (6 replicates), traditionally-managed pine plantations, and switchgrass-only plots (0.1 km 2 minimum) in Kemper Co., MS. We detected 59 breeding bird species from 11,195 detections. Neotropical migrants and forest-edge associated species were less abundant in intercropped plots than controls the first two years after establishment and more abundant in year three. Short distance migrants and residents were scarce in intercropped and control plots initially, and did not differ between these two treatments in any year. Species associated with pine-grass habitat structure were less abundant initially in intercropped plots, but converged with pine controls in subsequent years. Switchgrass monocultures provided minimal resources for birds. If songbird conservation is a management priority, managers should consider potential reductions of some breeding birds for one to two years following intercropping. It is unclear how these relationships may change outside the breeding season and as stands age.

Biomass and Bioenergy↗

USGS2012

Modelling effects of chemical exposure on birds wintering in agricultural landscapes: The western burrowing owl ( Athene cunicularia hypugaea ) as a case study

We describe an ecotoxicological model that simulates the sublethal and lethal effects of chronic, low-level, chemical exposure on birds wintering in agricultural landscapes. Previous models estimating the impact on wildlife of chemicals used in agro-ecosystems typically have not included the variety of pathways, including both dermal and oral, by which individuals are exposed. The present model contains four submodels simulating (1) foraging behavior of individual birds, (2) chemical applications to crops, (3) transfers of chemicals among soil, insects, and small mammals, and (4) transfers of chemicals to birds via ingestion and dermal exposure. We demonstrate use of the model by simulating the impacts of a variety of commonly used herbicides, insecticides, growth regulators, and defoliants on western burrowing owls ( Athene cunicularia hypugaea ) that winter in agricultural landscapes in southern Texas, United States. The model generated reasonable movement patterns for each chemical through soil, water, insects, and rodents, as well as into the owl via consumption and dermal absorption. Sensitivity analysis suggested model predictions were sensitive to uncertainty associated with estimates of chemical half-lives in birds, soil, and prey, sensitive to parameters associated with estimating dermal exposure, and relatively insensitive to uncertainty associated with details of chemical application procedures (timing of application, amount of drift). Nonetheless, the general trends in chemical accumulations and the relative impacts of the various chemicals were robust to these parameter changes. Simulation results suggested that insecticides posed a greater potential risk to owls of both sublethal and lethal effects than do herbicides, defoliants, and growth regulators under crop scenarios typical of southern Texas, and that use of multiple indicators, or endpoints provided a more accurate assessment of risk due to agricultural chemical exposure. The model should prove useful in helping prioritize the chemicals and transfer pathways targeted in future studies and also, as these new data become available, in assessing the relative danger to other birds of exposure to different types of agricultural chemicals.

Texas↗

USGS2014

Linking multi-temporal satellite imagery to coastal wetland dynamics and bird distribution

Ecosystems are characterized by dynamic ecological processes, such as flooding and fires, but spatial models are often limited to a single measurement in time. The characterization of direct, fine-scale processes affecting animals is potentially valuable for management applications, but these are difficult to quantify over broad extents. Direct predictors are also expected to improve transferability of models beyond the area of study. Here, we investigated the ability of non-static and multi-temporal habitat characteristics to predict marsh bird distributions, while testing model generality and transferability between two coastal habitats. Distribution models were developed for king rail ( Rallus elegans ), common gallinule ( Gallinula galeata ), least bittern ( Ixobrychus exilis ), and purple gallinule ( Porphyrio martinica ) in fresh and intermediate marsh types in the northern Gulf Coast of Louisiana and Texas, USA. For model development, repeated point count surveys of marsh birds were conducted from 2009 to 2011. Landsat satellite imagery was used to quantify both annual conditions and cumulative, multi-temporal habitat characteristics. We used multivariate adaptive regression splines to quantify bird-habitat relationships for fresh, intermediate, and combined marsh habitats. Multi-temporal habitat characteristics ranked as more important than single-date characteristics, as temporary water was most influential in six of eight models. Predictive power was greater for marsh type-specific models compared to general models and model transferability was poor. Birds in fresh marsh selected for annual habitat characterizations, while birds in intermediate marsh selected for cumulative wetness and heterogeneity. Our findings emphasize that dynamic ecological processes can affect species distribution and species-habitat relationships may differ with dominant landscape characteristics.

Ecological Modelling↗

USGS2013

Bird-vegetation associations in thinned and unthinned young Douglas-fir forests 10 years after thinning

Quantitative associations between animals and vegetation have long been used as a basis for conservation and management, as well as in formulating predictions about the influence of resource management and climate change on populations. A fundamental assumption embedded in the use of such correlations is that they remain relatively consistent over time. However, this assumption of stationarity has been rarely tested – even for forest birds, which are frequently considered to be 'indicator species' in management operations. We investigated the temporal dynamics of bird-vegetation relationships in young Douglas-fir (Pseudotsuga menziesii) forests over more than a decade following initial anthropogenic disturbance (commercial thinning). We modeled bird occurrence or abundance as a function of vegetation characteristics for eight common bird species for each of six breeding seasons following forest thinning. Generally, vegetation relationships were highly inconsistent in magnitude across years, but remained positive or negative within species. For 3 species, relationships that were initially strong dampened over time. For other species, strength of vegetation association was apparently stochastic. These findings indicate that caution should be used when interpreting weak bird-vegetation relationships found in short-term studies and parameterizing predictive models with data collected over the short term.

Oregon↗

USGS2016

Avian malaria in a boreal resident species: long-term temporal variability, and increased prevalence in birds with avian keratin disorder

The prevalence of vector-borne parasitic diseases is widely influenced by biological and ecological factors. Environmental conditions such as temperature and precipitation can have a marked effect on haemosporidian parasites ( Plasmodium spp.) that cause malaria and those that cause other malaria-like diseases in birds. However, there have been few long-term studies monitoring haemosporidian infections in birds in northern latitudes, where weather conditions can be highly variable and the effects of climate change are becoming more pronounced. We used molecular methods to screen more than 2,000 blood samples collected from black-capped chickadees ( Poecile atricapillus ), a resident passerine bird. Samples were collected over a 10 year period, mostly during the non-breeding season, at seven sites in Alaska, USA. We tested for associations between Plasmodium prevalence and local environmental conditions including temperature, precipitation, site, year and season. We also evaluated the relationship between parasite prevalence and individual host factors of age, sex and presence or absence of avian keratin disorder. This disease, which causes accelerated keratin growth in the beak, provided a natural study system in which to test the interaction between disease state and malaria prevalence. Prevalence of Plasmodium infection varied by year, site, age and individual disease status but there was no support for an effect of sex or seasonal period. Significantly, birds with avian keratin disorder were 2.6 times more likely to be infected by Plasmodium than birds without the disorder. Interannual variation in the prevalence of Plasmodium infection at different sites was positively correlated with summer temperatures at the local but not statewide scale. Sequence analysis of the parasite cytochrome b gene revealed a single Plasmodium spp. lineage, P43. Our results demonstrate associations between prevalence of avian malaria and a variety of biological and ecological factors. These results also provide important baseline data that will be informative for predicting future changes in Plasmodium prevalence in the subarctic.

Alaska↗

USGS2026

Contrasting haemosporidian infections in two ecologically distinct wading birds from breeding colonies in the southeastern United States

Wading birds may serve as ideal hosts for avian hemoparasites, as they are long-lived, undertake extensive movements, form dense breeding colonies, and inhabit water-associated environments that support vectors. Although previous studies have reported parasite species and prevalence in various wading bird species, little is known about their associations with bird behavior and life stage. To address this gap, we examined haemosporidian infections in two ecologically distinct species, white ibis ( Eudocimus albus ) and tricolored heron ( Egretta tricolor ), to explore differences in life stage and movement that may explain prevalence differences. We combined blood screening for hemoparasites with satellite tracking data describing birds’ movement patterns. We screened 95 white ibis (67 juveniles and 28 adults or subadults) and 69 tricolored herons (45 juveniles and 24 adults). We detected a single Haemoproteus plataleae lineage in both species, with higher infection prevalence in white ibis (42.1 %) than in tricolored herons (14.5 %). Among white ibis, adults showed a higher prevalence (67.9 %) than juveniles (31.3 %), whereas in tricolored herons, adults had a prevalence of 8.3 % and juveniles 17.8 %. Non-breeding season movement data showed that white ibis used both freshwater and saline habitats across the southeastern United States, which may also serve as habitats for vectors. In contrast, tricolored herons remained mainly along coastal areas, using saline habitats in the southeastern United States and wintering sites in Central America, which may be less favorable for vectors. Overall, white ibis may serve as major reservoirs and sources of reinfection for H. plataleae , whereas tricolored herons may facilitate parasite dispersal between breeding colonies along the coasts of the southeastern United States and wintering areas in Central America. This study presents the first direct comparison of hemoparasite infections in two ecologically distinct wading birds and highlights movement data as key to explaining infection differences, providing a baseline for future studies.

Alabama↗