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At least 109 records · Page 6Linked to original sources
USGS2022

Large-scale distribution models for optimal prediction of Eastern black rail habitat within tidal ecosystems

Eastern black rails ( Laterallus jamaicensis jamaicensis ) are among the rarest and least-studied birds in North America and were recently listed as threatened under the U.S. Endangered Species Act. Spatial models that predict habitat quality across the subspecies range are therefore needed to inform conservation, recovery, and monitoring efforts for this rare bird. We used data from 47,585 call-broadcast surveys collected at 7906 sites over a 3-decade period (1990s, 2000s, 2010s; 23 total years) to build species distribution models for eastern black rails. We used hierarchical Bayesian occupancy models and predictive model selection to develop multi-scale models that optimally predict habitat suitability for eastern black rails within tidal wetlands while also accounting for imperfect detection of these cryptic birds during field surveys. We also used raster regression techniques to translate model predictions into 30-m resolution maps of habitat suitability for eastern black rails within tidal wetlands along the eastern seaboard of the United States. The model predicted suitability of breeding habitat as a function of wetland attributes (e.g., cover of high marsh and terrestrial border), hydrologic modification, and disturbance from human development measured over multiple spatial scales. We also found differences in habitat relationships for eastern black rails when compared to models that included both North American subspecies of black rail. Important results included negative effects of shrub-scrub wetlands, and strong positive effects of high marsh, terrestrial border, and impoundments on breeding season occupancy. Our study provides an example of integrating detection-non-detection data and modern statistical methods to build predictive distribution models for an extremely rare species, while also providing rigorous predictions of breeding habitat quality for the eastern black rail within tidal wetlands. These models will facilitate optimal monitoring, habitat conservation, and recovery planning efforts for eastern black rails and provide a foundation for future research and conservation of this imperiled bird.

Global Ecology and Conservation↗
USGS2022

Reference values and comparison of blood chemistry and plasma protein values between gold standard analyzers and four point-of-care devices in free-ranging canvasbacks (Aythya valisineria)

Accurate, timely, and cost-effective blood chemistry analysis is an essential tool for directing emergency treatment, monitoring the health status of captive and free-ranging individuals and flocks, and improving the efficacy of conservation actions. Blood samples were obtained from 52 canvasbacks ( Aythya valisineria ) that were captured on San Francisco Bay, California, during December 2017 as part of a long-term study. Reference values and clinical agreement were determined for blood chemistry and plasma protein parameters among four commonly used point-of-care devices (VetScan ® VS2, i-STAT ® , AlphaTRAK ® 2 glucometer, refractometer) and two gold standard laboratory analyzers (Roche cobas ® c501, Helena SPIFE 3000 system). Canvasback reference values were generally within expected ranges for Anatidae species with the exception of higher upper limits for sodium and chloride. Creatine kinase and aspartate transaminase values exceeded a published threshold for diagnosis of capture myopathy even though study birds were captured using low-stress techniques and successfully released. With the exception of higher alkaline phosphatase in hatch-year canvasbacks, no age or sex differences were observed for any analyte in this population that was captured during a nonbreeding period. Analysis of analyzer agreement found raw VetScan aspartate transaminase, calcium, glucose, and uric acid values; corrected VetScan albumin, potassium, sodium, and total protein values; raw i-STAT glucose and potassium values; and corrected i-STAT sodium and chloride values were clinically interchangeable with Roche cobas values. Raw VetScan and i-STAT glucose values were also interchangeable. However, none of the Roche or point-of-care analyzer plasma protein values were in clinical agreement with gold standard electrophoresis values. The findings of this study highlight the need for analyzer- or technique-specific reference values and provide biologists and veterinarians quantitative reference values using currently available analyzers to better assess and respond to the health of individuals and populations.

California↗
USGS2019

How characteristic is the species characteristic selection scale?

Aim The importance of framing investigations of organism–environment relationships to interpret patterns at relevant spatial scales is increasingly recognized. However, most research related to environmental relationships is single-scaled, implicitly or explicitly assuming that a “species characteristic selection scale” exists. We tested the premise that a single characteristic scale exists to understand species–environment relationships within species by asking (a) what are the characteristic scales of species’ relationships with environmental predictors, and (b) is within-species, cross-predictor consistency in characteristic scales a general phenomenon. Location Nebraska, USA. Time period 2016. Major taxa studied Birds. Methods We used data from 86 species at > 500 locations to build hierarchical N-mixture models relating species abundance to land cover variables. By incorporating Bayesian latent indicator scale selection, we identified the spatial scales that best explain species–environment relationships with each land cover predictor. We quantified the extent of cross-predictor consistency in characteristic scales, and contrasted this to the expectation given a single species’ characteristic scale. Results We found no evidence for a characteristic spatial scale explaining all abundance–environment relationships within species, rather we found substantial variation in scale-dependence across multiple environmental attributes. Furthermore, 33% of species displayed evidence of multiple important spatial scales within environmental attributes. Major conclusions Within species there is little evidence for a single characteristic scale of environmental relationships and considerable variation in species’ scale dependencies. Because species may respond to multiple environmental attributes at different spatial scales, or single environmental attributes at multiple scales, we caution against any unoptimized single-scale studies. Our results demonstrate that until a framework is developed to predict the scales at which species respond to environmental characteristics, multi-scale investigations must be performed to identify and account for multi-scale dependencies. Natural selection acting on species’ response to distinct environmental attributes, rather than natural selection acting on species’ perception of spatial scales per se, may have shaped patterns of scale dependency and is an area ripe for investigation.

Nebraska↗
USGS2012

A risk-based approach to evaluating wildlife demographics for management in a changing climate: A case study of the Lewis's Woodpecker

Given the projected threat that climate change poses to biodiversity, the need for proactive response efforts is clear. However, integrating uncertain climate change information into conservation planning is challenging, and more explicit guidance is needed. To this end, this article provides a specific example of how a risk-based approach can be used to incorporate a species' response to climate into conservation decisions. This is shown by taking advantage of species' response (i.e., impact) models that have been developed for a well-studied bird species of conservation concern. Specifically, we examine the current and potential impact of climate on nest survival of the Lewis's Woodpecker ( Melanerpes lewis ) in two different habitats. To address climate uncertainty, climate scenarios are developed by manipulating historical weather observations to create ensembles (i.e., multiple sequences of daily weather) that reflect historical variability and potential climate change. These ensembles allow for a probabilistic evaluation of the risk posed to Lewis's Woodpecker nest survival and are used in two demographic analyses. First, the relative value of each habitat is compared in terms of nest survival, and second, the likelihood of exceeding a critical population threshold is examined. By embedding the analyses in a risk framework, we show how management choices can be made to be commensurate with a defined level of acceptable risk. The results can be used to inform habitat prioritization and are discussed in the context of an economic framework for evaluating trade-offs between management alternatives.

Idaho↗
USGS2020

Shared functional traits explain synchronous changes in long‐term count trends of migratory raptors

Aim Assessing long‐term shifts in faunal assemblages is important to understand the consequences of ongoing global environmental change. One approach to assess drivers of assemblage changes is to identify the traits associated with synchronous shifts in count trends among species. Our research identified traits influencing trends in 73 years of count data on migrating raptors recorded in the north‐eastern USA. Location Pennsylvania, USA. Time period 1946–2018. Major taxa studied Birds of prey/raptors. Methods Migrating raptors were counted during autumn, following a standardized protocol. We used a hierarchical breakpoint model to identify when count trends shifted and to assess the role of traits in driving these trends before and after the breakpoint. Specifically, we quantified the probability of the direction (PD) of an effect of body mass, habitat or dietary specialization, migratory behaviour and susceptibility to dichlorodiphenyltrichloroethane (DDT) on count trends. Results We documented an assemblage‐wide mean shift in count trends of migrating raptors in 1974. In general, species that exhibited negative count trends before the breakpoint exhibited positive count trends afterwards. We found that traits associated with resource use (diet and habitat specialization) had high probabilities of affecting count trends, pre‐ and post‐breakpoint (> 90%). Moreover, the direction of their effects differed during both periods. Unexpectedly, other traits we evaluated, including DDT susceptibility, had relatively weaker associations with count trends. Main conclusions Trait‐based frameworks have promise for testing generalized assumptions about drivers of population trajectories. Historically, DDT was considered a key driver of changes in raptor population trends. However, our analysis suggests that other factors were also relevant. Moreover, the positive association between count trends and generalist behaviour depended on the temporal context. This result has implications for other settings where demographic trends can be linked to traits and help to identify drivers of biodiversity change.

Pennsylvania↗
USGS2011

Home range dynamics, habitat selection, and survival of Greater Roadrunners

Greater Roadrunners (Geococcyx californianus) are common, poorly studied birds of arid and semi-arid ecosystems in the southwestern United States. Conservation of this avian predator requires a detailed understanding of their movements and spatial requirements that is currently lacking. From 2006 to 2009, we quantified home-range and core area sizes and overlap, habitat selection, and survival of roadrunners (N= 14 males and 20 females) in north-central Texas using radio-telemetry and fixed kernel estimators. Median home-range and core-area sizes were 90.4 ha and 19.2 ha for males and 80.1 ha and 16.7 ha for females, respectively. The size of home range and core areas did not differ significantly by either sex or season. Our home range estimates were twice as large (x??= 108.9 ha) as earlier published estimates based on visual observations (x??= 28-50 ha). Mean percent overlap was 38.4% for home ranges and 13.7% for core areas. Male roadrunners preferred mesquite woodland and mesquite savanna cover types, and avoided the grass-forb cover type. Female roadrunners preferred mesquite savanna and riparian woodland cover types, and avoided grass-forb habitat. Kaplan-Meier annual survival probabilities for females (0.452 ?? 0.118[SE]) were twice that estimated for males (0.210 ?? 0.108), but this difference was not significant. Mortality rates of male roadrunners were higher than those of females during the spring when males call from elevated perches, court females, and chase competing males. Current land use practices that target woody-shrub removal to enhance livestock forage production could be detrimental to roadrunner populations by reducing availability of mesquite woodland and mesquite savanna habitat required for nesting and roosting and increasing the amount of grass-forb habitat that roadrunners avoid. ??2011 The Authors. Journal of Field Ornithology ??2011 Association of Field Ornithologists.

Journal of Field Ornithology↗
USGS2005

The effect of varying protein levels on blood chemistry, food consumption, and behavior of captive seaducks

The Chesapeake Bay is a primary wintering area for scoters and the long-tailed ducks (Clangia hyemalis) that migrate along the Atlantic Flyway. Recently, the Chesapeake Bay had undergone an ecosystem shift and little is known about how this is affecting the seaduck populations. We are determining what are the preferred food sources of the seaducks wintering on the Bay and analyzing the factors influencing prey selection whether it is prey composition, energy assimilated, prey availability, or a combination of any or all of these factors. We have established a captive colony of surf (Melanitta perspicillata) and white-winged scoters (Melanitta fusca) as well as long-tailed ducks at Patuxent Wildlife Research Center to allow us to examine these factors in a more controlled environment. This project contains a multitude of experiments and the resultant data will be compiled into a compartmental model on the feeding ecology of seaducks wintering on the Bay. The first experiment entailed feeding groups of each species (four ducks per pen of equal sex ratio, if possible, and four pens per species) three diets varying in percent protein levels from November to February. Each diet was randomly assigned to each pen and the amount of food consumed was recorded each day. New feed was given when all existing food was consumed. Behavioral trials and blood profiles were completed on all study birds to determine the effects of the varying diets. There were no significant differences in food consumption, blood chemistry, and behavior detected at the 5% level among the diets for all three species of interest. There was a seasonal effect determined based on the food consumption data for white-winged scoters, but not for surf scoters or long-tailed ducks. The blood profiles of the surf scoters were compared to blood profiles of wild surf scoters and a there was no difference detected at the 5% level. As a health check of the ducks an aspergillosis test was run on the blood obtained during the experiment and it was found that surf scoters are more resistant to the disease than the other species. In the next two winters natural prey items available to seaducks wintering in the Chesapeake Bay will be offered on palettes to examine preference without the additional energetic costs of diving. Assimilation efficiency trials will be run on all three species to determine amount of energy the ducks obtain from each food source. Finally, using two large aquariums, prey preference will be analyzed with the additional energetic costs of diving and searching for prey. In addition, we will determine the effect of availability of a prey item on the prey selection of seaducks. We hope the model created from these experiments will allow managers to examine the effects of changes in the benthos on the seaduck populations wintering in the Chesapeake Bay.

Book chapter↗
USGS2013

The influence of study species selection on estimates of pesticide exposure in free-ranging birds

Field studies of pesticide effects on birds often utilize indicator species with the purpose 16 of extrapolating to other avian taxa. Little guidance exists for choosing indicator species to 17 monitor the presence and/or effects of contaminants that are labile in the environment or body, 18 but are acutely toxic, such as anticholinesterase (anti-ChE) insecticides. Use of an indicator 19 species that does not represent maximum exposure and/or effects could lead to inaccurate risk 20 estimates. Our objective was to test the relevance of a priori selection of indicator species for a 21 study on pesticide exposure to birds inhabiting fruit orchards. We used total plasma 22 cholinesterase (ChE) activity and ChE reactivation to describe the variability in anti-ChE exposure among avian species in two conventionally managed fruit orchards. Of seven 24 species included in statistical analyses, the less common species, chipping sparrow (Spizella 25 passerina), showed the greatest percentage of exposed individuals and the greatest ChE 26 depression, whereas the two most common species, American robins (Turdus migratorius) and 27 grey catbirds (Dumatella carolinensis), did not show significant exposure. Due to their lower 28 abundance, chipping sparrows would have been an unlikely choice for study. Our results show 29 that selection of indicator species using traditionally accepted criteria such as abundance and 30 ease of collection may not identify species that are at greatest risk. Our efforts also demonstrate 31 the usefulness of conducting multiple-species pilot studies prior to initiating detailed studies on 32 pesticide effects. A study such as ours can help focus research and resources on study species 33 that are most appropriate.

Environmental Management↗
USGS2010

Intraperitoneal injections as a possible means of generating varied levels of methylmercury in the eggs of birds in field studies

The ideal study of the effects of methylmercury on the reproductive success of a species of bird would be one in which eggs contained mercury concentrations ranging from controls to very heavily contaminated, all at the same site. Such a study cannot be realized at a mercury contaminated area or under laboratory conditions, but could be achieved by introducing methylmercury into breeding females and allowing them to deposit mercury in their eggs. Female mallards (Anas platyrhynchos) were intraperitoneally injected with solutions of methylmercury chloride dissolved in corn oil, propylene glycol, dimethyl sulfoxide, mineral oil, Olestra, Crisco, lard, hard paraffin, and a combination of hard and soft paraffin. In some cases, egg laying was delayed, either due to the solvent itself (in the case of Olestra, Crisco, and lard) or to the highest concentration of methylmercury chloride (500 &mu;g/g) in some of the solvents. Mercury in eggs ranged from a control level (< 0.1 &mu;g/g) to approximately 14 &mu;g/g on a wet weight basis, which more than covers the range of concentrations reported in wild bird eggs. Mercury concentrations in a series of eggs from the same female declined mostly due to excretion of mercury in prior eggs and not because of the length of time since the injection. Intraperitoneal injections hold promise in field studies where one would like to study the reproductive effects of a wide range of methylmercury levels in the eggs of a wild bird and under the natural conditions that exist in the field.

Environmental Toxicology and Chemistry↗
USGS1989

Chlamydial infections in free-living birds

Most studies of chlamydial infections in free-living wild birds have been limited to surveys for the presence of Chlamydia psittaci or antibody to C psittaci and have largely been done in association with the identification of chlamydiosis in human beings, commercial fowl, or pet birds. The emphasis of these studies has been to determine the prevalence of infection and the potential role of wild birds in the spread of chlamydiae to domestic birds and human beings. Little is known about the epizootiology of chlamydiosis in free-living birds or its affect on their population dynamics. The following article is a summary of reported studies of chlamydiosis in free-living wild birds in relation to host range, ecologic aspects of transmission and maintenance, and the prevalence of disease.

Journal of the American Veterinary Medical Associa↗
USGS2005

Incubation period and immune function: A comparative field study among coexisting birds

Developmental periods are integral components of life history strategies that can have important fitness consequences and vary enormously among organisms. However, the selection pressures and mechanisms causing variation in length of developmental periods are poorly understood. Particularly puzzling are prolonged developmental periods, because their selective advantage is unclear. Here we tested the hypotheses that immune function is stronger in species that are attacked at a higher rate by parasites and that prolonged embryonic development allows the development of this stronger immune system. Through a comparative field study among 12 coexisting passerine bird species, we show that species with higher blood parasite prevalence mounted stronger cellular immune responses than species with lower prevalence. These results provide support for the hypothesis that species facing greater selection pressure from parasites invest more in immune function. However, species with longer incubation periods mounted weaker cellular immune responses than species with shorter periods. Therefore, cellular immune responses do not support the hypothesis that longer development time enhances immunocompentence. Future studies should assess other components of the immune system and test alternative causes of variation in incubation periods among bird species. ?? Springer-Verlag 2005.

Oecologia↗
USGS2010

Why do some, but not all, tropical birds migrate? A comparative study of diet breadth and fruit preference

Annual migrations of birds profoundly influence terrestrial communities. However, few empirical studies examine why birds migrate, in part due to the difficulty of testing causal hypotheses in long-distance migration systems. Short-distance altitudinal migrations provide relatively tractable systems in which to test explanations for migration. Many past studies explain tropical altitudinal migration as a response to spatial and temporal variation in fruit availability. Yet this hypothesis fails to explain why some coexisting, closely-related frugivorous birds remain resident year-round. We take a mechanistic approach by proposing and evaluating two hypotheses (one based on competitive exclusion and the other based on differences in dietary specialization) to explain why some, but not all, tropical frugivores migrate. We tested predictions of these hypotheses by comparing diets, fruit preferences, and the relationships between diet and preference in closely-related pairs of migrant and resident species. Fecal samples and experimental choice trials revealed that sympatric migrants and residents differed in both their diets and fruit preferences. Migrants consumed a greater diversity of fruits and fewer arthropods than did their resident counterparts. Migrants also tended to have slightly stronger fruit preferences than residents. Most critically, diets of migrants more closely matched their preferences than did the diets of residents. These results suggest that migrants may be competitively superior foragers for fruit compared to residents (rather than vice versa), implying that current competitive interactions are unlikely to explain variation in migratory behavior among coexisting frugivores. We found some support for the dietary specialization hypothesis, propose refinements to the mechanism underlying this hypothesis, and discuss how dietary specialization might ultimately reflect past interspecific competition. We recommend that future studies quantify variation in nutritional content of tropical fruits, and determine whether frugivory is a consequence or a cause of migratory behaviour.

Evolutionary Ecology↗
USGS2008

Field Marks of a Celebration: Roger Tory Peterson's Centennial Birthday

A red letter day in my life was April 27, 1934, the day I first met Roger. A birding friend, Elisha Atkins, had invited Clinton Reynolds and me to dinner to meet a famous ornithologist. We would all be going on a field trip to Newburyport on the Massachusetts coast the next day. The dinner conversation revolved about a new field guide that Mr. Peterson had just completed and that would be available in a few days. I couldn?t wait to see it! I had been birding since 1930, keying out live birds with Chapman?s Handbook of Birds of Eastern North America (1912) and Hoffman?s Guide to the Birds of New England and Eastern New York (1904). Both books had extensive keys based on color, size, bill shape and season, and pictures of heads or feet of some species. Positive bird identification was a long and tedious process. The field trip the next day with Roger was memorable, not for finding any rare or unusual birds, but for learning how to identify birds to species at a single good glance. I recall asking Roger if he could find a ring-billed gull among a group of gulls resting on a roof beside the Merrimac River. He immediately said, ?No there aren?t any ring-bills there; they would be immediately apparent by their slimmer shape.? There was no need to check the foot color on each bird. While it is easy to say that Roger revolutionized field guides, I truly believe there are few people worldwide under the age of 90 who can really appreciate the difference between the old way of keying out birds and the instant recognition promoted by the Peterson system. Today we take for granted that amateurs can identify birds accurately. Monitoring bird populations by Breeding Bird Surveys, atlas studies, Breeding Bird Censuses, migration banding, and many other studies relies on it. None of these would be possible if we were still keying out live birds using books designed to identify dead birds in the hand.

Audubon Naturalist News↗
USGS2021

Bridging the research-implementation gap in avian conservation with translational ecology

The recognized gap between research and implementation in avian conservation can be overcome with translational ecology, an intentional approach in which science producers and users from multiple disciplines work collaboratively to co-develop and deliver ecological research that addresses management and conservation issues. Avian conservation naturally lends itself to translational ecology because birds are well studied, typically widespread, often exhibit migratory behaviors transcending geopolitical boundaries, and necessitate coordinated conservation efforts to accommodate resource and habitat needs across the full annual cycle. In this perspective, we highlight several case studies from bird conservation practitioners and the ornithological and conservation social sciences exemplifying the 6 core translational ecology principles introduced in previous studies: collaboration, engagement, commitment, communication, process, and decision-framing. We demonstrate that following translational approaches can lead to improved conservation decision-making and delivery of outcomes via co-development of research and products that are accessible to broader audiences and applicable to specific management decisions (e.g., policy briefs and decision-support tools). We also identify key challenges faced during scientific producer–user engagement, potential tactics for overcoming these challenges, and lessons learned for overcoming the research-implementation gap. Finally, we recommend strategies for building a stronger translational ecology culture to further improve the integration of these principles into avian conservation decisions. By embracing translational ecology, avian conservationists and ornithologists can be well positioned to ensure that future management decisions are scientifically informed and that scientific research is sufficiently relevant to managers. Ultimately, such teamwork can help close the research-implementation gap in the conservation sciences during a time when environmental issues are threatening avian communities and their habitats at exceptional rates and at broadening spatial scales worldwide.

Ornithological Applications↗
USGS2018

The epidemiology of avian pox and interaction with avian malaria in Hawaiian forest birds

Despite the purported role of avian pox ( Avipoxvirus spp.) in the decline of endemic Hawaiian birds, few studies have been conducted on the dynamics of this disease, its impact on free‐living avian populations, or its interactions with avian malaria ( Plasmodium relictum ). We conducted four longitudinal studies of 3–7 yr in length and used generalized linear models to evaluate cross‐sectional prevalence of active pox infection and individuals with healed deformities that had recovered from pox. Our goal was to understand how species, season, elevation, malaria infection, and other biological characteristics influenced pox infection in ʻApapane, Hawaiʻi ʻAmakihi, ʻIʻiwi, and Japanese White‐eye across low‐, mid‐, and high‐elevation forests on the island of Hawaiʻi. We also used multi‐state capture‐recapture (longitudinal) models to estimate pox infection rates, recovery rates, and potential pox‐related mortality. Pox infection rates were typically highest in low‐elevation forests, followed by mid‐elevation forests, and lowest in high‐elevation forests. We also found seasonal changes in pox prevalence throughout the annual cycle; typically increasing from spring through summer, peaking in fall, and declining in winter. These seasonal changes occurred in low‐ and mid‐elevation forests, but not in high elevations where pox infection was low. Seasonal and elevation patterns of pox infection are like those for avian malaria, strongly implicating mosquito vectors, rather than other biting arthropods or contact transmission, as the primary source of transmitting both diseases. Most native Hawaiian birds recovered from pox infection within 6 months; frequently without permanent lesions. Contrary to our expectations, we found no direct evidence that pox is a substantial mortality factor in any of the three native bird species we studied. Birds with chronic malaria infection were more likely to have both active pox infection and healed pox lesions suggesting a synergistic interaction that may influence the evolution of pox virulence. Because pox infection can be assessed visually, and birds have a high recovery rate, this disease may be a sensitive indicator of the seasonal and annual risk of transmission of malaria in Hawaiʻi.

Ecological Monographs↗