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At least 1,243 records · Page 69Linked to original sources

Evaluation of spatial models to predict vulnerability of forest birds to brood parasitism by cowbirds

We constructed alternative spatial models at two scales to predict Brown-headed Cowbird ( Molothrus ater ) parasitism rates from land cover maps. The local-scale models tested competing hypotheses about the relationship between cowbird parasitism and distance of host nests from a forest edge (forest-nonforest boundary). The landscape models tested competing hypotheses about how landscape features (e.g., forests, agricultural fields) interact to determine rates of cowbird parasitism. The models incorporate spatial neighborhoods with a radius of 2.5 km in their formulation, reflecting the scale of the majority of cowbird commuting activity. Field data on parasitism by cowbirds (parasitism rate and number of cowbird eggs per nest) were collected at 28 sites in the Driftless Area Ecoregion of Wisconsin, Minnesota, and Iowa and were compared to the predictions of the alternative models. At the local scale, there was a significant positive relationship between cowbird parasitism and mean distance of nest sites from the forest edge. At the landscape scale, the best fitting models were the forest-dependent and forest-fragmentation-dependent models, in which more heavily forested and less fragmented landscapes had higher parasitism rates. However, much of the explanatory power of these models results from the inclusion of the local-scale relationship in these models. We found lower rates of cowbird parasitism than did most Midwestern studies, and we identified landscape patterns of cowbird parasitism that are opposite to those reported in several other studies of Midwestern songbirds. We caution that cowbird parasitism patterns can be unpredictable, depending upon ecoregional location and the spatial extent, and that our models should be tested in other ecoregions before they are applied there. Our study confirms that cowbird biology has a strong spatial component, and that improved spatial models applied at multiple spatial scales will be required to predict the effects of landscape and forest management on cowbird parasitism of forest birds.

Iowa, Minnesota, Wisconsin↗

Extreme weather and experience influence reproduction in an endangered bird

Extreme weather events, such as droughts and heat waves, are expected to become more severe and more frequent in the coming years, and understanding their impacts on demographic rates is of increasing interest to both evolutionary ecologists and conservation practitioners. An individual's breeding probability can be a sensitive indicator of the decision to initiate reproductive behavior under varying environmental conditions, has strong fitness consequences, and can be considered the first step in a life history trade-off between allocating resources for breeding activities or self-survival. Using a 14-year time series spanning large variation in climatic conditions and the entirety of a population's breeding range, we estimated the effects of extreme weather conditions (drought) on the state-specific probabilities of breeding and survival of an endangered bird, the Florida Snail Kite ( Rostrhamus sociabilis plumbeus ). Our analysis accounted for uncertainty in breeding status assignment, a common source of uncertainty that is often ignored when states are based on field observations. Breeding probabilities in adult kites (>1 year of age) decreased during droughts, whereas the probability of breeding in young kites (1 year of age) tended to increase. Individuals attempting to breed showed no evidence of reduced future survival. Although population viability analyses of this species and other species often implicitly assume that all adults will attempt to breed, we find that breeding probabilities were significantly <1 for all 13 estimable years considered. Our results suggest that experience is an important factor determining whether or not individuals attempt to breed during harsh environmental conditions and that reproductive effort may be constrained by an individual's quality and/or despotic behavior among individuals attempting to breed.

Florida↗

Geographic coincidence of richness, mass, conservation value, and response to climate of U.S. land birds

Distributional patterns across the United States of five avian community breeding-season characteristics&mdash;community biomass, richness, constituent species' vulnerability to extirpation, percentage of constituent species' global abundance present in the community (conservation index, CI), and the community's position along the ecological gradient underlying species composition (principal curve ordination score, PC)&mdash;were described, their covariation was analyzed, and projected effects of climate change on the characteristics and their covariation were modeled. Higher values of biomass, richness, and CI were generally preferred from a conservation perspective. However, higher values of these characteristics often did not coincide geographically; thus regions of the United States would differ in their value for conservation depending on which characteristic was chosen for setting conservation priorities. For instance, correlation patterns between characteristics differed among Landscape Conservation Cooperatives. Among the five characteristics, community richness and the ecological gradient underlying community composition (PC) had the highest correlations with longitude, with richness declining from east to west across the contiguous United States. The ecological gradient underlying composition exhibited a demarcation near the 100th meridian, separating the contiguous United States grossly into two similar-sized avian ecological provinces. The combined score (CS), a measure of species' threat of decline or extirpation, exhibited the strongest latitudinal pattern, declining from south to north. Over &sim;75% of the lower United States, projected changes in June temperature and precipitation to year 2080 were associated with decreased averaged values of richness, biomass, and CI, implying decreased conservation value for birds. The two ecological provinces demarcated near the 100th meridian diverged from each other, with projected changes in June temperatures and precipitation from the year 2000 to 2080 suggesting increased ecological dissimilarity between the eastern and western halves of the lower United States with changing climate. Anticipated climate-related changes in the five characteristics by 2080 were more weakly correlated with latitude or longitude then the responses themselves, indicating less distinct geographic patterns of characteristic change than in the characteristics themselves. Climate changes projected for 2080 included geographic shifts in avian biomass, CS, and PC values, a moderate overall decline in CI, and general decline in species richness per site.

Ecological Applications↗

Estimating wind-turbine-caused bird and bat fatality when zero carcasses are observed

Many wind-power facilities in the United States have established effective monitoring programs to determine turbine-caused fatality rates of birds and bats, but estimating the number of fatalities of rare species poses special difficulties. The loss of even small numbers of individuals may adversely affect fragile populations, but typically, few (if any) carcasses are observed during monitoring. If monitoring design results in only a small proportion of carcasses detected, then finding zero carcasses may give little assurance that the number of actual fatalities is small. Fatality monitoring at wind-power facilities commonly involves conducting experiments to estimate the probability ( g ) an individual will be observed, accounting for the possibilities that it falls in an unsearched area, is scavenged prior to detection, or remains undetected even when present. When g < 1, the total carcass count ( X ) underestimates the total number of fatalities ( M ). Total counts can be 0 when M is small or when M is large and g ≪1. Distinguishing these two cases is critical when estimating fatality of a rare species. Observing no individuals during searches may erroneously be interpreted as evidence of absence. We present an approach that uses Bayes' theorem to construct a posterior distribution for M , i.e., P ( M | X , ĝ ), reflecting the observed carcass count and previously estimated g . From this distribution, we calculate two values important to conservation: the probability that M is below a predetermined limit and the upper bound ( M * ) of the 100(1 &minus; &alpha;)% credible interval for M . We investigate the dependence of M * on &alpha;, g , and the prior distribution of M , asking what value of g is required to attain a desired M * for a given &alpha;. We found that when g < ~0.15, M * was clearly influenced by the mean and variance of ĝ and the choice of prior distribution for M , but the influence of these factors is minimal when g > ~0.45. Further, we develop extensions for temporal replication that can inform prior distributions of M and methods for combining information across several areas or time periods. We apply the method to data collected at a wind-power facility where scheduled searches yielded X = 0 raptor carcasses

Ecological Applications↗

Dynamics of a recovering Arctic bird population: the importance of climate, density dependence, and site quality

Intrinsic and extrinsic factors affect vital rates and population-level processes, and understanding these factors is paramount to devising successful management plans for wildlife species. For example, birds time migration in response, in part, to local and broadscale climate fluctuations to initiate breeding upon arrival to nesting territories, and prolonged inclement weather early in the breeding season can inhibit egg-laying and reduce productivity. Also, density-dependent regulation occurs in raptor populations, as territory size is related to resource availability. Arctic Peregrine Falcons ( Falco peregrinus tundrius ; hereafter Arctic peregrine) have a limited and northern breeding distribution, including the Colville River Special Area (CRSA) in the National Petroleum Reserve–Alaska, USA. We quantified influences of climate, topography, nest productivity, prey habitat, density dependence, and interspecific competition affecting Arctic peregrines in the CRSA by applying the Dail-Madsen model to estimate abundance and vital rates of adults on nesting cliffs from 1981 through 2002. Arctic peregrine abundance increased throughout the 1980s, which spanned the population's recovery from DDT-induced reproductive failure, until exhibiting a stationary trend in the 1990s. Apparent survival rate (i.e., emigration; death) was negatively correlated with the number of adult Arctic peregrines on the cliff the previous year, suggesting effects of density-dependent population regulation. Apparent survival and arrival rates (i.e., immigration; recruitment) were higher during years with earlier snowmelt and milder winters, and apparent survival was positively correlated with nesting season maximum daily temperature. Arrival rate was positively correlated with average Arctic peregrine productivity along a cliff segment from the previous year and initial abundance was positively correlated with cliff height. Higher cliffs with documented higher productivity (presumably indicative of higher-quality habitat), are a priority for continued protection from potential nearby development and disturbance to minimize population-level impacts. Climate change may affect Arctic peregrines in multiple ways, including through access to more snow-free nest sites and a lengthened breeding season that may increase likelihood of nest success. Our work provides insight into factors affecting a population during and after recovery, and demonstrates how the Dail-Madsen model can be used for any unmarked population with multiple years of abundance data collected through repeated surveys.

Alaska↗

Bayesian cross-validation for model evaluation and selection, with application to the North American Breeding Bird Survey

The analysis of ecological data has changed in two important ways over the last 15 years. The development and easy availability of Bayesian computational methods has allowed and encouraged the fitting of complex hierarchical models. At the same time, there has been increasing emphasis on acknowledging and accounting for model uncertainty. Unfortunately, the ability to fit complex models has outstripped the development of tools for model selection and model evaluation: familiar model selection tools such as Akaike's information criterion and the deviance information criterion are widely known to be inadequate for hierarchical models. In addition, little attention has been paid to the evaluation of model adequacy in context of hierarchical modeling, i.e., to the evaluation of fit for a single model. In this paper, we describe Bayesian cross-validation, which provides tools for model selection and evaluation. We describe the Bayesian predictive information criterion and a Bayesian approximation to the BPIC known as the Watanabe-Akaike information criterion. We illustrate the use of these tools for model selection, and the use of Bayesian cross-validation as a tool for model evaluation, using three large data sets from the North American Breeding Bird Survey.

Ecology↗

Species richness, relative abundance, and habitat associations of nocturnal birds along the rio grande in Southern texas

The segment of the Rio Grande between International Falcon Reservoir and Del Rio, Texas (distance ca. 350 km), remains largely unexplored ornithologically. We surveyed nocturnal birds monthly during February-June 1998 at 19 stations along the Rio Grande (n = 6) and at upland stock ponds (n = 13) in Webb County, Texas. We conducted 10-min point counts (n = 89) after sunset and before moonset. Four species of owls and five species of nightjars were detected. Nightjars, as a group, were nearly five limes more abundant (mean number/count = 2.63) than owls (mean number = 0.55). The most, common owl, the great horned owl (Bubo virginianus), had a mean number of 0.25/point count. The mean for elf owls (Micrathene whitneyi) was 0.16/point count. The most common nightjars were the common poorwill (Phalaenoptilus nuttallii; 1.21/point count) and lesser nighthawk (Chordeiles acutipennir, 1.16/point count). Survey sites on the river supported more species (mean = 2.2) than did upland stock ponds (mean = 1.4). However, only one species (common pauraque, Nyctidromus albicollis) showed a preference for the river sites. Our results establish this segment of the Rio Grande in southern Texas as an area of high diversity of nightjars in the United States, matched (in numbers of species) only by southeastern Arizona and southwestern New Mexico.

Southwestern Naturalist↗

A nonlethal microsampling technique to monitor the effects of mercury on wild bird eggs

Methylmercury is the predominant chemical form of mercury reported in the eggs of wild birds, and the embryo is the most sensitive life stage to methylmercury toxicity. Protective guidelines have been based mainly on captive-breeding studies with chickens (Gallus gallus), mallards (Anas platyrhynchos), and ring-necked pheasants (Phasianus colchicus) or on field studies where whole eggs were collected and analyzed and the effects of the mercury were measured based on the reproductive success of the remaining eggs. However, both of these methods have limitations. As an alternative, we developed a technique that involves extracting a small sample of albumen from a live egg, sealing the egg, returning the egg to its nest to be naturally incubated by the parents, and then relating the hatching success of this microsampled egg to its mercury concentration. After first developing this technique in the laboratory using chicken and mallard eggs, we selected the laughing gull (Larus atricilla) and black-necked stilt (Himantopus mexicanus) as test subjects in the field. We found that 92% of the microsampled laughing gull eggs met our reproductive endpoint of survival to the beginning of hatching compared to 100% for the paired control eggs within the same nests. Microsampled black-necked stilt eggs exhibited 100% hatching success compared to 93% for the paired control eggs. Our results indicate that microsampling is an effective tool for nonlethally sampling mercury concentrations in eggs and, as such, can be used for monitoring sensitive species, as well as for improving studies that examine the effects of mercury on avian reproduction.

Environmental Toxicology and Chemistry↗

BbsAssistant: An R package for downloading and handling data and information from the North American Breeding Bird Survey

This R package contains functions for downloading and munging data from the U.S. Geological Surveys North American Breeding Bird Survey (BBS) via file transfer protocol (FTP) (Pardieck, Ziolkowski Jr, Lutmerding, & Hudson, 2018; J. R. Sauer et al., 2017). This package was created to allow the user to bulk-download the BBS point count and related (e.g., route-level conditions) via FTP, and to quickly subset the data by taxonomic classifications and/or geographical locations. This package also maintains data containing the trend and annual indices from the most recent (1996-2017) hierarchical population analyses (J. Sauer et al., 2017).

Journal of Open Source Software↗

Using the North American Breeding Bird Survey as a tool for conservation: A critique of Bart et al. (2004)

Bart et al. (2004) develop methods for predicting needed samples for estimation of long-term trends from Count survey data, and they apply these methods to the North American Breeding Bird Survey (BBS). They recommend adding approximately 40% more survey routes ill the BBS to allow for estimation of long-term (i.e., 20 year) trends for a collection of species. We critique several aspects of their analysis and suggest that their focus on long-term trends and expansion of the present survey design will provide limited benefits for conservation because it fails to either enhance the credibility of the survey or better tie the survey to regional management activities. A primary innovation claimed by Bart et al. (2004) is the incorporation of bias in estimation of study planning. We question the value of this approach, as it requires reliable estimates of range of future bias. We show that estimates of bias used by Bart et al. (2004) are speculative. Failure to obtain better estimates of this bias is likely to compromise the credibility of future analyses of the survey. We also note that the generic analysis of population trends that they provide is of questionable validity and is unlikely to be relevant for regions and species of management concern.

Journal of Wildlife Management↗

Nest success, cause-specific nest failure, and hatchability of aquatic birds at selenium-contaminated Kesterson Reservoir and a reference site

During 1983-1985, we studied the reproductive success of several species of aquatic birds (coots, ducks, shorebirds, and grebes) nesting at two sites in Merced County, California: a selenium-contaminated site (Kesterson Reservoir) and a nearby reference site (Volta Wildlife Area). We used a computer program (MICROMORT) developed for the analysis of radiotelemetry data (Heisey and Fuller 1985) to estimate nest success and cause-specific failure rates, and then compared these parameters and hatchability between sites and among years. Nest success and causes of failure varied by species, site, and year. The most important causes of nest failure were usually predation, desertion, and water-level changes. However, embryotoxicosis (mortality, deformity, and lack of embryonic development) was the most important cause of nest failure in Eared Grebes ( Podiceps nigricollis ) at Kesterson Reservoir. Embryotoxicosis also reduced the hatchability of eggs of all other species at Kesterson in one or more years; embryonic mortality occurred rarely at Volta, and abnormalities were not observed.

California↗

Bird specimens and documentation: Critical data for a critical resource

As governments impose increasingly stringent regulations on the collection of bird specimens and as man alters ever greater areas of habitat with the loss of many of their contained species, museum specimens increase immeasurably in importance. Yet at present, museum collections do not contain an adequate representation of the world's avifauna and, unfortunately, are not likely to do so. Thus, it is imperative that data associated with specimens that are obtained be as complete as possible. To this end, we describe categories of information with wide application to many types of studies, outline character states, and recommend standard forms of data notation. We recognize that under certain circumstances, it may be appropriate to record more limited data. However, we encourage at least those engaged in general collecting to record as many of these standard data as possible.

Condor↗

Potential roadside biases due to habitat changes along Breeding Bird Survey routes

Breeding Bird Surveys (BBS) are conducted along roadside routes to enable a large geographic area to be surveyed. Yet the potential biases of sampling populations only from roadsides have received little attention. We sampled aerial photography of BBS routes taken in the mid-1960s and late-1980s to evaluate whether habitat changes that occurred along roadsides were also occurring in the surrounding area, and whether the frequency of habitats encountered along roadsides were similar to that off-route. We examined 28 routes in Maryland and 25 routes in Ohio, and defined roadside area as within 200 m of the road, and off-route as 200-1,600 m from the road. Most habitat changes that occurred along BBS roadsides also were occurring in the off-route areas. However, increases in urban cover was significantly greater along the road in Maryland where urbanization of farmland was the predominant habitat change. The small increase in urban cover in Ohio was not significantly greater along the road. Construction of single family homes was greater along BBS roadsides in both states. In Ohio, the greatest change in habitat was the conversion of farmland back to forest, which was not significantly greater along the road. Changes associated with urbanization were more biased towards roadsides than the reforestation of farmland. Within one time period, roadside areas had less forest and more agricultural and urban cover types than occurred off-route.

Condor↗

Censusing wading bird colonies: An update on the 'flight-line' count method

1. Thirteen mixed-species heronries (10 in Florida, two in Virginia, one in North Carolina) were studied in 1980 as part of a project begun in 1979 aimed at evaluating the 'flight-line' census method..2. Standardized counts of Snowy and Cattle Egrets, Louisiana and Little Blue Herons flying to and from the nesting colony were made for three hr periods, followed by a nest count of the colony. 3.Significant differences were found in the flight rates (number of birds per nest x hour) of the four species at the Chincoteague colony. However, when Cattle Egrets and Louisiana Herons were compared at all 13 colonies, their respective flight rates were in opposite rank to those at Chincoteague. Colony differences, then, may mask species differences. 4. A linear regression model showed a strong fit (R2=0.92) between the hourly flight number (3 hr means) and the nest number, but point estimates (single colony) had very large confidence limits. A given colony might be over-or underestimated by a factor of 2, using the regression equation as a predictive model. 5. A more appropriate application of the method would be to determine regionwide (e.g., state), rather than colony-specific, population estimates. 'Total' estimates for all (n= 13) colonies were within 10% of the actual nest number.

Colonial Waterbirds↗

Remote characterization of marine bird habitats with satellite imagery

Remote sensing techniques such as radar altimetry, synthetic aperture radar, coastal zone color scanning, and infrared radiometry provide effective, instantaneous, and relatively inexpensive means for characterizing critical habitats of marine birds. In order to make optimal use of satellite-derived data, the rationale for marine habitat classification is presented, and advantages and limitations of different remote sensing techniques are discussed. An application of remote characterization is used to test for short-term habitat use and selection by the Black-Capped Petrel ( Pterodroma hasitata ). By comparing synoptic satellite mapping (e.g. infrared radiometry) with ship-board censusing, it was possible to demonstrate that petrels did not use all marine habitats equally, nor did petrels use habitats in proportion to their availability (areal extent).

Colonial Waterbirds↗

Population trends of black terns from the North American Breeding Bird Survey, 1966-1996

Data from the North American Breeding Bird Survey indicate a survey-wide decline in Black Terns (Chlidonias niger) at an average rate of 3.1% annually during 1966-1996. Black Terns in Canada decreased at an average annual rate of 3.5% during this interval, while the United States population showed no significant trends. The long-term declines largely reflect trends prior to 1980, when the continental, Canadian, and United States populations decreased at average annual rates of 7.5%, 5.6%, and 11.9%, respectively. Most population trends were reversed during the 1990s, causing trend estimates over the 1980-1996 interval to become more positive. Associations between patterns of change in Black Terns, Mallards (Anas platyrhynchos), and numbers of ponds in the northern Great Plains suggest some relationships exist between habitat availability and the population trajectories.

Colonial Waterbirds↗

Characterization of an avian cholera epizootic in wild birds in western Nebraska

Avian cholera killed an estimated 2500 birds in western Nebraska and eastern Wyoming from 28 November 1985 to late January 1986. Wild mallards (Anas platyrhynchos) suffered the most losses. Other wild waterfowl, wild turkeys (Meleagris gallopavo), a few domestic fowl, and a bald eagle (Haliaeetus leucocephalus) also died. Pasteurella multocida serotype 1 was the predominant isolate from these carcasses. Cold, wet weather persisted throughout the outbreak, but daily losses in the flock of 50,000 mallards using the area were low. Pasteurella multocida was isolated from nasal swabs of 35 of 37 cattle from a feedlot in which many of these mallards were feeding. Eighty percent of the cattle isolates had antigenic characteristics of serotype 3 or serotype 3 with cross-reactivity. Isolates from wild mallards, wild turkeys, and the bald eagle were virulent to game-farm mallards when inoculated subcutaneously, but P. multocida isolates from cattle were not.

Nebraska, Wyoming↗

Plastic adhesive tape for color-marking birds

Colored plastic adhesive tape wrapped around the tarsus has been used successfully for color-marking birds and has proved to be easy to put on, adaptable, permanent, and colorfast.

Journal of Wildlife Management↗