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At least 937 records · Page 52Linked to original sources
USGS2022

Detection of Splendidofilaria sp. (Onchocercidae:Splendidofilariinae) Microfilaria within Alaskan ground-dwelling birds in the grouse subfamily tetraoninae using taqman probe-based real-time PCR

Grouse and ptarmigan (Galliformes) harbor fairly diverse helminth faunas that can impact the host's health, including filarial nematodes in the genus Splendidofilaria . As host and parasite distributions are predicted to shift in response to recent climate change, novel parasites may be introduced into a region and impose additional stressors on bird populations. Limited information is available on the prevalence of filariasis in Alaska galliforms. To date, no molecular surveys have been completed. Past studies relied on examining blood smears or total body necropsies, which are time-consuming and may not detect filarial parasites with low prevalence in hosts. Therefore, we developed a TaqMan probe-based real-time PCR assay targeting the cytochrome c oxidase 1 gene ( COI ) of Splendidofilaria to decrease processing times and increase sensitivity as well as provide baseline data on the diversity of filariid infections in galliform species in Alaska. We screened a combined total of 708 galliform samples (678 unique individual birds) from different tissues (blood, muscle, and lung) for the presence of filarial DNA across the state of Alaska. Real-time PCR screening revealed an overall prevalence of filarial infection of 9.5% across species: Bonasa umbellus (0%, n = 23), Dendragapus fuliginosus (0%, n = 8), Falcipennis canadensis (26.8%, n = 198), Lagopus lagopus (2.6%, n = 274), Lagopus leucura (0%, n = 23), Lagopus muta (3%, n = 166), and Tympanuchus phasianellus (12.5%, n = 16). We observed microfilarial infections throughout most of Alaska except in Arctic regions and the Aleutian Islands where viable vectors may not be present.

Journal of Parasitology↗
USGS2006

Does body size affect a bird's sensitivity to patch size and landscape structure?

Larger birds are generally more strongly affected by habitat loss and fragmentation than are smaller ones because they require more resources and thus larger habitat patches. Consequently, conservation actions often favor the creation or protection of larger over smaller patches. However, in grassland systems the boundaries between a patch and the surrounding landscape, and thus the perceived size of a patch, can be indistinct. We investigated whether eight grassland bird species with different body sizes perceived variation in patch size and landscape structure in a consistent manner. Data were collected from surveys conducted in 44 patches of northern tallgrass prairie during 1998–2001. The response to patch size was very similar among species regardless of body size (density was little affected by patch size), except in the Greater Prairie-Chicken ( Tympanuchus cupido ), which showed a threshold effect and was not found in patches smaller than 140 ha. In landscapes containing 0%–30% woody vegetation, smaller species responded more negatively to increases in the percentage of woody vegetation than larger species, but above an apparent threshold of 30%, larger species were not detected. Further analyses revealed that the observed variation in responses to patch size and landscape structure among species was not solely due to body size per se, but to other differences among species. These results indicate that a stringent application of concepts requiring larger habitat patches for larger species appears to limit the number of grassland habitats that can be protected and may not always be the most effective conservation strategy.

Condor↗
USGS2017

Applying citizen-science data and mark-recapture models to estimate numbers of migrant golden eagles in an important bird area in eastern North America

Estimates of population abundance are important to wildlife management and conservation. However, it can be difficult to characterize the numbers of broadly distributed, low-density, and elusive bird species. Although Golden Eagles (Aquila chrysaetos) are rare, difficult to detect, and broadly distributed, they are concentrated during their autumn migration at monitoring sites in eastern North America. We used hawk-count data collected by citizen scientists in a virtual mark–recapture modeling analysis to estimate the numbers of Golden Eagles that migrate in autumn along Kittatinny Ridge, an Important Bird Area in Pennsylvania, USA. In order to evaluate the sensitivity of our abundance estimates to variation in eagle capture histories, we applied candidate models to 8 different sets of capture histories, constructed with or without age-class information and using known mean flight speeds 6 1, 2, 4, or 6 SE for eagles to travel between hawk-count sites. Although some abundance estimates were produced by models that poorly fitted the data ( ĉ > 3.0), 2 sets of population estimates were produced by acceptably performing models (cˆ less than or equal to 3.0). Application of these models to count data from November, 2002–2011, suggested a mean population abundance of 1,354 6 117 SE (range: 873–1,938). We found that Golden Eagles left the ridgeline at different rates and in different places along the route, and that typically ,50% of individuals were detected at the hawk-count sites. Our study demonstrates a useful technique for estimating population abundance that may be applicable to other migrant species that are repeatedly detected at multiple monitoring sites along a topographic diversion or leading line.

Pennslyvania↗
USGS2017

Model selection for the North American Breeding Bird Survey: A comparison of methods

The North American Breeding Bird Survey (BBS) provides data for >420 bird species at multiple geographic scales over 5 decades. Modern computational methods have facilitated the fitting of complex hierarchical models to these data. It is easy to propose and fit new models, but little attention has been given to model selection. Here, we discuss and illustrate model selection using leave-one-out cross validation, and the Bayesian Predictive Information Criterion (BPIC). Cross-validation is enormously computationally intensive; we thus evaluate the performance of the Watanabe-Akaike Information Criterion (WAIC) as a computationally efficient approximation to the BPIC. Our evaluation is based on analyses of 4 models as applied to 20 species covered by the BBS. Model selection based on BPIC provided no strong evidence of one model being consistently superior to the others; for 14/20 species, none of the models emerged as superior. For the remaining 6 species, a first-difference model of population trajectory was always among the best fitting. Our results show that WAIC is not reliable as a surrogate for BPIC. Development of appropriate model sets and their evaluation using BPIC is an important innovation for the analysis of BBS data.

Condor↗
USGS2018

Evaluating time-removal models for estimating availability of boreal birds during point count surveys: Sample size requirements and model complexity

We used conventional and finite mixture removal models with and without time-varying covariates to evaluate availability given presence for 152 bird species using data from point counts in boreal North America. We found that the choice of model had an impact on the estimability of unknown model parameters and affected the bias and variance of corrected counts. Finite mixture models provided better fit than conventional removal models and better adjusted for count duration. However, reliably estimating parameters and minimizing variance using mixture models required at least 200–1,000 detections. Mixture models with time-varying proportions of infrequent singers were best supported across species, indicating that accounting for date- and time-related heterogeneity is important when combining data across studies over large spatial scales, multiple sampling time frames, or variable survey protocols. Our flexible and continuous time-removal modeling framework can be used to account for such heterogeneity through the incorporation of easily obtainable covariates, such as methods, date, time, and location. Accounting for availability bias in bird surveys allows for better integration of disparate studies at large spatial scales and better adjustment of local, regional, and continental population size estimates.

Condor↗
USGS2012

Prevalence of a potentially lethal parasite of wading birds in natural and agricultural wetlands in south Louisiana

Gambusia affinis (Western Mosquitofish) were sampled from 18 sites representing marsh, forested wetlands, and agricultural wetlands in south Louisiana to determine distribution and infection parameters of Eustrongylides ignotus , a potentially lethal nematode parasite of wading birds, ( n = 400 per site). Overall, prevalence of infection was 0.3%, with significantly higher prevalence in agricultural wetlands than in marshes or swamps. Our findings are similar to work in Florida suggesting parasite prevalence is higher in disturbed wetlands, and suggest that birds foraging in crayfish ponds and rice fields may be at increased risk of exposure.

Louisiana↗
USGS2018

Photographs of wading bird depredation events to monitor invasion extent of Asian Swamp Eel (Monopterus albus)

Several anecdotes exist of wading birds depredating invasive Monopterus albus (Asian Swamp Eel) in waterways of the conterminous US. We present photographic evidence of 4 different wading bird species depredating adult Asian Swamp Eels in Georgia and Florida herein. Photographs taken by wildlife enthusiasts could provide a means for early detection of the Asian Swamp Eel and other aquatic species that are challenging to detect in waterways.

Florida, Georgia↗
USGS2012

Grassland bird communtiy response to large wildfires

We studied breeding season communities of grassland birds on short-grass and mixed-grass prairie sites during the second and third breeding seasons following two large wildfires in March 2006 in the Texas panhandle, USA. There was an apparent temporary shift in avian community composition following the fires due to species-specific shifts associated with life-history traits and vegetation preferences. Species that prefer sparse vegetation and bare ground on short-grass sites, such as Horned Lark ( Eremophila alpestris ), benefited from wildfires, while others, such as Western Meadowlark ( Sturnella neglecta ), that prefer more dense vegetation, were negatively impacted. Mixed-grass sites had species-specific shifts in 2007, two breeding seasons after the fires; grassland bird communities on burned plots were similar by 2008 to those on unburned plots. Avian communities appeared to return to pre-burn levels within 3 years following wildfires. Many of the responses in our study of wildfire were similar to those reported following prescribed fires elsewhere. Prescribed fires appear to have similar effects on the avian community despite differences in intensity and environmental conditions during wildfires.

Wilson Journal of Ornithology↗
USGS2025

Being loud to find a quiet bird: Surveying a secretive tropical avian species

Secretive birds are hard to detect, and thus, likely underestimated when surveyed, potentially preventing measures to protect them. We identified a sampling period and method that would yield the most reliable estimates of population numbers of the secretive Puerto Rican Lizard-Cuckoo ( Coccyzus vieilloti ). We addressed these objectives by comparing point counts (passive) and playback broadcast (active) survey methods from January to December, 2022 at Cambalache State Forest, Puerto Rico. We surveyed 20 stations (radius = 50 m each) between sunrise and 10 am, employing the time-of-detection method. We recorded strong responses from C. vieilloti after birds had been stimulated by playback broadcasts (recapture probabilities), corresponding to a behavioral response (M b ). For example, average capture (p) and recapture (c) probabilities within the peak breeding season for active surveys were 0.23 ± 0.10 and 0.49 ±0.08, respectively. Active surveys yielded higher estimates of C. vieilloti compared to passive surveys. For example, active survey expected population numbers (15.6 ha or area sampled) during peak breeding season were 42.87 ± 12.08 compared to 19.60 ± 2.08 individuals from passive surveys. Coefficients of variation population estimates of active surveys ranged between 10 and 16%, with one exception (28%), well within acceptable levels for wildlife studies. We show that secretive species like C. vieilloti can be reliably surveyed using playback broadcasts. Surveys should be conducted during the peak breeding season when estimates are higher and have better precision. Conducting similar tests on other secretive species could ensure that their status is not mischaracterized and that they receive the benefits of appropriate conservation measures, if warranted.

Cambalache State Forest, Puerto Rico↗
USGS2015

Bird species turnover is related to changing predation risk along a vegetation gradient

Turnover in animal species along vegetation gradients is often assumed to reflect adaptive habitat preferences that are narrower than the full gradient. Specifically, animals may decline in abundance where their reproductive success is low, and these poor-quality locations differ among species. Yet habitat use does not always appear adaptive. The crucial tests of how abundances and demographic costs of animals vary along experimentally manipulated vegetation gradients are lacking. We examined habitat use and nest predation rates for 16 bird species that exhibited turnover with shifts in deciduous and coniferous vegetation. For most bird species, decreasing abundance was associated with increasing predation rates along both natural and experimentally modified vegetation gradients. This landscape-scale approach strongly supports the idea that vegetation-mediated effects of predation are associated with animal distributions and species turnover.

Montana↗
USGS2015

Avian malaria in Hawaiian forest birds: Infection and population impacts across species and elevations

Wildlife diseases can present significant threats to ecological systems and biological diversity, as well as domestic animal and human health. However, determining the dynamics of wildlife diseases and understanding the impact on host populations is a significant challenge. In Hawai‘i, there is ample circumstantial evidence that introduced avian malaria ( Plasmodium relictum ) has played an important role in the decline and extinction of many native forest birds. However, few studies have attempted to estimate disease transmission and mortality, survival, and individual species impacts in this distinctive ecosystem. We combined multi-state capture-recapture (longitudinal) models with cumulative age-prevalence (cross-sectional) models to evaluate these patterns in Apapane, Hawai‘i Amakihi, and Iiwi in low-, mid-, and high-elevation forests on the island of Hawai‘i based on four longitudinal studies of 3–7 years in length. We found species-specific patterns of malaria prevalence, transmission, and mortality rates that varied among elevations, likely in response to ecological factors that drive mosquito abundance. Malaria infection was highest at low elevations, moderate at mid elevations, and limited in high-elevation forests. Infection rates were highest for Iiwi and Apapane, likely contributing to the absence of these species in low-elevation forests. Adult malaria fatality rates were highest for Iiwi, intermediate for Amakihi at mid and high elevations, and lower for Apapane; low-elevation Amakihi had the lowest malaria fatality, providing strong evidence of malaria tolerance in this low-elevation population. Our study indicates that hatch-year birds may have greater malaria infection and/or fatality rates than adults. Our study also found that mosquitoes prefer feeding on Amakihi rather than Apapane, but Apapane are likely a more important reservoir for malaria transmission to mosquitoes. Our approach, based on host abundance and infection rates, may be an effective alternative to mosquito blood meal analysis for determining vector-host contacts when mosquito densities are low and collection of blood-fed mosquitoes is impractical. Our study supports the hypothesis that avian malaria has been a primary factor influencing the elevational distribution and abundance of these three species, and likely limits other native Hawaiian species that are susceptible to malaria.

Hawai'i↗
USGS2017

Nesting ecology of grassland birds following a wildfire in the southern Great Plains

We studied the response of nesting grassland birds occupying short-grass and mixed-grass prairie sites 2 and 3 y following two, large-scale wildfires that burned ≥360,000 ha in the Texas Panhandle in March 2006. Nest success was greater on burned plots compared to unburned plots, though this varied by species and year. Woody vegetation cover was greater around nests on unburned plots compared to burned plots for Cassin's sparrow ( Peucaea cassinii ) and lark sparrow ( Chondestes grammacus ). Cassin's sparrows and lark sparrows nested in more-woody vegetation than did grasshopper sparrows ( Ammodramus savannarum ), and woody vegetation was reduced following the wildfires. The wildfires appear to have had few if any negative influences on the avian community 3 years postfire. This may be due to grassland breeding birds being adapted to landscapes in which, historically, periodic disturbance (e.g., wildfire, intensive grazing by bison [ Bison bison ]) resulted in vegetation heterogeneity.

Texas↗
USGS2014

Associations of wintering birds with habitat in semidesert and plains grasslands in Arizona

We studied associations with winter habitat for seven species of birds, one species-group (eastern and western meadowlarks combined), and total sparrows at seven sites in the semidesert and plains grasslands of southeastern Arizona from 1999–2001, sampling with mist-nets and survey-transects. We measured structure and composition of vegetation, assessing vegetative differences among sites, and modeled associations between indices of avian abundance and six vegetative variables using generalized linear models. For all vegetative variables, there were significant differences among sites. Numbers of northern harriers ( Circus cyaneus ) were positively associated with total number of sparrows. Indices of abundance for individual species of birds were statistically correlated with various measures of structure and composition of vegetation. In particular, grasshopper ( Ammodramus savannarum ) and vesper ( Pooecetes gramineus ) sparrows were negatively associated with amount of bare ground; horned larks ( Eremophila alpestris ) were negatively associated with vertical grass density; Baird's sparrows ( A. bairdii ) were negatively associated with shrub density; meadowlarks ( Sturnella magna and S. neglecta combined) were positively associated with native grass. Our results suggest that these species would benefit from management of habitat that affects the vegetative characteristics associated with their abundance.

Arizona↗
USGS1980

A necropsy procedure for sampling disease in wild birds

This paper presents a necropsy procedure for examining small wild birds, designed to be used by investigators without experience in avian pathology. It gives instructions on how to conduct a postmortem examination, lists the needed equipment, tells what parts of a bird to save when a disorder in encountered, and lists possible diseases which each may signify. This procedure would enable ornithologists to include parasites and diseases in their investigations of avian populations.

Condor↗
USGS1987

Latent population responses of summer birds to a catastrophic, climatological event

Catastrophic events can create ecological crunches for avian populations. Ornithologists generally assume that such events elicit immediate, dramatic declines in populations followed by rapid recolonization of a site with habitat recovery. Despite total inundation of habitats within the South Platte floodplain of eastern Colorado during the 1983 breeding season, populations of Brown Thrashers (Toxostoma rufum) and Rufoussided Towhees (Pipilo erythrophthalmus) did not decline significantly from 1982 densities. However, populations of both species declined significantly in 1984 and towhee populations remained low in 1985. These observations support speculations from recent studies of shrubsteppe bird populations that site tenacity may play a stronger role in determining annual densities of breeding birds than previously realized.

The Condor↗
USGS1989

Responses to human intruders by birds nesting in colonies: Experimental results and management guidelines

Colonies of nesting wading birds and seabirds were studied at coastal sites in Virginia and North Carolina to determine distances at which birds flushed in response to human intrusion. There were few statistically significant relationships between flushing distances and colony size. Similarly, there were few differences between responses during incubation compared to post-hatching periods.

Colonial Waterbirds↗
USGS1995

Pasteurella multocida isolated from wild birds of North America: a serotype and DNA fingerprint study of isolates from 1978 to 1993

Serotype and DNA fingerprint methods were used to study Pasteurella multocida isolated from 320 wild birds of North America. Isolates were collected during 1978-93. The HhaI profiles of 314 isolates matched the HhaI profile of somatic reference type 1, strain X-73; somatic type 1 antigen was expressed by 310 isolates, and the serotype of four isolates was undetected. Differentiation of the 314 isolates was observed by digestion of DNA with HpaII. None of the HpaII profiles matched the HpaII profile of X-73 (designated HhaI 001/HpaII 001). Three HpaII profiles were recognized among the somatic type 1 isolates: HpaII 002 (n = 18), HpaII 003 (n = 122), and HpaII 004 (n = 174). Profile HpaII 002 was found among isolates collected during 1979-83. Profile HpaII 003 was identified from isolates collected during 1979-89, with the exception of two isolates in 1992. The HpaII 004 profile was identified from isolates collected during 1983-93. Of the six remaining isolates, four expressed somatic type 4 and had HhaI profiles identical to the somatic type 4 reference strain P-1662 profile (designated HhaI 004); these isolates were differentiated by digestion of DNA with HpaII. One isolate was identified as serotype F:11, and another was serotype A:3,4. In the present study, 314 of 316 (99.4%) isolates from wild birds in the Central, Mississippi, and Pacific flyways during 1978-93, were P. multocida somatic type 1.

Avian Diseases↗
USGS1983

Nutritional value of the aril of Trichilia cuneata, a bird-dispersed fruit

Fruits of Trichilia cuneata (Meliaceae), a common tree in drier forests of Central America, are eaten by a number of birds. The fruits are 10 to 12 mm in diameter, covered by a yellowish-brown, capsular exocarp, and contain three to six seeds distributed among three locules. Each seed is covered by an orangish-red aril that averages 59.7 percent lipid and 15 1 percent protein, which makes this species one of the most nutritious known. The fleshy tissue of only 15 of 59 other species for which we found data contained at least 10 percent protein (dry wt.). Only nine species of 57 had fleshy tissue containing more than 40 percent lipid (dry wt.). Between 1971 and 1972, weights of whole fruits decreased by 36 percent, perhaps in response to a severe drought in the area. The decrease was not equally distributed among component tissues of the fruit. Exocarp decreased by 36 percent, aril by 4 percent, and seeds by 62 percent. However, the reduction in weight per seed was not so dramatic, for two reasons. First, the number of seeds per fruit decreased by 26 percent. Secondly, many seeds did not develop. Thus, the decrease in weight per normally developed seed was only 18 percent. The fruit of Trichilia cuneata was attractive to both specialized (4 species) and opportunistic (11 species) frugivorous birds and is intermediate ("a generalist") in several dispersal-related characteristics.

Biotropica↗