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At least 379 records · Page 21Linked to original sources
USGS2014

Relatively high prevalence of pox-like lesions in Henslow's Sparrow ( Ammodramus henslowii ) among nine species of migratory grassland passerines in Wisconsin, USA

Globally, Avipoxvirus species affect over 230 species of wild birds and can significantly impair survival. During banding of nine grassland songbird species ( n = 346 individuals) in southwestern Wisconsin, USA, we noted species with a 2–6% prevalence of pox-like lesions (possible evidence of current infection) and 4–10% missing digits (potential evidence of past infection). These prevalences approach those recorded among island endemic birds (4–9% and 9–20% for the Galapagos and Hawaii, respectively) for which Avipoxvirus species have been implicated as contributing to dramatic population declines. Henslow's Sparrow Ammodramus henslowii (n = 165 individuals) had the highest prevalence of lesions (6.1%) and missing digits (9.7%). Among a subset of 26 Henslow's Sparrows from which blood samples were obtained, none had detectable antibody reactive to fowlpox virus antigen. However, four samples (18%) had antibody to canarypox virus antigen with test sample and negative control ratios (P/N values) ranging from 2.4 to 6.5 (median 4.3). Of four antibody-positive birds, two had lesions recorded (one was also missing a digit), one had digits missing, and one had no signs. Additionally, the birds with lesions or missing digits had higher P/N values than did the antibody-positive bird without missing digits or recorded lesions. This study represents an impetus for considering the impacts and dynamics of disease caused by Avipoxvirus among North American grassland bird species.

Wisconsin↗
USGS1985

Atlantic Flyway review: Region V: Patuxent Wildlife Research Center, Laurel, Prince Georges County, MD (390-0764)

This was my 4th year of banding in a powerline right-of-way that is specially managed to encourage growth of dense scrub. Nets were run for 2 to 3 hours each morning, because activity dropped off rapidly after the sun hit the nets. I banded on 79 days, from 1 August to 22 November. Frost continues to be a problem late in the season; the frostpocket effect of the stream valley and the lack of vegetative cover over the nets result in frozen nets on more mornings than would be expected. Warblers continued to dominate, with as many as 16 species in one day and a season total of 33 plus a Brewster's hybrid. Net-hours declined from 8506 to 7672 because I discontinued six of my least productive nets; this change accounted for much of the increase in birds per 100 net-hours (Table 1). Overall effort was comparable to that of 1982.

Maryland↗
USGS2020

At the end of the road: Lessons learned from comparing model- and design-based approaches to estimate population sizes of boreal birds in Alberta, Canada

Estimating population abundance is a challenging task complicated by the amount, type, and quality of available data. Conservationists have relied on design-based estimates from Partners in Flight (PIF), which primarily uses roadside data from the North American Breeding Bird Survey (BBS) to estimate populations sizes. However, the BBS was not designed to estimate population sizes. We developed models incorporating land cover and climate variables based on roadside and off-road point-count surveys. We calculated spatially explicit, model-based population estimates for 81 landbird species in Bird Conservation Region 6 in Alberta, Canada, and compared these to PIF estimates. We also developed a framework to evaluate how the differences between the detection distance, time-of-day, roadside count, and habitat representation adjustments explain discrepancies between the two estimators. We showed that the key assumptions of the PIF population size estimator were commonly violated in this region, and the two approaches provided very different population size estimates for most species. The average differences between estimators were explained by differences in the detection distance and time-of-day components, but these adjustments left much unexplained variation among species. Differences in the roadside count and habitat representation components explained most of the among-species variation. The variation caused by these factors was large enough to change the population size ranking of the species. The roadside count bias needs serious attention when roadside surveys are used to extrapolate over off-road areas. Habitat representation bias is likely prevalent in regions sparsely and non-representatively sampled by roadside surveys, such as the boreal region of North America, and thus population size estimates for these regions need to be treated with caution for certain species. Model-based integration of available data sources and additional sampling can contribute towards more accurate population size estimates for conservation in remote areas of North America.

Alberta↗
USGS1980

Atlantic Flyway review: Region V

Four of last year's Maryland stations were either discontinued or banded too few birds to report their results in 1978; these were Cloisters in Baltimore County, Cylburn in Baltimore City, tum Suden Sanctuary in Harford County, and Sandy Point State Park in Anne Arundel County. Banding was severely curtailed at Damsite, Maryland's last remaining Eastern Shore Station. Each of the other stations in Region V, however, showed an increase in net-hours over 1977, and two new stations were welcomed to the network: McDonogh School in Baltimore County, and Jekyll Island on the coast of Georgia. Station activities are summarized in Table 1. The total net-hours of effort by participating stations in 1978 (68,627) was 2% greater than the effort in 1977 (67,410), but the total number of birds banded dropped 24%, from 23,881 to 18,180. If we compare only the eight stations that were operated fairly consistently both years (Adventure, Sandy Spring, Laurel, Towson, Fort Howard, Kiptopeke, Long Beach, and Gulf Breeze}, new birds banded per 100 net-hours dropped 31%, from 37.8 in 1977 to 26.0 in 1978.

North American Bird Bander↗
USGS2000

Combining information from monitoring programs: Complications associated with indices and geographic scale

To adequately monitor Neotropical migratory birds, information must be collected to assess population change at local, regional, and continent-wide scales. I suggest that large-scale survey results (such as those derived from the North American Breeding Bird Survey) should not be used to predict population attributes on parks, refuges, and other protected areas. These areas are often managed, and generally contain habitats that can be poorly sampled in large scale surveys, hence local bird populations might be quite different from those sampled in the large-scale surveys. Furthermore, we are limited in our capabilities to combine information from local surveys with large-scale survey data. Most surveys of bird populations collect indices of abundance which are often not comparable among surveys due to habitat and region specific differences in probabilities of detecting birds. In assessing the effects of management, it is important to understand the limitations of monitoring at different geographic scales and to design programs to monitor at the scale at which management is conducted.

Book chapter↗
USGS2011

Land use and climate influences on waterbirds in the Prairie Potholes

Aim We examined the influences of regional climate and land‐use variables on mallard ( Anas platyrhynchos ), blue‐winged teal ( Anas discors ), ruddy duck ( Oxyura jamaicensis ) and pied‐billed grebe ( Podilymbus podiceps ) abundances to inform conservation planning in the Prairie Pothole Region of the United States. Location The US portion of Bird Conservation Region 11 (US‐BCR11, the Prairie Potholes), which encompasses six states within the United States: Montana, North Dakota, South Dakota, Nebraska, Minnesota and Iowa. Methods We used data from the North American Breeding Bird Survey (NABBS), the National Land Cover Data Set, and the National Climatic Data Center to model the effects of environmental variables on waterbird abundance. We evaluated land‐use covariates at three logarithmically related spatial scales (1000, 10,000 and 100,000 ha), and constructed hierarchical spatial count models a priori using information from published habitat associations. Model fitting was performed using a hierarchical modelling approach within a Bayesian framework. Results Models with the same variables expressed at different scales were often in the best model subset, indicating that the influence of spatial scale was small. Both land‐use and climate variables contributed strongly to predicting waterbird abundance in US‐BCR11. The strongest positive influences on waterbird abundance were the percentage of wetland area across all three spatial scales, herbaceous vegetation and precipitation variables. Other variables that we included in our models did not appear to influence waterbirds in this study. Main conclusions Understanding the relationships of waterbird abundance to climate and land use may allow us to make predictions of future distribution and abundance as environmental factors change. Additionally, results from this study can suggest locations where conservation and management efforts should be focused.

Iowa, Minnesota, Montana, Nebraska, North Dakota, ↗
USGS1997

Changes in breeding bird populations in North Dakota: 1967 to 1992-93

We compared breeding bird populations in North Dakota using surveys conducted in 1967 and 1992-93. In decreasing order, the five most frequently occurring species were Horned Lark ( Eremophila alpestris ), Brown-headed Cowbird ( Molothrus ater ), Western Meadowlark ( Sturnella neglecta ), Red-winged Blackbird ( Agelaius phoeniceus ), and Eastern Kingbird ( Tyrannus tyrannus ). The five most abundant species - Horned Lark, Chestnut-collared Longspur ( Calcarius ornatus ), Red-winged Blackbird, Western Meadowlark, and Brown-headed Cowbird - accounted for 31-41% of the estimated statewide breeding bird population in the three years. Although species composition remained relatively similar among years, between-year patterns in abundance and frequency varied considerably among species. Data from this survey and the North American Breeding Bird Survey indicated that species exhibiting significant declines were primarily grassland- and wetland-breeding birds, whereas species exhibiting significant increases primarily were those associated with human structures and woody vegetation. Population declines and increases for species with similar habitat associations paralleled breeding habitat changes, providing evidence that factors on the breeding grounds are having a detectable effect on breeding birds in the northern Great Plains.

The Auk↗
USGS2002

Epizootiologic studies of avian vacuolar myelinopathy in waterbirds

Epizootic avian vacuolar myelinopathy (AVM) was first recognized as a neurologic disease in bald eagles (Haliaeetus leucocephalus) and American coots (Fulica americana) in Arkansas, USA in 1994 and 1996, respectively, but attempts to identify the etiology of the disease have been unsuccessful to date. Between 1998 and 2001, wing clipped sentinel birds (wild American coots and game farm mallards [Anas platyrhynchos]) were released at Lake Surf, North Carolina, a lake with recurrent outbreaks of AVM, in order to gain a better understanding of the epizootiology of the disease. As early as 5-7 days post-release, sentinel coots and mallards showed neurologic signs of disease and were confirmed with AVM upon histologic examination of their brains. Serial releases of sentinel mallards during the summer, fall, and winter of 2000-01 demonstrated that exposure to the causative agent at a threshold sufficient to manifest disease was seasonal and occurred over about a 2 mo period, during November and December. Our findings that disease onset can be very rapid (5-7 days) and that exposure to the causative agent of AVM is site-specific, seasonal (late fall to early winter), and occurs over a relatively short duration (several months) supports the hypothesis that the disease is caused by a chemical substance, most likely of natural origin.

North Carolina↗
USGS2008

Atlantic Flyway review: Region IV Piedmont-Coastal Plain, Fall 2007

Region IV welcomed another coastal station in 2007 with a report from Chris Snook at Charleston, South Carolina. The season was hot and dry throughout Region IV except in Florida where precipitation averaged above normal. Banders blamed their poor success on the lack of cold fronts in August, September, and the first half of October and on persistent strong east winds that blew the migrants farther inland. At Bill Baggs State Park in Miami no significant cold fronts were encountered until 25 Oct, and then on 29 Oct they banded over 100 Black-throated Blue Warblers that should have been on their West Indian wintering grounds by that date. Myrtle Warblers continued to be the most commonly banded species in Region IV, although numbers were down considerably from the previous autumn; their age ratios ranged from 25% hatching year (HY) at inland Tallahassee to 100% HY at coastal Chincoteague. Gray Catbird, which made the top ten list at all11 stations, was in second place, with percent of HYbirds ranging from 54% at Laurel to 95% at Chincoteague. Peak migration days ranged from 19 Sep in Laurel to 14 Nov at Kiptopeke, with five stations reporting their peak during 10-15 Oct. Thanks to the dedicated banders and assistants who contributed 61,825 net-hours in autumn 2007 to band 22,424 birds in Region IV. Thanks also to colleagues Deanna Dawson and John R. Sauer for their helpful comments.

North American Bird Bander↗
USGS2005

Atlantic Flyway review: Region IV, Piedmont-Coastal Plain, Fall 2004: Robbins Nest, Laurel, MD (390-0765)

The continuing decline in migratory species is depressing. For a 'migration station' to report Northern Cardinal as the species most commonly banded during the autumn months came as a real shock, especially when the cardinal was so far ahead of second-place catbird. I caught twice as many cardinals as all sparrows combined (including juncos), and the total for cardinals came within ten birds of the total for all warblers combined. Warblers comprised only 16.8% of this fall's catch, compared with an average of 21.7% for the previous five years. Hurricanes Bonnie and Frances passed to the east of us and Charles and Ivan to the west, but none was followed by a landfall of migrants. Last year I reported the sharp drop in Tufted Titmice and Carolina Chickadees locally and the small number of returns from prior years. This year, after no overwintering titmice, numbers have returned to nearly normal, but chickadee numbers are still only half normal. I recaptured cardinals from each year back to 1999, but the only other birds more than two years old were a Carolina Wren and two titmice banded in the autumn of 2000.

Maryland↗
USGS2014

Habitat availability is a more plausible explanation than insecticide acute toxicity for U.S. grassland bird species declines

Grassland bird species have experienced substantial declines in North America. These declines have been largely attributed to habitat loss and degradation, especially from agricultural practices and intensification (the habitat-availability hypothesis). A recent analysis of North American Breeding Bird Survey (BBS) “grassland breeding” bird trends reported the surprising conclusion that insecticide acute toxicity was a better correlate of grassland bird declines in North America from 1980–2003 (the insecticide-acute-toxicity hypothesis) than was habitat loss through agricultural intensification. In this paper we reached the opposite conclusion. We used an alternative statistical approach with additional habitat covariates to analyze the same grassland bird trends over the same time frame. Grassland bird trends were positively associated with increases in area of Conservation Reserve Program (CRP) lands and cropland used as pasture, whereas the effect of insecticide acute toxicity on bird trends was uncertain. Our models suggested that acute insecticide risk potentially has a detrimental effect on grassland bird trends, but models representing the habitat-availability hypothesis were 1.3–21.0 times better supported than models representing the insecticide-acute-toxicity hypothesis. Based on point estimates of effect sizes, CRP area and agricultural intensification had approximately 3.6 and 1.6 times more effect on grassland bird trends than lethal insecticide risk, respectively. Our findings suggest that preserving remaining grasslands is crucial to conserving grassland bird populations. The amount of grassland that has been lost in North America since 1980 is well documented, continuing, and staggering whereas insecticide use greatly declined prior to the 1990s. Grassland birds will likely benefit from the de-intensification of agricultural practices and the interspersion of pastures, Conservation Reserve Program lands, rangelands and other grassland habitats into existing agricultural landscapes.

PLoS ONE↗