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American barn owls (Tyto furcata) often rely on nest box networks for breeding, especially within agricultural landscapes. Nest boxes are commonly installed for pest management purposes and require regular maintenance, such as removal of pellet debris and repairs, to remain functional and safe for breeding owls. Ideally, nest box maintenance should be conducted before the breeding season begins to minimize nest disturbance. The timing of the barn owl breeding season is especially important to understand in California, USA, which has a high diversity of ecoregions and expansive latitudinal range. Our objective was to describe the barn owl breeding season throughout California using nestling records to assist with data‐driven management recommendations. We queried 96 years of barn owl nestling banding records (n = 22,670) from the United States Geological Survey Bird Banding Lab to estimate egg laying dates across California and summarized 39 years of intake records (n = 1,741) from the California Raptor Center in the Central Valley. Our results suggest that barn owls typically begin to lay eggs in California in winter months; the median egg laying date for the state was 20 February. Based on these reports, planning for barn owl nest box maintenance to begin in fall (Sep–Nov) would align with the season that breeding activity and nest disturbance may be lowest, especially in the Central Valley and Southern Coast ecoregions. [ABSTRACT FROM AUTHOR]

Overwintering is a key demographic stage for migratory birds but remains poorly understood, especially among multiple declining grassland bird species. The non‐breeding ranges all 4 species of longspur (i.e., chestnut‐collared [Calcarius ornatus], Smith's [C. pictus], Lapland [C. lapponicus], thick‐billed [Rhynchophanes mccownii]) overlap in Oklahoma and the Texas Panhandle, USA, making this region ideal to study their wintering ecology. We evaluated the relationship between wintering longspur occurrence and fine‐scale habitat characteristics using a combination of standardized bird surveys and vegetation plot sampling. Our study encompassed large, representative tracts of 3 prairie ecosystems (i.e., shortgrass, mixed‐grass, and tallgrass prairies) that intersect within the Southern Great Plains, during winters of 2018–2019 and 2019–2020. Using randomization tests and classification trees, we characterized longspur habitats and compared these associations across the 3 prairie ecosystems. Fine‐scale winter habitats (horizontal structure, vertical structure, and species compositions) varied among all 4 longspur species, varied at very fine scales, and differed between grassland types. Our findings can be applied to the management of grasslands such as decreasing vegetation height in mixed‐grass prairies for chestnut‐collared longspurs or removing woody vegetation in shortgrass prairies for thick‐billed longspurs to help develop full‐life cycle conservation for longspurs, which have experienced population declines. [ABSTRACT FROM AUTHOR]

Sandhill cranes (Antigone canadensis) were broadly extirpated from much of their historical range in North America at the beginning of the twentieth century. Various conservation‐related legislation, such as the United States Migratory Bird Treaty Act, have assisted with population recovery. The eastern population of sandhill cranes has been growing rapidly since the 1980s and is thought to have expanded its geographic range to Quebec, Canada. Understanding the colonization and habitat use by the species in previously unoccupied breeding areas is necessary to develop and apply management measures. Using a dynamic occupancy modeling approach, we investigated the recent colonization and extirpation patterns of sandhill cranes in Quebec from 2004–2019. We combined data from 3 data sets (helicopter surveys, breeding bird atlas surveys, and eBird) to increase the spatial coverage and the number of species occurrence records while accounting for imperfect detection probability. Detection probability was highest for the helicopter survey (0.70), whereas the 2 other data sets had relatively low detection levels (0.10–0.26). Based on a simulation study, we found that excluding the eBird data from the analysis produced more biased estimates than excluding the atlas and helicopter survey data sets. Throughout the study, sandhill cranes seemed to have completed their colonization of western Quebec and only recently started to nest in eastern areas. Initial occupancy increased with wetland cover and colonization probability increased weakly with the cover of agricultural areas, suggesting that in our study area sandhill cranes rely essentially on natural wetlands during the breeding season. [ABSTRACT FROM AUTHOR]

Birds that inhabit open lands such as grasslands and shrublands are rapidly declining across North America. A common practice for multi‐species management is to focus on umbrella species whose habitat requirements overlap with several other species. We evaluated whether the northern bobwhite (Colinus virginianus; bobwhite) could serve as an umbrella species for open‐land birds in Ohio, USA. We related landscape metrics to abundance patterns and assessed whether bobwhite occupancy positively predicts presence of open‐land birds. We combined bird survey data from the second Ohio Breeding Bird Atlas (2006–2011) with land cover data from the 2011 National Land Cover Database (Homer et al. 2015) to construct single‐season N‐mixture models to identify landscape metrics that influence bobwhite abundance. Bobwhite abundance was positively predicted by forest cohesion, percent agriculture, percent barren, and percent grassland. Of the 34 focal species, bobwhites were a significant positive predictor for 12, and a significant negative predictor for 10. The model with only bobwhite occupancy probability as a predictor was the best supported model for only willow flycatcher (Empidonax traillii). These results suggest that bobwhite land cover type requirements are too specialized to meet the needs of broader species guilds, instead affording protection for a narrower range of individual species that share specific habitat requirements with bobwhites. Management for bobwhites may still be able to promote co‐occurrence for declining species across multiple guilds by identifying locations where focused management can create more suitable conditions for species with positive co‐occurrence. [ABSTRACT FROM AUTHOR]

ABSTRACT European rice fields provide potential nocturnal foraging habitat to waterfowl during winter. Agricultural practices may influence seed density and accessibility, thereby influencing the extent to which ducks use this managed habitat. To assess the potential influence of post-harvest stubble-management practices (i.e., flooding, burning, chopping, disking, plowing, and their combinations) on waste rice and weeds, and to evaluate the link of the latter 2 with nocturnal duck abundance, we conducted an experiment in rice fields of the Camargue, France. We assessed the density of available seeds 3 times across the winter, from harvest in late October to departure of the wintering ducks in early February, over 2 winters (2012-2013, 2013-2014). We monitored nocturnal duck use of the fields during the second year. Initial post-harvest rice and weed seed densities were positively correlated and highly variable. Mean seed density was not dependent on straw management procedure (i.e., burning, chopping, disking). Average rice density decreased by 89% and weed seed density by 69% between harvest and late winter. Seed depletion rate was dependent on initial seed density, and was greatest in plowed fields for rice. Winter flooding did not significantly affect seed depletion rate but was the main determinant of nocturnal duck use of the fields. Duck numbers were lower in burned fields than in chopped or disked fields. One hectare of rice field could support an average of 43 mallard ( Anas platyrhynchos)-sized ducks/day for the entire wintering season (i.e., 5,202 duck-energy days/ha) given initial post-harvest seed densities. Harvested rice fields have a great potential as nocturnal foraging habitat for wintering ducks in the Camargue. Plowing should be avoided and flooding promoted to better allow ducks to use these fields. © 2016 The Wildlife Society. [ABSTRACT FROM AUTHOR]

ABSTRACT The Northern Great Plains (NGP) contains much of the remaining temperate grasslands, an ecosystem that is one of the most converted and least protected in the world. Within the NGP, the Prairie Pothole Region (PPR) provides important habitat for >50% of North America's breeding waterfowl and many species of shorebirds, waterbirds, and grassland songbirds. This region also has high wind energy potential, but the effects of wind energy developments on migratory and resident bird and bat populations in the NGP remains understudied. This is troubling considering >2,200 wind turbines are actively generating power in the region and numerous wind energy projects have been proposed for development in the future. Our objectives were to estimate avian and bat fatality rates for wind turbines situated in cropland- and grassland-dominated landscapes, document species at high risk to direct mortality, and assess the influence of habitat variables on waterfowl mortality at 2 wind farms in the NGP. From 10 March to 7 June 2013-2014, we completed 2,398 searches around turbines for carcasses at the Tatanka Wind Farm (TAWF) and the Edgeley-Kulm Wind Farm (EKWF) in South Dakota and North Dakota. During spring, we found 92 turbine-related mortalities comprising 33 species and documented a greater diversity of species ( n = 30) killed at TAWF (predominately grassland) than at EKWF ( n = 9; predominately agricultural fields). After accounting for detection rates, we estimated spring mortality of 1.86 (SE = 0.22) deaths/megawatt (MW) at TAWF and 2.55 (SE = 0.51) deaths/MW at EKWF. Waterfowl spring (Mar-Jun) fatality rates were 0.79 (SE = 0.11) and 0.91 (SE = 0.10) deaths/MW at TAWF and EKWF, respectively. Our results suggest that future wind facility siting decisions consider avoiding grassland habitats and locate turbines in pre-existing fragmented and converted habitat outside of high densities of breeding waterfowl and major migration corridors. © 2016 The Wildlife Society. [ABSTRACT FROM AUTHOR]

ABSTRACT In Québec, Canada, the American black duck ( Anas rubripes) breeds mainly in the boreal forest to the north, but a small segment of the population breeds in southern Québec in the densely populated agricultural areas surrounding the St. Lawrence River and Estuary. This agricultural breeding population faces increasing pressure from urbanization, competition with mallards ( A. platyrhynchos), landuse changes, and hunting. In Québec, approximately 69% of black ducks are harvested in agricultural landscapes. Most birds harvested in Québec are taken in September, during the first 3 weeks of the hunting season, when birds breeding in the boreal habitat are unlikely to have initiated their southbound fall migration. This additional pressure on the agricultural breeding population could be detrimental to its long-term sustainability. We measured carbon (δ13C), nitrogen (δ15N), hydrogen (δD), and sulfur (δ34S) isotopic compositions of feathers from hatching-year black ducks of known natal origin (banded birds) and used these to develop a multivariate logistic regression classification model based on habitat type. We then applied this model to feathers from birds harvested in Québec during the fall sport hunt in those same years to determine their natal origin. Sixty percent in 2004 and 17% in 2005 of black ducks harvested during the fall sport hunt in Québec originated from the agricultural segment of the population, compared to 36% and 72% in those same years originating from the boreal area. This is in stark contrast to the species' distribution in Québec, with only approximately 4% of the population breeding in the agricultural portion of the province. Our results suggest that this harvest bias toward the agricultural segment of the breeding population, which may be accentuated in years when migration is delayed, could compromise its long-term sustainability. We highlight the importance of existing regional survey programs, and the information gaps that exist concerning the natal origin of black ducks harvested in the northeastern United States, and the annual productivity of the agricultural black duck population in Québec. Stable isotopes from samples of known natal origin (banded birds) proved an effective tool to identify the natal origin of hunted birds. However, we caution against the use of published isotopic thresholds (δ13C, δ15N) to infer the origin of migrating organisms in small study areas. © 2014 The Wildlife Society. [ABSTRACT FROM AUTHOR]

ABSTRACT The National Marsh Bird Monitoring Program is being initiated to document population trends with call-broadcast surveys. We examined effects of site-estimated vocalization density (birds calling per ha), breeding stage, call type, and sex differences on marsh bird response probability to improve marsh bird surveys. We conducted 335 broadcast surveys 10 m from 113 known Virginia rail (Rallus limicola) and sora ( Porzana carolina) nests in 10 wetlands over 2 breeding seasons (2010-2011) to determine important variables for predicting response probability. The odds of both species responding to broadcast increased as vocalization density increased. Recent nest predation decreased the odds of both species responding and increasing nest age additionally decreased sora response. Both species responded similarly to broadcast during egg laying, incubation, and hatching. In addition, we present methods to confirm nesting stage during broadcast surveys using vocalization type. Both species possess 1) calls that we detected exclusively during the pre-nesting phase but not prior to replacement clutches, which may indicate unpaired birds; and 2) calls detected exclusively during the late incubation through brooding stages, which may be useful for inferring nest success from broadcast surveys. Spectrogram analysis of recorded vocalizations showed that male Virginia rails responded to broadcast calls with louder (possibly related to approach distance), longer, and faster calls (hence higher detectability) than females. We recommend that marsh bird population estimates account for detectability biases in density, stage, and sex and use call type to infer nonbreeding status and nest fate. © 2014 The Wildlife Society. [ABSTRACT FROM AUTHOR]

Northern spotted owls ( Strix occidentalis caurina) have received intense research and management interest since their listing as a threatened species by the United States Fish and Wildlife Service in 1990. For example, public and private forest managers in the Pacific Northwest, USA, conduct surveys to determine presence or absence of spotted owls prior to timber harvest operations. However, although recently developed statistical methods have been applied to presence-absence data collected during research surveys, the effectiveness of operational surveys for detecting spotted owls and evaluating site occupancy dynamics is not known. We used spotted owl survey data collected from 1995 to 2009 on a study area in interior northern California, USA, to evaluate competing occupancy models from Program PRESENCE using Akaike's Information Criterion (AIC). During 1,282 individual surveys, we recorded 480 spotted owl detections (37.4%) and 13 barred owl (1.0%) detections. Average per visit detection probability (85% CL) for single and paired spotted owls was 0.93 (0.90-0.96) for informed daytime, stand-based searches and 0.47 (0.43-0.51) for nighttime, station-based surveys (estimated from the best model); the average per visit detection probability from the null model was 0.67 (0.64-0.70). Average pair-only detection probabilities were 0.86 (0.81-0.90) for informed daytime, stand-based searches and 0.23 (0.18-0.29) for nighttime, station-based surveys; the average per visit detection probability from the null model was 0.63 (0.58-0.68). Site occupancy for any owl declined from 0.81 (0.59-0.93) in 1995 to 0.50 (0.39-0.60) in 2009; pair occupancy declined from 0.75 (0.56-0.87) to 0.46 (0.31-0.61). Our results suggest that a combination of 1 informed stand and 2 station-based operational surveys can support determinations of spotted owl site status (either a single or a pair) at desired levels of confidence. However, our information was collected in an area where barred owls were rarely detected. Surveys conducted in areas that support well-established barred owl populations are likely to be less effective for determining presence or absence of spotted owls and may require more surveys and/or different survey methods to determine site status with confidence. © 2012 The Wildlife Society. [ABSTRACT FROM AUTHOR]

Spatial modeling over broad scales can potentially direct conservation efforts to areas with high species-specific abundances. We examined the performance of regional models for predicting bird abundance at spatial scales typically addressed in conservation planning. Specifically, we used point count data on wood thrush ( Hylocichla mustelina) and blue-winged warbler ( Vermivora cyanoptera) from 2 time periods (1995-1998 and 2006-2007) to evaluate the ability of regional models derived via Bayesian hierarchical techniques to predict bird abundance. We developed models for each species within Bird Conservation Region (BCR) 23 in the upper midwestern United States at 800-ha, 8,000-ha, and approximately 80,000-ha scales. We obtained count data from the Breeding Bird Survey and land cover data from the National Land Cover Dataset (1992). We evaluated predictions from the best models, as defined by an information-theoretic criterion, using point count data collected within an ecological subregion of BCR 23 at 131 count stations in the 1990s and again in 2006-2007. Competing (Deviance Information Criteria <5) blue-winged warbler models accounted for 67% of the variability and suggested positive associations with forest edge and proportion of forest at the 8,000-ha scale, and negative associations with forest patch area (800 ha) and wetness (800 ha and 80,000 ha). The regional model performed best for blue-winged warbler predicted abundances from point counts conducted in Iowa during 1995-1996 ( rs = 0.57; P = 0.14), the survey period that most closely aligned with the time period of data used for regional model construction. Wood thrush models exhibited positive correlations with point count data for all survey areas and years combined ( rs = 0.58, P ≤ 0.001). In comparison, blue-winged warbler models performed worse as time increased between the point count surveys and vintage of the model building data ( rs = 0.03, P = 0.92 for Iowa and rs = 0.13, P = 0.51 for all areas, 2006-2007), likely related to the ephemeral nature of their preferred early successional habitat. Species abundance and sensitivity to changing habitat conditions seems to be an important factor in determining the predictive ability of regional models. Hierarchical models can be a useful tool for concentrating efforts at the scale of management units and should be one of many tools used by land managers, but we caution that the utility of such models may decrease over time for species preferring relatively ephemeral habitats if model inputs are not updated accordingly. © 2012 The Wildlife Society. [ABSTRACT FROM AUTHOR]

Management of crested caracaras ( Caracara cheriway), focuses on nests identified during surveys. If no nests are found, management can be suspended. Thus, false negatives can have substantial consequences. We surveyed 49 breeding territories to assess factors with the potential to cause false negatives in detecting nests of crested caracaras and in observing adult birds. The probability that a nest would be detected on any given visit increased by about 0.5% for each hour of observer experience up to about 70 hours (our maximum). Experience did not affect the probability of observing an adult. The probability of detecting a caracara nest or observing an adult caracara decreased by 2.0-3.5% each hour after sunrise that a visit began. If visibility during any portion of a visit was obscured by fog or rain, the probability of detecting a nest decreased by as much as 60%, and the probability of observing an adult caracara decreased by about 50%. We provide a tool managers can use to calculate the likelihood of successful surveys. We recommend that managers disregard negative results from surveys conducted under conditions that are unlikely to yield positive results, and repeat those surveys under better conditions. © 2011 The Wildlife Society. [ABSTRACT FROM AUTHOR]

In a recently published article Sleep et al. () suggested that 30-yr declines in Canada warbler (1975-2005) based on Breeding Bird Survey (BBS) data could be attributed to 30-yr declines in spruce budworm through a series of analyses based principally on correlations. We demonstrate that the relationship does not hold when a longer-term data set (1968-2008) is used for the analysis. Sleep et al. () also demonstrated a positive relationship between correlations of Canada warbler abundance and time and spruce budworm defoliation and time using provincial data sets. We examined the underlying BBS data and found that there were insufficient observations of Canada warbler in the western provinces (Alberta and Manitoba) to support the conclusion because most Canada warbler observations occurred far (>100 km) from any budworm defoliation. As well, we used a density-dependent stochastic population growth model as proposed by Sleep et al. () and found only 2 significant relationships (Nova Scotia, Alberta) between Canada warbler population growth rate and budworm defoliation at the provincial scale. We conclude that little analytical evidence exists to support the idea that Canada warbler decline is a function of spruce budworm decline. © 2011 The Wildlife Society. [ABSTRACT FROM AUTHOR]

Bird electrocution on power lines is an important conservation problem that affects many endangered species. We surveyed 3,869 pylons in the Barcelona Pre-littoral Mountains (Catalonia, NE Spain) and collected 141 carcasses of electrocuted birds, mainly raptors and corvids. Univariate analysis indicated that metal pylons with pin-type insulators or exposed jumpers, with connector wires, located on ridges, overhanging other landscape elements, and in open habitats with low vegetation cover were the most dangerous. A logistic regression model indicated that the probability of a pylon electrocuting a bird was mainly related to pylon conductivity, distribution of the conductive elements on the cross-arms, cross-arm configuration, habitat, topography, whether the pylon was overhanging other landscape elements, and presence of rabbits (Oryctolagus cuniculus). We validated the predictive power of this model by using a random sample of 20% of all pylons surveyed. We found that bird mortality was aggregated mainly on pylons assigned a high probability risk by the model. Pylons included in the very high electrocution risk category (9.2%) accounted for 53.2% of carcasses, whereas pylons classified in the low electrocution risk category (54.5%) only accounted for 3.5% of mortality. Power companies employed this classification to prioritize the correction of 222 pylons by installing alternate cross-arms and suspended jumpers and isolating wires and jumpers. We evaluated the effectiveness of this mitigation strategy. A significant fall in the mortality rate on corrected pylons combined with the lack of any reduction in the mortality rate in a sample of 350 noncorrected pylons indicated that the model selected adequately the most dangerous pylons and that the applied correction measures wereeffective. Consequently, our strategy may be a useful tool for optimizing efforts and resources invested in solving the problem of bird electrocution. [ABSTRACT FROM AUTHOR]

The migratory population of the king rail (Rallus elegans) has declined dramatically during the past 40 years, emphasizing the need to identify habitat requirements of this species to help guide conservation efforts. To assess distribution and habitat use of king rails along the Illinois and Upper Mississippi valleys, USA, we conducted repeated call-broadcast surveys at 83 locations in 2006 and 114 locations in 2007 distributed among 21 study sites. We detected king rails at 12 survey locations in 2006 and 14 locations in 2007, illustrating the limited distribution of king rails in this region. We found king rails concentrated at Clarence Cannon National Wildlife Refuge, an adjacent private Wetlands Reserve program site, and B. K. Leach Conservation Area, which were located in the Mississippi River floodplain in northeast Missouri. Using Program PRESENCE, we estimated detection probabilities and built models to identify habitat covariates that were important in king rail site occupancy. Habitat covariates included percentage of cover by tall (>1 m) and short ( ⩽1 m) emergent vegetation, percentage of cover of woody vegetation, and interspersion of water and vegetation (2007 only) within 50 m of the survey location. Detection probability was 0.43 (SE = 0.12) in 2006 and 0.35 (SE = 0.03) in 2007 and was influenced by observer identity and percentage of cover by tall herbaceous vegetation. Site occupancy was 0.11 (SE = 0.04) in 2006 and 0.14 (SE = 0.04) in 2007 and was negatively influenced most by percentage of cover by woody vegetation. In addition, we found that interspersion of vegetation and water was positively related to occupancy in 2007. Thus, nesting king rails used wetlands that were characterized by high water-vegetation interspersion and little or no cover by woody vegetation. Our results suggest that biologists can improve king rail habitat by implementing management techniques that reduce woody cover and increase vegetation-water interspersion in wetlands. [ABSTRACT FROM AUTHOR]

We estimated survival rates of 135 female greater sage-grouse (Centrocercus urophasianus) on 3 study areas in southeastern Oregon, USA during autumn and winter for 3 years. We used known-fate models in Program MARK to test for differences among study areas and years, investigate the potential influence of weather, and compute estimates of overwinter survival. We found no evidence for differences in survival rates among study areas, which was contrary to our original hypothesis. There also were no declines in survival rates during fall-winter, but survival rates varied among years and time within years. Average survival rate from October through February was 0.456 (SE=0.062). The coefficient of variation for this estimate was 13.6% indicating good precision in our estimates of survival. We found strong evidence for an effect of weather (i.e., mean daily min. temp, extreme min. temp, snow depth) on bi-weekly survival rates of sage-grouse for 2 of the study areas in one year. Extremely low (<15°C) temperatures over an 8-week period and accumulation of snow had a negative effect on survival rates during the winter of 1990-1991 on the 2 study areas at the higher (>1,500 m) elevations. In contrast, we found no evidence for an influence of weather on the low-elevation study area or during the winters of 1989-1990 and 1991-1992. Extreme weather during winter can cause lower survival of adult female sage-grouse, so managers should be aware of these potential effects and reduce harvest rates accordingly. [ABSTRACT FROM AUTHOR]

Legal removal of migratory birds from the wild occurs for several reasons, including subsistence, sport harvest, damage control, and the pet trade. We argue that harvest theory provides the basis for assessing the impact of authorized take, advance a simplified rendering of harvest theory known as potential biological removal as a useful starting point for assessing take, and demonstrate this approach with a case study of depredation control of black vultures (Coragyps atratus) in Virginia, USA. Based on data from the North American Breeding Bird Survey and other sources, we estimated that the black vulture population in Virginia was 91,190 (95% credible interval = 44,520-212,100) in 2006. Using a simple population model and available estimates of life-history parameters, we estimated the intrinsic rate of growth (rmax) to be in the range 7-14%, with 10.6% a plausible point estimate. For a take program to seek an equilibrium population size on the conservative side of the yield curve, the rate of take needs to be less than that which achieves a maximum sustained yield (0.53 x rmax). Based on the point estimate for rmax and using the lower 60% credible interval for population size to account for uncertainty, these conditions would be met if the take of black vultures in Virginia in 2006 was <3,533 birds. Based on regular monitoring data, allowable harvest should be adjusted annually to reflect changes in population size. To initiate discussion about how this assessment framework could be related to the laws and regulations that govern authorization of such take, we suggest that the Migratory Bird Treaty Act requires only that take of native migratory birds be sustainable in the long-term, that is, sustained harvest rate should be

Indices to population size have come under increasing criticism in recent years, on the grounds that indices might not faithfully represent the entire population. Most criticisms involve surveys of birds, particularly those based on point counts, which is my focus here. A variety of quantitative methods have been developed to reduce the bias of point counts, such as distance sampling, multiple-observer surveys, and time-of-detection methods. I argue that these developments are valuable, in that they enhance understanding of the detection process, but that their practical application may well be limited, likely to intensive studies focusing on a small number of species. These quantitative methods are not generally applicable to extensive, multiple-species surveys. Although criticism of the thoughtless use of indices is welcome, their wholesale rejection is not. [ABSTRACT FROM AUTHOR]

Annual surveys of wildlife populations provide information about annual rates of change in populations but provide no information about when such changes occur. However, by combining data from 2 annual surveys, conducted in different parts of the year, seasonal components of population change can be estimated. We describe a hierarchical model for simultaneous analysis of 2 continent-scale monitoring programs. The Christmas Bird Count is an early winter survey, whereas the North American Breeding Bird Survey is conducted in June. Combining information from these surveys permits estimation of seasonal population variance components and improves estimation of long-term population trends. The composite analysis also controls for survey-specific sampling effects. We applied the model to estimation of population change in northern bobwhites (Colinus virginianus). Over the interval 1969-2004, bobwhite populations declined, with trend estimate of -3.56% per year (95% CI = [-3.80%, -3.32%]) in the surveyed portion of their range. Our analysis of seasonal population variance components indicated that northern bobwhite populations changed more in the winter and spring portion of the year than in the summer and fall portion of the year. [ABSTRACT FROM AUTHOR]

Detection distance is an important and common auxiliary variable measured during avian point count surveys. Distance data are used to determine the area sampled and to model the detection process using distance sampling theory. In densely forested habitats, visual detections of birds are rare, and most estimates of detection distance are based on auditory cues. Distance sampling theory assumes detection distances are measured accurately, but empirical validation of this assumption for auditory detections is lacking. We used a song playback system to simulate avian point counts with known distances in a forested habitat to determine the error structure of distance estimates based on auditory detections. We conducted field evaluations with 6 experienced observers both before and after distance estimation training. We conducted additional studies to determine the effect of height and speaker orientation (toward or away from observers) on distance estimation error. Distance estimation errors for all evaluations were substantial, although training reduced errors and bias in distance estimates by approximately 15%. Measurement errors showed a nonlinear relationship to distance. Our results suggest observers were not able to differentiate distances beyond 65 m. The height from which we played songs had no effect on distance estimation errors in this habitat. The orientation of the song source did have a large effect on distance estimation errors; observers generally doubled their distance estimates for songs played away from them compared with distance estimates for songs played directly toward them. These findings, which we based on realistic field conditions, suggest measures of uncertainty in distance estimates to auditory detections are substantially higher than assumed by most researchers. This means aural point count estimates of avian abundance based on distance methods deserve careful scrutiny because they are likely biased. [ABSTRACT FROM AUTHOR]

Bottomland hardwood forests of the southeastern United States support a rich avifauna, including >20 species of conservation concern; understanding the impact of land use practices on these communities is critical to their conservation. Selective timber harvesting is a common management practice in southern bottomland hardwood forests, but little research has examined impacts >5 years after harvesting. We studied breeding bird communities in selectively harvested bottomland forests in northeastern Louisiana during 2003-2004. We conducted point counts in recently harvested stands (1-5 yr postharvest) and older harvests (12-18 yr postharvest); we paired each with a reference stand that had not been harvested for >30 years. Of 35 species with sufficient detections for analysis, we found evidence that abundances of 17 species differed among treatments. Three species were sensitive to creation of canopy openings by timber harvests, including 2 species of concern in the Mississippi Alluvial Valley, USA, prothonotary warbler (Protonotaria citrea) and Acadian flycatcher (Empidonax virescens). However, 4 species of concern often associated with densely vegetated canopy gaps were more abundant in older harvests than in reference stands: Swainson's warbler (Limnothlypis swainsonii), hooded warbler (Wilsonia citrina), white-eyed vireo (Vireo griseus), and Kentucky warbler (Oporornis formosus). As expected, a suite of species typically associated with shrub and forest-edge habitats was more abundant in recent harvests than in reference stands. We conclude that selective logging has a strong influence on bird abundances in both recent and older harvests in bottomland forests. With the exception of Acadian flycatcher, older harvests and reference stands supported similar abundances of the species typically found in closed-canopy bottomland forests. In addition, older harvests supported substantially higher abundances of gap-dependent species than other treatments. Our results should be useful to land managers and conservation planners evaluating short- and long-term effects of timber management practices on breeding birds in the Mississippi Alluvial Valley. However, measures of breeding productivity are necessary to evaluate more fully the habitat quality of harvested forests. [ABSTRACT FROM AUTHOR]

We evaluated an unverified index (auditory counts) used to estimate breeding populations of white-winged doves (Zenaida asiatica) in Texas, USA, Our objectives were to determine optimal survey time of day, year, and count duration, determine it a relationship existed between number of calling doves and population size (nest and dove density), and evaluate an electronic counter to estimate breeding density. We collected data on 15 sites in the Lower Rio Grande Valley of Texas during May-August of 2002-2003. Peak calling occurred between mid-May and late June during 0600-0800 hours. We detected about 60% of calling doves during 2-minute auditory counts. Estimates of breeding doves (pairs ha-1) as determined by auditory counts were positively correlated with both population density (r > 0.90, P < 0.01) and nest density (r > 0.94, P < 0.01). The electronic coo-counter tally also exhibited a positive relationship with population density (r > 0.77, P < 0.01) and nest density (r > 0.92, P < 0.04). However, the high correlations observed for auditory counts and electronic counter were influenced by 2 high dove-density sites. Our data did not provide convincing support for the premise underlying auditory counts of white-winged doves (i.e., number of doves calling reflects dove abundance). The electronic coo counter was limited in application because it tabulated dove calls based solely on acoustic frequency and therefore could not discriminate against other avian calls with acoustic frequencies similar to those of white-winged doves. Auditory counts may be appropriate as coarse-resolution reconnaissance surveys to locate new white-winged dove areas in need of monitoring but not to obtain reliable abundance estimates. The use of an electronic counter to estimate breeding populations of white-winged doves holds promise, given technical modifications, and warrants further research. Given the current limitations of both auditory counts and electronic counters, alternative survey methods that incorporate detection probabilities (e.g., distance sampling) need to be evaluated for white-winged doves. [ABSTRACT FROM AUTHOR]

Understanding factors underlying nest-site selection is important for effective conservation and management of a declining and economically important species. We measured vegetation characteristics at nest sites of northern bobwhites (Colinus virginianus; hereafter, bobwhites) and at random points in the Texas Panhandle. We used these data to develop a neural network classification model for predicting nest-site suitability. We also compared the characteristics of successful nests with those of failed nests using the bootstrapping method. We monitored a subset of nests using video cameras during incubation and for 3 days postcompletion (succeeded or failed) to determine nest fate, cause of fate, and nest activity after completion. Nest-canopy height, percent shrub cover, and bare-ground exposure were important vegetation characteristics influencing nest-site selection. Sites became more suitable as canopy height exceeded 40 cm, shrub cover exceeded 25 %, and as bare-ground exposure fell below 30%. Successful nests had higher canopies and more shrub cover than failed nests, but successful nests had more bare ground than failed nests. Nest visits were common at monitored nests after nest completion (failed, successful). Most visitors were adult bobwhites, but other species also visited nests. Such visits might bias the determination of nest fate if the determination is based on nest remains, especially if nests are not monitored daily. Bobwhites might select nest sites to maximize nest concealment compared with random locations. [ABSTRACT FROM AUTHOR]

Bart et al (2004a) proposed several approaches for enhancing the considerable value of the Breeding Bird Survey (BBS). Sauer et al. (2005) critiqued some of these approaches, and emphasized alternative goals for the survey. We agree with many of the suggestions of Sauer et al. (2005); notably that multispecies, large-scale surveys such as the BBS are most valuable for bird conservation if they achieve multiple objectives. Nevertheless, we strongly assert that estimation of long-term trends is of fundamental importance for identifying important conservation issues and determining which species represent priorities for conservation efforts, as has been repeatedly demonstrated in the past. We are confident that our recommendations for enhancing the ability of the BBS to detect trends—reducing bias, explicitly recognizing that all bias cannot be eliminated, and increasing sample size in poorly covered areas—can only enhance, and not detract from, the value of the BBS for other purposes. [ABSTRACT FROM AUTHOR]

This article presents information on the effect of reward band value on mid-continent mallard band reporting rates. Reward band studies were used previously to estimate band-reporting rates. In an attempt to increase the band-reporting rate, in 1995 the U.S. Geological Survey Bird Banding Lab and the U.S. Fish and Wildlife Service (FWS) began using toll-free bands. The FWS places bands on waterfowl to obtain information about their vital rates, especially survival and harvest. Presumably toll-free bands are more convenient to report, which researchers expected would increase the reporting rate and reduce the monetary incentive required to achieve a reporting rate of 1. Indeed, the reporting rate for standard bands apparently increased to approximately 0.82. Subsequent to the 1998-2001 pilot studies, in 2002, a large-scale, reward-banding effort was initiated to provide a more comprehensive evaluation of variation in band reporting and harvest rates. The use of new toll-free bands dramatically increased reporting rates.

Chronic marine oil pollution is an ongoing global problem, yet no model currently exists to assess seabird mortality from continuous low-level inputs of oil. Taking into account persistence and detection rates of birds on beaches, and the wind-dependent proportion of birds lost at sea, we present a general mathematical Oiled Seabird Mortality Model (OSMM) to assess seabird mortality due to chronic oil pollution along a given coastline, using birds counted during systematic beached-bird surveys. We applied our OSMM to Newfoundland, Canada, where the incidence of chronic oil pollution is among the highest in world. We estimated that between 1998 and 2000, an average of 315,000 ± 65,000 murres (common [Uria aalge] and thick-billed [U. lomvia]) and doveldes (Alle alle) were killed annually in southeastern Newfoundland due to illegal discharges of oil from ships. Thick-billed murres that overwinter on the Grand Banks made up 67% of this kill. This species already is subject to extensive summer and winter hunting in Greenland, as well as winter hunting in Newfoundland, which harvests an additional 250,000-300,000 birds/year. Although populations remain stable, these levels of sustained mortality make thick-billed murre populations vulnerable to pulse perturbations and ocean regime shifts and hamper our ability to set harvest at sustainable levels. [ABSTRACT FROM AUTHOR]

Reliable estimates of trends in population size are critical to effective management of landbirds. We propose a standard for considering that landbird populations are adequately monitored: 80% power to detect a 50% decline occurring within 20 years, using a 2-tailed test and a significance level of 0.10, and incorporating effects of potential bias. Our standard also requires that at least two-thirds of the target region be covered by the monitoring program. We recommend that the standard be achieved for species' entire ranges or for any area one-third the size of the temperate portions of Canada and the United States, whichever is smaller. We applied our approach to North American Breeding Bird Survey (BBS) data. At present, potential annual bias for the BBS is estimated at ±0.008. Further, the BBS achieves the monitoring standard for only about 42% of landbirds for which the BBS is considered the most effective monitoring approach. Achieving the proposed monitoring target for ≥80% of these species would require increasing the number of BBS--or similar survey--routes by several-fold, a goal that probably is impractical. We suggest several methods for reducing potential bias and argue that if our methods are implemented, potential bias would fall to ±0.003. The required number of BBS or similar routes would then be 5,106, about 40% more than in the current BBS program. Most of the needed increases are in 15 states or provinces. Developing a comprehensive landbird monitoring program will require increased support for coordination of the BBS (currently 2 people) and new programs for species that are poorly covered at present. Our results provide a quantitative goal for long-term landbird monitoring and identify the sample sizes needed, within each state and province, to achieve the monitoring goal for most of the roughly 300 landbird species that are well suited to monitoring with the BBS and similar surveys. [ABSTRACT FROM AUTHOR]

Deals with a study which evaluated the use of the North American Breeding Bird Survey (BBS) to meet information needs for conservation planning in bird conservation regions. Background on BBS; Methods; Results; Discussion; Implications for wildlife management.