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At least 217 records · Page 12Linked to original sources
USGS2002

Toward conservation of midcontinental shorebird migrations

Shorebirds represent a highly diverse group of species, many of which experience tremendous energy demands associated with long-distance migratory flights. Transcontinental migrants are dependent upon dynamic freshwater wetlands for stopover resources essential for replenishment of lipid reserves and completion of migration. Patterns of shorebird migration across midcontinental wetlands were detected from migration reports to American Birds and information provided by U.S. Fish and Wildlife Service national wildlife refuges. Patterns in species composition and abundance varied geographically, emphasizing the uniqueness of different regions to migrating shorebirds. Smaller species and neotropical migrants moved primarily across the Great Plains, whereas larger species and North American migrants predominated in assemblages in the intermountain west Shorebirds were broadly dispersed in wetland habitats with dynamic water regimes. Whereas populations of shorebirds in coastal systems appear to concentrate at sites of seasonally predictable and abundant food resources, we propose that transcontinental shorebirds disperse and use wetlands opportunistically. This migration system exemplifies the need for large-scale, coordinated regional management efforts that recognize the dynamic nature of ecosystem processes.

Conservation Biology↗
USGS2011

Severe bill deformity of an American Kestrel wintering in California

During a recent survey for West Nile virus in wild birds around the Sonny Bono Salton Sea National Wildlife Refuge, Imperial County, California (Dusek et al. 2010), we captured a female American Kestrel ( Falco sparverius ) with a severe bill deformity (Figure 1). The kestrel was captured on 9 March 2006, at 08:45, approximately 0.25 km south of the intersection of Wiest and Lindsey roads (33° 08' 42' N, 115° 26' 59' W) and 6 km east-northeast of Calipatria. It was caught on a bal-chatri trap baited with a domestic mouse (Berger and Mueller 1959), as were all the 208 kestrels captured during this study. The bird was initially perched on a high transmission line running along Wiest Road and was caught within 10 minutes of our setting the trap. In examining the bird, we observed that the maxilla beyond the cere was missing. The upper bill structure from the palatine process, which included part of the maxilla, the entire premaxilla, and the external rhamphotheca (the hardened keratin layer cover­ ing the premaxilla) was missing rostral to the bird's cere and nares (Threlfall 1968, Lucas and Stettenheim 1972, Proctor and Lynch 1993). The epidermal layer of the cere appeared to have fused over the remaining area between the nares where the upper bill normally would have been. The deformation did not appear to be recent or related to our trapping, as there were no obvious abrasions or open wounds in the region surrounding the nares and oropharynx or signs of recent trauma surrounding the oropharynx area. Both nares were clearly defined, and the tongue protruded from the open oropharynx area. After completing the physical examination, measurements, and obtaining a blood sample for testing for West Nile virus, we released the kestrel at the location of capture. After its release, we monitored the kestrel's behavior for approximately 30 minutes but did not observe any additional hunting.

California↗
USGS2024

An introduction to standardized sampling

In 2009, the first edition of Standard Methods for Sampling North American Freshwater Fishes was published. This was the first time in the history of fisheries science that standardization of methods and equipment had taken place on such a large geographic scale. Since its publication, the methods have been used extensively across North America by local, state, and federal agencies, organizations, and universities who have seen the advantages of large-scale data comparison. Authors have been invited to present these methods in other locations around the world to help with standard sampling programs on other continents. Now, with large-scale issues such as human-caused climate change, effects of landscape-scale regulations, and effects of habitat degradation continuing to increase in importance, the ability to compare data across wide regions and political boundaries, compare data over time, and collect data with improved accuracy and precision is more important than ever. This new edition of Standard Methods is sponsored by the American Fisheries Society (AFS), the U.S. Fish and Wildlife Service, and the Association of Fish and Wildlife Agencies (AFWA), with contributions by numerous state, provincial and federal agencies, and numerous academic institutions and nongovernmental organizations (NGOs). It is authored by over 100 experts in fisheries sampling from across Canada, Mexico, and the United States. Most techniques for water body types addressed in the first edition have been kept the same-in the interest of standardization over time; however, many important additions have been made. Like the first edition, these methods are designed for fish community assessments in North American aquatic systems (e.g., for this edition, lakes, ponds, rivers, and streams containing warmwater and coldwater species; the Great Lakes, wetlands, and cenotes). Although other methods may be available that better target a more specific size-group or species, these techniques were selected as most effective for general surveys of these systems and typically are the most effective for capturing the common fishes found in these waters.

Book chapter↗
USGS1994

Conservation reserve program: benefit for grassland birds in the northern plains

During the past few decades numbers of some species of upland-nesting birds in North America have declined. Duck species such as mallard (Anas platyrhynchos), northern pintail (A. acuta) and blue-winged teal (A. discors) have declined since the early 1970s and have remained low since 1985 (Caithamer et al. 1993). Some grassland-dependent nonwaterfowl species also have declined since 1966, as indicated by the North American Breeding Bird Survey (BBS) (Robbins et al. 1986). For prairie-nesting ducks, population declines can be attributed mostly to low recruitment, partially as a result of low nest success. Klett et al. (1988) concluded that nest success (probability of ≥1 egg of clutch hatches) in much of the U.S. Prairie Pothole Region was inadequate to maintain populations of the five most common upland-nesting duck species studied, and that predators were the most important cause of nest failure. Over the years, as grassland areas have been converted to cropland, ducks have concentrated their nesting in the remaining areas of available habitat, where predators such as red fox (Vulpes vulpes), striped skunk (Mephitis mephitis) and badger (Taxidea taxus) forage (Cowardin et al. 1983). The reasons for declining populations of grassland nonwaterfowl birds are not clear but the loss of suitable grassland-nesting habitat probably is an important factor. Currently, approximately 95 percent of the land in North Dakota is used for agricultural purposes, of which over 60 percent is used for annual crop production (Haugse 1990). Of the grassland that remains, 95 percent is used for livestock production. This probably had a severe impact on grassland bird species that seek idle grass cover for nesting. The 1985 and 1990 U.S. Farm Bills include provisions under the Food Security Act to fund a cropland-idling program called the Conservation Reserve Program (CRP). Over 36 million acres have been enrolled nationwide in the CRP since 1985 (Osborn 1993), and up to 25 percent of cropland in some counties has been converted primarily to grass. In North Dakota, nearly 3 million acres have been enrolled. Over 90 percent of the CRP plantings in North Dakota are grass and grass-legume mix composed primarily of wheatgrass (Agropyron spp.), smooth brome (Bromus inermis), alfalfa (Medicago saliva) and sweetclover (Melilotus spp.). Mixes of these species have been reported to attract high densities of nesting ducks (Duebbert and Kantrud 1974). According to the CRP provisions, the land must remain idle for the 10-year contract period, with the exception of emergency provisions for haying or grazing. CRP appears to have great potential for benefiting many species of grassland-nesting birds. There have been efforts to document the importance of the CRP to migratory birds in the Upper Great Plains of the U.S. Kantrud (1993) studied duck nest success in CRP cover and concluded that nest success was higher than in planted cover on U.S. Fish and Wildlife Service (FWS) Waterfowl Production Areas (WPAs). Johnson and Schwartz (1993a) measured the use of CRP fields by nonwaterfowl birds and reported that several species have responded positively by colonizing CRP fields. They concluded that CRP has the potential to help reverse the population declines of several species. We investigated the importance of CRP to upland-nesting ducks and certain other grassland-nesting birds. For ducks, we compared nest success in CRP cover with nest success in planted cover on WPAs in the same period (1992-93) and with that of an earlier period (1980-84). For nonwaterfowl, we used BBS data to compare the trends in populations of certain species found in CRP, for the periods 1966-86 (pre-CRP cover establishment) and 1987-92 (post-CRP cover establishment) in North Dakota.

North Dakota, South Dakota↗
USGS2022

Secretive marsh bird habitat relationships at mid-continent spring migration stopover sites

Despite several secretive marsh bird (SMB) species being listed as critically imperiled throughout the mid-continent of North America, limited information on SMB distribution and habitat use within primary migratory corridors results in uncertainty on contributions of wetlands in mid-latitude states toward their annual cycle needs. Our objectives were to quantify temporal patterns of SMB wetland occupancy during spring migration at a mid-latitude state and evaluate the relationships between SMB colonization probability and water-level management practices, and the resulting habitat conditions during spring migration. We conducted a 2-year, dynamic occupancy study (2013–2014) that included 6 rounds of repeated call-back surveys to detect the presence of 5 SMB species (i.e., Virginia rail [ Rallus limicola ], sora [ Porzana carolina ], king rail [ R. elegans ], least bittern [ Ixobrychus exilis ], and American bittern [ Botaurus lentiginosus ]) during spring (Apr–Jun) on 107 wetlands across 8 conservation areas and 4 national wildlife refuges throughout Missouri, USA. We detected sora most frequently, followed by least bittern, American bittern, Virginia rail, and king rail. Coefficient estimates indicated colonization probability for all species was positively associated with emergent vegetation cover and negatively associated with amount of open water. Open water was the only variable in the best supported model explaining American bittern site colonization, to which they were negatively associated. Virginia rail colonization had a strong positive association with vegetation height, whereas least bittern and sora site colonization were influenced positively by water depth and agriculture, respectively. Based on the habitat associations within and among SMB species identified in this study, wetland managers can tailor management strategies to optimize spring migration habitat for single- or multi-species objectives.

Missouri↗
USGS2005

Exposure to polybrominated diphenyl ethers (PBDEs): Changes in thyroid, vitamin A, glutathione homeostasis, and oxidative stress in American kestrels (Falco sparverius)

Polybrominated diphenyl ethers (PBDEs), a class of additive flame retardants, are temporally increasing in wildlife tissues and capable of disrupting normal endocrine function. We determined whether in ovo and post-hatch exposure of captive American kestrels ( Falco sparverius ) to environmentally relevant PBDEs alter thyroid, retinol, and oxidative stress measures. Control eggs were injected with safflower oil and subsequent nestlings fed the same vehicle; dosed eggs received PBDE congeners (BDE-47, -99, -100, -153), which mainly comprise the Penta-BDE commercial mixture, dissolved in safflower oil at concentrations (1500 ng/g total [Σ] PBDEs) approximating those in Great Lakes gull eggs. Nestlings hatching from dosed eggs were orally exposed for 29 days to variable ΣPBDE concentrations that are similar to levels reported in tissues of Great Lakes trout (100 ng/g). Treatment kestrels had lower plasma thyroxine (T 4 ), plasma retinol, and hepatic retinol and retinyl palmitate concentrations, but unaltered triiodothyronine (T 3 ) concentrations and thyroid glandular structure. BDE-47, -100, and -99 were negatively associated with plasma T 4 , plasma retinol (BDE-100, -99) and hepatic retinol (BDE-47). Despite an antioxidant-rich diet, PBDE exposure induced hepatic oxidative stress, particularly in females, with an increased hepatic GSSG:GSH ratio, a marginal increase in lipid peroxidation, and increased oxidized glutathione. Positive associations were found between concentrations of BDE-183 and thiols and, in males, between BDE-99 and reduced GSH, but a negative association occurred between BDE-99 and TBARS. Subsequently, concentrations of PBDE congeners in wild birds may alter thyroid hormone and vitamin A concentrations, glutathione metabolism and oxidative stress.

Toxicological Sciences↗
USGS2015

Introduction

This is the third iteration of the National Wildlife Health Center's (NWHC) field guide developed primarily to assist field managers and biologists address diseases they encounter. By itself, the first iteration, “Field Guide of Wildlife Diseases: General Field Procedures and Diseases of Migratory Birds,” was simply another addition to an increasing array of North American field guides and other publications focusing on disease in free-ranging wildlife populations. Collectively, those publications were reflecting the ongoing transition in the convergence of wildlife management and wildlife disease as foundational components within the structure of wildlife conservation as a social enterprise serving the stewardship of our wildlife resources. For context, it is useful to consider those publications relative to a timeline of milestones involving the evolution of wildlife conservation in North America.

Techniques and Methods↗
USGS2019

Validating the performance of occupancy models for estimating habitat use and predicting the distribution of highly-mobile species: A case study using the American black bear

Occupancy models have become a valuable tool for estimating wildlife-habitat relationships and for predicting species distributions. Highly-mobile species often violate the assumption that sampling units are geographically closed shifting the probability of occupancy to be interpreted as the probability of use. We used occupancy models, in conjunction with noninvasive sampling, to estimate habitat use and predict the distribution of a highly-mobile carnivore, the American black bear ( Ursus americanus ) in New Mexico, USA. The top model indicated that black bears use areas with higher primary productivity and fewer roads. The predictive performance of such models is rarely validated with independent data, so we validated our model predictions with 2-independent datasets. We first assessed the correlation between predicted and observed habitat use for 28 telemetry-collared bears in the Jemez Mountains. Predicted habitat use was positively correlated with observed use for all 3 years (2012: ρ = 0.81; 2013: ρ = 0.87; 2014: ρ = 0.90). We then predicted the probability of use within a cell where a bear mortality was documented using 2043 mortality locations from sport harvest, depredation, and vehicle collisions. The probability of habitat use at a mortality location was also positively correlated with observed use by the species (2012: ρ = 0.74; 2013: ρ = 0.89; 2014: ρ = 0.93). Our validation procedure supports the notion that occupancy models can be an effective tool for estimating habitat use and predicting the distribution of highly-mobile species when the assumption of geographic closure has been violated. Our findings may be of interest to studies that are estimating habitat use for highly-mobile species that are secretive or rare, difficult to capture, or expensive to monitor with other more intensive methods.

New Mexico↗
USGS2025

Assessing shifting technology in genetic monitoring of the North American plains bison Federal conservation herds

Human expansion is a major driver of both declining wildlife abundance and the contraction of species’ distributions, increasing the risk of genetic erosion and the need for genetic monitoring. Rapidly advancing technology has expanded the types of genetic data that are available for wildlife conservation. However, inferences from different genetic markers could result in different management decisions and, thus, must be considered carefully. Rebounding from near extinction in the early 1900s, the majority of North American plains bison ( Bison bison bison ) are managed as small and isolated herds. Microsatellite-based analyses have been used to inform management of the US Federal bison conservation herds since the early 2000s. Transitioning from monitoring with tens of multiallelic loci (e.g., microsatellite loci) to thousands of biallelic loci (e.g., single nucleotide polymorphisms [SNPs]) could increase genotyping efficiency and improve the precision of population genetic inference but would require an understanding of the inferential differences between genetic marker types. We compared microsatellite-based measures of genetic diversity, differentiation, and population structure for 20 bison conservation herds (17 Federal, 1 Tribal, 2 Canadian) to inference from SNP-based analyses for the Tribal herd and 15 of the Federal herds. Data from both genetic marker types found that all herds have remarkably high genetic diversity given the severity of the bottleneck from which these populations recovered, and that population structure was consistent with founding histories. Importantly, SNPs had greater power to describe differences in genetic diversity and groups of related herds, but only if analyses are based on 250 or more loci. Overall, we found that microsatellite and SNP data can provide comparable conservation insight, but SNPs must be carefully selected to ensure continuity in genetic monitoring and to achieve the increased precision in genetic diversity and differentiation among herds that we observed in this study.

Conservation Genetics↗
USGS2021

Estimates of abundance and harvest rates of female black bears across a large spatial extent

American black bears ( Ursus americanus ) are an iconic wildlife species in the southern Appalachian highlands of the eastern United States and have increased in number and range since the early 1980s. Given an increasing number of human-bear conflicts in the region, many management agencies have liberalized harvest regulations to reduce bear populations to socially acceptable levels. Wildlife managers need reliable population data for assessing the effects of management actions for this high-profile species. Our goal was to use DNA extracted from hair collected at barbed-wire enclosures (i.e., hair traps) to identify individual bears and then use spatially explicit capture-recapture methods to estimate female black bear density, abundance, and harvest rate. We established 888 hair traps across 66,678 km 2 of the southern Appalachian highlands in Georgia, North Carolina, South Carolina, and Tennessee, USA, in 2017 and 2018, arranged in 174 clusters of 2–9 traps/cluster. We collected 9,113 hair samples from those sites over 6 weeks of sampling, of which 1,954 were successfully genotyped to 462 individual female bears. Our spatially explicit estimator included a percent forest covariate to explain inhomogeneous bear density across the region. Densities ranged up to 0.410 female bears/km 2 and regional abundance was 5,950 (95% CI = 4,988–7,098) female bears. Based on hunter kill data from 2016 to 2018, mean annual harvest rates for females were 12.7% in Georgia, 17.6% in North Carolina, 17.6% in South Carolina, and 22.8% in Tennessee. Our estimated harvest rates for most states approached or exceeded theoretical maximum sustainable levels, and population trend data (i.e., bait-station indices) indicated decreasing growth rates since about 2009. These data suggest that the increased harvest goals and poor hard mast production over a series of prior years reduced bear population abundance in many states. We were able to obtain reasonable population abundance and density estimates because of spatially explicit capture-recapture methods, cluster sampling, and a large spatial extent. Continued monitoring of bear populations (e.g., annual bait-station surveys and periodic population estimation using spatially explicit methods) by state jurisdictions would help to ensure that population trajectories are consistent with management goals. © 2021 The Wildlife Society.

Georgia, North Carolina, South Carolina, Tennessee↗
USGS2017

Integrating Breeding Bird Survey and demographic data to estimate Wood Duck population size in the Atlantic Flyway

The U.S. Fish and Wildlife Service (USFWS) uses data from the North American Breeding Bird Survey (BBS) to assist in monitoring and management of some migratory birds. However, BBS analyses provide indices of population change rather than estimates of population size, precluding their use in developing abundance-based objectives and limiting applicability to harvest management. Wood Ducks ( Aix sponsa ) are important harvested birds in the Atlantic Flyway (AF) that are difficult to detect during aerial surveys because they prefer forested habitat. We integrated Wood Duck count data from a ground-plot survey in the northeastern U.S. with AF-wide BBS, banding, parts collection, and harvest data to derive estimates of population size for the AF. Overlapping results between the smaller-scale intensive ground-plot survey and the BBS in the northeastern U.S. provided a means for scaling BBS indices to the breeding population size estimates. We applied these scaling factors to BBS results for portions of the AF lacking intensive surveys. Banding data provided estimates of annual survival and harvest rates; the latter, when combined with parts-collection data, provided estimates of recruitment. We used the harvest data to estimate fall population size. Our estimates of breeding population size and variability from the integrated population model (N̄ = 0.99 million, SD = 0.04) were similar to estimates of breeding population size based solely on data from the AF ground-plot surveys and the BBS (N̄ = 1.01 million, SD = 0.04) from 1998 to 2015. Integrating BBS data with other data provided reliable population size estimates for Wood Ducks at a scale useful for harvest and habitat management in the AF, and allowed us to derive estimates of important demographic parameters (e.g., seasonal survival rates, sex ratio) that were not directly informed by data.

The Condor↗
USGS1993

Techniques for research into woodcocks: experiences and recommendations

We describe methods for the study of the American woodcock (Scolopax minor) at the Moosehorn National Wildlife Refuge. Described are techniques for the capture of particular age-sex cohorts during different times of the year, the aging and sexing, the evaluation of habitat components, and the estimation of population size. We describe successful and tried but rejected techniques with radio-telemetry for the study of survival and habitat use.

Biological Report↗
USGS2016

Off-road vehicles affect nesting behaviour and reproductive success of American Oystercatchers Haematopus palliatus

As human populations and associated development increase, interactions between humans and wildlife are occurring with greater frequency. The effects of these interactions, particularly on species whose populations are declining, are of great interest to ecologists, conservationists, land managers and natural resource policy-makers. The American Oystercatcher Haematopus palliatus , a species of conservation concern in the USA, nests on coastal beaches subject to various forms of anthropogenic disturbance, including aircraft overflights, off-road vehicles and pedestrians. This study assessed the effects of these human disturbances on the incubation behaviour and reproductive success of nesting American Oystercatchers at Cape Lookout National Seashore, on the Atlantic coast of the USA. We expanded on-going monitoring of Oystercatchers at Cape Lookout National Seashore by supplementing periodic visual observations with continuous 24-h video and audio recording at nests. Aircraft overflights were not associated with changes in Oystercatcher incubation behaviour, and we found no evidence that aircraft overflights influenced Oystercatcher reproductive success. However, Oystercatchers were on their nests significantly less often during off-road vehicle and pedestrian events than they were during control periods before the events, and an increase in the number of off-road vehicles passing a nest during incubation was consistently associated with significant reductions in daily nest survival (6% decrease in daily nest survival for a one-vehicle increase in the average number of vehicles passing a nest each day; odds ratio = 0.94; 95% confidence interval (CI) 0.90, 0.98) and hatching success (12% decrease in hatching success for a one-vehicle increase in the average number of vehicles passing a nest each day; odds ratio = 0.88; 95% CI 0.76, 0.97). Management of vehicles and pedestrians in areas of Oystercatcher breeding is important for the conservation of American Oystercatchers.

International Journal of Avian Science↗
USGS2019

Using pointing dogs and hierarchical models to evaluate American woodcock winter occupancy and densities

Use of dogs has increased for multiple wildlife research purposes ranging from carnivore scat detection to estimation of reptile abundance. Use of dogs is not particularly novel for upland gamebird biologists, and pointing dogs have been long considered an important research tool. However, recent advances in Global Positioning System (GPS) technology and the development of hierarchical modeling approaches that account for imperfect detection may improve estimates of occupancy and density of cryptic species such as the American woodcock (Scolopax minor; hereafter, woodcock). We conducted surveys for woodcock using a trained pointing dog wearing a GPS collar during the winters of 2010–2011 and 2011–2012 in East Texas, USA. We surveyed 0.5-km-radius circular plots ( n = 24; survey sites) randomly placed along secondary roads in Davy Crockett National Forest and on private timber property. Surveys lasted 1.5 hrs and were repeated 3–5 times each winter. We estimated woodcock occupancy and density using multiple modeling approaches at the survey site and forest stand scales within survey sites. Woodcock occupied 88% (21/24) of survey sites and 48% (39/82) of forest stands (i.e., unique cover types) within sites. Using a modified distance sampling technique, we estimated an average density of 0.16 birds/ha (SE = 0.13) throughout both study areas. We describe the first attempt to blend use of pointing dogs with hierarchical modeling approaches to derive estimates of regional diurnal woodcock occupancy and density, and describe relationships between these estimates of abundance and habitat covariates. Although forest stand occupancy estimates had the lowest coefficients of variation, our estimates of density provided the most useful inference of habitat use. Surveys using pointing dogs paired with hierarchical models of occupancy and density may provide a cost-efficient and effective approach to estimate habitat abundance at broad spatial scales.

Texas↗
USGS2014

Guidelines for use of fishes in research: Revised and expanded

The Guidelines for the Use of Fishes in Research (2014; 2014 Guidelines ), now available through the American fisheries Society (AFS) website and in print from the AFS bookstore, is a resource to aid researchers and regulatory authorities regarding responsible, scientifically valid research on fish and aquatic wildlife. The Guidelines for the Use of Fishes in Field Research (American Society of Ichthyologists and Herpetologists [ASIH] et al. 1987, 1988) emphasized field research and was followed by the 2004 Guidelines including laboratory research topics. Each version of the Guidelines has been jointly endorsed and/or published by the ASIH, the American Institute of Fishery Research Biologists (AIFRB), and AFS--each focusing on the scientific understanding, global conservation, and sustainability of aquatic animals, fisheries, and ecosystems. Changes with time necessitate revisions to make the Guidelines consistent with contemporary practices and scientific literature so to remain relevant as a technical resource. This document provides not only general principles relevant for field and laboratory research endeavors but includes specific requirements for researchers working within the United States and outside of the country. Within the scope of their expertise, the 2014 Uses of Fishers in Research (UFR) Committee members updated and revised sections, resulting in a 90-page 2014 Guidelines having undergone through peer review. As before, topical areas were addressed (see Table of Contents on page 416). Expanded coverage was provided on U.S. and international agencies and programs relevant to research with fishes. The Surgical Procedures and the Marking and Tagging section received special focus by a UFR Subcommittee. Feeds and Feeding and the Administration of Drugs, Biologics and Other Chemicals are just some of the newly added topics. The 2014 Guidelines is user-friendly by way of hyperlinks to external Internet sites, intradocument sections, and tables of acronyms with corresponding terms, low regulatory priority drugs, and Office of International des Epizooties notifiable disease agents. Again, the Institutional Animal Care and Use Committee (IACUC) role is explained, expectations for research are provided, and a brief checklist for IACUC readiness is included. Overall, the ,i>2014 Guidelines is the taxon-specific resource for our professional societies and is a principal document for standards on the care and use of fish and aquatic vertebrates in research.

Fisheries↗
USGS1990

North American Breeding Bird Survey Annual Summary, 1989

The North American Breeding Bird Survey (BBS) is run by approximately 2,000 skilled amateur ornithologists and is coordinated cooperatively by the U.S. Fish and Wildlife Service and the Canadian Wildlife Service. Since 1966, BBS cooperators have been collecting standardized information on North American bird populations. The BBS is a roadside survey, comprised of permanent routes that are surveyed yearly. Each route is 39.4 km (24.5 miles) long and consists of 50 stops spaced 0.8 km (0.5 mile) apart. All birds heard or seen during a 3-min observation period at each stop are recorded, and, for each species, the sum of the counts on individual stops is used as an index of species density on the route. Survey routes occur throughout the continental United States and most of Canada. Here, we present the population changes of the 251 bird species reported on the 50 or more BBS routes in the survey region during 1988 and 1989. Population trends for 1966-89 are presented for comparison. The direction and significance of population changes between the years for the 306 species occurring on 10 or more routes within States and Provinces are summarized in Appendix B. The pattern of population changes for selected species is graphically summarized on maps by physiographic stratum.

Biological Report↗