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USGS2010

Conserving migratory land birds in the New World: Do we know enough?

Migratory bird needs must be met during four phases of the year: breeding season, fall migration, wintering, and spring migration; thus, management may be needed during all four phases. The bulk of research and management has focused on the breeding season, although several issues remain unsettled, including the spatial extent of habitat influences on fitness and the importance of habitat on the breeding grounds used after breeding. Although detailed investigations have shed light on the ecology and population dynamics of a few avian species, knowledge is sketchy for most species. Replication of comprehensive studies is needed for multiple species across a range of areas. Information deficiencies are even greater during the wintering season, when birds require sites that provide security and food resources needed for survival and developing nutrient reserves for spring migration and, possibly, reproduction. Research is needed on many species simply to identify geographic distributions, wintering sites, habitat use, and basic ecology. Studies are complicated, however, by the mobility of birds and by sexual segregation during winter. Stable-isotope methodology has offered an opportunity to identify linkages between breeding and wintering sites, which facilitates understanding the complete annual cycle of birds. The twice-annual migrations are the poorest-understood events in a bird's life. Migration has always been a risky undertaking, with such anthropogenic features as tall buildings, towers, and wind generators adding to the risk, Species such as woodland specialists migrating through eastern North America have numerous options for pausing during migration to replenish nutrients, but some species depend on limited stopover locations. Research needs for migration include identifying pathways and timetables of migration, quality and distribution of habitats, threats posed by towers and other tall structures, and any bottlenecks for migration. Issues such as human population growth, acid deposition, climate change, and exotic diseases are global concerns with uncertain consequences to migratory birds and even lesscertain remedies. Despite enormous gaps in our understanding of these birds, research, much of it occurring in the past 30 years, has provided sufficient information to make intelligent conservation efforts but needs to expand to handle future challenges. ?? 2010 by the Ecological Society of America.

Ecological Applications↗

USGS2015

Ecology and conservation of North American sea ducks

The past decade has seen a huge increase in the interest and attention directed toward sea ducks, the Mergini tribe. This has been inspired, in large part, by the conservation concerns associated with numerical declines in several sea duck species and populations, as well as a growing appreciation for their interesting ecological attributes. Reflecting the considerable research recently conducted on this tribe, Ecology and Conservation of North American Sea Ducks examines the 15 extant species of sea ducks from North America. Chapters are organized conceptually to focus on, compare, and contrast the ecological attributes of the tribe. Experts provide in-depth treatments of a range of topics, including: Population dynamics and genetics Infectious diseases and parasites Breeding costs and cross-seasonal affects Contaminant burdens Foraging behavior and energetics Migration strategies, molt ecology, and habitat affinities and dynamics Breeding systems and reproductive behavior Harvest history The book presents a comprehensive synthesis of sea duck ecology, documents factors that have caused population declines of some species, and provides managers with measures to enhance recovery of depressed populations of sea ducks in North America. Capturing the current state of knowledge of this unique tribe, it provides a benchmark for where we are in conservation efforts and suggests future directions for researchers, managers, students, conservationists, and avian enthusiasts.

Book↗

USGS2025

U.S. Geological Survey science strategy to address highly pathogenic avian influenza and its effects on wildlife health 2025–29

Executive Summary Highly pathogenic avian influenza (HPAI) is an ecologically and economically important animal disease that can also directly affect humans (a “zoonotic” disease). HPAI was once limited almost exclusively to domestic poultry but has rapidly adapted to diverse animal hosts. Viruses causing HPAI now appear to be maintained and dispersed by wild birds largely independent of poultry, though HPAI continues to cause considerable economic losses and supply chain disruptions in the domestic poultry trade. Coincident with the adaptation of HPAI viruses to wild birds, particularly waterfowl and gulls, increasingly diverse wild bird hosts are becoming exposed to HPAI, often resulting in disease and death. More sporadically, HPAI has caused mass mortality events, particularly among seabirds. Furthermore, viral spillover to wild and domestic mammals has become more common. Spillover to wild mammals has resulted in mortality among diverse terrestrial and marine taxa, including episodic losses of such scale as to represent potential conservation challenges. Since approximately March 2024, HPAI has also affected dairy cows, which represents a new threat to the agricultural economy. Lastly, HPAI has increasingly affected humans through domestic animal exposures, exemplifying the considerable implications of this disease beyond animal health. Rapid changes in the ecology of HPAI are currently outpacing research efforts. For example, it is not entirely clear which newly established hosts may become reservoirs for HPAI viruses (in other words, capable of maintaining HPAI viruses within a broad population indefinitely) and how this may influence viral evolution and dissemination. As a result, there are considerable information gaps regarding HPAI in wildlife that, if filled, would improve the ability of scientists, managers, agricultural industry representatives, and healthcare professionals to understand and to anticipate the effects of HPAI on wild animal, domestic animal, environmental, and human health (“One Health”). The U.S. Geological Survey (USGS) is the lead Federal agency providing scientific research on avian influenza viruses (AIVs), including HPAI viruses, that affect wildlife for which the Department of the Interior (DOI) has management authority. States have jurisdiction over wildlife on Federal lands within their borders (43 CFR § 24.3), so the USGS Ecosystems Mission Area (EMA) coordinates with State natural resource management agencies. The EMA focuses its research on HPAI through priorities identified by the USGS Avian Influenza Science Team ( app. 1 ). Priorities identified by the USGS Avian Influenza Science Team are based on Administration priorities, Congressional direction, and discussions with State, Federal, and Tribal natural resource management agencies that identify specific scientific gaps that need to be filled to inform sound wildlife management decisions. Notable non-DOI Federal partners include the U.S. Department of Agriculture, the lead for the HPAI regulatory response in poultry and livestock, and the Centers for Disease Control and Prevention (CDC), the lead agency for the HPAI response pertaining to human health. The USGS offers unique expertise and capacity pertaining to research on diseases affecting free-ranging wildlife populations. This expertise has been critical to interjurisdictional surveillance and capacity-building efforts, including programs administered by the U.S. Department of Agriculture and the CDC. The USGS also provides resources, guidance, and tools to inform surveillance and interventions conducted by natural resource management agencies. More specifically, the USGS EMA provides objective and rigorous scientific data for inferring (1) the utility of new methods to detect and characterize AIVs, including those maintained in wildlife and the environment; (2) effects of HPAI on wildlife; (3) spatiotemporal patterns of wildlife host and AIV dispersal; (4) the presence and persistence of AIVs in the environment; (5) how HPAI in wildlife influences consumptive and nonconsumptive utilization of wildlife; (6) how new tools and scientific methods may promote sound management decisions for HPAI-affected wildlife, particularly species of conservation concern; and (7) the combined effects of HPAI and other stressors on ecosystem health and resiliency. This science strategy builds upon research outlined in a previous USGS science strategy for HPAI (2016–20) by Harris and others (2016) . This strategy also details research priorities identified by the Administration (for example, U.S. Department of Agriculture, 2025 ) and others based on USGS Avian Influenza Science Team discussions with natural resource management agencies to address HPAI and wildlife health over the next 5 years (2025–29). This strategy presents 7 goals and 26 objectives that focus USGS and partner efforts on priorities that will fill data gaps regarding the effects of HPAI on wildlife managed by or co-managed with the U.S. Department of the Interior such that agencies and partners might anticipate or limit adverse effects on public resources. This strategy also identifies research priorities intended to address HPAI in wildlife and wildlife habitat that are anticipated to support interjurisdictional One Health efforts.

Circular↗

USGS2022

Red knot stopover population size and migration ecology at Delaware Bay, USA, 2022

Red Knots (Calidris canutus rufa) stop at Delaware Bay on the mid-Atlantic coast of North America during northward migration to feed on eggs of horseshoe crabs (Limulus polyphemus). In the late 1990s and early 2000s, the number of Red Knots found at Delaware Bay declined from ~50,000 to ~13,000. Horseshoe crabs have been harvested for use as bait in eel (Anguilla rostrata) and whelk (Busycon) fisheries since at least 1990, and some avian conservation biologists hypothesized that horseshoe crab harvest levels in the 1990s prevented sufficient refueling for successful migration to the breeding grounds, nesting, and survival for the remainder of the annual cycle. Since 2013, the harvest of horseshoe crabs in the Delaware Bay region has been managed using an Adaptive Resource Management (ARM) framework. The objective of the ARM framework is to manage sustainable harvest of Delaware Bay horseshoe crabs while maintaining ecosystem integrity and supporting Red Knot recovery with adequate stopover habitat for Red Knots and other migrating shorebirds. For annual harvest recommendations, the ARM framework requires annual estimates of horseshoe crab population size and the Red Knot stopover population size. We conducted a mark-recapture-resight investigation to estimate the passage population of Red Knots at Delaware Bay in 2022. We used a Bayesian analysis of a Jolly-Seber model, which accounts for turnover in the population and the probability of detection during surveys. The 2022 Red Knot mark-resight dataset

Delaware, New Jersey↗

USGS2025

Disease-driven collapse of the native Kauaʻi avifauna and the rise of introduced bird species

Hawaii hosts one of Earth’s most unique and threatened avifaunas. Upslope migration of mosquito-vectored avian malaria on Kauaʻi (maximum elevation 1,598 m) has likely caused its rapid loss of avifaunal diversity; only 8 of 13 historic forest bird species remain. We update the status and trends of Kauaʻi forest bird populations since the original (1981) surveys using the latest (2023) survey data and distance sampling. We fit detection functions to species-specific count data and stratified estimates across the Interior (since 1981) and Exterior (since 2000) survey areas, and between low (900–1,100 m), medium (1,100–1,300 m) and high (> 1,300 m) elevation bands (since 2000). Log-linear trends of ʻakekeʻe ( Loxops caeruleirostris ), ʻanianiau ( Magumma parva ), ʻiʻiwi ( Drepanis coccinea ), and Kauaʻi ʻamakihi ( Chlorodrepanis stejnegeri ) steeply declined across the timeseries, with extinction of ʻakekeʻe and ʻiʻiwi expected before 2050. Undetected in 2023, ʻakikiki ( Oreomystis bairdi ) were excluded from analysis. ʻApapane ( Himatione sanguinea ), Kauaʻi ʻelepaio ( Chasiempis sclateri ), Chinese hwamei ( Garrulax canorus ), and white-rumped shama ( Copsychus malabaricus ) were stable overall. Northern cardinal ( Cardinalis cardinalis ) steadily declined, whereas Japanese bush warbler ( Horornis diphone ) and warbling white-eye ( Zosterops japonicus ) exponentially increased. Taxonomic and functional diversity did not vary greatly across our timeseries, while the proportion of introduced species in the Exterior increased from 34 to 59%. However, introduced species do not replace the losses of ecological functions from native species, whose populations are likely declining from avian malaria. Future monitoring can be used to evaluate forest bird population responses to mosquito suppression using the Incompatible Insect Technique.

Hawaii↗

USGS2019

Influence of forest harvest severity and time since perturbation on conservation of North American birds

I calculated avian conservation scores, based on published quantitative assessment of bird presence (typically relative abundance) and regional Partners in Flight conservation concern score of each species. I related these avian conservation scores to severity of forest perturbation (i.e., % retention) and number of years since perturbation for forest stands within North America. I characterized avian response to perturbation by comparing avian conservation score on perturbed stands with that of paired unperturbed reference stands. Positive avian response to perturbation, representative of improved avian conservation status, was found when forest retention was >20% of coniferous forests or 25%–75% of hardwood forests. Positive avian response was greatest ~10 years after perturbation that retained 58% of conifer forests or 49% of hardwood forests. Increased avian conservation scores following perturbation may last for up to 23 years after perturbation but occur and diminish sooner with greater forest retention. Average annual avian response, over 23 years post-perturbation, was greatest when 30%–50% of hardwood stands were retained and when 50%–70% of conifer stands were retained.

Forest Ecology and Management↗

USGS2002

Avian response to bottomland hardwood reforestation: The first 10 years

Bottomland hardwood forests were planted on agricultural fields in Mississippi and Louisiana predominantly using either Quercus species (oaks) or Populus deltoides (eastern cottonwood). We assessed avian colonization of these reforested sites between 2 and 10 years after planting. Rapid vertical growth of cottonwoods (circa 2–3 m/year) resulted in sites with forest structure that supported greater species richness of breeding birds, increased Shannon diversity indices, and supported greater territory densities than on sites planted with slower-growing oak species. Grassland birds ( Spiza americana [Dickcissel] and Sturnella magna [Eastern Meadowlark]) were indicative of species breeding on oak-dominated reforestation no more than 10 years old. Agelaius phoeniceus (Red-winged Blackbird) and Colinus virginianus (Northern Bobwhite) characterized cottonwood reforestation no more than 4 years old, whereas 14 species of shrub-scrub birds (e.g., Passerina cyanea [Indigo Bunting]) and early-successional forest birds (e.g., Vireo gilvus [Warbling vireo]) typified cottonwood reforestation 5 to 9 years after planting. Rates of daily nest survival did not differ between reforestation strategies. Nest parasitism increased markedly in older cottonwood stands but was overwhelmed by predation as a cause of nest failure. Based on Partners in Flight prioritization scores and territory densities, the value of cottonwood reforestation for avian conservation was significantly greater than that of oak reforestation during their first 10 years. Because of benefits conferred on breeding birds, we recommend reforestation of bottomland hardwoods should include a high proportion of fast-growing early successional species such as cottonwood.

Restoration Ecology↗

USGS2019

Evaluating community-level response to management actions across a diverse Hawaiian forest bird community

Although species‐specific approaches are necessary to understand the dynamics of individual species composing a community, they do not offer a framework for making optimal management decisions at the community level. Here, we present a simple framework for comparing the response of entire communities to multiple management scenarios. Our approach uses a weighted average of standardized species‐specific responses to produce a single integrative measure of the community response and employs mixed‐effect linear models to quantify the increase in the community response due to each management action, or combination of actions. We demonstrate our approach with a simulation study assessing the potential benefits of multiple management actions on the avian community of Hakalau Forest National Wildlife Refuge, Hawaiʻi, which is composed of eight native species with conservation status varying from endangered to least concern. Management actions considered included a reduction of avian malaria transmission risk, reducing rat predation, and increasing forest habitat. We used three different prioritization (weighting) schemes to assess whether the response to management actions differed along a conservation gradient (from endangered to least concern). We also investigated whether future changes in disease distribution as a result of climate change will alter the relationship between management practices and community response. Our community‐level analysis produced three important insights, highlighting the need to consider the response from multiple species to changing threats and management actions. First, increasing the amount of habitat always had the greatest positive impact on the avian community, regardless of the weighting scheme. Second, the community response to management was different under current vs. future conditions, with increased benefit in the future when disease risks were higher. Third, the response to management varied along the conservation gradient. Reducing malaria transmission risk in 2100 had the greatest benefit to endangered species, while increasing forest habitat had the greatest benefit to “least concern” species. However, reducing rat predation appeared to benefit a subset of species based on ecological factors unrelated to rarity, such as nest accessibility. Our approach is widely applicable using experimental, observational, or simulation‐based data, allowing managers to consider the response of all species while weighting their priority levels.

Hawaii↗

USGS2016

Flexible risk metrics for identifying and monitoring conservation-priority species

Region-specific conservation programs should have objective, reliable metrics for species prioritization and progress evaluation that are customizable to the goals of a program, easy to comprehend and communicate, and standardized across time. Regional programs may have vastly different goals, spatial coverage, or management agendas, and one-size-fits-all schemes may not always be the best approach. We propose a quantitative and objective framework for generating metrics for prioritizing species that is straightforward to implement and update, customizable to different spatial resolutions, and based on readily available time-series data. This framework is also well-suited to handling missing-data and observer error. We demonstrate this approach using North American Breeding Bird Survey (NABBS) data to identify conservation priority species from a list of over 300 landbirds across 33 bird conservation regions (BCRs). To highlight the flexibility of the framework for different management goals and timeframes we calculate two different metrics. The first identifies species that may be inadequately monitored by NABBS protocols in the near future (TMT, time to monitoring threshold), and the other identifies species likely to decline significantly in the near future based on recent trends (TPD, time to percent decline). Within the individual BCRs we found up to 45% (mean 28%) of the species analyzed had overall declining population trajectories, which could result in up to 37 species declining below a minimum NABBS monitoring threshold in at least one currently occupied BCR within the next 50 years. Additionally, up to 26% (mean 8%) of the species analyzed within the individual BCRs may decline by 30% within the next decade. Conservation workers interested in conserving avian diversity and abundance within these BCRs can use these metrics to plan alternative monitoring schemes or highlight the urgency of those populations experiencing the fastest declines. However, this framework is adaptable to many taxa besides birds where abundance time-series data are available.

Ecological Indicators↗

USGS2000

Relative species richness and community completeness: avian communities and urbanization in the mid-Atlantic states

The idea that local factors govern local richness has been dominant for years, but recent theoretical and empirical studies have stressed the influence of regional factors on local richness. Fewer species at a site could reflect not only the influence of local factors, but also a smaller regional pool. The possible dependency of local richness on the regional pool should be taken into account when addressing the influence of local factors on local richness. It is possible to account for this potential dependency by comparing relative species richness among sites, rather than species richness per se. We consider estimation of a metric permitting assessment of relative species richness in a typical situation in which not all species are detected during sampling sessions. In this situation, estimates of absolute or relative species richness need to account for variation in species detection probability if they are to be unbiased. We present a method to estimate relative species richness based on capture-recapture models. This approach involves definition of a species list from regional data, and estimation of the number of species in that list that are present at a site-year of interest. We use this approach to address the influence of urbanization on relative richness of avian communities in the Mid-Atlantic region of the United States. There is a negative relationship between relative richness and landscape variables describing the level of urban development. We believe that this metric should prove very useful for conservation and management purposes because it is based on an estimator of species richness that both accounts for potential variation in species detection probability and allows flexibility in the specification of a 'reference community.' This metric can be used to assess ecological integrity, the richness of the community of interest relative to that of the 'original' community, or to assess change since some previous time in a community.

Delaware, Maryland, New Jersey, New York, Pennsylv↗

USGS2009

Progress Report: Stratton Ecological Research Site - An Experimental Approach to Assess Effects of Various Grazing Treatments on Vegetation and Wildlife Communities Across Managed Burns and Habitat Controls

Understanding how management practices affect wildlife is fundamental to wise decisions for conservation of public lands. Prescribed fire and grazing timing are two management tools frequently used within publicly owned sagebrush ecosystems. We conducted a variety of surveys in order to assess the impacts of grazing timing strategies (early summer before peak green-up, mid-summer at peak green-up, and late summer after peak green-up) in conjunction with prescribed fire on avian and small mammal populations in a high-elevation sagebrush ecosystem. Avian surveys resulted in a large detection sample size for three bird species: Brewer's sparrow (Spizella breweri), horned lark (Eremophila alpestris), and vesper sparrow (Pooecetes gramineus). Brewer's sparrows had the lowest number of detections within the mid-summer grazing treatment compared to early and late summer grazing treatments, while horned larks and vesper sparrows had higher detection frequencies within the late summer grazing treatment. Summer and fall sage-grouse (Centrocercus urophasianus) pellet counts revealed that the greatest over-winter and over-summer use by sage-grouse occurred within the early summer grazing treatment with minimal use of burn treatment areas across all grazing treatments. Deer-mice (Peromyscus maniculatus) represented approximately 90 percent of small mammals captured and were most prevalent within the mid-summer grazing treatment. Sagebrush cover was greatest within the mid-summer grazing treatment. We monitored 50 and 103 nests in 2007 and 2008, respectively. The apparent success rate for shrub-obligate nesting species was 58 percent in 2007 and 63 percent in 2008. This research will support management of sagebrush ecosystems by providing public land managers with direct comparisons of wildlife response to management regimes.

Open-File Report↗

USGS2023

Disparate data streams together yield novel survival estimates of Alaska-breeding Whimbrels

Survival estimates are critical components of avian ecology. In well-intentioned efforts to maximize the utility of one's research, survival estimates often derive from data that were not originally collected for survival assessments, and such post hoc analyses may include unintentional biases. We estimated the survival of Whimbrels captured and marked at two breeding sites in Alaska using divergent data streams that in isolation were subject to methodological biases. Although both capture sites were chosen to study the migration ecology of Alaska-breeding Whimbrels, maximizing the conservation value of the data we collected was obviously desirable. We used multi-year telemetry information to infer survival from one site (Colville River) and mark-resight techniques to estimate survival from a second site (Kanuti River). At the Colville River, we could not feasibly include a control group of birds to assess potential survival effects of externally mounted transmitters, while at Kanuti River we were unable to accurately account for potential emigration events because we used resightings alone. We integrated these datasets in a Bayesian hierarchical framework, an approach that permitted insights across sites that moderated methodological biases within sites. Using telemetry enabled us to detect permanent emigration events from breeding sites in two of ten birds; results that informed estimates for birds without tracking devices. These datasets yielded point estimates of true survival of Whimbrels from Colville River equipped with solar-powered satellite transmitters that were higher (0.83) than true survival estimates of Whimbrels from Kanuti River marked with leg flags alone (0.74) or equipped with surgically implanted satellite transmitters (0.50), but the 95% credible intervals on these estimates overlapped across groups. For species like Whimbrels that are difficult and costly to study, combining information from disparate data streams allowed us to derive novel demographic estimates, an approach with clear application to other similar studies.

Alaska↗

USGS2007

Using conservation value to assess land restoration and management alternatives across a degraded oak savanna landscape

1. Managers considering restoration of landscapes often face a fundamental challenge - what should be the habitat composition of the restored landscape? We present a method for evaluating an important conservation trade-off inherent in making that decision. 2. Oak savannas and grasslands were historically widespread across central North America but are now rare. Today, in north-west Indiana, USA, habitats spanning a range of woody vegetation density, from nearly treeless open habitats to forests, occur across the conserved landscape where savannas probably once dominated. To understand the benefits of different potential landscape compositions, we evaluated how different proportions of five habitats - open, savanna, woodland, scrub and forest - might affect the conservation value of the north-west Indiana landscape for birds. Two variables of potential conservation importance were examined: species diversity, a measure of avian community richness, and conservation index, the percentage of a bird species' global population occurring on a hectare of landscape, summed across all bird species present. Higher values of conservation index were associated with higher local densities of globally more rare and more threatened species. 3. Conservation index and species diversity were correlated negatively across hypothetical landscapes composed of different proportions of the five habitats. Therefore, a management trade-off existed between conservation index and species diversity because landscapes that maximized species diversity differed from landscapes that maximized conservation index. 4. A landscape of 50% open, 22% savanna, 15% scrub and 13% forest was predicted to represent a compromise at which conservation index and species diversity reached the same percentage of their maxima. In contrast, the current landscape is dominated by forest. 5. Synthesis and applications. We quantified the trade-off between two potential aspects of a landscape's conservation value for birds - the landscape's ability to promote avian species diversity and the landscape's use by threatened avian species. This quantification allowed us to evaluate the ability of different landscape compositions to achieve preferable trade-off compromises, such as maximizing diversity for a given level of landscape use by threatened species. Managers can use these trade-off results to determine which landscape compositions are associated with particular conservation and management priorities.

Journal of Applied Ecology↗

USGS2008

The human footprint in the west: a large-scale analysis of anthropogenic impacts.

Anthropogenic features such as urbanization, roads, and power lines, are increasing in western United States landscapes in response to rapidly growing human populations. However, their spatial effects have not been evaluated. Our goal was to model the human footprint across the western United States. We first delineated the actual area occupied by anthropogenic features, the physical effect area. Next, we developed the human footprint model based on the ecological effect area, the zone influenced by features beyond their physical presence, by combining seven input models: three models quantified top-down anthropogenic influences of synanthropic predators (avian predators, domestic dog and cat presence risk), and four models quantified bottom-up anthropogenic influences on habitat (invasion of exotic plants, human-caused fires, energy extraction, and anthropogenic wildland fragmentation). Using independent bird population data, we found bird abundance of four synanthropic species to correlate positively with human footprint intensity and negatively for three of the six species influenced by habitat fragmentation. We then evaluated the extent of the human footprint in relation to terrestrial (ecoregions) and aquatic systems (major rivers and lakes), regional management and conservation status, physical environment, and temporal changes in human actions. The physical effect area of anthropogenic features covered 13% of the western United States with agricultural land (9.8%) being most dominant. High-intensity human footprint areas (class 8 – 10) overlapped highly productive low-elevation private landholdings and covered 7% of the western United States compared to 48% for low-intensity areas (class 1 – 3), which were confined to low-productivity high-elevation federal landholdings. Areas within 1 km of rivers were more affected by the human footprint compared to lakes. Percentage human population growth was higher in low-intensity human footprint areas. The disproportional regional effects of the human footprint on landscapes in the western United States create a challenge to management of ecosystems and wildlife populations. Using footprint models, managers can plan land use actions, develop restoration scenarios, and identify areas of high conservation value at local landscapes within a regional context. Moreover, human footprint models serve as a tool to stratify landscapes for studies investigating floral and faunal response to human disturbance intensity gradients.

Ecological Applications↗

USGS2016

Research on Golden-winged Warblers: Recent progress and current needs

Considerable advances have been made in knowledge about Golden-winged Warblers ( Vermivora chrysoptera ) in the past decade. Recent employment of molecular analysis, stable-isotope analysis, telemetry-based monitoring of survival and behavior, and spatially explicit modeling techniques have added to, and revised, an already broad base of published knowledge. Here, we synthesize findings primarily from recent peer-reviewed literature on Golden-winged Warblers, from this volume and elsewhere, and we identify some of the substantial remaining research needs. We have organized this synthesis by stages of the Golden-winged Warbler annual cycle. First, we discuss the relatively well-studied breeding-grounds ecology including nesting and post-fledging ecology and hybridization with closely related Blue-winged Warblers ( Vermivora cyanoptera ). Second, we discuss the much-less-studied, non-breeding-grounds ecology, including the first empirical studies of non-breeding-grounds cover-type associations and spatial and social behavioral ecology. Third, we address migratory connectivity and migration ecology, for which little is known and research has only just begun. Last, we close with cautious optimism that current knowledge is adequate to inform initial conservation and management plans for Golden-winged Warblers, and with a sobering acknowledgement of the quantity of research still needed.

Studies in Avian Biology↗

USGS2026

Potential for bird-based biotic indices in watershed assessments: A review of methods, applications, and suggestions for improvement

Birds are sensitive to changes in environmental conditions, and metrics such as species diversity, abundance, and guild composition that describe community-level responses to anthropogenic disturbance can be useful indicators of ecosystem condition. We reviewed published studies (56) of bird-based biotic indices developed for diverse ecosystems in 14 countries to evaluate their efficacy for bioassessments. The major categories of indices used included the index of biotic integrity (IBI; 18% of studies), the bird community index (BCI; 13%), and the index of ecological condition (IEC; 7%), with numerous specialized variants comprising the remaining 62% of studies, including indices adapted for specific ecosystems such as grasslands, wetlands, and urban areas. Index performance varied geographically, highlighting the importance of localized calibration. While few studies applied bird indices at landscape and regional scales, applications that included guild-based classification and habitat-specific metrics demonstrated potential for bird-based ecosystem monitoring and assessment. Bird communities were reliable ecological indicators at regional scales when indices incorporated locally derived disturbance and habitat gradients. This regional reliability indicates that expanding bird-based indices to watershed extents is feasible, especially given the availability of extensive resources such as citizen science bird data. There is an abundance of citizen science bird monitoring programs that potentially provide data for use in watershed-scale avian IBIs. Avian indices that combine data from multiple taxa, community-based metrics, and variables describing habitat quality can provide rigorous tools for watershed bioassessment and evidence-based conservation policy implementation.

Environmental Reviews↗

USGS1987

Ecology, behavior, and conservation of the Maui parrotbill

The distribution, habitat response, sexual dimorphism, foraging, breeding, and flocking behavior of Maui Parrotbills (Pseudonestor xanthophrys ) were studied over a five year period. The species' present range is confined to montane rainforest on eastern Maui, but dry lowland habitats on Maui and Molokai were occupied before Polynesian contact. Birds occurred from 1,250 to 2,150 m elevation, becoming most abundant at 1,750 to 2,000 m. In Kipahulu Valley, birds moved to lower elevations in some seasons. Birds tended to forage in the subcanopy and understory, with 66% of the prey captured 1 to 5 m above ground. Plant species use deviated from expectations based on availability. The most frequent means of prey capture was excavation for timber-boring insects in dead branches on live plants. Foraging accounted for 39% of the diurnal time budget; an average prey item appeared to account for 1% of the daily energy intake. The principal limiting factors appeared to be habitat loss, avian disease, habitat degradation, predation, and competition from exotic species. Control of pig populations is a needed management action.

Condor↗

USGS2025

AviList: A unified global bird checklist

Universally recognized scientific names for organisms are necessary for accurate and efficient communication. Incongruence in taxonomic treatments results in situations where one name is used for different entities or one entity is known by different names, with negative consequences for conservation, science, trade, legislation, law enforcement, and education, leading to discord among stakeholders and confusion among users. Within the ornithological community taxonomic incongruence among four widely adopted global bird checklists has led to calls for the development of a single unified global avian taxonomy or checklist. Here we introduce AviList, a comprehensive, collaborative and evolving effort towards developing a unified global avian taxonomy, spearheaded by representatives of most current global checklists and many major regional authorities, and supported by the International Ornithologists’ Union (IOU), BirdLife International and the Cornell Lab of Ornithology. AviList version 2025, the first version, was officially launched on 11 June 2025 and is available online as a comprehensive, searchable public-access database. It recognizes 11,131 bird species in 2376 genera, 252 families and 46 orders. This global effort has resolved over 1000 species-level taxonomic incongruences among existing checklists. With AviList’s launch, the IOC World Bird List and the Clements Checklist of Birds of the World have ceased any independent taxonomic updates, while BirdLife International is in the process of total alignment, leading to a harmonization in the classification underpinning a number of major bird projects, including eBird, Macaulay Library, Merlin Bird ID and the IUCN Red List. Adoption of AviList will improve inter-operability across global biodiversity, molecular, ecological and spatial databases (e.g. GBIF). Strong governance of AviList will ensure it is a “living” document that is regularly updated by a global community of bird taxonomists as new scientific advances are made, with positive impacts for conservation, academia and human society. It is hoped that AviList will support and encourage taxonomic science by identifying areas where further research is most needed, and that it will provide a blueprint for taxonomic authorities in other organismic groups endeavoring to achieve taxonomic harmonization.

Biodiversity and Conservation↗