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At least 505 records · Page 28Linked to original sources
USGS2017

An integrated population model for bird monitoring in North America

Integrated population models (IPMs) provide a unified framework for simultaneously analyzing data sets of different types to estimate vital rates, population size, and dynamics; assess contributions of demographic parameters to population changes; and assess population viability. Strengths of an IPM include the ability to estimate latent parameters and improve the precision of parameter estimates. We present a hierarchical IPM that combines two broad‐scale avian monitoring data sets: count data from the North American Breeding Bird Survey (BBS) and capture–recapture data from the Monitoring Avian Productivity and Survivorship (MAPS) program. These data sets are characterized by large numbers of sample sites and observers, factors capable of inducing error in the sampling and observation processes. The IPM integrates the data sets by modeling the population abundance as a first‐order autoregressive function of the previous year's population abundance and vital rates. BBS counts were modeled as a log‐linear function of the annual index of population abundance, observation effects (observer identity and first survey year), and overdispersion. Vital rates modeled included adult apparent survival, estimated from a transient Cormack‐Jolly‐Seber model using MAPS data, and recruitment (surviving hatched birds from the previous season + dispersing adults) estimated as a latent parameter. An assessment of the IPM demonstrated it could recover true parameter values from 200 simulated data sets. The IPM was applied to data sets (1992–2008) of two bird species, Gray Catbird ( Dumetella carolinensis ) and Wood Thrush ( Hylocichla mustelina ) in the New England/Mid‐Atlantic coastal Bird Conservation Region of the United States. The Gray Catbird population was relatively stable (trend +0.4% per yr), while the Wood Thrush population nearly halved (trend −4.5% per yr) over the 17‐yr study period. IPM estimates of population growth rates, adult survival, and detection and residency probabilities were similar and as precise as estimates from the stand‐alone BBS and CJS models. A benefit of using the IPM was its ability to estimate the latent recruitment parameter. Annual growth rates for both species correlated more with recruitment than survival, and the relationship for Wood Thrush was stronger than for Gray Catbird. The IPM's unified modeling framework facilitates integration of these important data sets.

Ecological Applications↗
USGS2022

Melanism in a Common Murre Uria aalge in Kachemak Bay, Alaska

In accord with melanism being uncommon in birds, we could find only six published records of completely melanistic Common Murres Uria aalge , one of the most widely and intensively studied of all seabirds. We added to the record by observing a Common Murre in completely dark, melanistic alternate plumage every summer from 2017 to 2021 at Gull Island in Kachemak Bay, Alaska, USA. In 2017, the bird frequented the colony periphery, indicating that it could have been a subadult. Subsequently, it occupied the same narrow rock ledge within the colony every summer from 2018 to 2021, an indication that it may have been attempting to breed. Because we have been conducting long-term monitoring on Gull Island, we are in the unique position to be able to monitor the attendance and reproductive performance of this distinctively marked murre into the future.

Alaska↗
USGS2025

Delayed incubation leads to hatching failure of a Burrowing Owl ( Athene cunicularia ) nest

Birds face strong selective pressures to complete individual nesting attempts as quickly as possible to minimize exposure of nests to predators and weather, maximize renesting potential, and maximize hatching success. As a result, the duration of developmental periods and of overall nest periods are often relatively constant within species. However, birds may sometimes be subject to acute energetic constraints that may preclude them from initiating incubation at the optimal time. We report an extraordinary case of delayed incubation by a female Burrowing Owl ( Athene cunicularia ) in Oregon, USA, which contrasted sharply with a large sample of nests monitored by motion-activated video cameras in western North America from 2015 to 2018. The focal female delayed incubation by 11 d following clutch completion and subsequently experienced near total hatching failure of her clutch. This observation corroborates previous experimental studies regarding the limits to egg viability and trade-offs between the timing of incubation onset and hatching success. These findings illustrate the acute trade-offs faced by nesting birds, and the cost of delayed incubation that we observed in this owl could help explain the cause of asynchronous hatching.

Oregon↗
USGS2017

Tributyltin: Advancing the science on assessing endocrine disruption with an unconventional endocrine-disrupting compound

Tributyltin (TBT) has been recognized as an endocrine disrupting chemical (EDC) for several decades. However, only in the last decade, was its primary endocrine mechanism of action (MeOA) elucidated—interactions with the nuclear retinoid-X receptor (RXR), peroxisome proliferator-activated receptor γ (PPARγ), and their heterodimers. This molecular initiating event (MIE) alters a range of reproductive, developmental, and metabolic pathways at the organism level. It is noteworthy that a variety of MeOAs have been proposed over the years for the observed endocrine-type effects of TBT; however, convincing data for the MIE was provided only recently and now several researchers have confirmed and refined the information on this MeOA. One of the most important lessons learned from years of research on TBT concerns apparent species sensitivity. Several aspects such as the rates of uptake and elimination, chemical potency, and metabolic capacity are all important for identifying the most sensitive species for a given chemical, including EDCs. For TBT, much of this was discovered by trial and error, hence important relationships and important sensitive taxa were not identified until several decades after its introduction to the environment. As recognized for many years, TBT-induced responses are known to occur at very low concentrations for molluscs, a fact that has more recently also been observed in fish species. This review explores the MeOA and effects of TBT in different species (aquatic molluscs and other invertebrates, fish, amphibians, birds, and mammals) according to the OECD Conceptual Framework for Endocrine Disruptor Testing and Assessment (CFEDTA). The information gathered on biological effects that are relevant for populations of aquatic animals was used to construct Species Sensitivity Distributions (SSDs) based on No Observed Effect Concentrations (NOECs) and Lowest Observed Effect Concentrations (LOECs). Fish appear at the lower end of these distributions, showing that they are as sensitive as molluscs, and for some species, even more sensitive. Concentrations in the range of 1 ng/L for water exposure (10 ng/g for whole-body burden) have been shown to elicit endocrine-type responses, whereas mortality occurs at water concentrations ten times higher. Current screening and assessment methodologies as compiled in the OECD CFEDTA are able to identify TBT as a potent endocrine disruptor with a high environmental risk for the original use pattern. If those approaches had been available when TBT was introduced to the market, it is likely that its use would have been regulated sooner, thus avoiding the detrimental effects on marine gastropod populations and communities as documented over several decades.

Book chapter↗
USGS1999

Le Conte's sparrows breeding in Conservation Reserve Program fields: precipitation and patterns of population change

The climate of the North American Great Plains is highly dynamic, with great year-to-year variability in precipitation and periodic, often extreme, wet and dry cycles (Bragg 1995). Drought is a major force of ecological disturbance on the Great Plains and has played a key role in directing the evolution of the grassland biota of this region (Knopf and Samson 1997). Although grassland birds may differ in their responses to enviromenental variations (Rotenberry and Wiens 1991), climatic variability and concomitant unpredictability of resources strongly influence populations of grassland birds across space and time (Wiens 1974, 1986; Cody 1985). Not surprisingly, breeding bird populations on the Great Plains are highly dynamic, exhibiting considerable annual variation in composition, abundance, and distribution (Johnson and Grier 1988, George et al. 1992, Zimmerman 1992, Igl and Johnson 1997). Recently, interest in grassland birds has increased with the recognition that many species are declining both continentally (Droege and Sauer 1994) and globally (Goriup 1988). Identification of the specific factors associated with grassland bird declines in North America, however, remains largely enigmatic (Herkert 1997), and it is complicated by the considerable annual fluctuations in grassland bird distribution and abundance (Igl and Johnson 1997). Although there is evidence that land-use changes on the breeding grounds may have contributed to grassland bird declines (e.g., Igl and Johnson 1997), there also is an indication that long-term drought conditions may have influenced recent population changes of some breeding birds on the Great Plains (Droege and Sauer 1989, Peterjohn and Sauer 1993, Bethke and Nudds 1995, Igl and Johnson 1997). Le Conte's Sparrow (Ammodramus leconteii) is a secretive grassland bird that breeds in central and southern Canada and the northcentral United States (Murray 1969). It winters primarily in the southern United States (Peterson 1980, 1990). Like populations of many grassland breeding birds in North America (Fretwell 1986, Igl and Johnson 1997), Le Conte's Sparrow populations exhibit numerical highs and lows depending on local moisture conditions (Peabody 1901, Stewart 1975, Knapton 1979, Zimmer 1979, Madden 1996). This observation, however, is based largely on anecdotal evidence or short-term observations. Long-term studies of Le Conte's Sparrow populations are limited. Le Conte's Sparrow is poorly represented on the North American Breeding Bird Survey (BBS) because of small sample sizes, poor coverage in the northern portion of its breeding range, and the species' furtive behavior (Sauer et al. 1995). Moreover, dramatic fluctuations in Le Conte's Sparrow abundance tend to obscure the species' long-term population trends on the BBS (Sauer et al. 1995). In this paper we examine long-term population changes of Le Conte's Sparrows breeding in perennial grassland fields enrolled in the Conservation Reserve Program (CRP) on the northern Great Plains. We discuss patterns of population change of Le Conte's Sparrows associated with changes in precipitation and moisture conditions.

Studies in Avian Biology↗
USGS2012

Nest defense- Grassland bird responses to snakes

Predation is the primary source of nest mortality for most passerines; thus, behaviors to reduce the impacts of predation are frequently quantified to study learning, adaptation, and coevolution among predator and prey species. Video surveillance of nests has made it possible to examine real-time parental nest defense. During 1999-2009, we used video camera systems to monitor 518 nests of grassland birds. We reviewed video of 48 visits by snakes to 34 nests; 37 of these visits resulted in predation of active nests. When adult birds encountered snakes at the nest (n = 33 visits), 76% of the encounters resulted in a form of nest defense (nonaggressive or aggressive); in 47% of the encounters, birds physically struck snakes. When defending nests, most birds pecked at the snakes; Eastern Meadowlarks (Sturnella magna) and Bobolinks (Dolichonyx oryzivorus) pecked most frequently in anyone encounter. Also, two Eastern Meadowlarks ran around snakes, frequently with wings spread, and three Bobolinks struck at snakes from the air. Nest defense rarely appeared to alter snake behavior; the contents of seven nests defended aggressively and two nests defended nonaggressively were partially depredated, whereas the contents of six nests defended each way were consumed completely. One fledgling was produced at each of three nests that had been aggressively defended. During aggressive defense, one snake appeared to be driven away and one was wounded. Our findings should be a useful starting point for further research. For example, future researchers may be able to determine whether the behavioral variation we observed in nest defense reflects species differences, anatomic or phylogenetic constraints, or individual differences related to a bird's prior experience. There appears to be much potential for studying nest defense behavior using video recording of both real and simulated encounters.

Studies in Avian Biology↗
USGS2001

Dicofol residues in eggs and carcasses of captive American kestrels

American kestrels ( Falco sparverius ) were fed diets containing 0 (control), 1, 3, 10, and 30 μg/g (wet wt) of Kelthane®. Residues of dicofol and its metabolites were then analyzed in the eggs and carcasses of females. Significant differences occurred among treatments for residues of both p,p ′‐dicofol and p,p ′‐dechlorodicofol (DCD) in both eggs and carcasses and for p,p ′‐dicholorbenzophenone (DCBP) in eggs. Residue concentrations increased with increasing treatment exposure. Residues of p,p ′‐dicofol, p,p ′‐DCD, and p,p ′‐DCBP in eggs were significantly correlated with eggshell quality parameters. Significant correlations also occurred among contaminants in eggs and for individual contaminants between eggs and carcasses. The lowest‐observed‐dietary‐effect concentration for eggshell thinning was 3 μg/g, whereas 1 μg/g may be considered to be near a no‐observable‐adverse‐effect concentration. Concentrations of dicofol in potential prey items and eggs of wild birds generally have been lower than dietary‐effect concentrations or concentrations in tissues or eggs associated with eggshell thinning and reduced reproductive success.

Environmental Toxicology and Chemistry↗
USGS1991

Oxygen-isotope exchange and mineral alteration in gabbros of the Lower Layered Series, Kap Edvard Holm Complex, East Greenland

Multiple intrusions of gabbros, mafic dikes, and syenites in the Kap Edvard Holm Complex gave rise to prolonged circulation of meteoric hydrothermal solutions and extreme isotope exchange and mineral alteration in the 3600-m-thick Lower Layered Series gabbros. In the Lower Layered Series, δ 18 O of plagioclase varies from +0.3‰ to -5.8‰, and it decreases with an increase in the volume of secondary talc, chlorite, and actinolite. In the same gabbros, pyroxenes have a more restricted range in δ 18 O, from 5.0‰ to 3.8‰ and values of δ 18 O pyroxene are independent of the abundance of secondary minerals, which ranges from 14% to 30%. These relations indicate that large amounts of water continued to flow through the rocks at temperatures of <500-600°C, altering the gabbros to assemblages of talc + chlorite + actinolite ± epidote ±albite and causing significant oxygen-isotope exchange in plagioclase, but not in pyroxene. The extensive low-temperature secondary mineralization and 18 O depletion of plagioclase in the Lower Layered Series are associated with the later emplacement of dikes and gabbros and syenites, which created new fracture systems and provided heat sources for hydrothermal fluid circulation. This produced subsolidus mineral alteration and isotope exchange in the Lower Layered Series that are distinct from those in the Skaergaard and Cuillin gabbros of the North Atlantic Tertiary province, but are similar to those observed in some oceanic gabbros.

Kap Edward Holm Complex↗
USGS2023

A Buteo sp. hawk predates a hummingbird (Trochilidae) during autumn migration

Predation can play a significant role on survival during migration as birds find themselves competing for resources in unfamiliar habitats. Here we describe the first documented observation of a Buteo platypterus (Broad-winged Hawk) predating an Archilochus colubris (Ruby-throated Hummingbird) during autumn migration. To our knowledge, this is the first documented record of any Buteo sp. hawk predating any Trochilidae (hummingbird). While predation on hummingbirds likely represents a minor source of mortality, identifying sources of predation and mortality is important in understanding the risk of migration for any species.

Southeastern Naturalist↗
USGS2000

Releasing captive-reared masked bobwhite for population recovery: A review

Efforts to re-establish the endangered masked bobwhite (Colinus virginianus ridgwayi) to it's former southern Arizona range have been ongoing since establishment of the Buenos Aires National Wildlife Refuge in 1986. Pre-release conditioning techniques developed prior to Refuge establishment continued to be utilized in an effort to improve post-release survival of captive-reared masked bobwhite chicks. Foremost among these techniques was the use of wild Texas bobwhite (C. v. texanus) males as foster parents which were paired with all broods released on the Refuge. The efficacy of this technique was evaluated using radio telemetry in 1994, and the results indicated that the use of foster Texas males was not as effective as had been presumed because post-release chick survival was poor. Therefore, in 1995 pre-release conditioning protocol were modified in an effort to improve post-release survival. The primary intent of these modifications was to emphasize wild behavior among chicks prior to release. Modifications to established protocol included imprinting chicks to adult bobwhites immediately after eggs hatched and exposing 1-to-2 day old chicks to natural foods (insects and seeds) while they were in brooder units. Foster parents and their respective broods were then placed in flight pens that mimicked the natural conditions that would confront broods upon release. Family groups were held in flight pens for several weeks for acclimatization purposes and then transported to temporary enclosures erected at release sites where they were held for a week and then released. Finally all releases were conducted during fall after covey formation was apparent to ensure that foster parents and released chicks remained with a group of birds. Preliminary results indicated that post-release chick survival was higher than what was observed in 1994. Pre-conditioning research will continue in an effort to further quantify post-release survival of masked bobwhite chicks. Although the results of this research project are preliminary, it is possible that pre-release conditioning techniques developed for masked bobwhites will prove useful to quail reestablishment efforts throughout North America.

Book chapter↗
USGS1989

Migration of radio-marked whooping cranes from the Aransas-Wood Buffalo population: Patterns of habitat use, behavior, and survival

Use of migration stop-overs by radio-tracked whooping cranes (Grus americana) was studied in fall 1981-83 and spring 1983-84. Information on habitat use, time-activity budgets, and hazards encountered is presented for a sample of 27 individuals, including 9 radio-marked birds. Survival rate is calculated for radio-marked birds and compared with estimates for birds not radio-marked. Distribution patterns of birds for which complete stopover information is available are contrasted with distributions derived from opportunistic observations.

Fish and Wildlife Technical Report↗
USGS2012

Arctic shorebirds in North America: A decade of monitoring

Each year shorebirds from North and South America migrate thousands of miles to spend the summer in the Arctic. There they feed in shoreline marshes and estuaries along some of the most productive and pristine coasts anywhere. With so much available food they are able to reproduce almost explosively; and as winter approaches, they retreat south along with their offspring, to return to the Arctic the following spring. This remarkable pattern of movement and activity has been the object of intensive study by an international team of ornithologists who have spent a decade counting, surveying, and observing these shorebirds. In this important synthetic work, they address multiple questions about these migratory bird populations. How many birds occupy Arctic ecosystems each summer? How long do visiting shorebirds linger before heading south? How fecund are these birds? Where exactly do they migrate and where exactly do they return? Are their populations growing or shrinking? The results of this study are crucial for better understanding how environmental policies will influence Arctic habitats as well as the far-ranging winter habitats used by migratory shorebirds.

Studies in Avian Biology↗
USGS2026

Designing biosurveillance using target analysis for a cryptic invasive species, the brown treesnake (Boiga irregularis)

Biosurveillance is especially important for invasive species that are difficult to control or remove once established. Target analysis, or the strategic evaluation of factors that affect or improve detection of organisms, is one approach to improve biosurveillance over time. Due to their ecologically and economically devastating effects, brown treesnakes ( Boiga irregularis ), an invasive snake in the United States territory of Guam, have a dedicated biosecurity program to prevent their spread. Guam has been occupied by brown treesnakes since the 1940s, and they are distributed throughout the island. The neighboring Saipan Island, otherwise known as Saipan, participates in biosecurity programs designed to prevent their establishment. We evaluated biosurveillance protocols within rapid response and detection exercises for brown treesnakes. Our goal was to identify, account for, and reduce potential error when inferring absence from lack of detection using data collected in Guam and Saipan. We evaluated 1) whether brown treesnake detection probability was density dependent; 2) whether using terrestrial environmental DNA ( eDNA ) sampling detected snakes in occupied areas; 3) the likelihood brown treesnakes would have been detected in Saipan, given sampling effort during a biosurveillance exercise, and whether lizards could be used as a proxy on snake-free islands for estimating factors that affect detection; 4) the effect of transect design on pacing and subsequently pacing on lizard counts; and 5) the importance of observer training in surveying for cryptic reptiles and completing broad versus targeted bioinventories. We found that brown treesnake detection probability was density dependent when using visual surveys and declined with abundance in Guam, supporting that greater effort was required to have high confidence that lack of detection supported absence in areas with low snake densities. The terrestrial eDNA sampling protocol we developed was effective at detecting snakes in occupied locations in Guam and may be a complementary tool. However, further validation of eDNA protocols would still be required for early detection application. We also found that among trained observers, the ability to detect lizards was positively predictive of the number of snakes they detected at the standard snake densities in Guam. Thus, lizard detection appeared to be a reasonable proxy for evaluating visual search protocols for snakes on snake-free islands. Overall, creating easy pace-setting relationships between time and distance (i.e., 10 m per min), with flagging that clearly marked location on a transect, greatly reduced variability in search pace across survey nights. Observers that were continuously trained to maintain brown treesnake search profiles detected twice as many, on average, cryptic reptiles compared to individuals who had never received training, which was not true for the non-reptiles (birds and small mammals). Additionally, conducting broad bioinventories with many target species reduced detection of the target species, and this was increasingly true as years since the observer completed training for the target species increased. We thus found that designing biosurveillance exercises to evaluate search protocols can help improve or refine survey methods to reduce noise in the data, and accounting for that can improve the estimated confidence that failure to detect an invasive species infers absence.

NeoBiota↗
USGS2018

Linking animals aloft with the terrestrial landscape

Despite using the aerosphere for many facets of their life, most flying animals (i.e., birds, bats, some insects) are still bound to terrestrial habitats for resting, feeding, and reproduction. Comprehensive broad-scale observations by weather surveillance radars of animals as they leave terrestrial habitats for migration or feeding flights can be used to map their terrestrial distributions either as point locations (e.g., communal roosts) or as continuous surface layers (e.g., animal densities in habitats across a landscape). We discuss some of the technical challenges to reducing measurement biases related to how radars sample the aerosphere and the flight behavior of animals. We highlight a recently developed methodological approach that precisely and quantitatively links the horizontal spatial structure of birds aloft to their terrestrial distributions and provides novel insights into avian ecology and conservation across broad landscapes. Specifically, we present case studies that (1) elucidate how migrating birds contend with crossing ecological barriers and extreme weather events, (2) identify important stopover areas and habitat use patterns of birds along their migration routes, and (3) assess waterfowl response to wetland habitat management and restoration. These studies aid our understanding of how anthropogenic modification of the terrestrial landscape (e.g., urbanization, habitat management), natural geographic features, and weather (e.g., hurricanes) can affect the terrestrial distributions of flying animals.

Book chapter↗
USGS2001

Forest fragmentation and bird community dynamics: Inference at regional scales

With increasing fragmentation of natural areas and a dramatic reduction of forest cover in several parts of the world, quantifying the impact of such changes on species richness and community dynamics has been a subject of much concern. Here, we tested whether in more fragmented landscapes there was a lower number of area-sensitive species and higher local extinction and turnover rates, which could explain higher temporal variability in species richness. To investigate such potential landscape effects at a regional scale, we merged two independent, large-scale monitoring efforts: the North American Breeding Bird Survey (BBS) and the Land Use and Land Cover Classification data from the U.S. Geological Survey. We used methods that accounted for heterogeneity in the probability of detecting species to estimate species richness and temporal changes in the bird communities for BBS routes in three mid-Atlantic U.S. states. Forest breeding bird species were grouped prior to the analyses into area-sensitive and non-area-sensitive species according to previous studies. We tested predictions relating measures of forest structure at one point in time (1974) to species richness at that time and to parameters of forest bird community change over the following 22-yr-period (1975–1996). We used the mean size of forest patches to characterize landscape structure, as high correlations among landscape variables did not allow us to disentangle the relative roles of habitat fragmentation per se and habitat loss. As predicted, together with lower species richness for area-sensitive species on routes surrounded by landscapes with lower mean forest-patch size, we found higher mean year-to-year rates of local extinction. Moreover, the mean year-to-year rates of local turnover (proportion of locally new species) for area-sensitive species were also higher in landscapes with lower mean forest-patch size. These associations were not observed for the non-area-sensitive species group. These results suggest that landscape structure may influence forest bird communities at regional scales through its effects on the total number of species but also on the temporal rates of change in community composition. Evidence for higher rates of local extinction and turnover in more fragmented landscapes suggests that bird communities function as metapopulations at a regional scale, and points out the importance of colonizations and recolonizations from surrounding landscapes to local community dynamics. Further, our results illustrate that the methods used to estimate the community parameters can be a powerful statistical tool in addressing questions relative to the dynamics of communities.

Ecology↗
USGS1999

Marsh birds and the North American Breeding Bird Survey: judging the value of a landscape level survey for habitat specialist species with low detection rates

The North American Breeding Bird Survey was started in 1966, and provides information on population change for >400 species of birds. it covers the continental United States, Canada, and Alaska, and is conducted once each year, in June, by volunteer observers. A 39.4 kIn roadside survey route is driven starting 30 min before sunrise, and a 3 min point count is conducted at each of 50 stops spaced every 0.8 kIn. Existing analyses of the data are internet-based (http://www.mbr-pwrc.usgs.govlbbslbbs.html), and include maps of relative abundance, estimates of population change including trends (%/yr), composite annual indices (pattern in time), and maps of population trend (pattern in space). At least 36 species of marsh birds are encountered on the BBS, and the survey provides estimates with greatly varying levels of efficiency for the species. It is often difficult to understand how well the BBS surveys a species. Often, efficiency is judged by estimating trend and its variance for a species, then by calculating power and needed samples to detect a prespecified trend over some time period (e.g., a 2%/yr trend over 31 yr). Unfortunately, this approach is not always valid, as estimated trends and variances can be of little use if the population is poorly sampled. Lurking concerns with BBS data include (1) incomplete coverage of species range; (2) undersampling of habitats; and (3) low and variable visibility of birds during point counts. It is difficult to evaluate these concerns, because known populations do not exist for comparison with counts, and detection rates are time-consuming and costly to estimate. I evaluated the efficiency of the BBS for selected rails (Rallidae) and snipes (Scolopacidae), presenting estimates of population trend over 1966-1996 (T), power to detect 2%/yr trend over 31 yr, needed samples to achieve power of 0.75 with alpha= 0.1, number of survey routes with data for the species (N), average abundance on survey routes (RA), and maps of relative abundance. Examples include Yellow Rail (Coturnicops noveboracensis) (T=12 %/yr; P= 0.0085; N =28; routes; RA=0.05; Power=0.37; Needed samples=85), Black Rail (Laterallus jamaicensis) (No trend data or power information available, N =8), Clapper Rail (Rallus longirostris) (T=1.9%/yr; P=0.55; N =64; RA=0.31; Power=0.35; Needed samples=590), King Rail (Rallus elegans) (T=-4.2 %/yr; P= 0.03; N =76; Power=0.41; Needed samples=159), Sora (Porzana carolina) (T=0.98 %/yr; P= 0.24; N =720; RA= 0.92; Power=0.69; Needed samples= 377), and Common Snipe (Gallinago gallinago) (T=-0.24 %/yr; P= 0.54; N =1412; RA= 2.19; Power=0.98; Needed samples=205). With regard to quality of BBS data, marsh birds fall into 3 categories: (1) almost never encountered on BBS routes; (2) encountered at extremely low abundances on BBS routes; and (3) probably fairly well sampled by BBS roadside counts. BBS data can provide useful information for many marsh bird species, but users should be aware of the limitations of the BBS sample for monitoring species that have low visibility from point counts and prefer habitats not often encountered on roadsides.

Book chapter↗
USGS2020

Reliability of external characteristics to age Barrow’s goldeneye

Accurate assignment of age class is critical for understanding most demographic processes. For waterfowl, most techniques for determining age class require birds in hand, reducing utility for quickly and efficiently sampling a large portion of the population. As an alternative, we sought to establish an observation‐based methodology, achievable in the field with standard optics, for determining age class of Barrow's goldeneyes ( Bucephala islandica ). We photographed heads, wings, and bellies of 232 Barrow's goldeneyes captured during late winter (February–April) of 2007–2015 along the north Pacific Coast. From these photographs, we focused on 5 external characteristics for both males and females, with binary states that putatively corresponded to 2 age classes—first‐year birds (<1 yr) and adults (>1 yr). For males, all 5 external traits (belly color, head color, eye color, facial crescent, median secondary coverts color) had binary states that were reliably distinguishable by observers. Moreover, all 5 external traits were highly predictive of age class (≥96% concordance between external vs. bursal‐derived ages), and novice observers, after receiving training, were able to accurately age 96% of first‐year and 99% of adult males. In contrast, patterns were weaker for females; putative external characteristics of female age class (belly color, bill radiance, bill blackness, eye color, median secondary coverts color) had 77–91% concordance with bursal‐derived age, compared with 96–100% for males, and observers misidentified age classes of 15% of females, compared with only 2% of males. Overall, age classes of male Barrow's goldeneyes were accurately and reliably distinguishable during winter based on several external characteristics, whereas those of females were not. Our technique may be used to estimate age composition of male Barrow's goldeneyes during winter, providing a useful metric for monitoring annual changes in adult‐to‐juvenile ratios and other important demographic parameters.

Alaska, British Columbia↗
USGS2024

Designing count-based studies in a world of hierarchical models

Advances in hierarchical modeling have improved estimation of ecological parameters from count data, especially those quantifying population abundance, distribution, and dynamics by explicitly accounting for observation processes, particularly incomplete detection. Even hierarchical models that account for incomplete detection, however, cannot compensate for data limitations stemming from poorly planned sampling. Ecologists therefore need guidance for planning count-based studies that follow established sampling theory, collect appropriate data, and apply current modeling approaches to answer their research questions. We synthesize available literature relevant to guiding count-based studies. Considering the central historical and ongoing contributions of avian studies to ecological knowledge, we focus on birds as a case study for this review, but the basic principles apply to all populations whose members are sufficiently observable to be counted. The sequence of our review represents the thought process in which we encourage ecologists to engage 1) the research question(s) and population parameters to measure, 2) sampling design, 3) analytical framework, 4) temporal design, and 5) survey protocol. We also provide 2 hypothetical demonstrations of these study plan components representing different research questions and study systems. Mirroring the structure of hierarchical models, we suggest researchers primarily focus on the ecological processes of interest when designing their approach to sampling, and wait to consider logistical constraints of data collection and observation processes when developing the survey protocol. We offer a broad framework for researchers planning count-based studies, while pointing to relevant literature elaborating on particular tools and concepts.

Journal of Wildlife Management↗