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USGS2019

Fire disturbance influences endangered Cape Sable Seaside Sparrow (Ammopiza maritima mirabilis) relative bird count

Periodicity of fire disturbance is a known driver of ecosystem function and is reported as important in both promoting and maintaining viable breeding habitat for the endangered Cape Sable Seaside Sparrow ( Ammospiza maritima mirabilis ; CSSS). In south Florida, the CSSS serves as a fine-scale indicator of the marl and mixed-marl prairie communities of the Florida Everglades. The CSSS distribution is affected by numerous well-documented physical drivers, including water depth and fire regime. Here, we fit zero-inflated negative binomial generalized linear mixed models and used model selection to determine the relationship between CSSS bird count observations from 1992 to 2014 and the spatially-specific fire return interval on the landscape. CSSS bird count was highest at a 5–8-year fire return interval and increased linearly with the percent of cell burned (400 × 400 m cells). The results of this study can inform management plans designed to maintain existing, and promote new, marl prairie habitat for conservation of the CSSS.

Florida↗

USGS2016

Breeding sites and winter site fidelity of Piping Plovers wintering in The Bahamas, a previously unknown major wintering area

Most of the known wintering areas of Piping Plovers ( Charadrius melodus ) are along the Atlantic and Gulf coasts of the United States and into Mexico, and in the Caribbean. However, 1066 threatened/endangered Piping Plovers were recently found wintering in The Bahamas, an area not previously known to be important for the species. Although representing about 27% of the birds counted during the 2011 International Piping Plover Winter Census, the location of their breeding site(s) was unknown. Thus, our objectives were to determine the location(s) of their breeding site(s) using molecular markers and by tracking banded individuals, identify spring and fall staging sites, and examine site fidelity and survival. We captured and color-banded 57 birds in January and February 2010 in The Bahamas. Blood samples were also collected for genetic evaluation of the likely subspecies wintering in The Bahamas. Band re-sightings and DNA analysis revealed that at least 95% of the Piping Plovers wintering in The Bahamas originated on the Atlantic coast of the United States and Canada. Re-sightings of birds banded in The Bahamas spanned the breeding distribution of the species along the Atlantic coast from Newfoundland to North Carolina. Site fidelity to breeding and wintering sites was high (88–100%). Spring and fall staging sites were located along the Atlantic coast of the United States, with marked birds concentrating in the Carolinas. Our estimate of true survival for the marked birds was 0.71 (95% CI: 0.61–0.80). Our results indicate that more than one third of the Piping Plover population that breeds along the Atlantic coast winters in The Bahamas. By determining the importance of The Bahamas to the Atlantic subspecies of Piping Plovers, future conservation efforts for these populations can be better focused on where they are most needed.

Journal of Field Ornithology↗

USGS2009

Long-term pair bonds in the Laysan Duck

We describe long-term pair bonds in the endangered Laysan Duck (Anas laysanensis), a dabbling duck endemic to the Hawaiian Archipelago. Individually marked birds were identified on Laysan Island between 1998 and 2006 (n = 613 marked adults). We recorded pair bonds while observing marked birds, and documented within and between year mate switches and multi-year pair bonds. Twenty pairs banded before 2001 had stable pair bonds lasting ???5 years with a maximum enduring pair bond of nine breeding seasons. Understanding reproductive strategy, including mate retention, would aid conservation planning and management efforts for the Laysan Duck. Further study is needed to characterize the social system of this endangered species.

Wilson Journal of Ornithology↗

USGS2024

Annual migratory movement, apparent molt-migration, migration schedule, and diffuse migratory connectivity of Hermit Warblers

Quantifying migratory connectivity and annual movement is key to sound conservation planning for migratory species. Hermit Warblers ( Setophaga occidentalis ) are an endemic-breeding species in the Pacific Northwest that winters in Mexico and the Central Americas. This species faces threats from mature forest loss and climate change throughout its range, but we know little about its migration ecology. To understand the annual movements and migratory connectivity of Hermit Warblers, we tracked 22 adult male Hermit Warblers from six breeding sites across the species’ breeding range using geolocators to examine migratory connectivity, spatiotemporal patterns, and migration routes. We found a high degree of mixing on the wintering grounds among birds from different breeding locations, indicating low migratory connectivity. However, birds breeding in Yosemite, the southernmost breeding location in our study, wintered farther east and south than birds from more northern breeding locations, providing weak evidence for potential chain migration. All birds showed much shorter and faster movements during spring migration than during fall migration. Birds arrived at breeding grounds from late April to mid-May and left breeding ranges from late June to mid-July. In fall, birds moved slowly from the breeding locations to montane regions in southern Oregon and California, which may indicate post-breeding molt before swiftly migrating to wintering grounds. Low migratory connectivity in this species implies that habitat and climate change across the broad wintering range may affect breeding populations throughout the species’ breeding range. A particularly compressed breeding schedule and departure of birds from the breeding grounds in early July may indicate that breeding is limited by a short window of favorable climatic conditions for breeding, which could signal heightened vulnerability under future climatic scenarios.

Avian Conservation and Ecology↗

USGS1996

How many seabirds were killed by the Exxon Valdez Oil Spill?

After the Exxon Valdez oil spill of 24 March 1989, 36,115 dead seabirds were recovered from beaches and processed at morgues. Most or all of 1,888 live oiled seabirds brought to rehabilitation centers also died and about 3,260 oiled carcasses were never delivered to morgues. Of these 41,263 carcasses accounted for, we estimated conservatively that only 30,000 were killed by oil pollution. Carcass drift and recovery experiments conducted in the affected area during the spill and 1 year later, along with historical experiments conducted in other oceanographic regions, suggest that only a fraction (range = 4-30%) of birds killed were likely to have been recovered from beaches. Regression analysis of these drift-recovery data predicts a 15% recovery rate (r' = 0.38, P = 0.015). We recognize uncertainties in the assumptions and parameter values used to extrapolate total mortality from drift-recovery data, but we have confidence that mortality fell within the extreme range of estimates (100,000-690,000 birds killed) because these reflect a very wide range of observed and experimentally determined parameter values. Total mortality can also be estimated by comparing pre- and postspill colony population estimates. Uncertainties about these census data are greater than those associated with drift-recovery data, but nonetheless provide an independent mortality estimate of similar magnitude. Taken together, all evidence suggests that about 250,000 seabirds were killed by Exxon Valdez oil.

Alaska↗

USGS2018

Delineating and identifying long-term changes in the whooping crane (Grus americana) migration corridor

Defining and identifying changes to seasonal ranges of migratory species is required for effective conservation. Historic sightings of migrating whooping cranes ( Grus americana ) have served as sole source of information to define a migration corridor in the Great Plains of North America (i.e., Canadian Prairies and United States Great Plains) for this endangered species. We updated this effort using past opportunistic sightings from 1942–2016 ( n = 5,055) and more recent (2010–2016) location data from 58 telemetered birds ( n = 4,423) to delineate migration corridors that included 50%, 75%, and 95% core areas. All migration corridors were well defined and relatively compact, with the 95% core corridor averaging 294 km wide, although it varied approximately ±40% in width from 170 km in central Texas to 407 km at the international border of the United States and Canada. Based on historic sightings and telemetry locations, we detected easterly movements in locations over time, primarily due to locations west of the median shifting east. This shift occurred from northern Oklahoma to central Saskatchewan at an average rate of 1.2 km/year (0.3–2.8 km/year). Associated with this directional shift was a decrease in distance of locations from the median in the same region averaging -0.7 km/year (-0.3–-1.3 km/year), suggesting a modest narrowing of the migration corridor. Changes in the corridor over the past 8 decades suggest that agencies and organizations interested in recovery of this species may need to modify where conservation and recovery actions occur. Whooping cranes showed apparent plasticity in their migratory behavior, which likely has been necessary for persistence of a wetland-dependent species migrating through the drought-prone Great Plains. Behavioral flexibility will be useful for whooping cranes to continue recovery in a future of uncertain climate and land use changes throughout their annual range.

PLoS ONE↗

USGS2016

Assessing the sensitivity of avian species abundance to land cover and climate

Climate projections for the Midwestern United States predict southerly climates to shift northward. These shifts in climate could alter distributions of species across North America through changes in climate (i.e., temperature and precipitation), or through climate-induced changes on land cover. Our objective was to determine the relative impacts of land cover and climate on the abundance of five bird species in the Central United States that have habitat requirements ranging from grassland and shrubland to forest. We substituted space for time to examine potential impacts of a changing climate by assessing climate and land cover relationships over a broad latitudinal gradient. We found positive and negative relationships of climate and land cover factors with avian abundances. Habitat variables drove patterns of abundance in migratory and resident species, although climate was also influential in predicting abundance for some species occupying more open habitat (i.e., prairie warbler, blue-winged warbler, and northern bobwhite). Abundance of northern bobwhite increased with winter temperature and was the species exhibiting the most significant effect of climate. Models for birds primarily occupying early successional habitats performed better with a combination of habitat and climate variables whereas models of species found in contiguous forest performed best with land cover alone. These varied species-specific responses present unique challenges to land managers trying to balance species conservation over a variety of land covers. Management activities focused on increasing forest cover may play a role in mitigating effects of future climate by providing habitat refugia to species vulnerable to projected changes. Conservation efforts would be best served focusing on areas with high species abundances and an array of habitats. Future work managing forests for resilience and resistance to climate change could benefit species already susceptible to climate impacts.

Ecosphere↗

USGS2021

Migration efficiency sustains connectivity across agroecological networks supporting sandhill crane migration

Preserving avian flyway connectivity has long been challenged by our capacity to meaningfully quantify continental habitat dynamics and bird movements at temporal and spatial scales underlying long-distance migrations. Waterbirds migrating hundreds or thousands of kilometers depend on networks of wetland stopover sites to rest and refuel. Entire populations may rely on discrete wetland habitats, particularly in arid landscapes where the loss of limited stopover options can have disproportionately high impacts on migratory cost. Here, we examine flyway connectivity in water-limited ecosystems of western North America using 108 GPS tagged greater sandhill cranes. Bird movements were used to reconstruct wetland stopover networks across three geographically unique sub-populations spanning 12 US-Mexican states and Canadian provinces. Networks were monitored with remote sensing to identify long-term (1988-2019) trends in wetland and agricultural resources supporting migration and evaluated using network theory and centrality metrics as a measure of stopover site importance to flyway connectivity. Sandhill crane space-use was analyzed in stopover locations to identify important ownership and landscape factors structuring bird distributions. Migratory efficiency was the primary mechanism underpinning network function. A small number of key stopover sites important to minimizing movement cost between summering and wintering locations were essential to preserving flyway connectivity. Localized efficiencies were apparent in stopover landscapes given prioritization of space-use by birds where the proximity of agricultural food resources and flooded wetlands minimized daily movements. Model depictions showing wetland declines from 16-18% likely reflect a new normal in landscape drying that could decouple agriculture-waterbird relationships as water scarcity intensifies. Sustaining network resilience will require conservation strategies to balance water allocations preserving agricultural and wetlands on private lands that accounted for 67-96% of habitat use. Study outcomes provide new perspectives of agroecological relationships supporting continental waterbird migration needed to prioritize conservation of landscapes vital to maintaining flyway connectivity.

western North America↗

USGS2024

Potential use of poultry farms by wild waterfowl in California's Central Valley varies across space, times of day, and species: implications for influenza transmission risk

Interactions between wildlife and livestock can lead to cross-species disease transmission, which incurs economic costs and threatens wildlife conservation. Wild waterfowl are natural hosts of avian influenza viruses (AIVs), are often abundant near poultry farms, and have been linked to outbreaks of AIVs in poultry. Interspecific and seasonal variation in waterfowl movement and habitat use means that the risk of disease transmission between wild birds and poultry inevitably varies across species, space, and time. Here, we used GPS telemetry data from 10 waterfowl species in and near California's Central Valley, a region where both wild waterfowl and domestic poultry are abundant, to study selection of poultry farms by waterfowl across diel, seasonal, and annual cycles. We found that waterfowl selected for wetlands, open water, protected areas, and croplands, which meant that they generally avoided habitats that were likely to be used for poultry farming. These selection patterns were linked to species' ecology and diel behavioral patterns, such that avoidance of poultry habitats was stronger for local or partial migrants than for long-distance migrants, and stronger during daytime than at night. We then combined these habitat selection results with data on poultry farm locations to map risk of waterfowl–poultry contact across the Central Valley. Average selection strength at poultry farms was low, suggesting that current placement of poultry farms is generally effective for limiting risk of contact with wild birds. When we combined these habitat selection results with data on species' abundances and AIV infection prevalence, we found dramatic variation in potential AIV transmission risk among species. These results could be used to prioritize surveillance and biosecurity efforts for regions and times of relatively high risk. More generally, these results highlight that fine-scale movement data can help identify interspecific, seasonal, and diel patterns in animal behaviors that affect wildlife and poultry health.

California↗

USGS2017

Survivorship across the annual cycle of a migratory passerine, the willow flycatcher

Annual survivorship in migratory birds is a product of survival across the different periods of the annual cycle (i.e. breeding, wintering, and migration), and may vary substantially among these periods. Determining which periods have the highest mortality, and thus are potentially limiting a population, is important especially for species of conservation concern. To estimate survival probabilities of the willow flycatcher Empidonax traillii in each of the different periods, we combined demographic data from a 10-year breeding season study with that from a 5-year wintering grounds study. Estimates of annual apparent survival for breeding and wintering periods were nearly identical (65–66%), as were estimates of monthly apparent survival for both breeding and wintering stationary periods (98–99%). Because flycatchers spend at least half the year on the wintering grounds, overall apparent survivorship was lower (88%) on the wintering grounds than on the breeding grounds (97%). The migratory period had the highest mortality rate, accounting for 62% of the estimated annual mortality even though it comprises only one quarter or less of the annual cycle. The migratory period in the willow flycatcher and many other neotropical migrants is poorly understood, and further research is needed to identify sources of mortality during this crucial period.

Journal of Avian Biology↗

USGS2019

Handbook to the partners in flight population estimates database, version 3.0

This document describes the content of Version 3.0 of the Partners in Flight (PIF) Population Estimates Database, which provides population estimates for breeding USA/Canada landbirds at several geographic scales following the Partners in Flight approach described initially in Rich et al. (2004) and by Rosenberg and Blancher (2005) and most recently refined by Stanton et al. (2019). The Handbook also provides details about how the estimates were derived, information on limitations and caveats, a guide to using the estimates, and future desired directions for improving the estimates. This version of the database is intended as a companion to the Partners in Flight Landbird Conservation Plan: 2016 Revision for Canada and Continental United States (Rosenberg et al. 2016), although estimates for most species included in the database have been updated from those used in the 2016 Plan. Most of the estimates in the database are based on North American Breeding Bird Survey (BBS) data for landbirds from the decade 2006–2015. The information in this 2019 Version of the Handbook, for Version 3.0 of the database, describes all changes that have been made to the database since 2007 (Version 1.0, cf. Blancher et al. 2007)—including the additions documented in the Handbook for Version 2.0 (Blancher et al. 2013)—and therefore serves as a single source document describing the current database. Version 3.0 of the database addresses some of the recommendations suggested by Thogmartin et al. (2006) but does not yet fully address other limitations noted by Thogmartin et al. (2006), Blancher et al. (2007), Thogmartin (2010), Matsuoka et al. (2012), and Twedt (2015). By far, the most substantial change to the database comprises the incorporation of quantitative uncertainty bounds around population estimates for most species (see Stanton et al. 2019 for details). PIF Science anticipates that future versions of the database will occur in stages: first, improving elements of the basic PIF approach (e.g., incorporating more recent BBS data, updating Time of Day Adjustments, and refining Pair Adjustments); next, addressing additional concerns inherent in the PIF approach (e.g., replacing average maximum detection distance bins with research-derived species-specific effective detection radii); and later, perhaps replacing the sample-based PIF approach with a spatially-explicit, model-based (pixel-based) approach that more deliberately incorporates habitat and road biases and the proportion of birds available but not detected by current sampling methodology. This current Version 3.1 of the Handbook updates citations in the Literature Cited and incorporates relatively minor improvements in text clarity over the previous 3.0 version. The content of the Population Estimates Database itself remains the same except for changes to the global and USA/Canada estimates for Northern Bobwhite and Black Vulture.

Partners in Flight Technical Publication↗

USGS2012

Selection indicates preference in diverse habitats: A ground-nesting bird ( Charadrius melodus ) using reservoir shoreline

Animals use proximate cues to select resources that maximize individual fitness. When animals have a diverse array of available habitats, those selected could give insights into true habitat preferences. Since the construction of the Garrison Dam on the Missouri River in North Dakota, Lake Sakakawea (SAK) has become an important breeding area for federally threatened piping plovers ( Charadrius melodus ; hereafter plovers). We used conditional logistic regression to examine nest-site selection at fine scales (1, 3, and 10 m) during summers 2006–2009 by comparing characteristics at 351 nests to those of 668 random sites within nesting territories. Plovers selected sites (1 m 2 ) that were lower than unused random sites, increasing the risk of nest inundation. Plovers selected nest sites that were flat, had little silt, and at least 1 cobble; they also selected for 3-m radius nest areas that were relatively flat and devoid of vegetation and litter. Ninety percent of nests had <38% coverage of silt and <10% slope at the site, and <15% coverage of vegetation or litter and <31% slope within the 3-m radius. Gravel was selected for at nest sites (11% median), but against in the area 10-m from the nest, suggesting plovers select for patches or strips of gravel. Although elevation is rarely evaluated in studies of ground-nesting birds, our results underscore its importance in habitat-selection studies. Relative to where plovers historically nested, habitat at SAK has more diverse topography, substrate composition, vegetation communities, and greater water-level fluctuations. Accordingly, our results provide an example of how habitat-selection results can be interpreted as habitat preferences because they are not influenced by desired habitats being scarce or absent. Further, our results will be useful for directing habitat conservation for plovers and interpreting other habitat-selection studies.

North Dakota↗

USGS2013

Diablotin Pterodroma hasitata : a biography of the endangered Black-capped Petrel

The Black-capped Petrel Pterodroma hasitata was believed extinct throughout much of the 20th century. It is the only gadfly petrel currently known to breed in the Caribbean Basin. Now seriously endangered, the species is presumed extirpated from Martinique, Dominica, and Guadeloupe, and breeding populations currently occur only on Hispaniola and perhaps Cuba. A related form (now considered a full species) once bred, but is now apparently extinct, on Jamaica. The Black-capped Petrel breeding population may number as few as 500 breeding pairs. Remaining populations suffer from multiple threats to terrestrial and pelagic habitats, including harvest by humans and predation by introduced mammals. The exact sizes, locations, and detailed chronologies of all Black-capped Petrel breeding sites remain poorly studied, although major colonies are today apparently restricted to steep sea and inland cliffs along the La Selle Ridge in Hispaniola. The largest known breeding population occurs in Haiti, although there is continued discussion about a possible breeding site in Cuba in the Sierra Maestra mountain range. Accounts from Cuba are based on the unverified assumption that birds observed at sea just offshore of that island are breeding locally. All evidence at present indicates that waters in or adjacent to the Florida Current and the Gulf Stream between north Florida and southern Virginia provide the primary foraging range of Black-capped Petrels. A small foraging area just off of southeast Cuba has also been reported, but the extent and seasonal use of this area are unknown. Concentrations of birds can be found along the Gulf Stream in southeastern US waters throughout the year, but are particularly common in May, August, and late December through early January. Concentrations of adult birds during winter, when peak breeding activity is underway, suggest that breeding birds forage along the Gulf Stream while commuting to and from breeding colonies. Such long-distance foraging is certainly possible for Pterodroma species. Potential threats to Black-capped Petrels include introduced predators, human encroachment on breeding and foraging habitats, and offshore oil, gas, and wind energy development. Increased mercury levels associated with petroleum production also pose a potential threat, as the Black-capped Petrel seems to be highly susceptible to mercury bioaccumulation compared with other pelagic species. In addition, fires and other bright light sources are known to attract Black-capped Petrels, making collisions with wires and other structures on lighted ships and platforms a potential concern. Haitian social-economic instability and increasing habitat loss suggest the likelihood of further population declines and increasing vulnerability of the species to extinction. Our findings are in accord with the recent decision by the US Fish and Wildlife Service (USFWS) to evaluate the need for additional protection of the species and the primary foraging habitat off the southeastern United States under the Endangered Species Act (USFWS 2012). Additional conservation measures and research strategies that warrant further consideration include (1) protection, monitoring, and management of known breeding populations and nesting habitat in the Dominican Republic and Haiti through controlling predators, installing artificial nest burrows in appropriate sites and hiring local wardens at breeding sites during the nesting season; (2) local and regional training, education and public awareness (e.g. Blanchard & Nettleship 1992); (3) restoration of the original common name Diablotin to common usage to promote the historical and cultural importance of this species; (4) studies to determine the distribution and genetic variability in the remaining populations; and (5) studies of satellite-tagged birds to assess their seasonal and geographic use of pelagic habitats.

Marine Ornithology: Journal of Seabird Research an↗

USGS2017

Nonbreeding home‐range size and survival of lesser prairie‐chickens

The lesser prairie‐chicken ( Tympanuchus pallidicinctus ), a species of conservation concern with uncertain regulatory status, has experienced population declines over the past century. Most research on lesser prairie‐chickens has focused on the breeding season, with little research conducted during the nonbreeding season, a period that exerts a strong influence on demography in other upland game birds. We trapped lesser prairie‐chickens on leks and marked them with either global positioning system (GPS) satellite or very high frequency (VHF) transmitters to estimate survival and home‐range size during the nonbreeding season. We monitored 119 marked lesser prairie‐chickens in 3 study areas in Kansas, USA, from 16 September to 14 March in 2013, 2014, and 2015. We estimated home‐range size using Brownian Bridge movement models (GPS transmitters) and fixed kernel density estimators (VHF transmitters), and female survival using Kaplan–Meier known‐fate models. Average home‐range size did not differ between sexes. Estimated home‐range size was 3 times greater for individuals fitted with GPS satellite transmitters ( = 997 ha) than those with VHF transmitters ( = 286 ha), likely a result of the temporal resolution of the different transmitters. Home‐range size of GPS‐marked birds increased 2.8 times relative to the breeding season and varied by study area and year. Home‐range size was smaller in the 2013–2014 nonbreeding season ( = 495 ha) than the following 2 nonbreeding seasons ( = 1,290 ha and = 1,158 ha), corresponding with drought conditions of 2013, which were alleviated in following years. Female survival ( ) was high relative to breeding season estimates, and did not differ by study area or year ( = 0.73 ± 0.04 [SE]). Future management could remain focused on the breeding season because nonbreeding survival was 39–44% greater than the previous breeding season; however, considerations of total space needs would benefit lesser prairie‐chickens by accounting for the greater spatial requirements during the nonbreeding season.

Kansas↗

USGS2023

Four different surgical approaches to vasectomies in male Texas bobwhite quail (Colinus virginianus texanus) and northern bobwhite quail (Colinus virginianus)

Vasectomies render a male sterile and have been used for various management purposes, including conservation efforts. This report evaluated 4 different surgical approaches (external approach, internal approach with dissection, internal approach with cautery, and internal approach caudally) to perform 177 vasectomies in Texas bobwhite ( Colinus virginianus texanus ; n = 171) and northern bobwhite quail ( Colinus virginianus ; n = 6) in a field setting. Birds were not randomized into groups for the different approaches. Survival was recorded in 83% (147/177) of the birds. The most common cause of death was hemorrhage from the common iliac vein due to damage during the surgical procedure. Other causes for death included transection of the ureter, parasitism, euthanasia, and undetermined causes. The approach that had the highest survival rate (89.8%, 132/147) was the internal approach with cautery, and based on these results the authors recommend this approach for vasectomies in Texas and northern bobwhite quail.

Journal of Avian Medicine and Surgery↗

USGS2018

Abundance and productivity of marbled murrelets (Brachyramphus marmoratus) off central California during the 2017 breeding season

Marbled murrelets ( Brachyramphus marmoratus ) have been listed as “Endangered” by the State of California and “Threatened” by the U.S. Fish and Wildlife Service since 1992 in California, Oregon, and Washington. Information regarding marbled murrelet abundance, distribution, population trends, and habitat associations is critical for risk assessment, effective management and evaluation of conservation efficacy, and ultimately to meet Federal- and State-mandated recovery efforts for this species. During June–August 2017, the U.S. Geological Survey Western Ecological Research Center continued previously established, long-term (1999–2016), at-sea surveys to estimate abundance and productivity of marbled murrelets in U.S. Fish and Wildlife Service Conservation Zone 6 (central California—San Francisco Bay to Monterey Bay). Using conventional distance sampling methods, we estimated marbled murrelet abundance using 189 detections of 321 individuals observed on nine unique surveys. The abundance estimated for the entire study area using all surveys in 2017 was 530 birds (95-percent confidence interval, 384–732 birds). Estimated abundance from 2017 is comparable to most prior years of study, except for 2008 and 2015, which had anomalously low abundances. We estimated productivity (calculated as the hatch-year [HY] to after-hatch-year [AHY] ratio) in 2017 using three detections of three individuals observed in six surveys. After date-correcting HY and AHY counts to account for birds expected to be absent from the water while inland at nests, the date-corrected juvenile ratio was 0.022 ± 0.014 standard error. We created a synthesized database of all marbled murrelet survey data from 1999 to 2017 to allow scientists and managers to evaluate established survey methods and assess trends in abundance and productivity estimates. Future modifications of survey design could help reduce variance in abundance estimation.

California↗

USGS2019

Abundance and productivity of marbled murrelets (Brachyramphus marmoratus) off central California during the 2018 breeding season

Executive Summary Marbled murrelets ( Brachyramphus marmoratus ) have been listed as “endangered” by the State of California and “threatened” by the U.S. Fish and Wildlife Service since 1992 in California, Oregon, and Washington. Information regarding marbled murrelet abundance, distribution, population trends, and habitat associations is critical for risk assessment, effective management, evaluation of conservation efficacy, and ultimately, to meet Federal- and State-mandated recovery efforts for this species. During June–August 2018, the U.S. Geological Survey Western Ecological Research Center continued previously established, long-term (1999–2018), at-sea surveys to estimate abundance and productivity of marbled murrelets in U.S. Fish and Wildlife Service Conservation Zone 6 (San Francisco Bay to Point Sur in central California). Using conventional distance sampling methods, we estimated marbled murrelet abundance using 137 detections of 227 individuals observed on 9 surveys. The abundance estimated for the entire study area using all surveys in 2018 was 370 birds (95-percent confidence interval, 250–546 birds). Estimated abundance from 2018 is comparable to most prior years of study, except for 2001–03, when greater abundances were estimated. In 2018, we estimated reproductive productivity (calculated as the hatch-year [HY] to after-hatch-year [AHY] ratio) using four detections of four HY individuals observed on six surveys. After date-correcting HY and AHY counts to account for birds expected to be absent from the water while inland at nests, the date-corrected juvenile ratio was 0.047 ± 0.024 standard error. We updated a synthesized database of all Zone 6 marbled murrelet survey data since 1999 with 2018 data to allow scientists and managers to evaluate established survey methods and assess trends in abundance and productivity estimates.

California↗

USGS2002

Avian responses to late-season grazing in a shrub-willow floodplain

Riparian vegetation in western North America provides important habitat for breeding birds and valuable forage for grazing livestock. Whereas a number of studies have documented the response of riparian vegetation to the removal of cattle, few have experimentally evaluated specific grazing systems. We evaluated the responses of vegetation and breeding birds to two cycles of late-season (August–September) grazing followed by 34 months of rest on the Arapaho National Wildlife Refuge, Colorado. We used a before-and-after control-impact (BACI) design, with two control (ungrazed) and two treatment ( grazed) pastures composing the experimental units. Vegetation characteristics and bird densities were quantified on sample plots prior to and following two cycles of the treatment. We found no statistical differences in vegetation change and few differences in bird-density change among pastures. Inspection of means for pastures, however, suggests that changes in shrub vigor and spatial pattern differed among ungrazed and grazed pastures and that changes in population density for three of the nine bird species and three guilds studied differed among pastures. Our results suggest that habitat for grazing-sensitive birds may be restored while still allowing late-season grazing, although the rate at which species are recovered will be slower than if all cattle are removed.

Conservation Biology↗