Point Blue Conservation science

Blue Point, United States

Point Blue Conservation science

Blue Point, United States
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Schaffer-Smith D.,Duke University | Swenson J.J.,Duke University | Barbaree B.,Point Blue Conservation Science | Reiter M.E.,Point Blue Conservation Science
Remote Sensing of Environment | Year: 2017

Satellite measurements of surface water offer promise for understanding wetland habitat availability at broad spatial and temporal scales; reliable habitat is crucial for the persistence of migratory shorebirds that depend on wetland networks. We analyzed water extent dynamics within wetland habitats at a globally important shorebird stopover site for a 1983–2015 Landsat time series, and evaluated the effect of climate on water extent. A range of methods can detect open water from imagery, including supervised classification approaches and thresholds for spectral bands and indices. Thresholds provide a time advantage; however, there is no universally superior index, nor single best threshold for all instances. We used random forest to model the presence or absence of water from > 6200 reference pixels, and derived an optimal water probability threshold for our study area using receiver operating characteristic curves. An optimized mid-infrared (1.5–1.7 μm) threshold identified open water in the Sacramento Valley of California at 30-m resolution with an average of 90% producer's accuracy, comparable to approaches that require more intensive user input. SLC-off Landsat 7 imagery was integrated by applying a customized interpolation that mapped water in missing data gaps with 99% user's accuracy. On average we detected open water on ~ 26000 ha (~ 3% of the study area) in early April at the peak of shorebird migration, while water extent increased five-fold after the migration rush. Over the last three decades, late March water extent declined by ~ 1300 ha per year, primarily due to changes in the extent and timing of agricultural flood-irrigation. Water within shorebird habitats was significantly associated with an index of water availability at the peak of migration. Our approach can be used to optimize thresholds for time series analysis and near-real-time mapping in other regions, and requires only marginally more time than generating a confusion matrix. © 2017 Elsevier Inc.

Strum K.M.,Audubon California | Dybala K.E.,Point Blue Conservation Science | Iglecia M.N.,Manomet PlymouthMA | David Shuford W.,Point Blue Conservation Science
San Francisco Estuary and Watershed Science | Year: 2017

The Central Valley of California provides important breeding habitat to numerous species of wetland-dependent birds, despite the loss of over 90% of naturally occurring wetlands. A majority of shorebirds breeding in this region rely on shallow-flooded habitat adjacent to sparsely vegetated uplands as provided by rice (Oryza sativa), managed wetlands, and other habitats. We estimated the current extent of potential breeding shorebird habitat provided by rice and managed permanent and semi-permanent wetlands in each of four major planning regions of the Central Valley, and estimated the average breeding densities and current population sizes of two species of shorebirds: the Black-Necked Stilt (Himantopus mexicanus) and American Avocet (Recurvirostra americana). Using a population status framework based on principles of conservation biology, we estimated that stilt populations are small (< 10,000 individuals) or very small (< 1,000 individuals) in three of the four planning regions, and avocet populations are small or very small in all four planning regions. We then used the framework to define long-term (100-year) population objectives for stilts, avocets, and a third species, Killdeer (Charadrius vociferous), designed to meet our long-term conservation goal of supporting self-sustaining, genetically robust, and resilient populations of breeding shorebirds in the Central Valley. We also estimated the long-term density and wetland habitat objectives necessary to achieve the population objectives for all three species. The corresponding short-term (10-year) conservation objectives are to restore semi-permanent wetlands to provide an additional 11,537 ha (28,508 ac) of habitat for breeding shorebirds (by planning region: 2,842 ha in Sacramento, 2,897 ha in Yolo-Delta, 2,943 ha in San Joaquin, and 2,855 ha in Tulare), and to enhance existing habitat to support density objectives. Our approach provides a transparent, repeatable process for defining science-based conservation objectives for breeding shorebirds and their habitats in the Central Valley, which can help unite stakeholders around common goals and motivate conservation actions.

Di R.T.,Point Blue Conservation Science | Dybala K.E.,Point Blue Conservation Science | Seavy N.E.,Point Blue Conservation Science | Gardali T.,Point Blue Conservation Science
San Francisco Estuary and Watershed Science | Year: 2017

In California's Central Valley, grassland and oak savannah ecosystems provide multiple economic and social benefits, ecosystem services, and vital bird habitat. There is a growing interest in protecting, restoring, and managing these ecosystems, and the Central Valley Joint Venture (CVJV) provides leadership in the formulation of conservation goals and objectives. We defined a long-term goal of protecting, restoring, and managing Central Valley grassland and oak savannah ecosystems so that they are capable of supporting genetically robust, self-sustaining, and resilient wildlife populations. To measure progress toward this goal, we selected a suite of 12 landbird focal species that primarily breed in grasslands and oak savannahs as indicators of the state of these ecosystems on the Central Valley floor (primary focus area) and in the Central Valley's surrounding foothills (secondary focus area). Using data on current densities and habitat extent, we estimated that at least three of the focal species populations in the primary focus area and at least two of the focal species populations in the secondary focus area are currently small (< 10,000 individuals) and may be vulnerable to extirpation. Furthermore, at least two species appear to have steeply declining population trends. We defined long-term (100-year) population objectives for each focal species that we expect to meet the goal of genetically robust, self-sustaining, and resilient populations. We then estimated corresponding short-term (10-year) habitat objectives of 4,183 ha of additional grassland and 3,433 ha of additional oak savannah that will be required to make progress toward the long-term objectives. We expect that habitat restoration and enhancement efforts aimed at reaching these long-term conservation objectives will result in improvements to the function of Central Valley grassland and oak savannah ecosystems.

David Shuford W.,Point Blue Conservation Science | Dybala K.E.,Point Blue Conservation Science
San Francisco Estuary and Watershed Science | Year: 2017

Birds associated with wetlands have declined historically across North America from extensive habitat loss and degradation. Among the regions most affected is California's Central Valley, where over 90% of the wetland base has been lost. Still, this region remains of continental importance to waterbirds. On-the-ground conservation efforts for all bird groups are the focus of the Central Valley Joint Venture, guided by a periodically updated implementation plan. To track progress toward goal attainment, that plan sets time-bound, quantitative conservation goals. Lacking robust data on the size and trends of populations of most species of waterbirds in the Central Valley, we set conservation goals for this group by selecting 10 focal species. These species are of heightened conservation concern or are otherwise representative of the habitat needs of Central Valley waterbirds. Given the great loss of historical habitat, we assumed focal species populations have declined by > 50%. Hence, we defined population objectives for most focal species as increasing their current populations by 10% over 10 years and doubling them in 100 years. The corresponding habitat objectives are to increase wetlands or enhance suitable crops for waterbirds in proportion to the population objectives. These include an increase over 10 years of 7,948 ha (19,641 acres) of winter seasonal wetlands, 921 ha (2,276 acres) each of semi-permanent and summer seasonal wetlands, and 573 ha (1,416 acres) of strategically placed riparian forest. Agricultural needs include additional winter flooding of 15,160 ha (37,461 acres) of rice and 2,137 ha (5,281 acres) of corn. We distributed the habitat objectives across five planning regions, in some cases favoring proportionally larger increases in those regions with the greatest need. To maximize success, however, conservationists must take into account the specific needs of individual waterbird species, as a one-size-fits-all approach will not support the highest diversity of waterbirds.

David Shuford W.,Point Blue Conservation Science | Hertel M.,Audubon California
San Francisco Estuary and Watershed Science | Year: 2017

Populations of many species of birds are declining worldwide from habitat loss and degradation and the effects of contamination, disease, and alien species. Effects have been great in California's Central Valley from the loss of over 90% of its historical wetland and riparian habitats. Conservation initiatives at various geographic scales have ranged from protecting and restoring habitats or ecosystems for broad suites of species to ones identifying individual declining and vulnerable taxa and spurring actions to halt or reverse their population declines. In taking the first approach, the Central Valley Joint Venture initially focused on restoring habitats and populations of wintering and breeding waterfowl but currently promotes the conservation of all birds. This joint venture is setting population and habitat objectives for seven taxonomic or habitat bird groups, but to date little attention has been paid to at-risk species of particular conservation concern. We identified 38 at-risk species, subspecies, or distinct populations of birds that warrant heightened conservation efforts in the Central Valley. At-risk birds are unevenly distributed among subregions and habitat types in this valley, but most face the primary threat of habitat loss and degradation. The treatment of at-risk species varies greatly among the seven bird groups considered by the joint venture, and, overall, conservation objectives are not addressed specifically for 50% of the region's at-risk taxa, though some surely benefit from objectives set for other groups. To adequately treat at-risk species, we recommend a framework for setting conservation objectives that evaluates assumptions about limiting factors, considers objectives already set for threatened and endangered species, assesses whether objectives set for other groups or focal species meet the needs of at-risk species lacking such objectives, establishes objectives for at-risk species for habitats or seasons not currently considered, and highlights information gaps to be filled to effectively set new or refined objectives.

Lescroel A.,University of Rennes 1 | Lescroel A.,CNRS Center of Evolutionary and Functional Ecology | Ballard G.,Point Blue Conservation Science | Gremillet D.,CNRS Center of Evolutionary and Functional Ecology | And 3 more authors.
PLoS ONE | Year: 2014

In the context of predicted alteration of sea ice cover and increased frequency of extreme events, it is especially timely to investigate plasticity within Antarctic species responding to a key environmental aspect of their ecology: sea ice variability. Using 13 years of longitudinal data, we investigated the effect of sea ice concentration (SIC) on the foraging efficiency of Adélie penguins (Pygoscelis adeliae) breeding in the Ross Sea. A 'natural experiment' brought by the exceptional presence of giant icebergs during 5 consecutive years provided unprecedented habitat variation for testing the effects of extreme events on the relationship between SIC and foraging efficiency in this sea-ice dependent species. Significant levels of phenotypic plasticity were evident in response to changes in SIC in normal environmental conditions. Maximum foraging efficiency occurred at relatively low SIC, peaking at 6.1% and decreasing with higher SIC. The 'natural experiment' uncoupled efficiency levels from SIC variations. Our study suggests that lower summer SIC than currently observed would benefit the foraging performance of Adélie penguins in their southernmost breeding area. Importantly, it also provides evidence that extreme climatic events can disrupt response plasticity in a wild seabird population. This questions the predictive power of relationships built on past observations, when not only the average climatic conditions are changing but the frequency of extreme climatic anomalies is also on the rise. © 2014 Lescroël et al.

Rockwood R.C.,Point Blue Conservation Science | Calambokidis J.,Cascadia Research Collective | Jahncke J.,Point Blue Conservation Science
PLoS ONE | Year: 2017

Mortality from collisions with vessels is one of the main human causes of death for large whales. Ship strikes are rarely witnessed and the distribution of strike risk and estimates of mortality remain uncertain at best. We estimated ship strike mortality for blue humpback and fin whales in U.S. West Coast waters using a novel application of a naval encounter model. Mortality estimates from the model were far higher than current minimum estimates derived from stranding records and are closer to extrapolations adjusted for detection probabilities of dead whales. Our most conservative model estimated mortality to be 7.8x, 2.0x and 2.7x the U.S. recommended limit for blue, humpback and fin whales, respectively, suggesting that death from vessel collisions may be a significant impediment to population growth and recovery. Comparing across the study area, the majority of strike mortality occurs in waters off California, from Bodega Bay south and tends to be concentrated in a band approximately 24 Nm (44.5 km) offshore and in designated shipping lanes leading to and from major ports. While some mortality risk exists across nearly all West Coast waters, 74%, 82% and 65% of blue, humpback and fin whale mortality, respectively, occurs in just 10% of the study area, suggesting conservation efforts can be very effective if focused in these waters. Risk is highest in the shipping lanes off San Francisco and Long Beach, but only a fraction of total estimated mortality occurs in these proportionally small areas, making any conservation efforts exclusively within these areas insufficient to address overall strike mortality. We recommend combining shipping lane modifications and re-locations, ship speed reductions and creation of ‘Areas to be Avoided’ by vessels in ecologically important locations to address this significant source of whale mortality. © 2017 Rockwood et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Michael P.E.,Hawaii Pacific University | Jahncke J.,Point Blue Conservation Science | Hyrenbach K.D.,Hawaii Pacific University
Fisheries Oceanography | Year: 2014

Effective conservation of highly mobile species requires an understanding of the factors that influence their habitat use patterns, locally and within a large-scale oceanographic context. We characterized the seasonal (chick-rearing, post-breeding) and inter-annual (2004-2008) distribution and abundance of black-footed albatross (Phoebastria nigripes; BFAL) along the central California continental shelf/slope using standardized vessel-based surveys. We used a hypothesis-based information-theoretic approach to quantify the relative influence of environmental conditions on BFAL occurrence and abundance by assessing their association with: (i) local static bathymetric features, (ii) local and regional dynamic oceanographic processes, and (iii) seasonal and inter-annual basin-wide variability. While the presence/absence models yielded stronger results than the abundance models, both revealed that static and dynamic features influence BFAL habitat use. Specifically, occurrence was greatest near the shelf-break, particularly in months with strong upwelling. High BFAL densities were associated with Rittenburg Bank, especially during the chick-rearing season, periods of positive North Pacific Gyre Oscillation index and large northern monthly upwelling, evidenced by cool, salty waters in the study area. BFAL aggregation intensity was greatest onshore of the shelf-break (200 m isobath). Behavioral observations reinforced the notion that transiting BFAL are widely dispersed near the shelf-break and concentrate in large flocks of birds sitting on the water farther onshore. These results underscore the need to consider oceanographic processes at multiple spatial scales when interpreting changes in BFAL dispersion within marine sanctuaries, and highlight the feasibility of implementing bathymetrically defined protected areas targeting predictable BFAL aggregations within these larger management jurisdictions. © 2013 John Wiley & Sons Ltd.

Elliott M.L.,Point Blue Conservation Science | Bradley R.W.,Point Blue Conservation Science | Robinette D.P.,Point Blue Conservation Science | Jahncke J.,Point Blue Conservation Science
Journal of Marine Systems | Year: 2015

The population, productivity and diet of two Brandt's cormorant (Phalacrocorax penicillatus) colonies located in the central California Current were compared. The offshore colony on Southeast Farallon Island has experienced a declining population over time and anomalously low productivity in recent years. The nearshore colony near Point Arguello has been increasing and its productivity has remained stable. The diets of cormorants at the two colonies elucidated by analysis of regurgitated pellets, while different, have shown similar decreases in the consumption of northern anchovy (Engraulis mordax) since 2008, followed by increased consumption of rockfish (Sebastes spp.) and flatfish (order Pleuronectiformes). By using the diet results from another seabird nesting in central California, the rhinoceros auklet (Cerorhinca monocerata), and one from which whole fish can be obtained, we found that the rockfish species assemblage has changed with offshore rockfish species decreasing while nearshore ones have increased. This change in the rockfish species has negatively impacted Brandt's cormorants at the offshore colony by forcing them to make longer foraging trips to meet energy needs of themselves and their chicks; this has led to low breeding success and a declining population at this site. On the other hand, the nearshore colony has abundant nearby food resources, and it has prospered. These results underscore the value of using seabird data from multiple colonies to better understand changes occurring in the marine environment. © 2014 Elsevier B.V.

Burnett R.D.,Point Blue Conservation Science | Roberts L.J.,Point Blue Conservation Science
PLoS ONE | Year: 2015

Whether by design or default, single species management often serves as an umbrella for species with similar habitat requirements. In recent decades the focus of National Forest management in the Sierra Nevada of California has shifted towards increasing closed canopy mature forest conditions through the protection of areas occupied by the California Spotted Owl (Strix occidentalis occidentalis). To evaluate the implications of these habitat changes and the potential umbrella resulting from a system of owl reserves on the broader avian community, we estimated occupancy of birds inside and outside of Spotted Owl Home Range Core Areas in northeastern California. We used point count data in a multispecies hierarchical Bayesian model incorporating the detection history of 81 species over a two-year time period (2005-2006). A small set of vegetation cover and topography covariates were included in the model to account for broad differences in habitat conditions, as well as a term identifying whether or not a site was within a Core Area. Seventeen species had a negative Core Area effect, seven had a positive effect, and the rest were not significant. Estimated species richness was significantly different with 23.1 species per 100 m radius circle outside Core Areas and 21.7 inside Core Areas. The majority of the species negatively associated with Core Areas are tied to early successional and other disturbance-dependent habitats. Conservation and climate vulnerability rankings were mixed. On average we found higher scores (greater risk) for the species positively associated with Core Areas, but a larger number of species with the highest scores were negatively associated with Core Areas. We discuss the implications for managing the Sierra Nevada ecosystem and illustrate the role of monitoring broader suites of species in guiding management of large complex ecosystems. © 2015 Burnett, Roberts.

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