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Densities of Eared Grebes (Podicepsnigricollis) (no./km²; EAGR), commercial brine shrimp cyst harvest boats (no./km²; boats), and adult brine shrimp (no./L; brine shrimp) in aerial survey strata within the Great Salt Lake, Utah, during the commercial brine shrimp cyst harvest season, 2009–2011
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Eared Grebes (Podiceps nigricollis Brehm, 1831) use saline ecosystems throughout much of their life cycle, and greater than 90% of the North American population stage during fall at two hypersaline lakes. At one of these lakes, Great Salt Lake (GSL), Utah, a commercial harvest of brine shrimp (Artemia franciscana Kellogg, 1906) cysts occurs during...
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... The likely origin of the nonlocal grebes corresponded to much of the breeding area from approximately the latitude of the Great Salt Lake and northward, whereas the likely region of origin of the local individuals included nonbreeding areas to the south of the Great Salt Lake, which includes Mono Lake and the sites where the carcasses were found (Figure 6c). Our results showed that a higher proportion of eared grebes had likely molted at the Great Salt Lake than at Mono Lake, which is consistent with historic population patterns at the two lakes (Roberts et al., 2013). This correspondence indicates there may be instances in which stable isotope data can be used to better understand species-level distributions for species less well known than these grebes. ...
Bird populations are declining globally. Wind and solar energy can reduce emissions of fossil fuels that drive anthropogenic climate change, yet renewable‐energy production represents a potential threat to bird species. Surveys to assess potential effects at renewable‐energy facilities are exclusively local, and the geographic extent encompassed by birds killed at these facilities is largely unknown, which creates challenges for minimizing and mitigating the population‐level and cumulative effects of these fatalities. We performed geospatial analyses of stable hydrogen isotope data obtained from feathers of 871 individuals of 24 bird species found dead at solar‐ and wind‐energy facilities in California (USA). Most species had individuals with a mix of origins, ranging from 23% to 98% nonlocal. Mean minimum distances to areas of likely origin for nonlocal individuals were as close as 97 to >1250 km, and these minimum distances were larger for species found at solar‐energy facilities in deserts than at wind‐energy facilities in grasslands (Cohen's d = 6.5). Fatalities were drawn from an estimated 30–100% of species’ desingated ranges, and this percentage was significantly smaller for species with large ranges found at wind facilities (Pearson's r = −0.67). Temporal patterns in the geographic origin of fatalities suggested that migratory movements and nonmigratory movements, such as dispersal and nomadism, influence exposure to fatality risk for these birds. Our results illustrate the power of using stable isotope data to assess the geographic extent of renewable‐energy fatalities on birds. As the buildout of renewable‐energy facilities continues, accurate assessment of the geographic footprint of wildlife fatalities can be used to inform compensatory mitigation for their population‐level and cumulative effects.
... Although all bird detections tend to increase at the beginning of the fall period in September, detections of water associates and water obligates continued to increase until the end of October, whereas detections of other birds declined steadily throughout the fall. Waterfowl, loons, and grebes are all known to move in comparatively large numbers in fall when weather conditions are favorable for migration [31,32,33]. Eared grebes stage at the Great Salt Lake in Utah, and synchronize migration with upwards of 100,000 to 200,000 birds departing simultaneously en route to the Gulf of California [34]. ...
Recent trends in renewable energy development in the United States (U.S.) show that new installed capacity of utility-scale solar energy has exceeded 30% of total installed capacity of all sources per year since 2013. Photovoltaic solar energy provides benefits in that no emissions are produced; however, there are potential impacts from photovoltaic solar development on birds that include habitat loss and potential for collision mortality. Only 2 papers in the peer-reviewed literature present fatality information from fatality monitoring studies at a photovoltaic utility-scale solar energy facility; however, more data exists in unpublished reports. To provide a more comprehensive overview of bird mortality patterns, we synthesized results from fatality monitoring studies at 10 photovoltaic solar facilities across 13 site-years in California and Nevada. We found variability in the distribution of avian orders and species among and within Bird Conservation Regions, and found that water-obligate birds, which rely on water for take-off and landing, occurred at 90% (9/10) of site-years in the Sonoran and Mojave Deserts Bird Conservation Region. We found that a cause of mortality could not be determined for approximately 61% of intact carcasses, and that approximately 54% of all carcasses were feather spots, introducing uncertainty into the interpretation of the fatality estimates. The average annual fatality estimate we calculated for photovoltaic solar (high-end estimate of 2.49 birds per megawatt per year) is lower than that reported by another study (9.9 birds per megawatt per year) that included one photovoltaic facility. Our results provide a summary of fatalities in bird conservation regions where the facilities are located, but expanding our conclusions to new regions is limited by the location of facilities with fatality monitoring data.
... Significantly, avian cholera (Pasteurella multocida), a more typical cause of a mortality event of this magnitude in eared grebes on the GSL, was not detected in submitted carcasses (11). In the late fall, migrating grebes congregate on the GSL and feed in dense flocks on macrozooplankton, such as brine shrimp (Artemia sp.), before continuing migration (12,13). Bald eagles also congregate on the shore of the GSL to feed on fish and migrating birds. ...
In November and December of 2013, a large mortality event involving 15,000 - 20,000 eared grebes ( Podiceps nigricollis ) occurred at the Great Salt Lake (GSL), UT. The onset of the outbreak in grebes was followed by a mortality event in > 86 bald eagles ( Haliaeetus leucocephalus ). During the die-off, West Nile virus (WNV) was detected by RT-PCR or viral culture in carcasses of grebes and eagles submitted to the National Wildlife Health Center. However, no mosquito activity, the primary vector of WNV, was detected by the State of Utah's WNV monitoring program. Transmission of WNV has rarely been reported during the winter in North America in the absence of known mosquito activity; however, the size of this die-off, the habitat in which it occurred, and the species involved are unique. We experimentally investigated whether WNV could survive in water with a high saline content, as found at the GSL, and whether brine shrimp, the primary food of migrating eared grebes on the GSL, could have played a role in transmission of WNV to feeding birds. We found that WNV can survive up to 72 h at 4°C in water containing 30 — 150 ppt NaCl and brine shrimp, incubated with WNV in 30 ppt NaCl, may adsorb WNV to their cuticle and, through feeding, may infect epithelial cells of their gut. Both mechanisms may have potentiated the WNV die-off in migrating eared grebes on the GSL.
IMPORTANCE Following a major West Nile virus die-off of eared grebes and bald eagles at the Great Salt Lake (GSL), UT in November -- December, 2013, this study assessed the survival of West Nile virus (WNV) in water as saline as the GSL and whether brine shrimp, the major food for migrating grebes, could have played a role as vectors for the virus. While mosquitoes are the major vector of WNV, under certain circumstances transmission may occur through contaminated water and invertebrates as food.
Most North American Eared Grebes (Podiceps nigricollis) undertake a post-breeding migration to two hypersaline lakes in the USA: Mono Lake in California and Great Salt Lake in Utah. Single air photo surveys were conducted in mid-October at Mono Lake from 1996-2012 and multiple fall surveys were conducted from 2013-2018, the latter to determine variation in abundance patterns within and across years. In four of the six years with multiple fall surveys, peak abundance occurred in mid-October as expected. However, in 2014 and 2015, Eared Grebe numbers declined dramatically soon after arrival, coinciding with low levels of their primary food, brine shrimp (Artemia monica). Abundance remained low from 2016-2018, and this could have been due to a shift to Great Salt Lake or to a massive mortality event. In 2017 and 2018, Eared Grebes breeding in south-central British Columbia, Canada were marked with Very High Frequency (VHF) radio transmitters and light-level geolocator (GLS) tags. Contrary to 1996, when the majority of VHF-tagged birds were molting/staging on Mono Lake, our 2017-2018 telemetry data indicated that most individuals were on Great Salt Lake. Our study provides insight into the variable abundance patterns at Mono Lake and novel information on Eared Grebe migration patterns.
Utah’s Great Salt Lake (GSL) is so saline that the only invertebrates that survive in the open water are brine fly larvae and brine shrimp. In the absence of competition from other invertebrates, they are incredibly abundant. Only a few avian species can take advantage of their abundance because a bird cannot eat them without also ingesting salt. Moreover, brine shrimp and brine flies are so tiny that only a few avian species can consume the massive number of brine shrimp and brine flies required to meet a bird’s nutritional needs. For example, eared grebes need to consume 28,000 adult brine shrimp each day to survive. To achieve this, an eared grebe has to spend 7 h daily foraging and needs to harvest one shrimp per second during foraging.
Microbialites are microbial communities that create a carbonate structure. They are abundant in the Great Salt Lake, a hypersaline lake in the arid Great Basin of the USA, where they contribute to overall primary production, seasonally up to 55%. While the microbial diversity of microbialites has been investigated, how abiotic factors affect the abundance of their primary constituents is not well understood. We examined how microbialite primary producers respond to varying levels of temperature, salinity, and nitrogen within ranges observed in the Great Salt Lake. All abiotic factors and their interactions significantly affected the maximum chlorophyll-a abundance, suggesting that these factors co-limit microbialite primary producers in the Great Salt Lake. Maximum chlorophyll-a concentrations increased with nitrogen additions and showed a parabolic relationship with salinity and temperature with peaks around 60 ppt and 20°C, respectively. While salinity had a strong effect on microbialite primary producers, we found that temperature and nitrogen were more impactful, accounting for 40 and 30% of the variance in maximum abundance, respectively, while salinity contributed just 15%. Our results show the importance of the interplay of abiotic factors on Great Salt Lake microbialites and highlight the need for increased study of benthic communities in inland saline lakes.
Waterbird species face numerous threats and many are declining globally, but knowledge of distribution, abundance, and trend remains poor for many species. Five species of marsh-nesting colonial waterbirds are poorly monitored in Canada, and especially so in the core of their range in the Canadian Prairie Provinces (Alberta, Saskatchewan, and Manitoba). We summarized published and unpublished data on abundance and distribution of breeding colonies of Western Grebe (Aechmophorus occidentalis), Franklin's Gull (Leucophaeus pipixcan), Black Tern (Chlidonias niger), Forster's Tern (Sterna forsteri), and Black-crowned Night-Heron (Nycticorax nycticorax) in Alberta, Saskatchewan, and Manitoba. We also examined the degree of overlap in nesting phenology (egg dates) and summarized survey methods that have been used to monitor the species during the breeding season—information that may be useful for the development of a multispecies monitoring program. For all species, the largest number of records of breeding colonies occurred in Alberta, with records declining eastward through Saskatchewan and Manitoba. We identified a number of breeding colonies occurring outside of currently defined species ranges, especially for the poorly studied Forster's Tern. Of 137 waterbodies hosting a colony of at least one species over the past 10 yr, 57 (41.6%) hosted colonies of at least 2 species, and 3 (2.2%) hosted colonies of all 5 species. Species tended to be reasonably synchronous in their breeding phenology, but Franklin's Gulls and Black-crowned Night-Herons tended to initiate nesting slightly earlier than the other species. We conclude that a multispecies survey timed in late May or early June to count nests and/or incubating adults, using either ground-based or aerial surveys, would likely be the most appropriate for monitoring all species jointly in the Prairie Provinces. The approach we take to compiling data from multiple sources on species occurrence and breeding phenology may be applicable to others wishing to examine the feasibility of a multispecies monitoring plan.
Great Salt Lake (GSL) is the largest hypersaline lake in North America and is the fall staging area for a high proportion of North America’s Wilson’s Phalaropes (Phalaropus tricolor) and Red-necked Phalaropes (Phalaropus lobatus). Unfortunately, diversion of freshwater for agriculture and development has decreased the size of GSL by 48%. To assess the potential impact of a smaller GSL on phalaropes, we collected data from 2013 to 2015 from sites where large, dense flocks of phalaropes congregated and sites where there were no phalaropes. At each site, we measured the densities of invertebrates that were preyed upon by phalaropes, including larval and adult brine flies (Ephydridae), adult brine shrimp (Artemia franciscana), chironomid larvae (Chironomidae), and corixid adults (Corixidae). Abiotic characteristics measured included water depth, water salinity, water temperature, wind speed, and benthic substrate. We analyzed high-salinity sites separately from low-salinity sites because they contained different invertebrates. High-salinity sites were in Carrington and Gilbert bays and were relatively deep (mostly <2 m). At the high-salinity sites, phalaropes exhibited a preference for sites with an abundance of adult brine flies and for microbialite substrates. The low-salinity sites were in Ogden and Farmington bays and were shallow (<1 m). At low-salinity sites, large phalarope flocks were more likely to occur at sites that were shallower, less saline, and had a high biomass of benthic macroinvertebrates. Our results indicate that physical features and prey availability are both important in determining phalarope habitat use at GSL. Phalaropes prefer to use shallower parts of GSL and brackish waters. These areas will be especially impacted by decreased freshwater inflow into GSL.
This study provides insight from the use of weather radar observations to understand the characteristics of the eared grebe migration near the Great Salt Lake (GSL) and provides unique information on weather conditions connected to these migration events. Doppler weather radar measurements from the Salt Lake City, Utah WSR-88D radar site (KMTX), along with meteorological surface and rawinsonde data, were used to identify and examine 281 eared grebe migration events across 15 winters from 1997/1998 through 2011/2012. An average of about 19 migration events occurred each winter with considerable interannual variability, as well as large variance in the spatial area and number of birds departing the GSL during each event. The migration events typically occurred during clear sky conditions in the presence of surface high pressure and colder than average surface temperatures. Migration events began 55 min after sunset, on average across the winter seasons, and in one case we demonstrate that an extended, nonstop flight was initiated of the departing eared grebes to northern Mexico. Eared grebes leaving the GSL largely flew above the freezing level with a mean northerly tailwind at flight altitude of 3.1 m s⁻¹ and a westerly, cross-flight wind of 5.0 m s⁻¹ while having an average flight speed at cruising altitude of 16.9 m s⁻¹, or 61 km h⁻¹. In addition to determining the variability of meteorological conditions during migration events across the 15 winters, atmospheric conditions during the largest migration event observed are presented and discussed.
