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At least 181 records · Page 10Linked to original sources

Evidence of red fox (Vulpes vulpes) depredating a Saltmarsh Sparrow (Ammospiza caudacuta) nest

Saltmarsh Sparrows ( Ammospiza caudacuta ), a tidal-marsh specialist, face severe population declines due to habitat loss, sea-level rise, and predation. While previous research suggests that predation pressure increases at the southern extent of the species’ breeding range, data on local predator communities remain limited. To address this, we deployed game cameras at 16 Saltmarsh Sparrow nests across four salt marshes on Virginia’s eastern shore, the southern-most extent of their breeding range. Our study provides camera-documented evidence of red fox ( Vulpes vulpes ) predation on Saltmarsh Sparrow nests. We detected a suspected predation event by white-tailed deer ( Odocoileus virginianus ) and four other potential nest predators. Additionally, we detected a Willet ( Tringa semipalmata ) aggressively displacing a nesting female, suggesting interspecific interactions may contribute to nest failure.

Virginia

Physiological impacts of sublethal Cyathocotyle bushiensis and Sphaeridiotrema pseudoglobulus infections in captive Lesser Scaup (Aythya affinis)

Thousands of Lesser Scaup ( Aythya affinis ) die annually in the Upper Mississippi River System, USA, from intestinal infections after birds consume exotic faucet snails, Bithynia tentaculata , infected with introduced parasites, Cyathocotyle bushiensis and Sphaeridiotrema pseudoglobulus . To date, the low frequency (biannual) and magnitude of mortality events from intestinal infections likely prevents trematode mortalities from being a major contributor to Lesser Scaup population declines. However, questions remain regarding the role sublethal infections may have on Lesser Scaup fitness along with the potential for carryover effects in the following breeding season. We examined the impact of a single sublethal C. bushiensis and S. pseudoglobulus infection on select physiological parameters in Lesser Scaup over a 10-day period post inoculation through three trials, each involving three experimental groups: baseline control, trial control, and treatment ( n = 96 scaup). We found that male Lesser Scaup that were in better body condition before the trial had fewer C. bushiensis and Sphaeridiotrema pseudoglobulus recovered from their intestines at necropsy. Individuals with the highest numbers of C. bushiensis and S. pseudoglobulus in their intestines lost the largest amounts of body mass during the trial. We found that blood urea nitrogen and triglycerides were lower when C. bushiensis and S. pseudoglobulus were present. Triglycerides and glucose declined from Day 0 to Day 5 but stabilized on Day 10 of the trial. Our results highlight changes in physiological metrics in Lesser Scaup from a sublethal infection with C. bushiensis and S. pseudoglobulus under experimental conditions. Changes in Lesser Scaup health parameters indicated that scaup surviving a single sublethal trematode infection may have reduced body condition, which could lead to negative health implications in the following breeding season.

Wilson Journal of Ornithology

Leucism in a family group and a review of color aberrations in Burrowing Owls ( Athene cunicularia )

Avian color aberrations capture public interest and sometimes indicate ecological problems. Diagnosing color aberration type can be difficult because nomenclature is inconsistent, appearance of color aberrations vary, typical coloration varies, and there are many undocumented color aberration types. One type of recognized avian color aberration is leucism. Leucism is often colloquially used to refer to all birds that are paler than normal but not albino, but it specifically refers to a plumage aberration in which, from hatching onward, birds are either all white or have patches of bilaterally symmetrical white feathers mixed with normally colored feathers, while retaining black pupils. Here, we document a case of leucism in a family of North American Burrowing Owls ( Athene cunicularia ). We observed a family group (two adults and five juveniles) of five leucistic, nearly all white owls, and two typically colored owls, in the Conata Basin, South Dakota, USA, in summer 2024. We also compiled all searchable records of color aberrations in Burrowing Owls across their North and South American range. We found 60 records of color aberrations, seven of which were cases of potential leucism. Twenty-five color aberrations were an unknown type in which only eye color was affected, all of them in Florida (USA) or south/central Brazil. Documenting color aberrations in birds can help expand our understanding of the types, causes, and consequences of color aberrations as well as the pigments and genetics that underly normal coloration.

South Dakota

The American Kestrel (Falco sparverius) genoscape: Implications for monitoring, management, and subspecies boundaries

Identifying population genetic structure is useful for inferring evolutionary process and comparing the resulting structure with subspecies boundaries can aid in species management. The American Kestrel ( Falco sparverius ) is a widespread and highly diverse species with 17 total subspecies, only 2 of which are found north of U.S./Mexico border ( F. s. paulus is restricted to southeastern United States, while F. s. sparverius breeds across the remainder of the U.S. and Canadian distribution). In many parts of their U.S. and Canadian range, American Kestrels have been declining, but it has been difficult to interpret demographic trends without a clearer understanding of gene flow among populations. Here we sequence the first American Kestrel genome and scan the genome of 197 individuals from 12 sampling locations across the United States and Canada in order to identify population structure. To validate signatures of population structure and fill in sampling gaps across the U.S. and Canadian range, we screened 192 outlier loci in an additional 376 samples from 34 sampling locations. Overall, our analyses support the existence of 5 genetically distinct populations of American Kestrels—eastern, western, Texas, Florida, and Alaska. Interestingly, we found that while our genome-wide genetic data support the existence of previously described subspecies boundaries in the United States and Canada, genetic differences across the sampled range correlate more with putative migratory phenotypes (resident, long-distance, and short-distance migrants) rather than a priori described subspecies boundaries per se. Based on our results, we suggest the resulting 5 genetically distinct populations serve as the foundation for American Kestrel conservation and management in the face of future threats.

Ornithology

Vegetation management on private forestland can increase avian species richness and abundance

Conservation efforts on private lands are important for biodiversity conservation. On private lands in South Carolina, in the southeastern United States, forestry management practices (prescribed burning, thinning, herbicide application) are used to improve upland pine habitat for wildlife and timber harvest and are incentivized through U.S. Department of Agriculture Farm Bill cost-share programs. Because many forest-dependent avian species have habitat requirements created primarily through forest management, data are needed on the effectiveness of these management activities. We studied privately owned loblolly pine ( Pinus taeda ) stands in the South Carolina Piedmont region. Our objective was to understand how management practices influence avian species richness and abundance at local (forest stand) and landscape levels in relatively small stands (average ~28 ha). We surveyed 49 forest stands during 2 bird breeding seasons with traditional point counts and vegetation surveys. We evaluated the effects of management on pine stand characteristics, avian species richness, and abundance of state-designated bird species of concern. Repeated burning and thinning shifted stand conditions to open pine woodlands with reduced basal area and herbaceous understories. Stands with lower basal area supported greater avian species richness. Some species increased in abundance in response to active management (e.g., Brown-headed Nuthatch [ Sitta pusilla ] and Indigo Bunting [ Passerina cyanea ]), but relationships varied. Some species responded positively to increases in forest quantity at a landscape scale (1–5 km; e.g., Northern Bobwhite [ Colinus virginianus ]). We found species-rich avian communities and species of conservation concern on working timber lands, indicating that incentivized forest management on private lands can provide valuable habitat for wildlife.

South Carolina

Evaluation of genetic change from translocation among Gunnison Sage-Grouse (Centrocercus minimus) populations

Maintenance of genetic diversity is important for conserving species, especially those with fragmented habitats or ranges. In the absence of natural dispersal, translocation can be used to achieve this goal, although the success of translocation can be difficult to measure. Here we evaluate genetic change following translocation in Gunnison Sage-Grouse ( Centrocercus minimus ), a species reduced to 7 discrete populations with low levels of gene flow and high levels of genetic differentiation. Between 2000 and 2014, 306 birds from the largest and most genetically diverse population (Gunnison Basin) were translocated to 5 much smaller satellite populations to augment local population size and increase genetic diversity. Although the magnitude of the effect varied by population, we found evidence of increased genetic variation, decreased genetic differentiation from Gunnison Basin, and reproduction between translocated individuals and resident birds. These results suggest that translocations are impacting satellite populations, with current data providing a new baseline for genetic diversity among populations of this imperiled species.

Colorado, Utah

Proximity to unconventional shale gas infrastructure alters breeding bird abundance and distribution

Unconventional shale gas development is a rapidly expanding driver of forest loss and fragmentation in the central Appalachian region. We evaluated the relationship between breeding passerine abundances and distance from shale gas development at a long-term (2008–2017) study site in northern West Virginia, USA. We examined responses of 27 species within 3 habitat guilds: forest interior, early successional, and synanthropic. More than half of the species evaluated showed sensitivity to distance from unconventional shale gas infrastructure (e.g., well pads, access roads, pipelines). Five forest interior species occurred in greater abundances farther from shale gas development, whereas 3 forest interior gap specialists increased in abundance closer to shale gas. Early successional and synanthropic species, including the nest-parasitic Brown-headed Cowbird ( Molothrus ater ), generally occurred in greater abundances closer to shale gas infrastructure. We used interpolated distributions of 4 focal species to assess their spatial response to unconventional shale gas development over time. Our results indicate that breeding passerine distributions and community composition are changing with forest disturbance driven by unconventional shale gas energy development.

West Vigninia

Barred Owls reduce occupancy and breeding propensity of Northern Spotted Owl in a Washington old-growth forest

Protected lands like national parks are important refuges for threatened and endangered species as environmental pressures on wildlife and their habitats increase. The Northern Spotted Owl ( Strix occidentalis caurina ), a species designated as threatened under the Endangered Species Act, occurs on public lands throughout the western United States including Mount Rainier National Park (MRNP), Washington. With virtually no history of timber harvest or large forest disturbance within MRNP boundaries since the park’s creation in 1899, MRNP provides an ideal place to evaluate potential impacts of climate change and invasive Barred Owls ( Strix varia ) on the Northern Spotted Owl. We used a multi-state, multi-season occupancy model to investigate how Northern Spotted Owl occupancy dynamics and breeding propensity are related to the presence of Barred Owls, local and regional weather, and habitat characteristics at MRNP from 1997 to 2016. Historical occupancy of Northern Spotted Owl breeding territories in MRNP has declined by 50% in the last 20 yr, and territory occupancy by breeding Northern Spotted Owls also decreased, reaching a low of 25% in 2016. Occupancy rates were higher on territories with steeper terrain and breeding rates were lower when Barred Owls were detected within historical territories. Our results also indicated that breeding propensity was higher when early nesting season temperatures during March and April were higher. In addition, the ability to detect breeding Northern Spotted Owls decreased when Barred Owls were present in the territory. Habitat variables from LiDAR were not correlated with Northern Spotted Owl occupancy dynamics, likely reflecting the dominance of old-growth forest in this protected park. This study illustrates the strong relationship between Barred Owls and Northern Spotted Owl demographics and breeding site selection in a landscape where habitat loss by timber harvest and fire has not occurred.

Washington

Nest microclimates of Greater Sage-Grouse in a post-megafire landscape: does selection equate to success?

Temperature at fine spatial scales is an important driver of nest site selection for many avian species during the breeding season and can influence nest success. Sagebrush ( Artemisia spp. ) communities have areas with high levels of vegetation heterogeneity and high thermal variation; however, fire removes vegetation that provides protection from predators and extreme environmental conditions. To examine the influence of microclimates on Greater Sage-Grouse ( Centrocercus urophasianus ) nest site selection and nest success in a fire affected landscape, we measured black bulb temperature (Tbb) and vegetation attributes (e.g. visual obstruction) at 3 spatial scales (i.e. nest bowl, microsite, and landscape) in unburned and burned areas. Nest bowls exhibited greater buffering of Tbb than both nearby microsites and the broader landscape. Notably, nest bowls were warmer in cold temperatures, and cooler in hot temperatures, than nearby microsites and the broader landscape, regardless of burn stage. Nest survival was higher for nests in unburned areas compared to nests in burned areas (unburned NS = 0.43, 95% CI: 0.33 to 0.54; burned NS = 0.24, 95% CI: 0.10 to 0.46). Amount of bare ground was negatively associated with nest survival, but effects diminished as the amount of bare ground reached very low levels. Shrub height and visual obstruction were positively associated with nest survival during the entire study period whereas, minimum Tbb had a weaker effect. Our findings demonstrate that thermoregulatory selection by Greater Sage-Grouse at nest sites had marginal effects on their nest survival. However, given that increases in vegetation structure (e.g. shrub height) provides thermal refuge and increases nest survival, vegetation remnants or regeneration in a post-fire landscape could be critical to Greater Sage-Grouse nesting ecology.

Oregon, Nevada

Integrating tracking and resight data enables unbiased inferences about migratory connectivity and winter range survival from archival tags

Archival geolocators have transformed the study of small, migratory organisms but analysis of data from these devices requires bias correction because tags are only recovered from individuals that survive and are re-captured at their tagging location. We show that integrating geolocator recovery data and mark–resight data enables unbiased estimates of both migratory connectivity between breeding and nonbreeding populations and region-specific survival probabilities for wintering locations. Using simulations, we first demonstrate that an integrated Bayesian model returns unbiased estimates of transition probabilities between seasonal ranges. We also used simulations to determine how different sampling designs influence the estimability of transition probabilities. We then parameterized the model with tracking data and mark–resight data from declining Painted Bunting ( Passerina ciris ) populations breeding in the eastern United States, hypothesized to be threatened by the illegal pet trade in parts of their Caribbean, nonbreeding range. Consistent with this hypothesis, we found that male buntings wintering in Cuba were 20% less likely to return to the breeding grounds than birds wintering elsewhere in their range. Improving inferences from archival tags through proper data collection and further development of integrated models will advance our understanding of the full annual cycle ecology of migratory species.

Ornithological Applications

Range-wide population genetic analysis of Seaside Sparrows (Ammospiza maritima) supports at least five distinct population segments that do not align with current subspecies descriptions

As an obligate salt marsh species, Seaside Sparrows ( Ammospiza maritima ) are vulnerable to numerous threats including climate change, coastal erosion, sea-level rise, and both natural and anthropogenic disasters. Of the 9 recognized subspecies, 2 are extinct and 1 is endangered. Previous genetic analyses of mitochondrial DNA (mtDNA) and microsatellite loci showed that current taxonomy does not accurately reflect underlying genetic diversity, with possible consequences for the distribution of conservation resources. To further inform Seaside Sparrow management, we comprehensively describe genetic structure among 24 range-wide sampling locations that include all extant subspecies. We inferred population structure from several thousand single-nucleotide polymorphisms collected from 272 individuals via restriction-site-associated DNA sequencing. Principal components, pairwise F ST values, and clustering approaches suggest that Seaside Sparrows on the Atlantic and Gulf Coasts are distinct and consist of at least 5 genetic clusters: 1 in southern Texas, 1 ranging from Aransas County, Texas, to Mississippi; 1 in western Florida; and 2 or 3 genetic groups intermixed along a gradient on the Atlantic Coast. These genetic clusters are not consistent with current subspecies taxonomy and could be used as distinct population segments (DPSs) to inform the most efficient allocation of resources to Seaside Sparrow conservation. Our results regarding the endangered subspecies, A. m. mirabilis , from southern Florida are inconclusive due to low sample size, but indicate that it is distinct and may represent a sixth DPS. Based on our genetic results, we recommend additional song and morphometric analyses in western Florida and a closer study of the boundary between the breeding distributions of A. m. maritima and A. m. macgillivraii to ensure the proper identification of DPSs.

Atlantic Ocean, Gulf of Mexico

Fully accounting for nest age reduces bias when quantifying nest survival

Accurately measuring nest survival is challenging because nests must be discovered to be monitored, but nests are typically not found on the first day of the nesting interval. Studies of nest survival therefore often monitor a sample that overrepresents older nests. To account for this sampling bias, a daily survival rate (DSR) is estimated and then used to calculate nest survival to the end of the interval. However, estimates of DSR (and thus nest survival) can still be biased if DSR changes with nest age and nests are not found at age 0. Including nest age as a covariate of DSR and carefully considering the method of estimating nest survival can prevent such biases, but many published studies have not fully accounted for changes in DSR with nest age. I used a simulation study to quantify biases in estimates of nest survival resulting from changes in DSR with nest age under a variety of scenarios. I tested four methods of estimating nest survival from the simulated datasets and evaluated the bias and variance of each estimate. Nest survival estimates were often strongly biased when DSR varied with age but DSR was assumed to be constant, as well as when the model included age as a covariate but calculated nest survival from DSR at the mean monitored nest age (the method typically used in previous studies). In contrast, biases were usually avoided when nest survival was calculated as the product of age-specific estimates of DSR across the full nesting interval. However, the unbiased estimates often showed large variance, especially when few nests were found at young ages. Future field studies can maximize the accuracy and precision of nest survival estimates by aiming to find nests at young ages, including age as a covariate in the DSR model, and calculating nest survival as the product of age-specific estimates of DSR when DSR changes with nest age.

Ornithological Applications

Golden Eagle dietary shifts following wildfire and shrub loss have negative consequences for nestling survivorship

Wildfires and invasive species have caused widespread changes in western North America’s shrub-steppe landscapes. The bottom–up consequences of degraded shrublands on predator ecology and demography remain poorly understood. We used a before–after paired design to study whether Golden Eagle ( Aquila chrysaetos ) diet and nestling survivorship changed following wildfires in southwestern Idaho, USA. We assessed burn extents from 1981 to 2013 and vegetation changes between 1979 (pre-burn) and 2014 (post-burn) within 3 km of Golden Eagle nesting centroids. We measured the frequency and biomass of individual prey, calculated diet diversity indexes, and monitored nestling survivorship at 15 territories in 1971–1981 and 2014–2015. On average, 0.70 of the area within 3 km of nesting centroids burned between 1981 and 2013, and the mean proportion of unburned shrubland decreased from 0.73 in 1979 to 0.22 in 2014. Diets in post-burn years were more diverse and had a lower proportion of some shrub-associated species, such as black-tailed jackrabbits ( Lepus californicus ) and mountain cottontails ( Sylvilagus nuttallii ), and a higher proportion of American Coots ( Fulica americana ), Mallards ( Anas platyrhynchos ), Piute ground squirrels ( Urocitellus mollis ), and Rock Pigeons ( Columba livia ) compared with pre-burn years. A high proportion of waterfowl represented a novel change in Golden Eagle diets, which are typically dominated by mammalian prey. Nestling survivorship was positively associated with the proportion of black-tailed jackrabbits and negatively associated with the proportion of Rock Pigeons in eagle diets. Rock Pigeons are a vector for Trichomonas gallinae , a disease-causing protozoan lethal to young eagles. Nesting attempts were more likely to fail (all young die) in the post-burn period compared with the pre-burn period. Dietary shifts are a common mechanism for predators to cope with landscape change, but shifts away from preferred prey to disease vectors affect nestling survivorship and could lead to population-level effects on productivity.

Idaho

Offspring of translocated individuals drive the successful reintroduction of Columbian Sharp-tailed Grouse in Nevada, USA

Translocations of North American prairie-grouse (genus Tympanuchus ) present a conservation paradox wherein they are performed to augment, restore, or reintroduce populations, but translocated individuals exhibit a diminished ability to contribute to population restoration. For reintroduced populations without immigration, persistence can only be achieved through reproductive contributions by translocated individuals and their progeny. Due to the disruptive nature of translocation (e.g., physiological chronic stress), progeny produced at restoration sites may outperform founder populations in terms of demographics, but this hypothesis has yet to be tested. We reintroduced Columbian Sharp-tailed Grouse ( T. phasianellus columbianus ; CSTG) to north central Nevada from 2013 to 2017 and used integrated population models (IPMs) to evaluate the process of population establishment and estimate latent contributions of progeny hatched at the restoration site to population rate of change ( ⁠ λ ^ "> λ ^ ⁠ ). Specifically, we used annual lek (i.e. communal breeding arenas) counts and demographic data from translocated individuals to build two separate IPMs to estimate λ ^ "> λ ^ ⁠ . While keeping demographic contributions by translocated individuals identical between models, one IPM assumed local progeny performance was demographically similar to translocated individuals (i.e. the baseline-IPM), and the second assumed that local progeny performed demographically similar to non-translocated CSTG (i.e. the informative-IPM). The baseline-IPM predicted strong population declines following the conclusion of translocations and extirpation by 2020, and it failed to predict observed lek counts. Conversely, the informative-IPM predicted population growth rates ( ⁠ λ ^ "> λ ^ = 1.17, 95% credible interval [CI]: 0.74–1.50) that were more similar to field observations. Offspring of translocated individuals likely perform at similar levels to non-translocated populations, and by not accounting for demographic differences between translocated individuals and non-translocated progeny hatched at the restoration site, managers could underestimate population performance and persistence. Thus, translocation practices that maximize the number of offspring immediately recruited into restoration sites are likely to be the most successful.

Nevada

Galliform exclusion from the Migratory Bird Treaty Act has produced an alternate conservation path, but no evidence for differences in population status

The Migratory Bird Treaty Act (MBTA) is critical to avian conservation in the United States, both through its protection of migratory birds and as a catalyst for a century of coordinated avian conservation. While more than 1,000 species are protected by MBTA, of extant bird species native to the continental U.S., only 20 species belonging to the order Galliformes are explicitly excluded. Management of galliforms has occurred largely without direct federal oversight, placing this group on a fundamentally different conservation path during the century following MBTA passage. In this paper, we review the historical context and biological justification for exclusion of galliforms from MBTA and synthesize how their present-day conservation differs from that of migratory birds. We find the most prominent difference between the two groups involves the scope of coordination among stakeholders. The U.S. government, primarily via the Department of Interior, acts as de facto coordinating body for migratory bird conservation and plays the central role in oversight, funding, and administration of management in the United States. In contrast, galliform management falls primarily to individual state wildlife agencies, and coordinated conservation efforts have been more ad hoc and unevenly spread across species. Migratory birds benefit from an almost universally greater scope of research and monitoring, scale of habitat conservation, and sophistication of harvest management compared with galliforms. Galliform harvest management plans, in particular, are less likely to use measurable objectives, reporting of uncertainty in population parameters, and explanation of harvest management techniques. Based on a review of species status lists (e.g., the U.S. Endangered Species Act), we found no evidence that galliforms were more frequently listed than migratory species. Regional trend estimates from the North American Breeding Bird Survey (BBS) were more likely to be negative for galliforms over the period 1966–2015, but this was primarily driven by Northern Bobwhite ( Colinus virginianus ). Data to assess galliform population status are generally poor, which complicates assessment for roughly half of galliform species. Increased support for coordination among state agencies and other stakeholders, similar to that applied to migratory birds, could help to ensure that galliform conservation is poised to tackle forthcoming challenges associated with global change.

North America

Highly specialized recreationists contribute the most to the citizen science project eBird

Contributory citizen science projects (hereafter “contributory projects”) are a powerful tool for avian conservation science. Large-scale projects such as eBird have produced data that have advanced science and contributed to many conservation applications. These projects also provide a means to engage the public in scientific data collection. A common challenge across contributory projects like eBird is to maintain participation, as some volunteers contribute just a few times before disengaging. To maximize contributions and manage an effective program that has broad appeal, it is useful to better understand factors that influence contribution rates. For projects capitalizing on recreation activities (e.g., birding), differences in contribution levels might be explained by the recreation specialization framework, which describes how recreationists vary in skill, behavior, and motives. We paired data from a survey of birders across the United States and Canada with data on their eBird contributions (n = 28,926) to test whether those who contributed most are more specialized birders. We assigned participants to 4 contribution groups based on eBird checklist submissions and compared groups’ specialization levels and motivations. More active contribution groups had higher specialization, yet some specialized birders were not active participants. The most distinguishing feature among groups was the behavioral dimension of specialization, with active eBird participants owning specialized equipment and taking frequent trips away from home to bird. Active participants had the strongest achievement motivations for birding (e.g., keeping a life list), whereas all groups had strong appreciation motivations (e.g., enjoying the sights and sounds of birding). Using recreation specialization to characterize eBird participants can help explain why some do not regularly contribute data. Project managers may be able to promote participation, particularly by those who are specialized but not contributing, by appealing to a broader suite of motivations that includes both appreciation and achievement motivations, and thereby increase data for conservation.

Ornithological Applications

Habitat edges influence the distribution of nest predators for Seaside Sparrows, but not nest placement or success

Nest failure for coastal marsh bird species is primarily caused by predation and nest flooding. As sea level rise makes nest flooding more likely, the threat of nest predation will constrain the potential adaptive responses of marsh nesting species. Thus, understanding the predictors of nest predation is important for the conservation of salt marsh-dwelling bird species, such as the Seaside Sparrow ( Ammospiza maritima ). Predator activity may be influenced by landscape features (particularly habitat edges), potentially making nest predation predictable. We aimed to understand the predictability of Seaside Sparrow nest predation relative to two major landscape features: roads and tidal rivers, as both of these edges may be entryways or attractants for predators in marshes. In coastal Georgia, USA, we assessed mammalian predator activity relative to the two features of interest, and hypothesized that mammalian predator activity would be greater close to roads and tidal rivers. We also recorded Seaside Sparrow nest locations and nest predation events and hypothesized that nest predation events would increase with increasing predator activity. Consistent with our first hypothesis, mammalian predator activity increased close to roads and tidal rivers, but mammalian predator distribution did not explain the spatial variation in Seaside Sparrow nest predation thus not supporting our second hypothesis. Seaside Sparrows also placed their nests in locations with high mammalian predator activity, indicating that the ability to avoid nesting in high-risk areas may be constrained by habitat or resource limitations. Additionally, mammals may not be the primary nest predators, as we found that one bird species—Marsh Wren ( Cistothorus palustris )—contributed substantially to nest predation rates. Understanding the predictability of mammalian predator distribution can allow for focused predator management efforts, such as exclusion, to habitat edges where we found the highest mammalian predator activity, which could relax the constraint of nest predation on Seaside Sparrow’s ability to respond to the intensifying threat of sea level rise.

Georgia

Influence of fine-scale habitat characteristics on sage-grouse nest site selection and nest survival varies by mesic and xeric site conditions

Resource managers and scientists across western U.S. agencies seek methodologies for identifying environmental attributes important to both wildlife conservation and broad-scale land stewardship. The Greater Sage-Grouse ( Centrocercus urophasianus ; hereafter, sage-grouse) exemplifies a species in need of this broad-scale approach given widespread population declines that have resulted from loss and degradation of habitat from natural and anthropogenic disturbances. These include agricultural land conversion, conifer expansion, energy development, and wildfire coupled with ecological conversion by invasive plants such as cheatgrass ( Bromus tectorum ). Development of habitat assessments and conservation actions for sage-grouse benefit from studies that link demographic responses to habitat selection patterns. To address this, we examined nest survival of sage-grouse in relation to fine-scale habitat patterns (i.e., field-based habitat measurements) that influenced nest site selection, using data from nests of telemetered females at 17 sites over 6 years in Nevada and northeastern California, USA. Importantly, sites spanned mesic and xeric average precipitation conditions that contributed substantially to vegetation community structure across cold desert ecosystems of the North American Great Basin. Vegetative cover immediately surrounding sage-grouse nests was important for both nest site selection and nest survival, but responses varied between mesic and xeric sites. For example, while taller perennial grasses were selected at xeric sites, we found no evidence of selection for perennial grass at mesic sites, indicating a functional response to availability of habitat features between hydrographic regions. Furthermore, perennial grass height and forb height both had positive effects on nest survival at xeric sites, but we found varying effects at mesic sites. We emphasize that precipitation conditions driving ecosystem productivity vary regionally among sagebrush communities, shaping vegetation structure and suitable habitat conditions for nesting sage-grouse.

Ornithological Applications