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Conservation partners are concerned that oil and gas development in the Prairie Pothole Region may reduce the abundance of breeding duck pairs using associated wetland habitat. We conducted wetland-based surveys for breeding pairs of 5 species of dabbling ducks in the Bakken oil field during 2015–2017 across a gradient of oil and gas development intensity to test the hypothesis that the abundance of breeding duck pairs on survey wetlands would decrease as the development of oil and gas resources increased. We included covariates traditionally used to predict breeding duck pairs (i.e. wetland size and class) and a spatiotemporal index of disturbance when developing zero-inflated Poisson models relating pair abundance to environmental predictors. Similar to past analyses, pair abundance was strongly associated with wetland size. Our results were mixed and suggested that the abundance of early and late nesting species was positively and negatively related, respectively, to an index of disturbance that was largely driven by oil and gas development. Regardless of the direction of the relationship, effect sizes were small and not considered biologically significant. Our findings indicate that in our study area, strategies to conserve wetland resources for breeding duck pairs should not deviate from previous prioritization metrics within the range of oil and gas development we observed. We believe that our findings may have implications to similar landscapes within the Bakken.
LAY SUMMARY
Since 2008, the oil and gas development in the North Dakota and Montana portion of Bakken Oil Formation has increased dramatically.
There is considerable overlap between the Bakken Oil Formation and important Prairie Pothole Region wetlands critical for waterfowl production.
We surveyed breeding Blue-winged Teal, Gadwall, Mallard, Northern Pintail, and Northern Shoveler pairs from 2015 to 2017 to determine if breeding pair abundance was lower in proximity to a gradient of disturbance from oil and gas development.
Our results were mixed but regardless, changes in pair abundance were small and we considered the potential biological effect to be small.
We recommend that existing conservation tools continue to be used to identify important grassland and wetland resources in the region given that we did not observe a biologically significant reduction in breeding duck pairs.
The understanding that motherhood impacts career paths is so pervasive among early-career scientists that some feel they must choose parenthood or a career. The penalties associated with motherhood can contribute to the “leaky pipeline,” which equates to the high attrition rate of women due to social, economical, or temporal factors as they proceed through their career and exacerbates persistent gender gaps at mid- and late-career stages. Here, we review the literature and summarize common challenges faced by ornithologist mothers and nonbinary parents, and we adopt a full lifecycle approach to recommend evidence-based strategies for overcoming those challenges. The American Ornithological Society (AOS) is well positioned to support and celebrate women and nonbinary ornithologists who choose parenthood, and we highlight progress made by the AOS to improve gender diversity, equity, and inclusion within the Society. For example, AOS caregiver grants allow more parents to attend and participate in conferences. We suggest additional initiatives (e.g., elevating role models, hosting mentoring networks, and disseminating best practices) that could further support women who want to become or already are parents while also achieving rewarding careers in ornithology. AOS leadership can take steps to close the gender gap in ornithology and other Science, Technology, Engineering, and Mathematics fields. With a larger, more diverse, and talented community, the Society will be better equipped to achieve its mission: conserving and understanding bird life on earth, enriching ornithology as a profession, and mentoring young professionals.
LAY SUMMARY
Mothers and nonbinary parents face unique challenges for remaining in ornithology, leading to a “leaky pipeline.”
The American Ornithological Society's (AOS) continued support for parents aims to close the gender gap in early-, mid-, and late-career stages.
We describe how a full lifecycle approach to advancing diversity and equity can enrich the field of ornithology.
Access to role models, mentors, and resources for field and lab research, together with family-friendly conferences, can alleviate some of these challenges.
Disseminating best practices to the ornithological community can further position the AOS as a leader.
The AOS is well positioned to advance the understanding and stewardship of birds on earth while demonstrating a commitment to mentoring young professionals.
Greater Sage-Grouse (Centrocercus urophasianus) is a species of conservation concern and is highly susceptible to mortality from West Nile virus (WNV). Culex tarsalis, a mosquito species, is the suspected primary vector for transmitting WNV to sage-grouse. We captured, radio-tagged, and monitored female sage-grouse to estimate breeding season (April 15 to September 15) survival, 2016–2017. Deceased sage-grouse were tested for active WNV; live-captured and hunter-harvested sage-grouse were tested for WNV antibody titers. Additionally, we trapped mosquitoes with CO2-baited traps 4 nights per week (542 trap nights) to estimate WNV minimum infection rate (MIR). Eight sage-grouse mortalities occurred during the WNV seasons of 2016 and 2017, 5 had recoverable tissue, and 1 of 5 tested positive for WNV infection. Survival varied temporally with sage-grouse biological seasons, not WNV seasonality. Survival was 0.68 (95% CI: 0.56–0.78; n = 74) during the reproductive season (April 1 to September 15). Mammalian predators were the leading suspected cause of mortality (40%), followed by unknown cause (25%), avian predation (15%), unknown predation (15%), and WNV (5%). These results indicate WNV was not a significant driver of adult sage-grouse survival during this study. Three sage-grouse (1.9%; 95% CI: 0.5–5.9%) contained WNV antibodies. We captured 12,472 mosquitoes of which 3,933 (32%) were C. tarsalis. The estimated WNV MIR of C. tarsalis during 2016 and 2017 was 3.3 and 1.6, respectively. Our results suggest sage-grouse in South Dakota have limited exposure to WNV, and WNV was not a significant source of sage-grouse mortality in South Dakota during 2016 and 2017. Based on our finding that a majority of sage-grouse in South Dakota are susceptible to WNV infection, WNV could potentially have an impact on the population during an epizootic event; however, when WNV is at or near-endemic levels, it appears to have little impact on sage-grouse survival.
LAY SUMMARY
West Nile virus is a new disease to the United States. The Greater Sage-Grouse is susceptible to mortality from West Nile virus.
We captured and radio-tagged sage-grouse to monitor survival. We collected blood from sage-grouse to test for West Nile virus antibodies. We captured and tested Culex tarsalis mosquitoes for West Nile virus. C. tarsalis is a species commonly associated with transmitting West Nile virus.
Most sage-grouse (70%) died from predation and one of 20 sage-grouse mortalities (5%) was caused by West Nile virus. Overall, we observed low sage-grouse exposure to West Nile virus (<2%). We did not document a decrease in survival during West Nile virus season and found that survival varies with breeding season events for sage-grouse (nesting and brood rearing).
One caveat is that we found low numbers of mosquitoes carrying West Nile virus, indicating that conditions were not suitable for an outbreak during our study.
Twenty percent of the Brazilian Amazon has now been deforested, and deforestation rates are increasing. This compels us to evaluate the conservation potential of human-modified landscapes; yet the ecological value of regenerating and fragmented Amazonian forests remains poorly understood. To date, most faunal studies in disturbed forests have examined metrics derived from presence or abundance. Although valuable, these data cannot tell us how old-growth species are using disturbed forests. In this study, we complement presence data with breeding observations to assess more comprehensively the habitat quality of disturbed forests in central Amazonia. We synthesized breeding evidence from standardized passive mist-netting, mixed-species flock-following, and opportunistic nest-searching across a full annual cycle in 30–35-year-old secondary forest, 10-ha fragments, and undisturbed forest. We then used multistate occupancy models to estimate the number of undetected breeding species in each forest type, which illustrated that fewer species bred in secondary forest (–43%) and 10-ha fragments (–17%) than in undisturbed forest. Both these losses are larger than the associated decrease in species richness alone (–17% and –10%, respectively). Notably, we confirmed breeding by only three terrestrial and near-ground insectivores in fragments and secondary forest combined (of the 9 species found in undisturbed forest). Disturbed forests also supported fewer breeding individuals (–35% to –50%) and, in secondary forest, fewer successful breeding attempts (–24%). Encouragingly, however, some forest-dependent birds are breeding and producing fledglings in disturbed forests, including representatives from almost every guild. This was especially apparent for mixed-species flocks and army-ant followers, two guilds that have historically been considered vulnerable to anthropogenic disturbance. Therefore, despite a loss of breeding habitat in disturbed forests, these data suggest that landscapes composed of regenerating forest and small fragments have conservation potential for forest bird populations.
LAY SUMMARY
Twenty percent of the Brazilian Amazon has now been deforested, yet the value of regenerating and fragmented forests for plants and animals remains poorly understood.
To indicate how forest-dependent birds are using these disturbed forests, we used a variety of field methods to synthesize evidence of local breeding.
We found that small forest fragments and, especially, secondary forest support fewer breeding species than undisturbed forest.
In particular, species that forage on or near the ground were absent from the breeding bird communities of fragments and secondary forest.
However, many forest-dependent birds are reproducing in small fragments and secondary forest, indicating that these forests have conservation potential for forest bird populations.
Standardized monitoring is critical for conservation because reliable survey data are used to inform the necessity, type, and effectiveness of conservation actions. Many of the avian monitoring data used for conservation are collected by “comprehensive” programs that survey for all species observed; however, there are some species that have low availability for detection during comprehensive surveys and are instead monitored with targeted programs. Unfortunately, those targeted programs are rarely evaluated relative to existing programs and management objectives to inform allocation of effort. We assessed the statistical performance of the comprehensive North American Breeding Bird Survey (BBS), the targeted Canadian Nightjar Survey (CNS), and the two programs combined for the Common Nighthawk (Chordeiles minor). First, we used parameters from the existing datasets to simulate population declines and determined the probability of detecting those declines. Analyses that combined both datasets resulted in higher probability of detecting a 30% population decline (BBS: 38%, CNS: 64%, combined: 69%). Next, we built probability of occurrence models and assessed the predictive performance of those models. Combined analyses had similar predictive performance to the CNS and moderated poor performance of the BBS in the north (mean Cohen's kappa; BBS: 0.40, CNS: 0.46, combined: 0.50). Our results suggest that data from targeted monitoring is important for evaluation of Common Nighthawk population trend and habitat relationships but is best combined with BBS data. Comprehensive and targeted monitoring programs may be better when considered together, and exploration of data combination should become the rule, not the exception. We suggest that the framework we present can be used as a starting point for evaluating targeted monitoring programs relative to defined objectives and existing programs, with the potential to explore hypothetical management scenarios.
LAY SUMMARY
Not all species are well detected during “comprehensive” bird surveys like the Breeding Bird Survey.
Targeted monitoring at particular times of day or in specific locations can help detect those species and help wildlife managers conserve them.
The Common Nighthawk is a crepuscular bird that is poorly detected during comprehensive dawn surveys.
We showed that the targeted Canadian Nightjar Survey improves the precision of Common Nighthawk population trends and accuracy of habitat predictions.
Combining information from the Breeding Bird Survey and the Canadian Nightjar Survey can further improve population trend estimates and habitat predictions.
Our study suggests that targeted monitoring can be important for some species and that combining it with comprehensive monitoring is important for evaluating existing and proposed conservation programs.
Bird migration patterns are changing worldwide due to current global climate changes. Addressing the effects of such changes on the migration of birds in South America is particularly challenging because the details about how birds migrate within the Neotropics are generally not well understood. Here, we aim to infer the potential effects of future climate change on breeding and wintering areas of birds that migrate within South America by estimating the size and elevations of their future breeding and wintering areas. We used occurrence data from species distribution databases (VertNet and GBIF), published studies, and eBird for 3 thrush species (Turdidae; Turdus nigriceps, T. subalaris, and T. flavipes) that breed and winter in different regions of South America and built ecological niche models using ensemble forecasting approaches to infer current and future potential distributions throughout the breeding and wintering periods of each species. Our findings point to future shifts in wintering and breeding areas, mainly through elevational and longitudinal changes. Future breeding areas for T. nigriceps, which migrates along the Andes Mountains, will be displaced to the west, while breeding displacements to the east are expected for the other 2 species. An overall loss in the size of future wintering areas was also supported for 2 of the species, especially for T. subalaris, but an increase is anticipated for T. flavipes. Our results suggest that future climate change in South America will require that species shift their breeding and wintering areas to higher elevations in addition to changes in their latitudes and longitude. Our findings are the first to show how future climate change may affect migratory birds in South America throughout the year and suggest that even closely related migratory birds in South America will be affected in different ways, depending on the regions where they breed and overwinter.
LAY SUMMARY
Bird ranges are changing worldwide due to current global climate changes.
Bird migration is common in South America, with more than 200 species of Neotropical austral migrants, yet we still understand little about how these species are impacted by climate change.
We modeled future breeding and winter distributions of 3 species of migratory thrushes in South America.
Our results suggest that future wintering and breeding areas for migratory birds in South America will decrease, change in latitude and longitude, and shift to higher regions although patterns will likely vary by species.
Conspecific presence can indicate the location or quality of resources, and animals settling near conspecifics often gain fitness benefits. This can result in adaptive conspecific attraction during breeding habitat selection as demonstrated in numerous terrestrial, territorial birds. There is growing interest in using simulated conspecific social cues (e.g., decoys, broadcasted vocalizations) to manage bird distributions, yet it remains unclear when this approach is likely to succeed. We reviewed published studies to evaluate whether the strength of conspecific attraction in terrestrial birds is mediated by characteristics of species (life history traits), simulated cues (e.g., timing and duration), sites (e.g., quality), and how conspecific attraction was measured. We identified 31 experiments that simulated social cues and compared conspecific settlement between treatment and control sites. We then used phylogenetically controlled meta-regression to assess the impacts of 19 moderators on settlement. Nearly all species included in these experiments were migratory passerines, and social cues generally had a strong, positive influence on their settlement decisions, as the odds of site occupancy were 3.12× (95% CI: 0.81–11.69) greater in treatment sites relative to control sites. Within this group, conspecific attraction was evolutionarily conserved with ≥25.5% (95% CI: 5.1%–65.4%) of the variance in treatment effects explained by phylogenetic relatedness. However, we found no evidence that any covariates influenced the response to social cues, and we posit this stems from limited research specifically designed to identify the mechanisms mediating conspecific attraction. We therefore developed a research agenda that provides a framework for testing mechanistic hypotheses regarding how cue characteristics, species traits, and spatial contexts may mediate attraction to conspecifics. Evaluating these hypotheses will greatly advance the field by helping managers understand when, where, and why simulating social cues can be used to enhance populations of species that are of conservation concern.
LAY SUMMARY
Simulating the presence of terrestrial birds often attracts breeders of the same species, though how this varies among species, simulated cues, or locations remains unknown.
We reviewed 31 experiments that examined conspecific attraction to simulated social cues in terrestrial breeding birds and tested the effects of 19 variables on attraction.
These experiments, which focused primarily on migratory songbirds, revealed strong effects of simulated presence on settlement rates, but no strong evidence that any other variables affected settlement rate.
Simulating social cues such as vocalizations could be useful for managers interested in attracting migratory songbirds, although whether this extends to other terrestrial species remains unknown.
A greater understanding of how and where to use this technique will improve its utility as a tool for enhancing populations of species of conservation concern.
Subtropical grasslands are highly susceptible to habitat conversion and number among South America's most threatened ecosystems. The grasslands of northeastern Argentina have been identified as a priority conservation area for threatened capuchino seedeaters because they constitute the main breeding area of these migratory birds. The Iberá Seedeater (Sporophila iberaensis) is a newly described species in the Iberá Wetlands in Argentina whose biology is still poorly understood. The endangered species inhabits grasslands but has only been reported to breed in the Iberá Wetlands ecoregion of northeastern Argentina. To explore the species' association with grassland vegetation, we studied the breeding biology (clutch size, hatching success, and fledgling production) of the Iberá Seedeater and the main parameters that influence nest survival and nest-site selection. We conducted nest searches and banded adults and nestlings in Iberá National Park during the breeding seasons of 2016–2018. The breeding season of the Iberá Seedeater was highly synchronous and the cumulative probability of nest survival was 0.16. The daily nest survival rate decreased as the breeding season advanced, survival was lower for nests supported by Rhynchospora corymbosa than Paspalum durifolium, the two main nest substrates, and the main causes of nest failure were nest predation and strong winds. Additionally, the population exhibited male-biased site fidelity and a low female return rate. In contrast to other capuchinos, whose breeding biology is associated with upland grasslands, the Iberá Seedeater nested exclusively in flooded lowland grasslands on marsh plants. Thus, effective lowland grassland management is key to maintain the vegetation structure required for reproduction in the Iberá Seedeater.
LAY SUMMARY
Capuchino seedeaters are austral migrants strongly associated with subtropical grasslands, which are among the ecosystems that suffer the highest rates of habitat conversion.
The Iberá Seedeater is a recently described, endangered species that has a poorly understood biology, restricted breeding range, and faces unknown threats.
We located and monitored nests, banded adults and nestlings, and took vegetation measurements to assess nest-site selection between 2016 and 2018 in Iberá National Park.
Breeding site fidelity was male-biased, and nest survival was relatively low, decreased as time of breeding advanced, and differed among nest substrates.
Breeding occurred exclusively in flooded lowland grasslands, suggesting that the species could be sensitive to changes in vegetation structure and water levels.
Tropical mountains are global hotspots for birdlife. However, there is a dearth of baseline avifaunal data along elevational gradients, particularly in Africa, limiting our ability to observe and assess changes over time in tropical montane avian communities. In this study, we undertook a multi-year assessment of understory birds along a 1,750 m elevational gradient (1,430–3,186 m) in an Afrotropical moist evergreen montane forest within Ethiopia's Bale Mountains. Analyzing 6 years of systematic bird-banding data from 5 sites, we describe the patterns of species richness, abundance, community composition, and demographic rates over space and time. We found bimodal patterns in observed and estimated species richness across the elevational gradient (peaking at 1,430 and 2,388 m), although no sites reached asymptotic species richness throughout the study. Species turnover was high across the gradient, though forested sites at mid-elevations resembled each other in species composition. We found significant variation across sites in bird abundance in some of the dietary and habitat guilds. However, we did not find any significant trends in species richness or guild abundances over time. For the majority of analyzed species, capture rates did not change over time and there were no changes in species' mean elevations. Population growth rates, recruitment rates, and apparent survival rates averaged 1.02, 0.52, and 0.51 respectively, and there were no elevational patterns in demographic rates. This study establishes a multi-year baseline for Afrotropical birds along an elevational gradient in an under-studied international biodiversity hotspot. These data will be critical in assessing the long-term responses of tropical montane birdlife to climate change and habitat degradation.
LAY SUMMARY
There is a dearth of baseline avifaunal data along elevational gradients, especially in Africa, impeding efforts to evaluate temporal changes in tropical montane bird communities.
We assessed species richness, community composition, abundance, elevational occurrence, and demographic rates of montane understory avifauna along an elevational gradient in Ethiopia's Bale Mountains.
We found a bimodal pattern is observed and estimated species richness, with high species turnover across the gradient.
There were few significant changes in guild or species capture rates over time, yet we documented eight species at elevations higher than documented in the established literature.
This six-year study establishes an important baseline for East African understory montane birds along an elevational gradient in an under-studied international biodiversity hotspot.
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.
LAY SUMMARY
Recent advances in the miniaturization of tracking devices have transformed the ability of researchers to track small migratory birds throughout their journeys. However, the small size of these devices prevents transmitting the data to satellites, so birds must be recaptured to obtain the tracking data.
Because tracking data can only be obtained from individuals that survive and return the following year, these data underestimate how many birds migrate to regions where they are less likely to survive, which may lead to incorrect conclusions about what areas are most important to a species.
We show that more accurate estimates of migratory patterns can be obtained by combining the data from the tracking tags with information about the survival of individuals within each population.
Application of this method to tracking data from Painted Buntings revealed that males wintering in Cuba experience nearly 15–20% lower survival than males wintering elsewhere in the range.
Seaside Sparrows (Ammospiza maritima) are tidal salt marsh endemic passerines found along the Atlantic and Gulf coasts of North America. Currently, there are 7 described subspecies, and “MacGillivray's” Seaside Sparrow (A. m. macgillivraii) is the name given to the Atlantic coast subspecies breeding from North Carolina to northern Florida. In 2019 the US Fish and Wildlife Service received a petition to list this subspecies under the Endangered Species Act due to shrinking populations and loss of marsh habitat, which necessitated a Species Status Assessment. As part of the Species Status Assessment, we analyzed genetic (microsatellite and mitochondria) data from 464 Seaside Sparrows from Connecticut to Florida, USA, to infer population connectivity (gene flow) among Atlantic coast populations, and to assess the concordance of population genetic data with the putative ranges of the subspecies. Bayesian cluster analysis (program STRUCTURE) indicates three genetically distinct population segments: (1) Florida + Georgia, (2) Charleston, South Carolina, and (3) North Carolina to Connecticut. The population in Charleston, South Carolina was the most strongly differentiated based on microsatellite data, and harbored a unique mitochondrial haplotype not shared by other sampling locations, possibly reflecting long-standing isolation. Our results indicate population genetic discordance with currently described ranges of the subspecies of Seaside Sparrow and provide grounds for the consideration of separate management plans for the three populations.
LAY SUMMARY
“MacGillivray's” Seaside Sparrow is the name given to the Atlantic coast Seaside Sparrow subspecies breeding from North Carolina to northern Florida. The U.S. Fish and Wildlife Service received a petition to list this subspecies under the Endangered Species Act due to shrinking populations and loss of marsh habitat.
We analyzed genetic data from Seaside Sparrows from Connecticut to northern Florida to ask whether Atlantic Seaside Sparrows are one large population or multiple smaller populations.
Our analyses suggest at least three populations: (1) a Florida + Georgia group, (2) a North Carolina and northward group, and (3) a group in South Carolina that blends into the other two groups.
From a conservation perspective, we suggest “MacGillivray's” Seaside Sparrow (as a unit) is not the best way to identify potentially at-risk populations. Rather, we think it makes sense to consider different management strategies for (at least) the three groups we identified using genetic data.
Reduced rainfall in tropical regions decreases the availability of food resources for overwintering songbirds, with negative impacts on their body condition. Increasingly dry conditions at tropical wintering sites as a result of climate change may impact the ability of temperate-breeding songbirds to prepare for and execute their spring migration. We studied the carryover effects of natural climatic fluctuations created by the El Niño–Southern Oscillation (ENSO) in tropical overwintering areas on 7 long-distance migratory songbirds at a Canadian stopover site. We used the Normalized Difference Vegetation Index as a proxy for tropical habitat productivity and resource availability and a 34-year bird banding dataset from Long Point, Ontario, Canada to assess migration timing and stopover body condition. To increase our ability to detect potential carry-over effects, we employed a novel approach of using recent migratory connectivity studies to restrict the wintering ranges to areas most likely used by individuals passing through southern Ontario. Using linear models, we found that overwinter habitat productivity was significantly negatively influenced by dry ENSO events in the overwintering ranges in 3 of 7 species, with a fourth near-significant. Subregional differences in the effect of ENSO on precipitation patterns may explain why we did not detect a consistent effect of ENSO on overwinter habitat productivity for all species. Despite restricting the wintering range and using a robust dataset for species with diverse life histories, we detected only weak and often conflicting evidence of population-level carry-over effects from dry ENSO events and overwinter habitat productivity. Negative carry-over effects may be strongest and most evident during the earlierstages of migration because birds may be able to compensate to some extent for poor departure condition and late departure while en route.
LAY SUMMARY
Increasingly dry conditions in the tropics have been shown to reduce food availability and thus body condition of overwintering songbirds.
Low food availability at wintering sites is hypothesized to cause negative carry-over effects by delaying spring migration and reducing body condition while on migration.
We used 34 years of bird banding data at a northern stopover site to assess how migratory birds have historically responded to dry conditions in their tropical overwintering areas.
We found only weak negative effects from dry winters on the body condition and migratory timing of songbirds arriving to southern Ontario in the spring, and results were contradictory within and among species.
Migratory songbirds may compensate for the negative impacts of dry winters in tropical habitats while en route to northern breeding sites.
Climate change, including directional shifts in weather averages and extremes and increased interannual weather variation, is influencing demography and distributions for many bird species. The Ouachita Mountains ecoregion in southeast Oklahoma and west-central Arkansas contains 2 populations of the Red-cockaded Woodpecker (Dryobates borealis, RCW), a federally endangered, cooperatively breeding species. Since this region is at the RCW's northwestern range periphery, ecological thresholds likely are limiting for the species. Therefore, populations in this region may be more sensitive to climate change-associated weather variation and unpredictability. We used 26 years of nesting data (1991–2016) from the 2 RCW populations to determine if interannual weather variation has affected nesting phenology and productivity. For each population, we used daily temperature and precipitation data for 3 periods (30 and 60 days before nesting; 40 days overlapping the nesting period) to determine how weather influences median nesting date and average clutch size and numbers of fledglings. In a separate analysis, we used shorter time windows with individual nests as replicates to determine how discrete weather events (e.g., minimum and maximum temperatures and intense precipitation events) affect nest success and partial brood loss. For both Oklahoma and Arkansas populations, warmer early spring temperatures generally advanced nesting and increased clutch size and fledgling number. However, the effects of average precipitation varied depending on the amount and duration of precipitation in different time periods. At the nest level, most variables reflecting discrete temperature and precipitation events were unrelated to nest success and brood loss, suggesting that factors other than weather (e.g., habitat quality and predation) more strongly influenced the nesting output of individual RCW broods. Our results indicate RCWs are responding to interannual weather variation in complex and variable ways. However, warming trends may generally be having positive effects on the species at the northwestern edge of its range.
LAY SUMMARY
Climate change is influencing distributions and demography for many bird species. Understanding effects on populations at the edge of species' ranges will be crucial for adapting management to prevent climate-caused declines and extinctions.
For the endangered Red-cockaded Woodpecker, we used 26 years of nest monitoring data to evaluate how interannual climate variation has affected nesting timing and productivity at the northwestern edge of the species' range.
Warmer temperatures in early spring generally advanced Red-cockaded Woodpecker nesting dates and increased nest productivity. Precipitation effects were variable, depending on the amount and duration of rainfall in different time periods before and during the nesting season.
Although climate effects on Red-cockaded Woodpecker nesting ecology appear complex, conditions may be changing in ways that increase nest productivity at the northwestern edge of the species' range. Managing habitat in this part of the range may become increasingly important to Red-cockaded Woodpecker conservation as climate change continues.
Effects of global climate change on local climate and dynamics of animal populations can be extreme at high latitudes and high elevation. Here, we investigated climate variation and its effects on the diversity and dynamics of a subalpine bird community in California's Sierra Nevada over 32 years (1978–2009). For the first 16 years, we also assessed the effects of climate on fledging timing, fledging success, and fledgling numbers. We considered 4 climate variables: snowmelt timing, spring mean temperature, summer minimum temperature, and summer precipitation. Climate metrics were highly variable among years and exhibited evidence of temporal pattern. Cooler years with late-melting snowpack were less common in later years, and summer temperature increased, while summer precipitation tended to decrease, over the study period. Years of early snowmelt were associated with higher species richness, more breeding territories, population increases, earlier fledging, and fewer fledglings/successful breeding territory. After accounting for snowmelt timing, spring temperature was positively associated with population change and, although variable among species, negatively associated with fledging date and productivity metrics. Summers with higher minimum temperatures were associated with higher fledging success and (although variable among species) more fledglings. Three species showed evidence of population trend: Yellow-rumped Warbler (Setophaga coronata; increasing), Clark's Nutcracker (Nucifraga columbiana; declining), and Chipping Sparrow (Spizella passerina; declining). We suggest that enhanced diversity and population growth in mild springs were driven primarily by the recruitment of young first-time breeders, which may also help explain lower productivity in those years. Spring and summer temperatures may have also affected productivity through effects on predator activity or on dynamics of moisture, vegetation, and food availability. Finally, summer precipitation was largely accumulated through summer storms, which were observed to cause occasional deaths to eggs and nestlings. Our results highlight the value of long-term single-site multispecies data in understanding population and community dynamics at an environmental extreme with high annual variability.
LAY SUMMARY
Long-term local studies of bird populations and communities and their responses to climate variation can inform conservation.
We mapped territories (32 years) and monitored productivity (16 years) in a subalpine breeding bird community on a 1-km2 study area in the Sierra Nevada, California.
Although highly variable, winter snowpack was lighter and melted earlier in later years, and summer temperatures increased while summer rainfall decreased over the study.
We found more species and breeding territories in years with mild springs and early snowmelt, suggesting the importance of immigration in driving population dynamics.
Young fledged earlier in warmer years with early snowmelt; spring and summer climate conditions had variable effects on fledging success and numbers of fledglings observed.
Our results highlight the value of intensive long-term monitoring in elucidating community-level population dynamics and demography in a high-elevation ecosystem undergoing rapid climate change.
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