Marbled Murrelets prefer stratified waters close to freshwater inputs in Haida Gwaii, British Columbia, Canada

The Marbled Murrelet (Brachyramphus marmoratus) is a small seabird that is currently listed as threatened in Canada. Understanding this species’ marine habitat preferences plays a vital role in our ability to focus conservation planning. We used the longest-running at-sea survey dataset available in British Columbia to examine hotspot persistence and habitat use at Laskeek Bay, Haida Gwaii, BC. The Laskeek Bay Conservation Society has been conducting spring and summer surveys along fixed transect routes in open and shoreline waters from 1997 to 2018. Along with analyzing this long-term dataset, we conducted surveys to measure oceanographic variables (2018–2019) and tested whether Marbled Murrelets in the same area used prey and oceanographic information to select marine habitat in conjunction with physical habitat features. Our hotspot persistence map, defined as areas that repeatedly had counts above a 75% threshold relative to other areas during a given survey, showed that murrelets consistently preferred shoreline transects. Murrelets also preferred shallow marine areas closer to streams, above higher proportions of sandy substrate and closer proximity to abundant nesting habitat. Modeling weather and time variables contributed little additional predictive power. Nonetheless, models that included physical environmental, oceanographic, and prey variables outperformed those with only physical environmental variables. Stratified water was the oceanographic variable most strongly related to higher counts. Our study suggests that stratified waters could work with stream systems to create productive zones for foraging murrelets, and highlights the importance of murrelets having access to marine areas with the preferred physical features.

Disturbed Amazonian forests support diminished breeding bird communities

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.

Combination of targeted monitoring and Breeding Bird Survey data improves population trend estimation and species distribution modeling for the Common Nighthawk

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.

Community characteristics of forest understory birds along an elevational gradient in the Horn of Africa: A multi-year baseline

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.

Oil and gas development does not reduce duck pair abundance in the Prairie Pothole Region

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.

Greater Sage-Grouse survival varies with breeding season events in West Nile virus non-outbreak years

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.

Future climate change will impact the size and location of breeding and wintering areas of migratory thrushes in South America

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.

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.