Point Counts Research Articles

Physics‐based model to predict the acoustic detection distance of terrestrial autonomous recording units over the diel cycle and across seasons: Insights from an Alpine and a Neotropical forest

Abstract Passive acoustic monitoring of biodiversity is growing fast, as it offers an alternative to traditional aural point count surveys, with the possibility to deploy long‐term acoustic surveys in large and complex natural environments. However, there is still a clear need to evaluate how the frequency‐ and distance‐dependent attenuation of sound as well as the ambient sound level impact the acoustic detection distance of the soniferous species in natural environments over the diel cycles and across seasons. This is of great importance to avoid pseudoreplication and to provide relevant biodiversity indicators, including species richness, species abundance and species density. To address the issue of detection distance, we tested a field‐based protocol in a Neotropical rainforest (French Guiana, France) and in an Alpine coniferous forest (Jura, France). This standardized and repeatable method consists in a recording session of the ambient sound directly followed by an experiment using a calibrated white noise sound broadcast at different positions along a 100 m linear transect. We then used acoustic laws to reveal the basic physics behind sound propagation attenuation. We demonstrate that habitat attenuation in two different kinds of forests can be modelled by an exponential decay law with a linear dependence on frequency and distance. We also report that habitat attenuation, as first approximation, can be summarized by a single value, the coefficient of attenuation of the habitat. Finally, we show that the detection distance can be predicted knowing the contribution of each attenuation factor, the coefficient of attenuation of the habitat, the ambient sound pressure level and the amplitude and frequency bandwidth characteristics of the transmitted sound. We show that the detection distance mostly depends on the ambient sound and may vary by a factor of up to 5 over the diel cycle and across seasons. These results reinforce the need to take into account the variation of the detection distance when performing passive acoustic surveys and producing reliable biodiversity indicators.

Weather and nest cavity characteristics influence fecundity in mountain chickadees.

Examining direct and indirect effects on reproduction at multiple scales allows for a broad understanding of species' resilience to environmental change. We examine how the fecundity of the mountain chickadee (Poecile gambeli), a secondary cavity-nesting, insectivorous bird, varied in relation to factors at three scales: regional weather conditions, regional- and site-level food availability, site-level community dynamics, and nest-level cavity characteristics. We hypothesized that earlier laying dates and higher fecundity (clutch size, nest survival, brood size) would be associated with milder climatic conditions, increased food from insect outbreaks, lower densities of conspecifics and nest predators (red squirrel; Tamiasciurus hudsonicus), and safer (smaller, higher) cavities. We collected data on laying date, clutch size, brood size, nest fate (success/failure), and cavity characteristics from 513 mountain chickadee nests in tree cavities in temperate mixed coniferous-broadleaf forest in interior British Columbia, Canada, from 2000 to 2011. We surveyed annual abundances of mountain chickadees and squirrels using repeated point counts, and mountain pine beetle (Dendroctonus ponderosae) and lepidopteran defoliators by monitoring host trees and by using regional-scale aerial overview forest insect survey data. We used weather data (temperature, rain, snow) from a local Environment and Climate Change Canada weather station. We modeled laying date, clutch size, daily nest survival, and brood size as a function of predictors at regional-, site-, and nest-scales. Measures of fecundity varied dramatically across years and spatial scales. At the regional (study-wide) scale, chickadees laid earlier and larger first clutches in warmer springs with minimal storms, and daily nest survival (DSR) increased with a 2-year lag in growing season temperature. Despite a doubling of mountain chickadee density that roughly accompanied the outbreaks of mountain pine beetle and lepidopteran defoliators, we found little evidence at the site scale that fecundity was influenced by insect availability, conspecific density, or predator density. At the nest scale, DSR and brood size increased with clutch size but DSR declined with nest cavity size indicating a positive reproductive effect of small-bodied cavity excavators. Double-brooding, rare in chickadees, occurred frequently in 2005 and 2007, coinciding with early breeding, high food availability from insect outbreaks, and warm spring temperatures with 0-1 spring storms. Our results support the idea that fecundity in secondary cavity-nesting species is impacted directly and indirectly by weather, and indirectly through changes in community dynamics (via cavity resource supply). We stress the importance of adopting holistic, community-level study frameworks to refine our understanding of fecundity in opportunistic and climate-sensitive species in future.

Reduction in animal abundance and oxygen availability during and after the end-Triassic mass extinction.

The end-Triassic biodiversity crisis was one of the most severe mass extinctions in the history of animal life. However, the extent to which the loss of taxonomic diversity was coupled with a reduction in organismal abundance remains to be quantified. Further, the temporal relationship between organismal abundance and local marine redox conditions is lacking in carbonate sections. To address these questions, we measured skeletal grain abundance in shallow-marine limestones by point counting 293 thin sections from four stratigraphic sections across the Triassic/Jurassic boundary in the Lombardy Basin and Apennine Platform of western Tethys. Skeletal abundance decreased abruptly across the Triassic/Jurassic boundary in all stratigraphic sections. The abundance of skeletal organisms remained low throughout the lower-middle Hettangian strata and began to rebound during the late Hettangian and early Sinemurian. A two-way ANOVA indicates that sample age (p < .01, η2 =0.30) explains more of the variation in skeletal abundance than the depositional environment or paleobathymetry (p < .01, η2 =0.15). Measured I/Ca ratios, a proxy for local shallow-marine redox conditions, show this same pattern with the lowest I/Ca ratios occurring in the early Hettangian. The close correspondence between oceanic water column oxygen levels and skeletal abundance indicates a connection between redox conditions and benthic organismal abundance across the Triassic/Jurassic boundary. These findings indicate that the end-Triassic mass extinction reduced not only the biodiversity but also the carrying capacity for skeletal organisms in early Hettangian ecosystems, adding to evidence that mass extinction of species generally leads to mass rarity among survivors.

Refining manual annotation effort of acoustic data to estimate bird species richness and composition: The role of duration, intensity, and time.

Manually annotating audio files for bird species richness estimation or machine learning validation is a time-intensive task. A premium is placed on the subselection of files that will maximize the efficiency of unique additional species identified, to be used for future analyses. Using acoustic data collected in 17 plots, we created 60 subsetting scenarios across three gradients: intensity (minutes in an hour), day phase (dawn, morning, or both), and duration (number of days) for manual annotation. We analyzed the effect of these variables on observed bird species richness and assemblage composition at both the local and entire study area scale. For reference, results were also compared to richness and composition estimated by the traditional point count method. Intensity, day phase, and duration all affected observed richness in decreasing respective order. These variables also significantly affected observed assemblage composition (in the same order of effect size), but only the day phase produced compositional dissimilarity that was due to phenological traits of individual bird species, rather than differences in species richness. All annotation scenarios requiring equal sampling effort to point counts yielded higher species richness than the point count method. Our results show that a great majority of species can be obtained by annotating files at high sampling intensities (every 3 or 6 min) in the morning period (post-dawn) over a duration of two days. Depending on a study's aim, different subsetting parameters will produce different assemblage compositions, potentially omitting rare or crepuscular species, species representing additional functional groups and natural history guilds, or species of higher conservation concern. We do not recommend one particular subsetting regime for all research objectives, but rather present multiple scenarios for researchers to understand how intensity, day phase, and duration interact to identify the best subsetting regime for one's particular research interests.

The Diversity and Potential of Avitourism in Peat Swamp Ecosystem of Ayer Hitam Utara Forest Reserve, Johor

Avitourism is a responsible tourism activity where birdwatchers perform bird-watching, which can be either a hobby or a dedicated practice. Bird-watching is an act of observing and identifying birds in their natural environment. It can be performed by using the naked eye, using binoculars or scope for visual enhancement, listening to bird songs, or using public cams. Ayer Hitam Utara Forest Reserve is a peat swamp forest, a type of tropical moist forest with a dense layer of acidic peat and serves as a habitat for a diverse range of species. This study aims to identify bird species present in Ayer Hitam Utara Forest Reserve and evaluate the potential of avitourism in Ayer Hitam Utara Forest Reserve. A questionnaire was passed to 51 respondents to collect their opinions on developing Ayer Hitam Utara Forest Reserve as an avitourism site. Point count method and mist-netting were performed to record bird species spotted during the sampling period. The sampling has recorded 33 species in total, where there are 2 Vulnerable, 3 Near-Threatened, and 1 Endangered species, and 20 out of 33 species are totally protected under Wildlife Conservation Act 2010. The respondents have given generally positive response and are interested in visiting Ayer Hitam Utara Forest Reserve. Avitourism can potentially benefit Ayer Hitam Utara Forest Reserve economically, socially, and environmentally to local people.

Monitoring Colonies of Large Gulls Using UAVs: From Individuals to Breeding Pairs.

Measuring success or failure in the conservation of seabirds depends on reliable long-term monitoring. Traditionally, this monitoring has been based on line transects and total or point counts, all of which are sensitive to subjective interpretation. Such methods have proven to consistently record fewer individuals than intensive efforts, while requiring many hours of fieldwork and resulting in high disturbance. New technologies, such as drones, are potentially useful monitoring tools, as they can cover large areas in a short time, while providing high-resolution data about bird numbers and status. This study conducted two types of Uncrewed Aerial Vehicle (UAV) surveys in a big colony of multispecies breeding gulls. From a 25 m height, we photographed 30 circle plots where nests were also counted on the ground, showing that the number of occupied nests/breeding pairs could be estimated accurately by multiplying the number of counted individuals with a 0.7 conversion factor. A fixed-wing UAV was used to photograph the entire island to compare drone counts with counts conducted by traditional methods, were we counted a higher number of breeding pairs than the traditional count (1.7-2.2 times more individuals). It was concluded that UAVs provided improved estimates of colony size with much reduced monitoring effort.

Components of symmetric wide-matrix varieties

Abstract We show that if X n {X_{n}} is a variety of c × n {c\times n} -matrices that is stable under the group Sym ⁡ ( [ n ] ) {\operatorname{Sym}([n])} of column permutations and if forgetting the last column maps X n {X_{n}} into X n - 1 {X_{n-1}} , then the number of Sym ⁡ ( [ n ] ) {\operatorname{Sym}([n])} -orbits on irreducible components of X n {X_{n}} is a quasipolynomial in n for all sufficiently large n. To this end, we introduce the category of affine 𝐅𝐈 𝐨𝐩 {\mathbf{FI^{op}}} -schemes of width one, review existing literature on such schemes, and establish several new structural results about them. In particular, we show that under a shift and a localisation, any width-one 𝐅𝐈 𝐨𝐩 {\mathbf{FI^{op}}} -scheme becomes of product form, where X n = Y n {X_{n}=Y^{n}} for some scheme Y in affine c-space. Furthermore, to any 𝐅𝐈 𝐨𝐩 {\mathbf{FI^{op}}} -scheme of width one we associate a component functor from the category 𝐅𝐈 {\mathbf{FI}} of finite sets with injections to the category 𝐏𝐅 {\mathbf{PF}} of finite sets with partially defined maps. We present a combinatorial model for these functors and use this model to prove that Sym ⁡ ( [ n ] ) {\operatorname{Sym}([n])} -orbits of components of X n {X_{n}} , for all n, correspond bijectively to orbits of a groupoid acting on the integral points in certain rational polyhedral cones. Using the orbit-counting lemma for groupoids and theorems on quasipolynomiality of lattice point counts, this yields our Main Theorem. We present applications of our methods to counting fixed-rank matrices with entries in a prescribed set and to counting linear codes over finite fields up to isomorphism.

Tissue concentration of vascular endothelial growth factor is not related to the depth of trophoblastic invasion in ampullary pregnancies-A pilot study.

Introduction: The factors that modulate trophoblastic invasion into the tubal wall remain uncertain. Moreover, it is known that the concentration of vascular endothelial growth factor (VEGF) is increased in cases of deeper trophoblastic invasion in the fallopian tubes. Objective: This study aimed to assess if there is a correlation between VEGF tissue expression and the depth of trophoblastic infiltration into the tubal wall in patients with ampullary pregnancy. Methods: A cross-sectional study was conducted in patients with a diagnosis of tubal pregnancy in the ampullary region who underwent salpingectomy. Inclusion criteria were spontaneously conceived singleton pregnancies, diagnosis of tubal pregnancy in the ampullary region, and radical surgical treatment. A lack of agreement regarding the location of the tubal pregnancy and impossibility of either anatomopathological or tissue VEGF analysis were the exclusion criteria. Histologically, trophoblastic invasion into the tubal wall was classified as grade I when limited to the tubal mucosa, grade II when it reached the muscle layer, and grade III when it comprised the full thickness of the tubal wall. A total of 42 patients fulfilled the inclusion criteria and were selected to participate in the study. Eight patients were excluded. After surgery, tissue VEGF expression was measured by immunohistochemistry and the point counting technique. Results: Histological analysis revealed that eight patients had stage I tubal infiltration, seven had stage II, and 19 had stage III. The difference between the percentage of VEGF expression in the trophoblastic tissue was not significant in relation to the degree of trophoblastic invasion (p = 0.621) (ANOVA). Trophoblastic tissue VEGF showed no statistical difference for prediction of both degrees of trophoblastic invasion (univariate multinomial regression). Conclusion: The depth of trophoblastic penetration into the tubal wall in ampullary pregnancies is not associated with tissue VEGF expression.

Spatial distribution, activity zone preference, and activity intensity of senior park users in a metropolitan area

Urban parks can bring multiple health benefits to seniors and thus are important to their lives. This study investigated seniors’ spatial distribution, preferred activity zones, and activity intensity during park visits. We used GPS trackers to collect spatial location information and accelerometers to record metabolic equivalent of energy (MET) at an interval of 10 s, and examined differences in activity intensity according to activity zone type. Data from 286 seniors in two large urban parks in Shanghai, China were included. We identified eight park activity zone types: pathway, paved open space, sports area, children’s playground, lawn, water, other natural area, building, and other area. Grid cells of 5 m by 5 m were created and hotspot analysis was utilized to identify the activity zones most frequently used by seniors. ANOVA post-hoc analysis was applied to investigate the variance between activity zone cells in terms of mean visit point counts, total visit point MET, and average MET. We also utilized latent class analysis to identify distinctive subgroups of seniors.The results indicate that seniors’ spatial distributions vary vastly both between and within park activity zones. Of the eight zone types, paved open space was used most frequently, and seniors were most active on pathways. Other natural area also had high usage, and featured higher average activity intensity than sports area, water, and building and other area. Children’s playground had higher average activity intensity than lawn or water. Finally, three distinctive groups of seniors were identified: short-stay active walker, long-stay light walker, and short-stay transient. These findings have direct implications for park design practice. Paved open space and pathways should be carefully designed based on the specific seniors’ activity patterns. Furthermore, seniors’ needs should be considered in the design of playgrounds in parks, where they accompany their grandchildren, and of other natural area, where they stretch their bodies and enjoy fresh air. The diverse activity patterns of the subgroups of seniors should be addressed in future studies.

2-Adic point counting on K3 surfaces

This article reports on an approach to point counting on algebraic varieties over finite fields that is based on a detailed investigation of the 2-adic orthogonal group. Combining the new approach with a p-adic method, we count the number of points on some K3 surfaces over the field mathbb {F}_{!p}, for all primes p < 10^8.

Estimating species richness and density of a bird community in a coastal lagoon on the Mexican Pacific

In this study we assess the bias in estimates of bird richness in a tropical wetland. We used 18 months of data from point counts to estimate the species richness in a coastal lagoon in Oaxaca and computed eight species richness estimators. We evaluated estimate inaccuracy using the sum of total richness that we obtained with combined sampling techniques between 2006 and 2010. We selected the richness estimator of minimum inaccuracy and used randomized species accumulation curves to investigate differences in species densities obtained with 10 and 20-minute counts. To ascertain if habitat type influenced richness estimates, we compared the bird diversity associated with contrasting mangrove and estuarine environments. The total richness for the lagoon was 185 species and the jackknife 2 richness estimator showed the minimum inaccuracy. The randomized accumulation curves of 10 and 20 minutes displayed partially overlapping confidence intervals and an increasing time lag between the count durations at equivalent densities. The rarefaction curves from contrasting habitat types showed significantly higher richness and species density in the estuary while the jackknife 2 estimator indicated similar sample coverage in both habitats. We identify important consequences of the sampling methodology that we used and conclude that point count sampling resulted in incomplete species detection but facilitated comparative analyses.

Changes in Meteorological Dry Conditions across Water Management Zones in Uganda

This study analysed trends and variability in extreme precipitation and potential evapotranspiration (PET) indices across Uganda. We made use of daily precipitation and temperature datasets from 1979 to 2013 obtained from the Climate Forecast System Reanalysis (CFSR) products of the National Centres for Environmental Prediction (NCEP). The PET was estimated using the Hargreaves method based on the minimum and maximum temperature. Analysis was focused on the level of Water Management Zones (WMZs). Examples of the extracted extreme climatic indices included the annual maximum number of consecutive days with precipitation intensity < 1 mm/day (CDD1) or < 5 mm/day (CDD5), annual sum of PET for days with PET rate > 5 mm/day (SPETD5), and spell of high evaporative demand (or annual maximum number of consecutive days with PET > 5 mm/day) (CDPET5). Attributes of the variability in meteorological dry conditions were investigated. Trend and variability were investigated using an approach based on the cumulative sum of difference (CSD) between exceedance and non-exceedance counts of data points. The magnitudes of the linear decrease or increase in the precipitation and PET indices were determined using Sen's method. To apply these methods, the CSD-based Sub (Trend) and Variability Analysis Tool (CSD-VAT) was used. The long-term mean of the extracted indices showed Kyoga and Victoria to be the driest and wettest WMZs, respectively. An increase in the number of dry days (indicating increasing severity of meteorological dry conditions) was confined to the Karamoja region or the eastern parts of the Upper Nile and Kyoga WMZs. However, the rest of the country generally experienced negative trends in the precipitation and PET indices. Extreme precipitation indices of Kyoga and the Upper Nile WMZs exhibited consecutive positive and negative sub-trends over the early 1980s and from 1985 to 2013, respectively. Victoria and Albert WMZs mainly exhibited negative sub-trends for both precipitation and PET indices especially from the mid-1980s to the end of the data. Across Victoria and Albert WMZs, we found that the variability in extreme precipitation indices such as CDD1 and CDD5 was significant (p<0.05). However, these WMZs were characterized by insignificant (p>0.05) variability of the PET indices such as SPETD5 and CDPET5. Changes in the precipitation and PET indices were significantly (p<0.05) found to be positively linked to the quasi-biennial oscillation. The meteorological drought indicators were significantly (p<0.05) negatively correlated with the Indian Ocean dipole and Atlantic multidecadal oscillation. Our findings based on NCEP's CFSR data show that variation in sub-trends of the meteorological dry conditions across Uganda resonates well with the changes in some indicators of large-scale ocean-atmosphere conditions. This is important for planning predictive adaptation to the impacts of climate variability on water resources applications which are sensitive to the severity of meteorological dry conditions. Apart from our findings, we introduced a number of extreme PET indices which can be used for analysis of meteorological dry conditions or drought.

Forest Management Practice Influences Bird Diversity in the Mid-Hills of Nepal.

Forest management practice plays a critical role in conserving biodiversity. However, there are few studies on how forest management practice affects bird communities. Here, we compare the effectiveness of the Panchase Protection Forest (PPF; protected forest with government administration) and the Tibrekot Community Forest (TCF; community forest with community forest users' group administration) in hosting bird diversity in the mid-hills of Nepal. We examined 96 point count stations during summer and winter in 2019 and recorded 160 species of birds with three globally threatened vultures (red-headed vulture Sarcogyps calvus, slender-billed vulture Gyps tenuirostris, and white-rumped vulture Gyps bengalensis). Forest management practice, season, and elevation all influenced the richness and abundance of birds. The diversity, richness, and abundance of birds and the most common feeding guilds (insectivore, omnivore, and carnivore) were higher in TCF than in PPF; however, globally threatened species were only recorded in PPF. We also recorded a higher bird species turnover (beta diversity) in TCF than in PPF. Our study indicates that community-managed forests can also provide quality habitats similar to those of protected forests managed by the government, and provide refuge to various bird species and guilds. However, we recommend more comparative studies in other tropical and sub-tropical areas to understand how different forest management practices influence bird diversity.

Habitat use of the mistle thrush (Turdus viscivorus): the importance of urban areas and permanent crops

The mistle thrush is a species that occurs in old-growth forests, especially coniferous forests, in hilly and mountain areas and avoids warm and dry areas and human settlements. Despite this, in recent decades, the mistle thrush has colonised Apulia, southern Italy's lowlands and coasts, in rural and urban contexts. This study investigates the habitat selection of this species in central Apulia, in both the breeding season and winter, by carrying out 301 point counts and 264 linear transects. Data were collected to build a Species Distribution Model (SDM) for each season with the MaxEnt algorithm and the regional land use map, selecting variables through the Akaike Information Criterion. Overlap in the suitability of both seasons was measured using Schoener's D. A total of 133 observations of mistle thrush were noted during the breeding season and 85 observations during winter. During the breeding season, the mistle thrush selected olive orchards, especially those near vineyards and urban areas, where it could find food and safe places to nest. In this period, however, it was also found in coniferous woodlands. The mistle thrush also used vineyards in winter, whereas it avoided urban areas in this period, possibly due to food scarcity. Non-irrigated arable lands were avoided all year round, whereas natural grasslands were only avoided during the winter. Irrigated arable lands positively affected the species. Furthermore, 60% of habitat characteristics were similar between the breeding and winter seasons. It is unclear what makes the mistle thrush shift its range southward and downslope. However, it is likely due to the general increase in forest cover, a positive rainfall trend in Central Italy during summer, and the absence of competition with similar species in central Apulia.

Population density and distribution of the Endangered Black Shama Kittacincla cebuensis

Summary The Endangered Black Shama Kittacincla cebuensis is endemic to the island of Cebu, Philippines. We surveyed 11 forest patches from February 2018 to March 2020 to determine current distribution, habitat requirements, and population density of the Black Shama. A total of 111 point count stations was surveyed resulting in 93 Black Shama detections. Using point count Distance sampling, the population density was estimated at 313 individuals/km2 for a total population of 11,839 individuals (9,160–15,415). The largest sub-population (10,470) was in Alcoy, followed by Argao (711), and Dalaguete (325). Our total population estimate and sub-population estimates were higher than the estimate of 6,650 individuals made by BirdLife International for the International Union for the Conservation of Nature. The species was found to survive in a variety of habitats in at least 20 localities covering roughly 37 km2 of karst forest. We did not encounter the bird in seven areas of its former range. Protection of the remaining forests of Cebu and the establishment of plantations of native tree species in between forest patches are crucial to the survival of the species.

Habitat use and niche overlap of ground-nesting steppic birds

Steppic habitats host an extremely high proportion of birds with unfavourable conservation status in Europe, such as larks. This research aims to both investigate habitat-lark relationships and assess the niche overlap among larks in southern Italy during the breeding season. Studied in particular were the Eurasian Skylark ( Alauda arvensis), the Greater Short-toed Lark ( Calandrella brachydactyla), the Calandra Lark ( Melanocorypha calandra), the Crested Lark ( Galerida cristata) and the Woodlark ( Lullula arborea). During the 2012 breeding season, 301 point counts were carried out, and these were randomly placed in the study area according to a stratified sampling design. Resource selection probability functions were used to build two models for each species: (i) a binary logistic regression using the presence units as the dependent variable and (ii) a GLM with Poisson’s error distribution using the abundance of larks in each sampling point as the dependent variable. In the first model, the land cover in the cells of a 100-m-grid superimposed onto the study area was used as a covariate, whereas in the second model, the same covariate was measured, but in a 300-m-buffer around the sampling points. Finally, niche overlap was measured by Hurlbert’s Index with bootstrap resampling. Results showed that the Skylark, Short-toed Lark, Calandra Lark and Crested Lark are tightly associated with both non-irrigated crops and dry grasslands, with these species selecting areas in which both habitats are present in particular. Furthermore, there is a strong niche overlap at macrohabitat level among the species, with the exception of the Woodlark, which is an ecotonal species.

The loss of vegetation cover has distinct but short-term impact on multiple vertebrate taxa in a grassland ecosystem

Vegetation cover in grasslands typically fluctuates over time, for example, declining with grazing and disappearing entirely with burning. This temporal change in vegetation cover may impact the composition of vertebrate communities by altering habitats or perceived predation pressure. We manipulated vegetation cover in a high-elevation (ca. 1240–1500 m above sea level) grassland ecosystem and measured its effect on the community structure of birds and small mammals using a Before-After-Control-Impact study design. We established 12 plots (each plot 100 × 100 m) at Telperion Nature Reserve, Mpumalanga, South Africa, which were assigned to three treatments: mowed with cut grass left in situ (mowed-litter), mowed with cut grass cleared (mowed-cleared), and non-mowed (control). We sampled birds and small mammals over three sampling periods: before the treatment (August 2019), immediately after the treatment (October 2019), and three months after treatment (January 2020). We used point counts and Sherman live traps to surveys birds and small mammals, respectively. We observed a total of 2801 individuals of 38 species of birds and 98 individuals of eight species of small mammals. Species richness and diversity of small mammals and birds was significantly higher in the non-mowed plots compared with the mowed plots. Birds also showed differences in community composition in mowed and non-mowed treatments immediately after mowing but these differences disappeared three months after mowing, whereas small mammal composition did not differ before and after mowing. The best performing generalized additive model showed that vegetation biomass had a significant positive influence on bird species richness but not rodents. On the other hand, diversity of both taxa was significantly influenced by grass biomass. Our study suggests that loss of vegetation cover in grasslands has significant short-term effects on birds and small mammals, but that these faunal communities rapidly return to pre-loss conditions within a few months. Hence controlled vegetation removal (e.g. mowing) could be considered an appropriate tool for managing these high-elevation grasslands.

A cautionary tale comparing spatial count and partial identity models for estimating densities of threatened and unmarked populations

Population monitoring is critical to wildlife conservation, but density estimation is difficult for wide-ranging, unmarked species inhabiting remote habitats. Furthermore, recent investigations into density estimation with camera trap data has revealed unmarked models to be potentially unreliable, prompting cautious application and continued model development. Two related approaches with increasing appeal include spatial count (SC), which infer latent identities from the spatial pattern of detections, and spatial partial identity models (SPIM), which additionally leverage partial identity covariates (e.g., sex, antler point count, and presence of GPS/radio collar). To assess the performance of unmarked density models, we applied SC and SPIM to camera trap data of threatened boreal caribou in Canada, which are declining but have few rigorous density estimates across their broad distribution to inform conservation efforts. In particular, we focused on two spatially proximate caribou ranges in northern Alberta, Canada that differ in estimated caribou demographic trends, disturbance histories, and abundances of caribou predators and apparent competitors. Estimates of caribou density varied over a 4 year period (2016 – 2019), and were higher in the region with more stable reported growth rates and less anthropogenic disturbance (mode SPIM estimates: 155 – 225/1000 km 2 vs. 19 – 96/1000 km 2 ). However, density estimates differed by modeling approach and had low and variable precision, hindering inferences about population status and trajectories. Simulations suggest that SPIM estimates may have been less biased and more precise. SC models likely underestimated density by mistaking detections of neighboring individuals as recaptures of a single individual, although SPIM may also have overestimated density by inflating assignment probabilities of detections to non-existent individuals. Findings highlight the need to explore how grouping dynamics and non-independent movement violate assumptions and reduce the ability to distinguish individuals. We advocate continued investigation into the accuracy of unmarked density estimation approaches, the ecological and sampling conditions appropriate for different unmarked density models, and coordination across sampling efforts and analyses to improve population inferences.

Importance of private working lands for the conservation of neotropical birds on an urban-wilderness gradient

Global biodiversity and land conservation initiatives rely on an accurate understanding of the spatial distribution of species populations and communities. Identifying the spatial habitat use of wildlife communities across land uses and levels of human modification provides the opportunity to produce more efficient and effectual conservation plans. Our goal was to model breeding bird community occupancy across a complete spectrum of human land use modification to determine the habitat characteristics that best maximized the conservation of bird diversity. We used repeat-visit point counts on private and public lands to record the detection/non-detection of breeding bird species across the land use gradient. We modeled multiple proportional land cover and landscape structure covariates and employed a hierarchical multi-species occupancy model to analyze the habitat use of each species and to estimate guild-level species richness dynamics across the study area. We detected a total of 70 breeding bird species and our model estimated a total of 78 species within the total metacommunity. We found that insectivorous species richness was lowest in urban and suburban areas (xˆ = 7), but highest on multiple use working lands with low to moderate levels of human modification (xˆ = 22), not in the fully preserved protected areas (xˆ = 16). In contrast, the richness of the predominately human commensal omnivorous species was highest in urban and suburban areas (xˆ = 10) and across much of the more human modified landscape and lowest in the preserved lands (xˆ = 3). Moderately disturbed working lands, which primarily consisted of a mixture of rotating silvicultural tracts, agriculture, low density housing, and riparian corridors, supported the most species (xˆ = 36) and were especially important for the occupancy of breeding neotropical insectivores. These findings highlight the potential conservation benefits for incorporating private working lands with multiple land uses and land covers into future conservation planning scenarios, both for their wildlife conservation potential and as buffers around traditional protected areas.

Microhabitat variables influencing the presence and abundance of birds in floodplain grassland of the lower Ganges and Brahmaputra rivers, Bangladesh

Grassland bird communities are likely declining in all major grassland ecosystems globally due to habitat loss and modification, yet knowledge of the status of many tropical grassland bird communities is relatively poor. This study investigated the bird community structure and its associations with vegetation characteristics and potential human impacts in seasonal floodplain grassland along the lower Ganges and Brahmaputra Rivers, Bangladesh (part of the Indo-Gangetic Plain) during 2018–2019 through point counts of birds combined with vegetation surveys. Bird responses were assessed by diversity indexes, non-metric multidimensional scaling ordination and linear models. Results show that the total resident bird community (31 grassland specialists, 34 generalists and 10 waterbirds) overlapped among the four major vegetation types in the study area (forbs and bushes, Saccharum sp., Cynodon sp. and cropland). The diversity of the total bird community increased with cover of forbs and bushes, while the overall diversity of grassland specialists (those adapted to and reliant on some variety of grassland habitat for part or all of their life cycle whether feeding or breeding.) increased with Saccharum sp. cover but decreased with increased crop cover. The diversity of the total bird community and all grassland specialist birds showed no variation with vegetation height. However, the abundance of grassland specialists showed a strong increase with increases in vegetation height. Among the grassland specialists, nine species that were entirely dependent on tall grasses for breeding were considered as obligate tall grass breeders. The abundance of these tall grass breeders decreased with greater cover of both Cynodon sp. and crops but increased with greater cover of Saccharum sp. The retention of vegetation with heights > 150 cm was therefore important to conservation and management of this community. Regular seasonal herding of cattle in these floodplain grasslands was widespread and it was therefore difficult to compare grazed with ungrazed areas. The diversity of neither the total bird community nor the overall grassland specialists showed any association with grazing intensity. However, grazing impacted negatively on the abundance of obligate tall grass breeders. Limited grass harvesting increased the overall diversity of the grassland specialist bird community. The estimated density of nine species of obligate tall grass breeders ranged from 0.19 to 4.41 birds/ha. Continuing rapid agricultural expansion was observed and is a prominent threat to these birds. More habitat-specific information and monitoring are required to quantify risks and aid conservation planning.