Point-count Surveys Research Articles

A post‐processing framework for assessing BirdNET identification accuracy and community composition

Passively collected acoustic data have become increasingly common in wildlife research and have prompted the development of machine‐learning approaches to extract and classify large sets of audio files. BirdNET is an open‐source automatic prediction model that is popular because of its lack of training requirements for end users. Several studies have sought to test the accuracy of BirdNET and illustrate its potential in occupancy modelling of single or multiple species. However, these techniques either require extensive statistical knowledge or computational power to be applied to large datasets. In addition, there is a lack of comparisons of occupancy and community composition calculated using BirdNET and typical field methods. Here we develop a framework for assessing the accuracy of BirdNET using generalized linear mixed models to determine species‐specific confidence score thresholds. We then compare community composition under our model and another post‐processing approach to field data collected from co‐located point count surveys in northeastern Vermont. Our framework outperformed the other post‐processing method and resulted in species composition similar to that of point count surveys. Our work highlights the potential mismatch between accuracy and confidence score and the importance of developing species‐specific thresholds. The framework can facilitate research on large acoustic datasets and can be applied to output from BirdNET or other automatic prediction models.

Low-intensity urbanisation alters community composition across multiple trophic levels on Lipsi Island, Greece.

Urbanisation has reduced the abundance and diversity of many taxonomic groups, and the effects may be more pronounced on islands, which have a smaller regional species pool to compensate. Green spaces within urban environments may help to safeguard wildlife assemblages, and the associated habitat heterogeneity can even increase species diversity. Here, total abundance and species diversity of butterflies, birds, and vegetation at nine rural and nine urban locations were quantified on Lipsi Island, Greece. Sites were assessed using Pollard walks for butterflies, point-count surveys for birds, and quadrats for vegetation. There was no significant difference in the abundance or species diversity of butterflies or vegetation among rural and urban locations, which could pertain to the low building density within urbanised areas and the minimal extent of urbanisation on the island. However, urban areas hosted a significantly greater abundance, richness, and diversity of birds compared to rural sites. The community composition of butterflies, birds, and vegetation also differed significantly between urban and rural locations, highlighting the impact of urbanisation on species across a broad range of trophic groups. This study contributes to ecological knowledge on the impacts of urbanisation across multiple trophic levels in island ecosystems, with comparisons across a gradient of island size and urbanisation intensity needed in future research.

Enhancing bird conservation in tropical urban parks through land sparing and sharing strategies: Evidence from occupancy data

Urban green spaces such as parks, play a vital role in relieving pressure on urban biodiversity. In Southeast Asia, urban park management often prioritises aesthetic appeal over urban biodiversity conservation. Management of wildlife habitat at the stand and landscape scales is necessary to support land-sharing and land-sparing conservation strategies in urban environments. To date, few studies have looked at the occurrence of urban birds in the context of land sharing and sparing strategies. We investigated how resident and migratory birds utilise urban parks based on stand-level habitat characteristics and landscape metrics. We conducted point count surveys at 49 points to estimate site occupancy and detection probability in 40 parks within highly urbanised Klang Valley, Peninsular Malaysia. Out of 90 species recorded, 14 species had more than 50 % site occupancy. The abundance of palm trees, percentage of shrub, and height of ground vegetation and woody trees positively influenced the occupancy of Black-naped Oriole, Javan Myna, House Crow, Oriental Magpie-Robin, and Yellow-vented Bulbul. While the number of woody trees and elevation negatively influenced the occupancy of Asian Glossy Starling, Spotted Dove, Zebra Dove, and Common Myna. Our findings can contribute to the effective management of urban parks, considering both stand and landscape-level characteristics to support urban biodiversity, ultimately benefiting both resident and migratory bird populations. Our research emphasises the significance of implementing both land-sparing and land-sharing strategies in urban park management. By doing so, we can promote greater avian biodiversity, preserve diverse habitats for birds, and establish crucial ecological corridors within urban landscapes.

Bird Species Use of Bioenergy Croplands in Illinois, USA—Can Advanced Switchgrass Cultivars Provide Suitable Habitats for Breeding Grassland Birds?

Grassland birds have sustained significant population declines in the United States through habitat loss, and replacing lost grasslands with bioenergy production areas could benefit these species and the ecological services they provide. Point count surveys and autonomous acoustic monitoring were used at two field sites in Illinois, USA, to determine if an advanced switchgrass cultivar that is being used for bioenergy feedstock production could provide suitable habitats for grassland and other bird species. At the Brighton site, the bird use of switchgrass plots was compared to that of corn plots during the breeding seasons of 2020–2022. At the Urbana site, the bird use of restored prairie, switchgrass, and Miscanthus × giganteus was studied in the 2022 breeding season. At Brighton, Common Yellowthroat, Dickcissel, Grasshopper Sparrow, and Sedge Wren occurred on switchgrass plots more often than on corn; Common Yellowthroat and Dickcissel increased on experimental plots as the perennial switchgrass increased in height and density over the study period; and the other two species declined over the same period. At Urbana, Dickcissel was most frequent in prairie and switchgrass; Common Yellowthroat was most frequent in miscanthus and switchgrass. These findings suggest that advanced switchgrass cultivars could provide suitable habitats for grassland birds, replace lost habitats, and contribute to the recovery of these vulnerable species.

Over the river and through the woods: Multi-scale habitat associations of two at-risk bird species in riparian forests of the Central Appalachians

Several species-specific habitat management guidelines have been created over the past decade to help recover declining populations of forest birds in eastern North America. Conserving eastern forest birds through forest management requires understanding the factors driving species occurrence patterns and how the needs of various species complement or contrast with each other. Our study assessed and compared occupancy patterns of two at-risk species associated with riparian forests: the Wood Thrush (Hylocichla mustelina) and the Canada Warbler (Cardellina canadensis). We conducted point-count surveys and vegetation sampling at 304 unique locations along 33 stream sections in central and southwestern Pennsylvania from May – June 2018 and 2019. We used single-season occupancy models to examine the influence of vegetation composition (i.e., microhabitat conditions), forest structure (i.e., from Light Detection and Ranging data, “LiDAR”), and other factors (i.e., stream order and elevation) on focal species occurrence patterns. Wood Thrush occupancy (mean ᴪˆ: 0.57) was best explained by the presence of mountain laurel (Kalmia latifolia; negative effect), elevation (negative effect), canopy height (positive effect), and canopy structural heterogeneity (positive effect). Canada Warbler occupancy (mean ᴪˆ: 0.55) was best explained by the presence of mountain laurel (positive effect), stream order (positive effect), elevation (positive effect), density of understory vegetation (positive effect), and canopy structural heterogeneity (negative effect). While both bird species occurred relatively frequently in riparian forests, our results indicate that habitat factors at multiple spatial scales play a role in regulating their occurrence patterns. Moreover, the two species exhibited contrasting habitat associations. Specifically, Canada Warblers preferred sites supporting dense mountain laurel, typically at elevations >600 m, and with a largely intact canopy. These patterns were reversed for Wood Thrushes. These contrasting associations will limit opportunities to manage riparian forests in a manner that conveys co-benefits for our two focal species. As a general rule, forest managers in our study region can target habitat management for Canada Warblers in riparian areas above 600 m and in areas below 600 m for Wood Thrushes. Given our focal species’ use of other (non-riparian) forest types as breeding habitat and broad geographic distributions, it is important to recognize that our findings may not apply outside of riparian forests or beyond the Central Appalachian Mountains.

Diversity, Encounter Rate and Detection of Non-Volant Nocturnal Mammals on Two Malaysian Islands.

Nocturnal mammals constitute a crucial component of tropical faunal diversity, but not much is known about the effects of anthropogenic disturbance on the habitat use and detectability of these species. We investigated which habitat and environmental variables impact the detectability of non-volant nocturnal arboreal mammals across varying habitat types at two tropical islands with different levels of anthropogenic development in Malaysia. We conducted night transect line and point count surveys following pre-existing paths in Penang Island and Langkawi Island between 2019 and 2020. We used a head torch with red filter and a thermal imaging device (FLIR) to enhance animal detection success. We calculated the encounter rates (individual km-1) for each species as a proxy for abundance. Overall, we detected 17 species, but did not find higher species diversity in intact forested environments compared to disturbed areas. Encounter rates of the most observed species were influenced by 'time after sunset' on the highly developed island of Penang, whereas on the rural island of Langkawi, detection was higher in sites with better canopy connectivity. Different species of non-volant nocturnal arboreal mammals use their respective habitats differently and thus, are differently impacted by varying levels of anthropogenic activities. Our results provided baseline data on the diversity, encounter rate, and detectability of these highly elusive species, which can also help to further improve methodologies for the detection of nocturnal wildlife.

Birds of the Burn: Avian Community and Functional Guild Variation Five Years Post-Fire in Warm–Dry Mixed Conifer, Southwest Colorado

Birds contribute to the trophic interactions within mixed conifer ecosystems and provide a suite of services, such as nutrient transport, seed dispersal, habitat creation, and insect regulation. Avian communities vary in response to the structure and composition of their habitat, which may be drastically altered by fire, the predominant disturbance of western mixed conifer forests. We conducted avian point count surveys during the peak breeding season, five years post-fire, across four burn severities (unburned, low, moderate, and high) within the 416 Fire perimeter, a 55,000-acre mixed-severity fire that burned near Durango, Colorado in 2018. Avian communities in each burn severity were evaluated for richness, diversity, differentiation, indicator species, and functional guild composition. Species assemblages were significantly different across all burn severities, excluding the low to moderate areas comparison, with differentiation driven by live tree and snag density. Avian species’ richness and diversity were not significantly different across burn severities, highlighting the importance of utilizing multivariate community analysis. Unburned and high-burn areas had significant variation in functional guilds and numerous indicator species. This study provides evidence of avian community differentiation by burn severity, suggesting that management practices promoting heterogenous stand structure in warm–dry mixed conifer will positively influence avian biodiversity.

Habitat and species segregation of Strigiformes in the Brazilian Atlantic Forest

The order Strigiformes contains approximately 250 owl species distributed worldwide, and the majority of them live in forests. Although basic information is available on many owls, few have been studied in-depth; consequently, little is known about the role of vegetation in their lives. This study aimed to investigate Strigiformes in a fragment of the Atlantic Forest using point count surveys conducted from January 2018 to December 2019. Twelve points were sampled for 30 min/month, totaling 144 h. Data on vegetation structure were collected for analysis. The numbers of individuals and species were then estimated. Twenty-six individuals of four species were recorded: 12 Strix virgata, 6 Pulsatrix koeniswaldiana, 5 Megascops atricapilla, and 3 Megascops choliba. Strix virgata was associated with sites with typical mature forest characteristics, although it tolerated variation in some parameters (e.g., average canopy height). Pulsatrix koeniswaldiana was a generalist in terms of habitat characteristics, even when using edge areas. Megascops choliba was scarce within the sampled area and seemed to avoid mature forest. Megascops atricapilla occurred from sites with a lower canopy to more mature forest areas. Altogether, this study highlighted the importance of conserving forest fragments in the Atlantic Forest, which harbors considerable biodiversity, especially of owls.

Evaluation of an autonomous acoustic surveying technique for grassland bird communities in Nebraska.

Monitoring trends in wildlife communities is integral to making informed land management decisions and applying conservation strategies. Birds inhabit most niches in every environment and because of this they are widely accepted as an indicator species for environmental health. Traditionally, point counts are the common method to survey bird populations, however, passive acoustic monitoring approaches using autonomous recording units have been shown to be cost-effective alternatives to point count surveys. Advancements in automatic acoustic classification technologies, such as BirdNET, can aid in these efforts by quickly processing large volumes of acoustic recordings to identify bird species. While the utility of BirdNET has been demonstrated in several applications, there is little understanding of its effectiveness in surveying declining grassland birds. We conducted a study to evaluate the performance of BirdNET to survey grassland bird communities in Nebraska by comparing this automated approach to point count surveys. We deployed ten autonomous recording units from March through September 2022: five recorders in row-crop fields and five recorders in perennial grassland fields. During this study period, we visited each site three times to conduct point count surveys. We compared focal grassland bird species richness between point count surveys and the autonomous recording units at two different temporal scales and at six different confidence thresholds. Total species richness (focal and non-focal) for both methods was also compared at five different confidence thresholds using species accumulation curves. The results from this study demonstrate the usefulness of BirdNET at estimating long-term grassland bird species richness at default confidence scores, however, obtaining accurate abundance estimates for uncommon bird species may require validation with traditional methods.

Paired acoustic recordings and point count surveys reveal Clark's nutcracker and whitebark pine associations across Glacier National Park.

Global declines in tree populations have led to dramatic shifts in forest ecosystem composition, biodiversity, and functioning. These changes have consequences for both forest plant and wildlife communities, particularly when declining species are involved in coevolved mutualisms. Whitebark pine (Pinus albicaulis) is a declining keystone species in western North American high-elevation ecosystems and an obligate mutualist of Clark's nutcracker (Nucifraga columbiana), an avian seed predator and disperser. By leveraging traditional point count surveys and passive acoustic monitoring, we investigated how stand characteristics of whitebark pine in a protected area (Glacier National Park, Montana, USA) influenced occupancy and vocal activity patterns in Clark's nutcracker. Using Bayesian spatial occupancy models and generalized linear mixed models, we found that habitat use of Clark's nutcracker was primarily supported by greater cone density and increasing diameter of live whitebark pine. Additionally, we demonstrated the value of performing parallel analyses with traditional point count surveys and passive acoustic monitoring to provide multiple lines of evidence for relationships between Clark's nutcracker and whitebark pine forest characteristics. Our findings allow managers to gauge the whitebark pine conditions important for retaining high nutcracker visitation and prioritize management efforts in whitebark pine ecosystems with low nutcracker visitation.

Effects of forest management on private lands in West Virginia on Cerulean Warblers (Setophaga cerulea) and the avian community

The USDA Natural Resources Conservation Service (NRCS) supports private lands conservation projects across the United States to benefit imperiled focal wildlife species using conservation practices to restore habitat. The Cerulean Warbler Appalachian Forestland Enhancement Project (CWAFEP) was initiated in 2015 to help stabilize or reverse Cerulean Warbler population declines by using forest management to create or enhance breeding habitat on private lands in Appalachian focal areas. We evaluated Cerulean Warbler occupancy on CWAFEP sites treated using NRCS conservation practices to inform adaptive management strategies. We also assessed associated forest focal species’ occupancy and species richness of avian guilds to evaluate the effects of conservation practice implementation on the avian community. We conducted point count surveys at 194 locations on 21 private properties enrolled in the CWAFEP in West Virginia during May – July 2019 and 2020. We compared occupancy among four treatments: reference, pre-treatment, 1-year post-treatment, and 2 – 4 years post-treatment sites. To examine how vegetation structure changes among treatments affected occupancy, we also collected and included vegetation variables. Cerulean Warbler occupancy estimates were not different among treatments, suggesting that post-treatment study sites surveyed did not achieve their goal of increasing Cerulean Warbler occupancy. Cerulean Warbler occupancy decreased by 91 % as elevation increased from 200 to 800 m and increased by 397 % as sapling cover increased from 0 to 100 %. Occupancy for three forest focal species (Blue-gray Gnatcatcher, Eastern Wood-pewee, and Scarlet Tanager) and species richness of four avian guilds also were not different among treatments. Thus, Cerulean Warbler occupancy and selected avian community demographics were not related to recent conservation practice implementation in the short-term (1 – 4 years post-treatment), but there are opportunities to improve NRCS conservation practice implementation for more effective Cerulean Warbler conservation. We suspect that the lack of differences in occupancy and species richness estimates was due to site selection related to ecoregion, small treatment areas, and challenges associated with private lands conservation efforts resulting in insufficient reduction in basal area. If NRCS conservation practices implemented through CWAFEP are going to help reverse Cerulean Warbler population declines, CWAFEP sites need to achieve the recommended basal area range of ∼ 9.2 – 20.7 m 2/ha (40 – 90 ft2/ac) during contract implementation. Our conclusions are critical to updating our knowledge for Cerulean Warbler best management practices and informing future regional conservation implementation.

Distance sampling and spatial capture-recapture for estimating density of Northern Bobwhite

Obtaining accurate density estimates is critical for managers making decisions regarding wildlife populations. A variety of methods have been used to estimate population density, with two of the most common being distance sampling (DS) and spatial capture recapture (SCR). We evaluated precision and bias of density estimators through a simulation study of DS using data collected from either human observer point counts or automated recording units (ARUs), and SCR using trapping data or trapping data augmented with telemetry data. We then fit each of the four models to empirical data collected during autumn 2016–2018 for a population of northern bobwhite Colinus virginianus on Di-Lane Wildlife Management Area in Georgia. Density estimates in our simulation study were relatively unbiased using all four methods but were most accurate for the two SCR methods. Empirical density estimates were similar across methods and years, with annual averages of 0.41 birds per ha in 2016, 0.44 birds per ha in 2017 and 0.31 birds per ha in 2018. In general, both SCR methods were also the most precise using the empirical data, although ARU distance sampling did also produce comparable density estimates and precision values. Although SCR methods performed the best overall, cost and increased labor of these monitoring programs should be evaluated in relation to the relative ease of ARU deployment or point count surveys, which also provided adequate, and often similar, density estimates. Integrating these constraints into a structured decision-making framework will aid managers weighing decisions regarding how to monitor, and ultimately make management decisions.

Census of breeding birds in the Pyrenees in the early 1980s: A publicly available dataset for ecological research.

The Pyrenees is a mountain range in south-western Europe that supports a rich diversity of bird species. In 1981, point count surveys of breeding birds (passerines and picidae) were carried out in the Vanera valley, a valley in the eastern Pyrenees, resulting in a data set of 228 counts. These data provide valuable information on the distribution and abundance of bird populations on 5350 ha of heterogeneous land (including cropland, grasslands, heaths and river banks, and pine forest) at altitudes ranging from 1100 to 2600 meters. Additional point count surveys were carried out in the pine forest from 1982 to 1985, resulting in a data set of 144 counts. Habitat descriptors (percentage of herbaceous and ligneous plant cover at different heights - 0-1m, 1-4m and more than 8m; vegetation type) and altitude were assessed around each point count. This dataset provides a complete picture of the breeding bird community in a typical valley of eastern Pyrenees in the early 1980s, which could be compared with future censuses to contribute to a variety of research questions, such as quantifying changes in birds between the early 1980s and now in mountain areas, understanding the effects of climate change on bird populations, examining the effects of habitat fragmentation and land-use change, and identifying priority areas for conservation and management. These data could inspire new research and contribute to our collective understanding of bird ecology in the Pyrenees.

Ecological Considerations When Designing Mitigation Translocations: An Australian Reptile Case Study.

Translocation science has made considerable progress over the last two decades; however, reptile translocations still frequently fail around the world. Major knowledge gaps surround the basic ecology of reptile species, including basic factors such as habitat preference, which have a critical influence on translocation success. The western spiny-tailed skink (Egernia stokesii badia) is used here as a case study to exemplify how empirical research can directly inform on-ground management and future translocation planning. A combination of studies, including LiDAR scanning of microhabitat structures, camera trapping, plasticine replica model experiments and unbounded point count surveys to assess predation risk, and visual and DNA analysis of dietary requirements, were all used to better understand the ecological requirements of E. s. badia. We found that the skinks have specific log pile requirements, both native and non-native predator management requirements, and a largely herbivorous, broad diet, which all influence translocation site selection and management planning. The use of E. s. badia as an Australian case study provides a clear strategic framework for the targeted research of meaningful ecological factors that influence translocation decision-making. Similar approaches applied to other reptile species are likely to fundamentally increase the capacity for effective management, and the likelihood of future successful translocations.

A spatially explicit modeling framework to guide management of subsidized avian predator densities

AbstractAnthropogenic resource subsidization across western ecosystems has contributed to widespread increases in generalist avian predators, including common ravens (Corvus corax; hereafter, raven). Ravens are adept nest predators and can negatively impact species of conservation concern. Predation effects from ravens are especially concerning for greater sage‐grouse (Centrocercus urophasianus; hereafter, sage‐grouse), which have experienced prolonged population decline. Our objectives were to quantify spatiotemporal patterns in raven density, evaluate sage‐grouse nest success concurrent with fluctuating raven densities, and demonstrate a spatially explicit decision support tool to guide management applications to appropriate conflict areas. We combined ~28,000 raven point count surveys with data from more than 900 sage‐grouse nests between 2009 and 2019 within the Great Basin, USA. We modeled variation in raven density using a Bayesian hierarchical distance sampling approach with environmental covariates on detection and abundance. Concurrently, we modeled sage‐grouse nest survival using a hierarchical frailty model as a function of raven density and other environmental covariates that influence the risk of nest failure. Raven density commonly exceeded 0.5 ravens km−2and increased at low elevations with more anthropogenic development and/or agriculture. Reduced sage‐grouse nest survival was strongly associated with elevated raven density (e.g., >0.5 ravens km−2) and varied with topographic ruggedness, shrub cover, and burned areas. For conservation application, we developed a spatially explicit planning tool that predicts nest survival under current and reduced raven numbers within the Great Basin to help direct management actions to localized areas where sage‐grouse nests are at highest risk of failure. Our modeling framework can be generalized to multiple species where spatially registered abundance and demographic data are available.

Efficacy of aural detection methods for detecting Northern Pika (Ochotona hyperborea) occupancy in rocky and densely vegetated habitats

Abstract Wildlife monitoring plays a key role in species conservation, with growing importance under the threat of climate change. The Northern Pika (Ochotona hyperborea) is a cold-adapted species found in Hokkaido, Japan, presumably vulnerable to such threats. However, its high elusiveness hinders detailed population surveys, and visual detection methods—often used for other pika species—are not applicable to its densely vegetated habitats. In this study, we assessed the efficacy of aural detection methods to survey the occupancy of Northern Pika through their distinct vocalizations. We conducted two types of point-count surveys—auditory observation and playback—during 2021 at 18 sites in and around Daisetsuzan National Park. We then assessed the efficacy of these methods in detecting presence and compared time until first detection of the animal. The Northern Pika was present at 11 of all surveyed sites, with a predominance at higher elevations. Our results suggest that both auditory observation and playback are effective at detecting presence, but playback is more time-efficient. We discuss the advantages and disadvantages of each method given these results. In conclusion, our results demonstrate that both survey methods are applicable for Northern Pika population surveys—even in densely vegetated habitats—representing valid and affordable survey methods that can help to improve current monitoring and conservation efforts, and will be of increasing value given potentially negative effects of climate change on persistence of the species.

Physicochemical Parameters of Water and Its Implications on Avifauna and Habitat Quality

Wetland ecosystems are essential for maintaining biological diversity and are significant elements of the global landscape. However, the biodiversity of wetlands has been significantly reduced by more than 50% worldwide due to the rapid expansion of urban areas and other human activities. The aforementioned factors have resulted in drastic antagonistic effects on species composition, particularly aquatic avifauna. The decline in wetland avifauna, which can be attributed to changes in water quality that impact aquatic habitats, is a major concern. In this study, we evaluated the impact of physicochemical parameters on aquatic avifauna in India’s first Conservation Reserve, a Ramsar site and an Important Bird Area. Water samples were collected on a monthly basis across nine different sites and various parameters, such as temperature, electrical conductivity, pH, biological oxygen demand, dissolved oxygen, total dissolved solids and salinity, were analyzed for pre-monsoon and post-monsoon seasons, while point count surveys were conducted to assess species richness and the density of waterbirds. Our findings show a positive correlation of species density with water temperature (r = 0.57), total dissolved solids (r = 0.56) and dissolved oxygen (r = 0.6) for pre-monsoon season and a negative correlation for dissolved oxygen (r = −0.62) and biological oxygen demand (r = −0.69) for post-monsoon season. We suggest that a synergistic effect of pH, salinity, biological oxygen demand and total dissolved solids may affect aquatic bird populations in Asan Conservation Reserve. Poor water quality was observed in a few sampling sites, which may negatively affect the number and density of waterbirds present. The findings of this study emphasize the importance of water quality in wetland conservation, particularly for aquatic avifauna.

Occupancy and detectability of African crowned eagles in an urban mosaic landscape: The importance of natural forest areas

Diminishing forests as a result of anthropogenic activities continues to impact the persistence of terrestrial species negatively. Raptors are particularly susceptible to human activities because of their low population densities and large home range sizes. In this study, we investigated the occupancy and detection probabilities of the Near-Threatened African crowned eagle (Stephanoaetus coronatus) in Durban, EThekwini Municipality, South Africa. Using point count surveys, we documented the presence/absence of African crowned eagles in 42 sampling sites in the urban mosaic landscape of Durban. We used the presence/absence data to model their occupancy and detection probability in our surveyed sites. The naïve occupancy of African crowned eagles was 0.6, and the estimated occupancy and detection probability were 0.78 + 0.061 and 0.40 + 0.085, respectively. Based on the best models, the occupancy of African crowned eagles was positively influenced by forests (β = 1.24 + 0.69) and negatively influenced by disturbance (β = −1.69 + 0.78) and roads. The detection probability of these eagles was positively influenced by disturbance (β = 0.34 + 0.29) and the presence of exotic tree plantations (β = 0.33 + 0.47) and negatively influenced by the type of surrounding settlements (i.e., urban or rural) (β = −0.59 + 0.43). Based on the averaged models, occupancy is positively influenced by forests (β = 0.15 + 1.48) and negatively influenced by roads (β = −0.05 + 0.34), building density (β = −0.07 + 0.79) and disturbance (β = −0.24 + 3.36). Detection probability is negatively influenced by surrounding settlement (β = −0.12 + 0.41) and positively influenced by disturbance (β = 0.04 + 3.21) and plantations (β = 0.01 + 0.12). Overall, our results showed the persistence of African crowned eagles in the urban mosaic landscape as a consequence of natural and managed green spaces, especially forests. This highlighted the importance of natural forests and exotic tree plantations in ensuring the survival and thriving of African crowned eagles and the key role these green spaces play in species conservation in this urban mosaic landscape.

Housing or habitat: what drives patterns of avian species richness in urbanized landscapes?

ContextConservation of biodiversity in cities depends on ecologically sensitive urban planning, informed by an understanding of patterns of species distributions and richness. Because urbanized landscapes are heterogeneous mosaics, and many species move between different land-cover types, it is valuable to compare ‘whole landscapes’ (broad-scale spatially heterogeneous areas) that systematically differ in landscape structure.ObjectivesWe tested the relative influence of housing cover and canopy tree cover on avian species richness, to identify the components of landscape structure that most strongly influence landscape-scale richness (i.e., the pooled richness of multiple sites within a whole landscape).MethodsWe selected 30 residential landscapes (each 1 km2) in Melbourne, Australia, stratified to represent concurrent gradients of housing and canopy tree cover. Five point-count surveys were conducted at each of 10 sites per landscape (for a total of 50 surveys per landscape) and the data pooled to represent the whole landscape mosaic.ResultsUp to 82% of variation in avian richness was explained by properties of the whole landscape. Housing cover was most dominant and a strong predictor for multiple response groups including native, terrestrial, forest, and aquatic birds. As housing cover increased, the richness of all groups decreased. Tree cover, primarily comprised of scattered trees in residential areas, had less influence on richness. Nonetheless, for forest birds, the extent of native vegetation surrounding a landscape had an important positive influence, indicating the value of potential source habitat for urban bird populations.ConclusionsCities can be home to a diverse avifauna. The strong influence of landscape structure on species richness indicates a scope to plan and manage urbanized areas to support a diversity of birds that require natural habitat elements. We conclude that urbanizing environments can best be designed to benefit native birds by protecting patches of native vegetation (particularly large source areas) combined with localized higher housing cover, rather than uniform (lower) housing cover across the entire landscape.

Long-term trends in grassland bird relative abundance on focal grassland landscapes in Missouri.

North American grassland birds have widely declined over the past 50 years, largely due to anthropogenic-driven loss of native prairie habitat. In response to these declines, many conservation programs have been implemented to help secure wildlife habitat on private and public lands. The Grasslands Coalition is one such initiative established to advance the conservation of grassland birds in Missouri. The Missouri Department of Conservation conducted annual point count surveys for comparison of grassland bird relative abundance between focal grassland areas and nearby paired (i.e., containing no targeted management) sites. We analyzed 17 years of point count data with a generalized linear mixed model in a Bayesian framework to estimate relative abundance and trends across focal or paired sites for nine bird species of management interest that rely on grasslands: barn swallow (Hirundo rustica), brown-headed cowbird (Molothrus ater), dickcissel (Spiza americana), eastern meadowlark (Sturnella magna), grasshopper sparrow (Ammodramus savannarum), Henslow's sparrow (A. henslowii), horned lark (Eremophila alpestris), northern bobwhite (Colinus virginianus), and red-winged blackbird (Agelaius phoeniceus). Relative abundance of all species except eastern meadowlarks declined regionally. Relative abundance of barn swallows, brown-headed cowbirds, dickcissels, eastern meadowlarks, Henslow's sparrows, and northern bobwhites was higher in focal than paired sites, though relative abundance trends were only improved in focal vs. paired areas for dickcissels and Henslow's sparrows. Relative abundance increased with increasing grassland cover at the local (250-m radius) scale for all species except horned larks and red-winged blackbirds and at the landscape (2,500-m radius) scale for all species except dickcissels, eastern meadowlarks, and northern bobwhites. Our results suggest focal areas contained greater relative abundances of several grassland species of concern, likely due to increased availability of grassland habitat at local and landscape scales. Further efforts to decrease landscape-scale fragmentation and improve habitat quality may be needed to achieve conservation goals.