Occupancy Patterns of Breeding American Black Ducks

Occupancy patterns can assist with the determination of habitat limitation during breeding or wintering periods and can help guide population and habitat management efforts. American black ducks (Anas rubripes; black ducks) are thought to be limited by habitat and food availability during the winter, but breeding sites may also limit the size or growth potential of the population. The Canadian Wildlife Service conducts an annual breeding waterfowl survey that we used to explore the hypothesis that black duck carrying capacity is limited by wetlands available for breeding in Québec, Canada. We applied single-visit, multi-species occupancy models to the 1990–2015 population survey data to determine if there was evidence the black duck population was limited by breeding habitat. Using a dynamic (multi-season) occupancy modeling approach, we estimated latent occupancy (occupancy accounting for imperfect detection) of black ducks and then used latent occupancy estimates to derive occupancy, colonization, and extirpation rates. We jointly modeled the occupancy dynamics of black ducks and other duck species in wetlands where both species were present. Throughout the duration of the survey, 44% of wetlands were never observed to be occupied by black ducks. Occupancy models showed wetland size was positively associated with occupancy at the first time step (initial occupancy) and colonization. All 2-species models indicated initial black duck occupancy, persistence (continued occupancy), and colonization were positively associated with the presence of a second species. Colonization rate over the 26-year period ranged from 7% to 27% across all models. Extirpation rates were similar and were constant through time within each model. Low occupancy rates, combined with approximately equal colonization and extirpation rates, suggest there are available wetlands for breeding black ducks in their core breeding area. If breeding habitats are not saturated, this suggests migration or wintering areas may be more limiting to black duck population abundance. © 2019 The Wildlife Society.     

Determining the Effects of Cattle Grazing Treatments on Yosemite Toads (Anaxyrus [=Bufo] canorus) in Montane Meadows

Amphibians are experiencing a precipitous global decline, and population stability on public lands with multiple uses is a key concern for managers. In the Sierra Nevada Mountains (California, USA), managers have specifically identified livestock grazing as an activity that may negatively affect Yosemite toads due to the potential overlap of grazing with toad habitat. Grazing exclusion from Yosemite toad breeding and rearing areas and/or entire meadows have been proposed as possible management actions to alleviate the possible impact of cattle on this species. The primary objective of this study was to determine if different fencing treatments affect Yosemite toad populations. We specifically examined the effect of three fencing treatments on Yosemite toad breeding pool occupancy, tadpoles, and young of the year (YOY). Our hypothesis was that over the course of treatment implementation (2006 through 2010), Yosemite toad breeding pool occupancy and early life stage densities would increase within two fencing treatments relative to actively grazed meadows due to beneficial changes to habitat quality in the absence of grazing. Our results did not support our hypothesis, and showed no benefit to Yosemite toad presence or early life stages in fenced or partially fenced meadows compared to standard USDA Forest Service grazing levels. We found substantial Yosemite toad variation by both meadow and year. This variation was influenced by meadow wetness, with water table depth significant in both the tadpole and YOY models.     

Pond-Breeding Amphibian Species Richness and Habitat Selection in a Beaver-Modified Landscape

ABSTRACT Beaver (Castor canadensis) activity creates wetland habitats with varying hydroperiods important in maintaining habitat diversity for pond-breeding amphibians with significantly different breeding habitat requirements. We documented pond-breeding amphibian assemblages in 71 freshwater wetlands in Acadia National Park, Maine, USA. Using 15 variables describing local pond conditions and wetland landscape characteristics, we developed a priori models to predict sites with high amphibian species richness and used model selection with Akaike's Information Criterion to judge the strength of evidence supporting each model. We developed single-species models to predict wood frog (Rana sylvatica), bullfrog (R. catesbeiana), and pickerel frog (R. palustris) breeding site selection. Sites with high species richness were best predicted by 1) connectivity of wetlands in the landscape through stream corridors and 2) wetland modification by beaver. Wood frog breeding habitat was best predicted by temporary hydroperiod, lack of fish, and absence of current beaver activity. Wood frog breeding was present in abandoned beaver wetlands nearly as often as in nonbeaver wetlands. Bullfrog breeding was limited to active beaver wetlands with fish and permanent water. Pickerel frog breeding sites were best predicted by connectivity through stream corridors within the landscape. As beavers have recolonized areas of their former range in North America, they have increased the number and diversity of available breeding sites in the landscape for pond-breeding amphibians. The resulting mosaic of active and abandoned beaver wetlands both supports rich amphibian assemblages and provides suitable breeding habitat for species with differing habitat requirements. Land managers should consider the potential benefits of minimal management of beavers in promoting and conserving amphibian and wetland diversity at a landscape scale.     

Predicted Effect of Landscape Position on Wildlife Habitat Value of Conservation Reserve Enhancement Program Wetlands in a Tile‐drained Agricultural Region

Justification for investment in restored or constructed wetland projects are often based on presumed net increases in ecosystem services. However, quantitative assessment of performance metrics is often difficult and restricted to a single objective. More comprehensive performance assessments could help inform decision‐makers about trade‐offs in services provided by alternative restoration program design attributes. The primary goal of the Iowa Conservation Reserve Enhancement Program is to establish wetlands that efficiently remove nitrates from tile‐drained agricultural landscapes. A secondary objective is provision of wildlife habitat. We used existing wildlife habitat models to compare relative net change in potential wildlife habitat value for four alternative landscape positions of wetlands within the watershed. Predicted species richness and habitat value for birds, mammals, amphibians, and reptiles generally increased as the wetland position moved lower in the watershed. However, predicted average net increase between pre‐ and post‐project value was dependent on taxonomic group. The increased average wetland area and changes in surrounding upland habitat composition among landscape positions were responsible for these differences. Net change in predicted densities of several grassland bird species at the four landscape positions was variable and species‐dependent. Predicted waterfowl breeding activity was greater for lower drainage position wetlands. Although our models are simplistic and provide only a predictive index of potential habitat value, we believe such assessment exercises can provide a tool for coarse‐level comparisons of alternative proposed project attributes and a basis for constructing informed hypotheses in auxiliary empirical field studies.     

Habitat specialization of birds in the Czech Republic: comparison of objective measures with expert opinion

Capsule Expert‐based classification of bird species as habitat specialists and as generalists agrees with objective measures of species’ habitat requirements based on large‐scale monitoring data.

Aims To compare habitat specialization of 137 common bird species breeding in the Czech Republic using three different measures and to test their relationships to species’ abundance and habitat associations.

Methods Data on bird abundance and surveyed habitats were collected through a standardized monitoring scheme of common breeding species in the Czech Republic. From these data we calculated a quantitative species specialization index (SSI). Canonical correspondence analysis (CCA) was applied to calculate species’ habitat niche breadth and the level of association of each species to the main habitats. A panel of 11 local bird experts classified each species as habitat generalist or habitat specialist.

Results Species classified as habitat specialists by expert opinion showed higher habitat specialization according to the SSI, as well as according to CCA‐based habitat niche breadth. These species were also more closely associated with one of the main habitat types. These relationships were significant even after controlling for abundance.

Conclusions As expert opinion accords with the level of species’ habitat specialization expressed using two quantitative objective measures, we suggest that these characteristics reflect real interspecific variation in the breadth of habitat requirements in birds. Interspecific differences in habitat specialization are not caused solely by the variability in abundance among species.     

Commercially cut reed as a new and sustainable habitat for the globally threatened Aquatic Warbler

The Aquatic Warbler (Acrocephalus paludicola) is a song bird breeding in fen mires and similarly structured other wetlands with a water depth of 1–10 cm. Widespread in central-European wetlands at the beginning of the 20th century, the species is now globally threatened. The westernmost and genetically distinct Pomeranian population is even on the verge of extinction. The major challenge in the conservation of remaining habitat is the cost-efficient removal of biomass. About 50% of the Pomeranian population survives in a valley fen near Rozwarowo in Northwest Poland, where between 1993 and 2007 a conspicuous change in breeding habitat has taken place from summer grazed sedge meadows to commercial winter cut reed beds. We compared vegetation structure, site conditions, and potential prey abundance with the distribution and abundance of Aquatic Warblers in Rozwarowo Marshes and studied temporal changes and the compatibility of conservation and reed cutting interests. Aquatic Warblers now occur almost exclusively in sparsely growing, low reed with abundant Thelypteris palustris, Carex elata, and Lysimachia vulgaris. This vegetation type provides more potential prey for Aquatic Warblers than the higher productive tall reed, whereas the patches of sedge vegetation have become too small following succession after abandonment. Currently, commercial reed cutting maintains suitable Aquatic Warbler breeding habitat. Considering the impending changes in the reed market, there is a need for flexible agri-environmental schemes (AES) to ensure that stripes are left uncut and to prevent eutrophication by high and long flooding of the site.     

四川美姑大风顶国家级自然保护区鸟类物种及垂直多样性研究

2016年12月—2018年6月采用样带法和样点法对四川美姑大风顶国家级自然保护区的鸟类资源进行了调查,根据调查并结合相关文献记录,统计出保护区分布有鸟类268种,隶属17目56科。其中,留鸟146种(54.5%)、夏候鸟91种(34.0%)、冬候鸟18种(6.7%)、旅鸟13种(4.9%),以繁殖鸟为主。繁殖鸟类中,以东洋界物种为主(67.5%)。保护区的珍稀濒危鸟类物种数量较多,有国家Ⅰ级重点保护野生鸟类2种、国家Ⅱ级重点保护野生鸟类16种;列入濒危野生动植物种国际贸易公约附录Ⅰ1种、附录Ⅱ12种;列入世界自然保护联盟濒危物种红色名录濒危(EN)1种、易危(VU)3种、近危(NT)2种;中国特有种14种。各生境类型中的鸟类丰富度为针叶林>阔叶林>针阔混交林>灌丛及灌草丛>高山灌丛草甸>水域;针叶林、阔叶林、针阔混交林之间的鸟类群落结构相似性最高,水域与其他生境的最低。保护区鸟类物种丰富度在2600~3000m的中海拔地区最高,在高海拔和低海拔较低,物种垂直分布呈中峰模式。本研究丰富了保护区和凉山山系的鸟类资料,为鸟类垂直多样性研究提供了重要案例。     

Community Structure of Wetland Birds During Spring Migration Through the Rainwater Basin

Abstract: Staging areas and migratory stopovers of wetland birds have the potential to function as geographic bottlenecks; entire populations within a flyway may be affected by the quality and quantity of available wetland habitat at stopover sites. Although approximately 90% of playa wetlands in the Rainwater Basin (RWB) region of south-central Nebraska, USA, have been destroyed, the area still provides essential stopover habitat for >10 million waterfowl each spring. We evaluated community patterns and species associations to assess importance of assembly rules in structuring wetland bird communities during migration and to better facilitate multispecies conservation and management strategies. We surveyed 36–40 playas twice weekly in the RWB and observed approximately 2.6 million individual migratory wetland birds representing 72 species during 3 spring migrations 2002–2004. We evaluated spatial and temporal species co-occurrence patterns of geese, dabbling ducks, diving ducks, and shorebirds using null model analysis. Goose species co-occurrence scores did not differ from random in any year of the study, suggesting that goose species frequently use the same habitats during migration. Co-occurrence patterns among dabbling ducks were not different than expected by chance in any year; however, when we evaluated co-occurrence at a weekly scale, dabbling ducks co-occurred less often than expected during weeks of peak migration (high abundance), indicating that dabbling duck species spatially segregated at high densities. Diving duck co-occurrence patterns did not differ from random in any year, suggesting that diving duck species used the same habitats during migration. Shorebird species co-occurred less often than expected in 2002 and 2004, and during weeks of high shorebird abundance, indicating that shorebird communities were distinctly structured during those times. Most association values among lesser snow geese (Chen caerulescens) and dabbling duck species were positive, indicating dabbling ducks did not avoid wetlands with snow geese, a concern for waterfowl managers. However, we frequently observed snow geese and dabbling ducks using different microhabitats within a wetland, which indicate species associations and co-occurrence patterns may have occurred at a finer spatial scale than we measured. This approach of co-occurrence analysis will allow wildlife managers charged with multispecies management at migration stopover sites to make informed conservation and management decisions based on community structure rather than historic single-species approaches.     

敦煌西湖湿地鸟类栖息地重要性模糊综合评判

根据2007～2008年在甘肃敦煌西湖国家级自然保护区进行的湿地鸟类调查种类和数量数据,运用模糊综合评判法对保护区内的8块湿地进行了湿地鸟类栖息地重要性评价. 评判中隶属度的确定采用最佳因子值法,并分春、秋两种最佳因子值进行评判.结果表明:(1)春季各湿地均比秋季的重要性程度高,春季是管理的重点;(2)春秋两季南湖湿地重要性(0.938和0.966)都要远大于其它的湿地.春季盐池湾、羊水海子、南大湖的结果较相近,重要性程度次之,可持有相同程度的管理水平.党河水库、墩子湾、马圈湾、南园湖的重要性程度较低,只需一般水平的管理;(3)秋季各湿地水平除了南湖外普遍较低,羊水海子和盐池湾的重要性(0.340和0.269)相对较高些,但也只需一般水平的管理.     

Long-term monitoring of wetlands along the Western-Greek Bird Migration Route using Landsat and ASTER satellite images: Amvrakikos Gulf (Greece)

The west coast of Greece is an important migration route for migratory waterbirds. The wetlands along this coast are important stopover sites during bird migration between wintering and breeding sites. The use of remote sensing methods for mapping bird migration habitats and for temporal monitoring of changes in these habitats was investigated. The Amvrakikos Gulf, a coastal wetland complex along the west coast of Greece, was selected as the study area. Landsat TM and ETM+ images and ASTER VNIR images were used to perform a post-classification change detection over a time period of 15 years (1989–2004). In order to assess the spatial quality of existing wetland patches, spatial metrics (such as patch area, distance between the patches, and proximity) were calculated. To study changes in the degree of fragmentation of the stopover area, a binary patch structure was used in which the focal patches were embedded in a neutral matrix. The results showed that Landsat and ASTER VNIR satellite images can be used to trace small wetlands of approximately 0.5 ha minimum. These data sources are suitable for monitoring changes in wetlands, in particular marshes and mudflats, which are important habitats for migratory waterbirds. In the 15-year period that has been studied there was an estimated 32% decrease in marsh and mudflat area. Among this decrease, 25% went to water surface and 7% to vegetation in the months of August and September. Within the same period of time, a higher degree of fragmentation of the potential bird migration habitat has also been recorded. For this purpose, the remote sensing approach used in this study where change detection is performed on freely available Landsat and ASTER satellite images could be an interesting tool for policy makers and managers, as they allow easy recognition and monitoring of changes in wetlands and therefore contribute to an evaluation of the efficiency of protection and management schemes applied by countries for their wetlands.     

A novel approach to understanding bird communities using informed diversity estimates at local and regional scales in northern California and southern Oregon

Assessment and preservation of biodiversity has been a central theme of conservation biology since the discipline's inception. However, when diversity estimates are based purely on measures of presence–absence, or even abundance, they do not directly assess in what way focal habitats support the life history needs of individual species making up biological communities. Here, we move beyond naïve measures of occurrence and introduce the concept of “informed diversity” indices which scale estimates of avian species richness and community assemblage by two critical phases of their life cycle: breeding and molt. We tested the validity of the “informed diversity” concept using bird capture data from multiple locations in northern California and southern Oregon to examine patterns of species richness among breeding, molting, and naïve (based solely on occurrence) bird communities at the landscape and local scales using linear regression, community similarity indices, and a Detrended Correspondence Analysis (DCA). At the landscape scale, we found a striking pattern of increased species richness for breeding, molting, and naïve bird communities further inland and at higher elevations throughout the study area. At the local scale, we found that some sites with species‐rich naïve communities were in fact species‐poor when informed by breeding status, indicating that naïve richness may mask more biologically meaningful patterns of diversity. We suggest that land managers use informed diversity estimates instead of naïve measures of diversity to identify ecologically valuable wildlife habitat.     

SHOREBIRD HABITAT USE AND NEST-SITE SELECTION IN THE PLAYA LAKES REGION

Abstract: Wetlands in the Playa Lakes Region (PLR) provide important habitats for wintering waterfowl, cranes, and both migrant and breeding shorebirds. Playa Lakes Region wetlands experience naturally fluctuating hydroperiods but are exposed to anthropogenic stresses, which are exacerbated during summer and may influence PLR wetland occupancy and selection by breeding shorebirds. We examined wetland-scale habitat use and nest-site selection of the 4 dominant shorebirds (American avocets [Recurvirostra americana], black-necked stilts [Himantopus mexicanus], killdeer [Charadrius vociferus], snowy plovers [C. alexandrinus]) nesting in playas, saline lakes, and in both created and riparian wetlands in the PLR of Texas, USA. All 4 species nested in saline lakes. Only avocets and killdeer nested in playas, and snowy plovers nested in riparian wetlands. No nests were found in created wetlands. Wetland habitat changed (P < 0.001) during the breeding season, while water habitats generally decreased. Used (i.e., shorebirds found nesting) wetlands had more (P < 0.05) mudflats than non-used (i.e., shorebirds not found nesting) wetlands, which had more (P < 0.05) dry habitats. Used and non-used wetlands had similar (P > 0.05) amounts of water habitats. Nests were located close to vegetation on bare dry ground and dry ground with vegetation. Because water is ephemeral in PLR wetlands, shorebirds must select—in a somewhat predictive manner upon arrival—wetlands with suitable nest-site and brood-rearing habitat. Although surface water is necessary for nesting, its presence is not adequate for delineating suitable PLR wetland habitat for breeding shorebirds. Our findings that created wetlands cannot compensate for regional wetland losses in habitat or function highlights the need for conservation of natural PLR wetlands     

Classifying habitat characteristics of wetlands using a self-organizing map

Wetlands are nutrient-rich and biodiverse ecosystems that provide habitats for various animals and plants and protect against flooding. Classification of wetlands provides information to conservation planners and resource managers for ecosystem service determination. Many ecological case studies illuminate the self-organizing map (SOM) as a robust and powerful data classification and visualization tool. In this study, we use the SOM to analyze the habitat characteristics of inland wetlands in South Korea. We surveyed the plants, benthic macroinvertebrates, and bird species inhabiting 530 nationwide wetlands for four years from 2016 to 2019. Nine environmental features, including the proportion of urban area, farmland, grassland, a forest within a 1 km buffer zone, distance from the river and nearest wetland, area, perimeter, and average slope of wetland polygons, were used to train the SOM and examine the habitat characteristics of the surveyed living components. A map size of 10 × 11 pixels was considered for SOM training, and the output data were classified into eight clusters. Based on the occurrence frequency of the surveyed species group, most species were distributed in all clusters, whereas some dominated in specific clusters. We believe that our study contributes significantly to the literature because it highlights the significance of the SOM approach to cluster wetlands with dependent habitats and provides ecological information to build sustainable wetland conservation policies.     

Management of modern agricultural landscapes increases nest predation rates in Black‐tailed Godwits Limosa limosa

Effective conservation of endangered species requires a solid understanding of the demographic causes of population change. Bird populations breeding on agricultural grasslands have declined because their preferred habitat of herb‐rich meadows has been replaced by grassland monocultures. The timing of agricultural activities in these monocultural grasslands is critical, as they often coincide with the nesting phase of breeding birds. Here, we aim to identify the effect of habitat management and targeted nest protection on nest survival of Black‐tailed Godwits Limosa limosa in the Netherlands, a population that has shown a 70% reduction in breeding population size since the 1970s. To protect nests in monocultures from destruction, farmers are paid to either delay mowing or leave a patch of unmown grass around the nest, a patch which in practice varied in size. In herb‐rich meadows, which are typically managed for bird conservation purposes, mowing occurs after hatching. Nest survival declined as the season advanced, more steeply on monocultures than on meadows. Targeted nest protection was only partially successful, as nest predation was considerably higher on mown grassland monocultures with small unmown patches around the nest than in mown monocultures with large unmown patches and in unmown fields. Increased predator densities over the years have been suggested as an important cause of the trend towards lower nest survival, but here we show that nest survival was higher on herb‐rich meadows than on monocultures, and similar to the 1980s. It thus seems that increased predator densities are an increased threat during the egg stage only if habitat quality is low. High‐quality habitat in the form of herb‐rich meadows therefore provides a degree of protection against predators.     

Identifying important bird habitats in a sub-arctic area undergoing rapid land-use change

Capsule Habitats in lowland South Iceland sustain bird populations of international importance, with highest densities in wet habitats.

Aims In areas important for biodiversity there is an urgent need to assess large-scale variation in the biodiversity value of habitats to inform management. We carried out a large-scale survey to assess the conservation value of sub-arctic, Icelandic bird habitats.

Methods Bird counts were carried out on 200 transects in the five most common vegetated habitat types in South Iceland. Based on these counts, breeding bird density and diversity were compared between habitats and total population sizes of common species in these habitats were calculated.

Results Overall, eight species (seven waders and Meadow Pipit) composed over 95% of all birds counted. The combined density of those species exceeded 275 birds/km² in all habitats. The two wettest habitat types had the highest density of birds.

Conclusion Wet habitats in lowland South Iceland held particularly high densities of breeding birds, notably waders, which constitute populations of international importance. Wet habitat types are generally of higher value for more species, than dryer ones.     

Implications of Climate Change for Bird Conservation in the Southwestern U.S. under Three Alternative Futures

Future expected changes in climate and human activity threaten many riparian habitats, particularly in the southwestern U.S. Using Maximum Entropy (MaxEnt3.3.3) modeling, we characterized habitat relationships and generated spatial predictions of habitat suitability for the Lucy’s warbler (Oreothlypis luciae), the Southwestern willow flycatcher (Empidonax traillii extimus) and the Western yellow-billed cuckoo (Coccyzus americanus). Our goal was to provide site- and species-specific information that can be used by managers to identify areas for habitat conservation and/or restoration along the Rio Grande in New Mexico. We created models of suitable habitat for each species based on collection and survey samples and climate, biophysical, and vegetation data. We projected habitat suitability under future climates by applying these models to conditions generated from three climate models for 2030, 2060 and 2090. By comparing current and future distributions, we identified how habitats are likely to change as a result of changing climate and the consequences of those changes for these bird species. We also examined whether land ownership of high value sites shifts under changing climate conditions. Habitat suitability models performed well. Biophysical characteristics were more important that climate conditions for predicting habitat suitability with distance to water being the single most important predictor. Climate, though less important, was still influential and led to declines of suitable habitat of more than 60% by 2090. For all species, suitable habitat tended to shrink over time within the study area leaving a few core areas of high importance. Overall, climate changes will increase habitat fragmentation and reduce breeding habitat patch size. The best strategy for conserving bird species within the Rio Grande will include measures to maintain and restore critical habitat refugia. This study provides an example of a presence-only habitat model that can be used to inform the management of species at intermediate scales.     

Estimating the per‐capita contribution of habitats and pathways in a migratory network: a modelling approach

Every year, migratory species undertake seasonal movements along different pathways between discrete regions and habitats. The ability to assess the relative demographic contributions of these different habitats and pathways to the species’ overall population dynamics is critical for understanding the ecology of migratory species, and also has practical applications for management and conservation. Metrics for assessing habitat contributions have been well‐developed for metapopulations, but an equivalent metric is not currently available for migratory populations. Here, we develop a framework for estimating the demographic contributions of the discrete habitats and pathways used by migratory species throughout the annual cycle by estimating the per capita contribution of cohorts using these locations. Our framework accounts for seasonal movements between multiple breeding and non‐breeding habitats and for both resident and migratory cohorts. We illustrate our framework using a hypothetical migratory network of four habitats, which allows us to better understand how variations in habitat quality affect per capita contributions. Results indicate that per capita contributions for any habitat or pathway are dependent on habitat‐specific survival probabilities in all other areas used as part of the migratory circuit, and that contribution metrics are spatially linked (e.g. reduced survival in one habitat also decreases the contribution metric for other habitats). Our framework expands existing theory on the dynamics of spatiotemporally structured populations by developing a generalized approach to estimate the habitat‐ and pathway‐specific contributions of species migrating between multiple breeding and multiple non‐breeding habitats for a range of life histories or migratory strategies. Most importantly, it provides a means of prioritizing conservation efforts towards those migratory pathways and habitats that are most critical for the population viability of migratory species.     

Predicting changes in the abundance of African wetland birds by incorporating abundance–occupancy relationships into habitat association models

Aim To map changes in the abundance of African wetland birds using remotely derived habitat data. We show that abundance–occupancy relationships can be coupled with habitat association models to map changes in abundance. As conservation resources are more easily allocated when spatial and temporal patterns of abundance are known, our method provides guidance for conservation planning. Location Papyrus, Cyperus papyrus, swamps in east central Africa. Methods Presence/absence surveys of six bird species in 93 wetlands were used to construct models predicting probability of occurrence from habitat characteristics. Densities were then determined from surveys in 23 additional wetlands and modelled as functions of occurrence probability. We then used satellite imagery to derive habitat characteristics remotely in two time periods (1984–87 and 2000–03) and used the modelled relationships between (1) habitat and occupancy and (2) occupancy and density, to infer changes in abundance in all c. 30,000 wetlands within the study area. Results Wetlands within the region declined by 8.6% between the two time periods, but by > 75% in regions of high human population density. Bird densities were also highest in these regions, which comprised wetlands subject to high levels of disturbance. The geographical coincidence of high densities and habitat loss and the existence of positive associations between bird density and occurrence meant that birds declined by much more than the average rate of their habitat. Main conclusions Targeting conservation efforts in areas with high drainage would protect a high proportion of the bird populations. Encouraging people to derive income from disturbance to which the birds are tolerant, rather than drainage, is likely to be an effective strategy. Because habitat characteristics are a key driver of abundance–occupancy relationships, we conclude that there is wide‐scale scope to couple abundance–occupancy relationships with remote habitat mapping to efficiently inform conservation planning.     

Habitat heterogeneity drives bird species richness,nestedness and habitat selection by individual species in fluvial wetlands of the Paraná River,Argentina

We assessed the relationship between habitat heterogeneity and bird species richness and composition within wetlands of the floodplain of the Middle Paraná River, Argentina. Given the high habitat heterogeneity in these wetland systems, we sought to determine whether (i) there was a positive relationship between bird species richness and habitat heterogeneity; (ii) whether bird species richness was associated with certain types of individual habitat types; (iii) whether there was a pattern of species nestedness and turnover between sites as a function of habitat heterogeneity and composition, respectively; and (iv) whether individual species exhibited associations with habitat heterogeneity. Point counts were used to survey birds at 60 sites. We estimated the area of eight habitat types found within a 200‐m radius from the centre of each site and calculated number and Pielou's evenness of habitat types. These indices, together with area proportion of each habitat type, were used as explanatory factors of bird species richness in linear regression models. Habitat heterogeneity per se rather than area of individual habitat types was a more important predictor of species richness in these fluvial wetlands. Sites with more habitat types supported more bird species. Results showed that individual bird species were associated with different habitat types and, therefore, sites that contained more habitat types contained more species. Number of habitat types accounted for species nestedness between sites whereas composition of habitat types accounted for species turnover between sites. Results suggest that selection of heterogeneous sites by individual species could help explain the positive heterogeneity–species richness relationship. Our findings highlight the importance of habitat heterogeneity per se resulting from flood disturbances in maintaining bird richness in fluvial systems.     

Applying indicators of disturbance from plant ecology to vertebrates: The hemeroby of bird species

In plant ecology, hemeroby is a widely used indicator reflecting the anthropogenic disturbance level of a habitat. It is scaled on a range of point scores, higher scores of hemeroby meaning higher level of disturbance. In this study two indicators of sensitivity to disturbance based on the habitat preferences of bird species were used: HS (mean hemeroby score), calculated on the habitat types where each species occurs, and HH (mean hemerobiotic habitat diversity), indicating the level of a species generalism with respect to the range of disturbance levels characterizing the habitat where it occurs. Although already known in plant ecology, HS, so far, has never been applied to a group of vertebrates, while HH is a newly proposed index based on Shannon diversity. Both indexes are based on species position and range, along a gradient of disturbance, from pristine to completely man-made habitats. Drawing from a recently published atlas of bird species, it was possible to calculate the ecological preferences for a large number of habitat types in 75 common breeding bird species found in Latium (Central Italy). For each habitat, the average level of disturbance (based on hemeroby) within a 5-point scale was assessed. From the occurrences of birds in each habitat, HS (averaged disturbance calculated on the habitat types where each species occurs) and HH (the level of a species generalism with respect to the range of disturbance levels characterizing the habitats where it occurs) were calculated. The distribution of bird species number along the gradient showed a pattern of intermediate disturbance. Two different trends were found when analyzing the relationship between HS and HH: (i) a hump-shaped curve peaking at intermediate levels of HS, suggesting that generalism (HH) is maximum at intermediate levels of disturbance, and (ii) a second linear relationship pointing to a decrease of HH with increasing HS for a sub-set of synanthropic species (i.e., species linked to man-made habitats). The latter developed a further arm on the right of the hump-shaped curve: synanthropic species occurred only at higher levels of disturbance, and showed an increasing specialization with increasing levels of disturbance. Such a distribution was confirmed by analysing other data sets obtained from a real case study: the fraction of species with low values of HS sharply decreased from forest to urban habitats, while the fraction with high values increased; species with mid values of HS showed a maximum in crop-lands. HS and HH indexes are promising tools both in theoretical study and in practice, e.g. in management and monitoring of vertebrate communities.