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Nesting habitat preference and breeding of Asian Woollyneck (Ciconia episcopus) in Nepal
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Abstract
Background: Asian Woollyneck Ciconia episcopus is large wading bird whose conservation status has been recently down-listed, despite a lack of general knowledge on its nesting ecology and breeding success. Thus, in this study we conducted the most comprehensive survey on the nesting ecology of this species to date. Methods: We located 39 nesting sites across 18 districts of Nepal and recorded nest tree characteristics for the nine tree species they nested in. We also used Maxent modelling to further understand factors important for nesting habitat suitability and to identify new areas for future surveys. Results: They most commonly nested in Simal Bombax ceiba (n =21), followed by Sal Shorea robusta (n=6) and Salla Pinus roxburghii (n=4). The mean height of the nesting tree, nest height and tree diameter were 29.8 ± 5.8m (±SD), 1.03 ± 0.35m & 25.3 ± 5.8 m respectively. Nesting and fledging success were additionally recorded from 31 nesting attempts at 19 of these nesting sites between 2016 and 2020. Woollyneck had an estimated nesting success probability of 0.81 ± 0.07 and a mean fledging success of 1.94 ± 0.25 (±SE) chicks per nest. MaxEnt modelling identified a total potential suitable nesting habitat area of 9.64 % (14228km2) of total area in Nepal, with this located within 72 districts (out of 77), mostly in the western part of Nepal. The modelling parameters suggest that slope, land-use, precipitation and forest were important determinants of nesting habitat suitability. Conclusions: The most likely district reported by the model for Woollyneck nesting habitat has not previously reported nests which suggests additional survey effort in this region is warranted. We recommend that priority should be given to conserve taller trees close to settlements and cropland, and future studies should consider the potential impact of climate change on nesting suitability of this species.
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Vultures are ecologically important primarily because of their scavenging role in cleaning
carcasses of the environment. Because of anthropogenic impacts, the Egyptian vulture (Neophron percnopterus) has suffered catastrophic declines in parts of its range and, thus, information about its global distribution and factors influencing its occurrence within this range are essential for its conservation. To this end, we estimated the global distribution of Egyptian vulture and variables related to this distribution. We used occurrence points (n= 4740) from online data sources and literature, environmental variables related to these sites, and Maximum Entropy software to model the distribution of this species and its relationship to environmental variables during the entire year, breeding and overwintering. Out of~ 49 million km2 study area, the Egyptian vulture had a
predicted range of 6,599,508 km2 distributed across three continents: Africa, Asia and Europe. The densest distribution was in Southern Europe, India and Northern Africa and a sparser distribution was around Mid and Western Africa, the Middle East and Afghanistan. Climate was related to the vulture’s most probable range: in particular medium temperature seasonality and low precipitation during the coldest yearly quarter were important variables regardless of the season of observations examined. Conservation of identifed habitats and mitigation of anthropogenic impacts to conserve these vultures are recommended for immediate and long-term conservation of the Egyptian vulture globally.
Conservation of biodiversity alongside agriculture is now a global priority. Tree-nesting waterbirds have a tenuous relationship with farmlands because their survival requires farmers to retain trees and wetlands amid croplands. Research on such birds is rare on tropical and sub-tropical agricultural landscapes where high human densities and intensive farming ostensibly deteriorate breeding conditions. We explored breeding ecology and nest site selection by the single-nesting Woolly-necked Stork (Ciconia episcopus) in Haryana, north India using 298 nests from 166 locations discovered between 2016 and 2020. We determined the relative strengths of association of nest locations with natural features (trees, wetlands), human presence (habitation) and artificial water sources (irrigation canals) to understand cues used by breeding storks to situate nests. Woolly-necked Stork brood size from 42 successful nests was relatively high (3.1 ± 0.9 SD), with nests close to human habitation and wetlands having smaller broods. Storks showed high nest site fidelity (44.5% of sites used > 1 year), rarely nested on man-made structures (electricity pylons; 8.4%), and distributed nests in a clumped pattern. Woolly-necked Storks situated nests ambivalent to natural features but associated strongly with man-made features (positively with irrigation canals; negatively with human habitation). Contrary to expectations, most nests were not on the tallest trees but on the medium sized, native Dalbergia sissoo though storks situated nests on two tall trees (native Ficus religiosa and exotic Eucalyptus sp.) far more than the trees’ availability. All three tree species were favoured either for traditional agroforestry or local religious beliefs. Traditional agriculture in Haryana supported a substantial breeding population of Woolly-necked Storks facilitated by agriculture-related components rather than existing natural features. This novel scenario contradicts conventional narratives that suggest multi-season small holder tropical and sub-tropical agriculture degrades breeding conditions for waterbirds. Our findings in Haryana reiterate the need to assemble a diverse conservation toolkit of different locally relevant mechanisms supporting biodiversity amid cultivation.
The Asian Woollyneck Ciconia episcopus is a stork found throughout Asia whose international conservation status is currently being considered for reclassification from vulnerable to near-threatened. However, much of what is known about this species is fragmented across observational reports and small studies making a comprehensive assessment of population trends difficult. Here, we bring together all available published information to see what is known and what research questions still need answering in order to make reliable assessments of regional population trends and identify probable drivers of decline. Despite the species likely being extinct in the extremes of its former range and evidence of dramatic declines in Southeast Asia, Asian Woollyneck appears to be stable or increasing in India, Sri Lanka and Nepal. Observations of its preferred foraging and nesting habitats in South versus Southeast Asia show some obvious differences that may explain regional variations in population trends. In South Asia the bird is common in open grasslands and agricultural areas, while in Southeast Asia it is mostly observed in forested areas. Also, reports of the Asian Woollyneck nesting on cell phone towers is increasing in South Asia. However, because of a severe lack of reporting from Southeast Asia, it is unclear if or how these regional differences in population trends and habitat use are linked. Structured surveys and studies into the Asian Woollyneck foraging, nesting and movement ecology are urgently needed to understand the extent and drivers of decline in Southeast Asia. Therefore, researchers should focus future studies on population trends across the species' range, and aim to identify the local factors influencing recent changes in population growth. Without such knowledge, reassessment of its conservation status may be premature.
Rangewide distribution patterns and environmental requirements of the African Ciconia microscelis and Asian C. episcopus Woollyneck Storks are poorly understood, which has confounded the ability to develop empirical conservation status assessments for either species. We collated thousands of records for each species to create the first objective distribution maps, and used these data to model environmental suitability at the continental and regional scales in Africa and Asia with the machinelearning program MaxEnt. We found the African Woollyneck to be fairly widespread in southern and East Africa but its distribution in West Africa was fragmented. The Asian Woollyneck had a widespread distribution in south Asia, an isolated population segment in Cambodia and Vietnam, and was sparsely distributed on the southeast Asian islands. Predictions of suitable distributions and responses to climate variables in the MaxEnt models were scaledependent for both species. Annual and seasonal precipitation were most important in Africa, and the most influential variables differed across Asian models. Field studies testing these findings will bolster the knowledge of ecological requirements, as well as help determine how responses to environmental variation influence population dynamics. While our findings indicate neither species are of immediate conservation concern, there is evidence of population declines and range fragmentation and contractions in some regions. Understanding factors that have caused these changes is especially important in the face of ongoing environmental change on both continents.
Crowded agricultural landscapes of the tropics and subtropics are assumed to be responsible for the decline of many waterbird species. This includes Woollynecked Storks, one of the least studied large waterbirds, with no longterm multiscale information on its ecology. In this study we provide densities, population size, flock size and habitat use of the species in agricultural landscapes across seven districts in lowland Nepal and India using the largest available field data set of Woollynecked Stork observations (N = 8,906 individuals in 3,133 flocks observed seasonally between 2014 and 2019). With this data, we asked whether these metrics showed variation by season and location. Woollynecked Stork densities fluctuated considerably, both with season in each location and across locations. Estimated population of Woollynecked Storks in the study area was 1,689 ± 922 (SD) which extrapolated to the known distribution range of the species in south Asia provided a coarse population estimate of 2,38,685 ± 1,24,471 (SD). Woollynecked Storks were seen mostly in small flocks of 14 birds (86% of flocks) with few extraordinarily large flocks. Flocks were significantly larger in Jhajjar and Kheda districts, in winter, and in fallow fields and wetlands. Most Woollynecked Storks were observed in agriculture fields (64% of 1,874 observations) with much fewer in wetlands (9%). In three locations where seasonal habitat use was measured, Woollynecked Storks varied habitat use seasonally in all locations. Of six locations where habitat preference was assessed, storks preferred wetlands in five locations. Results of this study suggest that the largest known global population of this species is resident in agricultural landscapes, and coarse population estimates suggests that the population size of this species was previously underestimated. Results also showed considerable variations in flock size and habitat use with location and season suggesting that Woolly necked Storks show plasticity in response to changing conditions on agricultural landscapes. These findings will be helpful to revise the species' status assessment and understanding its conservation requirements.
Asian Woollyneck Ciconia episcopus is a globally threatened stork found across south and southeast Asian countries. In Nepal, it is considered as a fairly common resident species although
categorized as ‘NearThreatened’. Here, we report on Asian Woollyneck occurrences in 116 transects (farmland100, forest8, river8)
each measuring 500 m across four districts of lowland Nepal
(Kapilvastu, Chitwan, Sarlahi and Sunsari) and surveyed in multiple seasons from April 2018 to December 2019 for a total of 985 transect counts. Despite our extensive survey, we recorded Asian Woollynecks in only 14 transect counts of which eight were along the buffer zone of Chitwan National Park (CNP). All sightings were of small flocks with 1-2 storks. Majority of the sightings (85%) were in farmlands, remaining in river but not in forest. We observed one nest on a Sal Shorea robusta tree along the buffer zone of CNP in 2019 from which one chick fledged in early October. Our study adds to the meager information available on Asian Wollyneck in Nepal and indicates that this species is sparsely distributed in the lowland farmlands.
Asian Woollyneck is a globally "Vulnerable" stork species found in Asia. Information on its status in Bangladesh is scanty. In this note, we provide successful breeding records of Asian Woollyneck from Rajshahi and Chapainawabganj Districts confirming the breeding of the species in Bangladesh.
(1) The analyses were based on the comparison of three wood-dwelling, medium sized raptor species with 366 nest-years in Buzzards Buteo buteo, 110 nest-years in Goshawks Accipiter gentilis and 34 nest-years in Honey Buzzards Pernis apivorus. (2) Field data from 52 different nesting-habitat plots of Buzzards, 25 plots of Goshawks and 28 plots of Honey Buzzards were evaluated by discriminantanalysis and revealed differences in nest-habitat selection between these species. (3) Nesting-habitat features (measured in these plots) which were found to be associated with habitat selection in a principal-component-analysis, were also related to reproductive success with some differences between the species. These differences were similar to the different habitat selection found in the discriminant- analysis. The gradient (from poor to good) in habitat selection is slightly different between the species considered. Goshawk and Buzzard were found to be more closely related in habitat use than either were to the Honey Buzzard. (4) None of the species used their nesting-territories at random from year to year. Therefore, certain places had nests more often than expected by chance at the population levels found and others less often. (5) This use was related to nest-success. On average, the most often used territories showed the greatest success in all species. (6) From both parts of my analyses (2 and 3 and 4 and 5) the same nesting- habitat features were associated with good breeding success: habitat-parameters which gave good correlations to breeding success were found to be overrepresented in the more frequently used territories.
Cereal farming is on the increase globally, and trees on these agricultural landscapes are selectively removed by farmers. Waterbird populations, supported on many cereal farmlands, need trees to place heronries and can be impacted by farmers’ habits. In a cereal-dominated landscape in lowland Nepal, a landscape-scale field design was used to quantify characteristics of existing trees (density, species, girth, height), and contrasted against heronry trees to understand how choice of nest trees by select Ciconiiformes species was affected by farmers’ habits. Tree density was patchy and tree species richness low, dominated by two tree species that had direct utility to farmers (Dalbergia sissoo – timber; Mangifera indica – fruits). Heronries were preferentially located on two wild tree species that were 8% of available trees and were either revered in local religion (Ficus religiosa; 6% of all heronries) or favored for agroforestry (Bombax ceiba; 42%). Heronries were preferentially located on larger trees. Availability of suitable trees for heronries was reduced by farmers’ habits, but religious beliefs and agroforestry continued to support multi-functionality of cereal-dominated cropfields in lowland Nepal.
Egyptian vultures (Neophron percnopterus) play an important ecological role in central Asia, but conservation planning is hindered because basic information about their habitat requirements is lacking. We used 66 observations of roosting vultures to identify factors related to their presence, and MaxEnt model to predict areas of suitable roosting sites in the mid-hills of Nepal (∼20% of the district appeared suitable based on roosting observations). Vultures preferred riverbanks and areas near human settlements and pathways, probably because of access to animal carcasses. This relationship to local people and livestock should be considered when producing conservation plans for this species.
Natural nest sites are important breeding resource in terms of population dynamics, especially in forest systems where nest trees limit populations or timber harvesting destroys nests. Nest structures usually have a long life and can be reused by breeding pairs across multiple breeding seasons, so studying their dynamics is of relevance for biodiversity conservation. In this study, we develop a dynamic model to evaluate nest site availability and its influence on the breeding settlement of a forest raptor community composed of booted eagle (Hieraaetus pennatus), common buzzard (Buteo buteo) and northern goshawk (Accipiter gentilis) in a Mediterranean forest ecosystem in southeast Spain. This model approach is also applied to analyse the influence of forestry practices on the dynamics of occupied nests for a simulated period (2010–2050). The simulated scenarios include unmanaged forest and timber harvesting practices of clearcuttings every ten years considering two factors: the age class of trees for clearcutting (40, 50, 60 and 70 years old) and the type of forest management (with or without nest protection). Our simulated results show that the number of breeding pairs is constant during the period without timber harvest, whereas breeding pairs gradually decrease in the scenario of clearcutting trees aged from 70 to 50-years without nest protection, and populations become extinct with the clearcutting of 40-year old trees. Considering the practice of clearcutting and nest protection, nest occupancy can reach the maximum number of occupied nests for the scenarios of cutting 70 and 60-year old trees, and maintain populations without extinction for the scenarios of cutting 40-year old trees. We conclude that nest sites (whether occupied or not) are key resources for increasing the occupancy of the forest raptor community and that nest protection measures buffer the effects of clearcuttings, thus preventing population extinction.
The White Stork is a farmland and wetland bird that has become part of village communities by nesting in urban areas. Despite breeding close to people, allowing easy access for monitoring, its population in Eastern Europe is poorly studied. This paper presents the breeding success and habitat selection of a White Stork population from Eastern Romania. During the 2016 breeding season their breeding performance was poor compared to other European countries; on average only 2.25 nestlings fledged per nest. With respect to their habitat selection, the Eastern Romanian population uses similar habitats to storks elsewhere in Europe. Parameters influencing their breeding success could include weather conditions, geomorphology, habitat, landscape and intraspecific variables. To find those variables involved in the fluctuation of chick numbers General Linear Model (GLM) analyses, with a step procedure selection, were used. These analyses covered 55 variables. The best model of breeding success included altitude (P = 0.001); a higher elevation is associated with a lower number of chicks per nest. The number of river sectors (P = 0.045) and the distance to the nearest empty nest (P = 0.001) also have a positive influence on breeding success. These two variables could relate to the food availability in the study area. —Fasolă-Mătăsaru, L., Baltag, E.Ş., Ichim, P. & Cojocaru, D. (2018). Factors influencing the breeding success of White Storks Ciconia ciconia in Eastern Romania. Ardeola, 65: 271–282.
Biotic and abiotic factors are increasingly acknowledged to synergistically shape broad-scale species distributions. However, the relative importance of biotic and abiotic factors in predicting species distributions is unclear. In particular, biotic factors, such as predation and vegetation, including those resulting from anthropogenic land-use change, are underrepresented in species distribution modeling, but could improve model predictions. Using generalized linear models and model selection techniques, we used 129 estimates of population density of wild pigs (Sus scrofa) from 5 continents to evaluate the relative importance, magnitude, and direction of biotic and abiotic factors in predicting population density of an invasive large mammal with a global distribution. Incorporating diverse biotic factors, including agriculture, vegetation cover, and large carnivore richness, into species distribution modeling substantially improved model fit and predictions. Abiotic factors, including precipitation and potential evapotranspiration, were also important predictors. The predictive map of population density revealed wide-ranging potential for an invasive large mammal to expand its distribution globally. This information can be used to proactively create conservation/management plans to control future invasions. Our study demonstrates that the ongoing paradigm shift, which recognizes that both biotic and abiotic factors shape species distributions across broad scales, can be advanced by incorporating diverse biotic factors.
The Woolly-necked Stork Ciconia episcopus is a resident bird species commonly found breeding in the dry lowlands of Sri Lanka, preferably nesting in remote areas with minimal disturbance, although the breeding and nesting behavior has not yet been adequately documented. Here we report its nesting behavior, for the first time in lowland wet zone Sri Lanka, from Thalagolla, Beddawela in Kegalle District. Although its usual breeding season is in the dry zone from February to March with a second breeding cycle from November to early January, here we report breeding in the lowland wet zone from July–October in 2013–2014. Further, it was interesting to note presumably the same couple of birds used the same nest in 2014 with minimum renovation. In 2015 the nest had disintegrated and fallen due to continuous heavy rain and there have been no records till June 2016. Breeding was again recorded from June–September in 2016 with a new nest in a different platform of twigs in the same tree.
Abstract: When organisms with similar phenotypes have conflicting management and conservation initiatives, approaches are needed to differentiate among subpopulations or discrete groups. For example, the eastern metapopulation of the Double-crested Cormorant (Phalacrocorax auritus) has a migratory phenotype that is culled because they are viewed as a threat to commercial and natural resources, whereas resident birds are targeted for conservation. Understanding the distinct breeding habitats of resident versus migratory cormorants would aid in identification and management decisions. Here, we use species distribution models (SDM: Maxent) of cormorant nesting habitat to examine the eastern P. auritus metapopulation and the predicted breeding sites of its phenotypes. We then estimate the phenotypic identity of breeding colonies of cormorants where management plans are being developed. We transferred SDMs trained on data from resident bird colonies in Florida and migratory bird colonies in Minnesota to South Carolina in an effort to identify the phenotype of breeding cormorants there based on local landscape characteristics. Nesting habitat characteristics of cormorant colonies in South Carolina more closely resembled those of the Florida phenotype than of birds of the Minnesota phenotype. The presence of the resident phenotype in summer suggests that migratory and resident cormorants will co-occur in South Carolina in winter. Thus, there is opportunity for separate management strategies for the two phenotypes in that state. We found differences in nesting habitat characteristics that could be used to refine management strategies and reduce human conflicts with abundant winter migrants and, at the same time, conserve less common colonies of resident cormorants. The models we use here show potential for advancing the study of geographically overlapping phenotypes with differing conservation and management priorities.
Occurrence models that account for imperfect detection of species are increasingly used for estimating geographical range, for determining species-landscape relations and to prioritize conservation actions worldwide. In 2010, we conducted a large-scale survey in Río Muni, the mainland territory of Equatorial Guinea, which aimed to estimate the probabilities of occurrence and detection of threatened mammals based on environmental covariates, and to identify priority areas for conservation. Interviews with hunters were designed to record presence/absence data of seven species (golden cat, leopard, forest elephant, forest buffalo, western gorilla, chimpanzee and mandrill) in 225 sites throughout the region. We fitted single season occupancy models and recently developed models which also include false positive errors (i.e. species detected in places where it actually does not occur), which should provide more accurate estimates for most species, which are susceptible to mis-identification. Golden cat and leopard had the lowest occurrence rates in the region, whereas primates had the highest rates. All species, except gorilla, were affected negatively by human settlements. The southern half of Río Muni showed the highest occurrence of the species studied, and conservation strategies for ensuring the persistence of threatened mammals should be focused on this area.
The main objectives of this national Bird Red Data Book are to provide comprehensive accounts of all the bird
species found in Nepal, assess their status applying the IUCN Guidelines at Regional Levels (IUCN 2003),
identify threats to bird species and recommend the most practical measures for their conservation. The
species nomenclature in this Red Data Book follows IUCN approved names which are the same as those used
by BirdLife International.
Breeding habitat suitability analysis has significance for the timely conservation and scientific management of threatened species. Zhalong Nature Reserve is one of the main breeding sites of the western group red-crowned crane (Grus japonensis) migratory population, with a large, dynamic breeding population. With the objective of predicting the nesting habitat of red-crowned crane in Zhalong Nature Reserve, we obtained nesting occurrence records for this species from the study area collected from 2012-2013, extracted the environmental factors from the thematic mapper (TM) image of Zhalong Nature Reserve in 2013. We analyzed the nesting habitat suitability of red-crowned crane by the combined use of a GIS and MAXENT model. The results showed that the accuracy of the MAXENT model was excellent (training data area under the curve=0.901). The greenness vegetation index (34.9%), man-made interference (namely, the distance to frequently disturbed zones from human activity, 17.1%), soil wetness index (16.3%), and elevation (15.7%) were the main environmental factors influencing the nesting habitat selection of red-crowned crane. The central and south regions of the core zone were the main suitable nesting zones, and there was a small area of suitable habitat in the buffer zone and the experimental zone; the suitable nesting habitat area was 35857.35 hm2, representing about 17.07% of the whole reserve. The results showed that the core zone is the most important management zone for red-crowned crane nesting, and the reserve should also pay more attention to the small reed marsh area in the buffer zone and the experimental zone.
conservation. Key findings There were a total of 98 individuals in pre-breeding and 240 individuals of lesser adjutant stork in post-breeding periods (94 chicks and 146 adults) in the study area. On average, there were 1.29 chicks per nest. Bombax ceiba and Adina cordifolia were found to be the most preferred nesting trees for lesser adjutant storks. Habitat preference of lesser adjutant storks revealed that colonies were more likely to occur in farmlands and swamps. All the nests of lesser adjutant storks were found on trees above 30 m height, the average tree height was 42.5 ± 6.8 m and the average nest height was 34.4 ± 4.3 m. Questionnaire surveys revealed that people were not aware about conservation of lesser adjutant storks. More than 80% of respondents (n=145) opined that forest destruction was the most serious threat to storks followed by human disturbance (79%), poaching (73%), pesticide use (52%), and urbanization/industrialization (43%). Conservation implications Protection of nesting tree species such as Bombax ceiba and Adina cordifolia should be given a high priority for the conservation of storks in the eastern Nepal. Conservation education programs to control excessive pesticides in the rice fields should also be carried out in the region.
Studies conducted in the Keoladeo National Park during 1994-1997 on nest-site selection in the Blacknecked
Stork (Ephippiorhynchus asiaticus) and White-necked Stork (Ciconia episcopus) showed that
girth at breast height (GBH), height and canopy spread were the major factors governing the placement of
nests. There were significant differences between the height, canopy spread, and GBH of nesting and nonnesting
trees used by the two stork species. The Black-necked Stork nested on top canopies of tall Babool
Acacia nilotica trees with high GBH, while the White-necked Stork nested on Mitragyna parvifolia, in the
dense middle foliage.
All birds construct nests in which to lay eggs and/or raise offspring. Traditionally, it was thought that natural selection and the requirement to minimize the risk of predation determined the design of completed nests. However, it is becoming increasingly apparent that sexual selection also influences nest design. This is an important development as while species such as bowerbirds build structures that are extended phenotypic signals whose sole purpose is to attract a mate, nests contain eggs and/or offspring, thereby suggesting a direct tradeoff between the conflicting requirements of natural and sexual selection. Nest design also varies adaptively in order to both minimize the detrimental effects of parasites and to create a suitable microclimate for parents and developing offspring in relation to predictable variation in environmental conditions. Our
understanding of the design and function of birds’ nests has increased considerably in recent years, and the evidence suggests that nests have four nonmutually exclusive functions. Consequently, we conclude that the design of birds’ nests is far more sophisticated than previously realized and that nests are multifunctional
structures that have important fitness consequences for the builder/s.
Livestock contributes directly to the livelihoods and food security of almost a billion people and affects the diet and health of many more. With estimated standing populations of 1.43 billion cattle, 1.87 billion sheep and goats, 0.98 billion pigs, and 19.60 billion chickens, reliable and accessible information on the distribution and abundance of livestock is needed for a many reasons. These include analyses of the social and economic aspects of the livestock sector; the environmental impacts of livestock such as the production and management of waste, greenhouse gas emissions and livestock-related land-use change; and large-scale public health and epidemiological investigations. The Gridded Livestock of the World (GLW) database, produced in 2007, provided modelled livestock densities of the world, adjusted to match official (FAOSTAT) national estimates for the reference year 2005, at a spatial resolution of 3 minutes of arc (about 5×5 km at the equator). Recent methodological improvements have significantly enhanced these distributions: more up-to date and detailed sub-national livestock statistics have been collected; a new, higher resolution set of predictor variables is used; and the analytical procedure has been revised and extended to include a more systematic assessment of model accuracy and the representation of uncertainties associated with the predictions. This paper describes the current approach in detail and presents new global distribution maps at 1 km resolution for cattle, pigs and chickens, and a partial distribution map for ducks. These digital layers are made publically available via the Livestock Geo-Wiki (http://www.livestock.geo-wiki.org), as will be the maps of other livestock types as they are produced.
Aim
Species distribution models have been widely used to tackle ecological, evolutionary and conservation problems. Most species distribution modelling techniques produce continuous suitability predictions, but many real applications (e.g. reserve design, species invasion and climate change impact assessment) and model evaluations require binary outputs, and thresholds are needed for these transformations. Although there are many threshold selection methods for presence/absence data, it is unclear whether these are suitable for presence‐only data. In this paper, we investigate mathematically and empirically which of the existing threshold selection methods can be used confidently with presence‐only data.
Location
We used real spatially explicit environmental data derived from the western part of the state of V ictoria, south‐eastern A ustralia, and simulated species distributions within this area.
Methods
Thirteen existing threshold selection methods were investigated mathematically to see whether the same threshold can be produced using either presence/absence data or presence‐only data. We further adopted a simulation approach, created many virtual species with differing prevalences in a real landscape in south‐eastern A ustralia, generated data sets with different proportions of pseudo‐absences, built eight types of models with four modelling techniques, and investigated the behaviours of four threshold selection methods in these situations.
Results
Three threshold selection methods were not affected by pseudo‐absences, including max SSS (which is based on maximizing the sum of sensitivity and specificity), the prevalence of model training data and the mean predicted value of a set of random points. Max SSS produced higher sensitivity in most cases and higher true skill statistic and kappa in many cases than the other methods. The other methods produced different thresholds from presence‐only data to those determined from presence/absence data.
Main conclusions
Max SSS is a promising method for threshold selection when only presence data are available.
I studied 423 nests of six raptor species in east-central Estonia to (1) distinguish the essential features of the nest sites, (2) link the nest-tree and nest-stand characteristics, and (3) explore whether the availability of potential nest trees and stands limits raptor populations in managed forest landscapes. Aquila pomarina was the only species having distinct preferences for a few site types, while Accipiter gentilis and Falco subbuteo selected stands according to composition rather than site type. Coniferous trees, particularly spruce, were greatly favoured for nest-building by all species, probably due to better protective cover. Size of the nest tree was more important than its age; though on poor soils, nest trees were both older and smaller. A. gentilis, A. pomarina, and Buteo buteo appeared to be most prone to the lack of potential nest trees in managed forests, e.g. stands < 80 years old were generally inhabitable only if these contained older trees. Green-tree retention could greatly add nest sites for these raptors in managed forests. However, nest-site selectivity did not correlate with the population sizes of the six species, suggesting that nest-sites were not the main limiting factor for them.
Species distribution modelling is increasingly used in ecological studies and is particularly useful in conservation planning. Models are, however, typically created with a coarse resolution, although conservation planning often requires a high resolution. In this study we created high resolution models and explored central aspects of the modelling procedure; transferability and predictive performance of the models. We created models for two breeding water bird species, common eider Somateria mollissima and herring gull Larus argentatus, based on data from two regions in the Finnish archipelago (234 islands). We used seven variables which we considered as potential predictors of nest site location: distance to forest, distance to rock and distance to low vegetation, exposure, elevation, slope and curvature of the land surface. We tested the predictive ability of the models crosswise between the areas by using area under the receiver operating characteristic curve. The models were transferable between our study areas and the predictive performance varied from fair to excellent. The most important predictors overall were exposure and distance to forest. More general models, with higher regularization values in the Maxent software, had better transferability regarding predictive performance. However, when we fitted a model based on 60% of the data from both regions and evaluated the model on the remaining 40%, the most complex model had the highest accuracy. Extrapolation of SDMs, evaluated on data from the same region, should therefore always be done with caution as the most accurate model might not have the best transferability if it is not general enough.
Nepal is a mountainous country in the central Himalayas, which occupies about one third of (800 km) of the entire length of
the Himalayan mountain range. Nepal alone claims eight out of the top ten tallest mountains in the world, including Mount
Everest (8,848 m). Apart from the mountains, deep gorges, river valleys and the flat lands it provides a unique assemblage
of very different habitats and a great biodiversity within a small geographical area. The 147 181 km2 that make up Nepal is slightly less than 0.1% of the global land mass, but contains a disproportionately large diversity
of plants and animals. The country’s 118 ecosystems harbour over 2% of the flowering plants, 3% of the pteridophytes and 6%
of the bryophytes in the world’s flora. Similarly, the country harbours 3.9% of the mammals, 8.9% of the birds and 3.7% of
the world’s fauna of butterflies (Table 1.1).
The use of statistical models to predict the likely occurrence or distribution of species is becoming an increasingly important tool in conservation planning and wildlife management. Evaluating the predictive performance of models using independent data is a vital step in model development. Such evaluation assists in determining the suitability of a model for specific applications, facilitates comparative assessment of competing models and modelling techniques, and identifies aspects of a model most in need of improvement. The predictive performance of habitat models developed using logistic regression needs to be evaluated in terms of two components: reliability or calibration (the agreement between predicted probabilities of occurrence and observed proportions of sites occupied), and discrimination capacity (the ability of a model to correctly distinguish between occupied and unoccupied sites). Lack of reliability can be attributed to two systematic sources, calibration bias and spread. Techniques are described for evaluating both of these sources of error. The discrimination capacity of logistic regression models is often measured by cross-classifying observations and predictions in a two-by-two table, and calculating indices of classification performance. However, this approach relies on the essentially arbitrary choice of a threshold probability to determine whether or not a site is predicted to be occupied. An alternative approach is described which measures discrimination capacity in terms of the area under a relative operating characteristic (ROC) curve relating relative proportions of correctly and incorrectly classified predictions over a wide and continuous range of threshold levels. Wider application of the techniques promoted in this paper could greatly improve understanding of the usefulness, and potential limitations, of habitat models developed for use in conservation planning and wildlife management.
Nepal is a typically mountainous landlocked country. In recent years, land cover in Nepal has changed significantly due to climate changes, population growth and economic development. This study used four periods of land cover change data (1990–2000, 2000–2005, 2005–2010 and 2010–2015) produced by the object-oriented change detection method, to reveal the spatial patterns of land cover change and its driving forces in Nepal since 1990. The result showed that the total change area from 1990 to 2015 in Nepal is 1665.58 km², accounting for 1.13% of the land. Among these changes, forests, wetlands and permanent ice/snow presented a trend of decrease, whereas croplands, artificial surfaces and bare lands had been continuously increasing. The prominent land cover changes included mutual transformation between wetlands and croplands, wetland class inner shifts and the conversion of forests to croplands. These changes varied among different development regions and during different periods. In general, the intensities of land cover change in Eastern and Central Development Regions were higher than in other development regions. The annual change area was 59.26 km²/year during 1990–2000, reached to 98.44 km²/year during 2000–2005 and turned to slowly decline after 2005. The analysis and discussion indicated that major driving forces of land cover change in Nepal include climate changes, natural hazards, population growth, urbanization, economic development and government policy implementation. A comprehensive understanding of the relationships between land cover change and various driving forces in Nepal was given in this study, which would be valuable for policymaking, land planning, resource development and protection. Simultaneously, it could be also benefit to China’s “Belt and Road Initiative.”
The sections on Field characters, Habitat, Distribution, Population, Movements, Food and Breeding have been rewritten and updated. New sections or sub-sections have been added on Abundance (population density), Breeding settlement, resettlement, site fidelity, Age structure and survival, and Conservation. The 5th International White Stork Census, carried out in 1994-95, was the most complete up to now, covering almost the entire breeding range of the species. A detailed description of the population status and development of the White Stork, including the most recent data available, is therefore one of the priorities of this account. The data are of particular interest, as since the mid-1980s the population trend of the species has changed, from rather constant declines in most countries to moderate and, in several countries, considerable increases. The section on Population now gives, country by country, a clear picture of the population status of the White Stork in its entire breeding range. It also presents an updated distribution map. Knowledge on White Stork migration has considerably improved during the last few years. This development has been strongly supported by the introduction of new research methods, particularly satellite and radar tracking. The updated account now provides a comprehensive overview of migration routes, migration behaviour, and ecology of the species during migration, based on the most recent findings. Population biology of local and regional White Stork populations has been the subject of a large number of research projects during the last few years. From these studies, data on abundance, population structure, settlement, age, and survival, which are of general interest concerning the overall population of the species, were extracted and are presented in new and updated sections of the account. The same applies to the subject of feeding ecology and breeding biology of the White Stork, the relevant sections having been updated accordingly. A new section deals with the conservation status of the White Stork. It suggests the separation of the overall population into different core and peripheral populations and describes factors responsible for particular population trends, as well as measures needed to conserve White Stork populations in the long term.
A wide range of modelling algorithms is used by ecologists, conservation practitioners, and others to predict species ranges from point locality data. Unfortunately, the amount of data available is limited for many taxa and regions, making it essential to quantify the sensitivity of these algorithms to sample size. This is the first study to address this need by rigorously evaluating a broad suite of algorithms with independent presence-absence data from multiple species and regions. We evaluated predictions from 12 algorithms for 46 species (from six different regions of the world) at three sample sizes (100, 30, and 10 records). We used data from natural history collections to run the models, and evaluated the quality of model predictions with area under the receiver operating characteristic curve (AUC). With decreasing sample size, model accuracy decreased and variability increased across species and between models. Novel modelling methods that incorporate both interactions between predictor variables and complex response shapes (i.e. GBM, MARS-INT, BRUTO) performed better than most methods at large sample sizes but not at the smallest sample sizes. Other algorithms were much less sensitive to sample size, including an algorithm based on maximum entropy (MAXENT) that had among the best predictive power across all sample sizes. Relative to other algorithms, a distance metric algorithm (DOMAIN) and a genetic algorithm (OM-GARP) had intermediate performance at the largest sample size and among the best performance at the lowest sample size. No algorithm predicted consistently well with small sample size (n < 30) and this should encourage highly conservative use of predictions based on small sample size and restrict their use to exploratory modelling.
The building of dams and subsequent diversion of water from the Macquarie River have had a significant impact on the breeding of colonial waterbirds in the Macquarie Marshes, New South Wales, southeastern Australia. Annual flows (1978, 1986-1996), measured at Oxley where the Marshes begin, were significantly related to total colony size (number of nests) and sizes of six nesting Ciconiidae (Intermediate Egret Ardea intermedia, Rufous Night Heron Nycticorax caledonicus, Glossy Ibis Plegadis falcinellus, Straw-necked Ibis Threskiornis spinicollis, Australian White Ibis Threskiornis mollucca and Royal Spoonbill Platalea regia) colonies. We used these results and available historical flow data extending back to 1944 to demonstrate the probable impact of water diversions on breeding in these colonial nesting species. The impact of Burrendong Dam, opened in 1967, and Windamere Dam, opened in 1984, on the numbers of nests would have been significant. Instead of a colony of more than 100,000 nests in 1969, a colony of less than 10,000 probably established. Similarly, in 1984, a colony of more than 100,000 could have been established with no water diversions, but in all likelihood the colony was less than 5,000. Generally colony sizes were significantly less (100,000 over 11 years) than would be expected without diversions of water upstream. Colony sizes of more than 100,000 nests estimated during the floods of the 1950s are unlikely to occur again. Numbers of annual breeding events also declined with water diversions from ten to seven (1963-1973); eight to seven (1974-1984) and eight to five (1985-1995).
The number of White Storks (Ciconia ciconia) has been decreasing in many parts of Europe at least since the middle of the 20th century. Intensification of agriculture and continuous conversion of natural habitats, such as wetlands, into agricultural landscapes have been recognized as the most important determinants of dramatic reductions in population sizes of this species. For this reason, providing quantitative estimates of habitat requirements may allow us to identify the key biota which should be prioritized for conservation. The aim of this study was to investigate White Storks' habitat selection in a mosaic agricultural landscape in central Poland. We found that territories associated with large river valleys were highly preferred by first-arriving storks. We also recorded lower intensity of brood reduction and higher reproductive success of storks breeding in such territories. Thus, it seems likely that location of nests close to river valleys provided easy access to rich food resources associated with wetlands. In fact, distance to nearest wetland was the second strongest predictor of nest-site selection in the studied population. We also demonstrated that pairs nesting in the territories with a high proportion of wetlands showed lower levels of brood reduction in comparison to pairs having poorer access to wet habitat patches. Finally, we found that although early arriving storks avoided settling in an urbanized landscape, they selected nesting sites located close to buildings. The results of this study confirmed high importance of wet grasslands for the core central European population of White Storks.
Species distribution models are increasingly used to address conservation questions, so their predictive capacity requires careful evaluation. Previous studies have shown how individual factors used in model construction can affect prediction. Although some factors probably have negligible effects compared to others, their relative effects are largely unknown.
We introduce a general ’virtual ecologist’ framework to study the relative importance of factors involved in the construction of species distribution models.
We illustrate the framework by examining the relative importance of five key factors – a missing covariate, spatial autocorrelation due to a dispersal process in presences/absences, sample size, sampling design and modelling technique – in a real study framework based on virtual plants in a mountain landscape at regional scale, and show that, for the parameter values considered here, most of the variation in prediction accuracy is due to sample size and modelling technique. Contrary to repeatedly reported concerns, spatial autocorrelation has only comparatively small effects.
This study shows the importance of using a nested statistical framework to evaluate the relative effects of factors that may affect species distribution models.
Food limitation is generally thought to underlie much of the variation in life history traits of birds. I examined variation and covariation of life history traits of 123 North American Passeriformes and Piciformes in relation to nest sites, nest predation, and foraging sites to examine the possible roles of these ecological factors in life history evolution of birds. Annual fecundity was strongly inversely related to adult survival, even when phylogenetic effects were controlled. Only a little of the variation in fecundity and survival was related to foraging sites, whereas these traits varied strongly among nest sites. Interspecific differences in nest predation were correlated with much of the variation in life history traits among nest sites, although energy trade-offs with covarying traits also may account for some variation. For example, increased nest predation is associated with a shortened nestling period and both are associated with more broods per year, but number of broods is inversely corr
Reports of nesting success that do not take into account the time span of observation for each nest usually understate losses, and sometimes the error can be very large. More than a decade ago I pointed out this problem and proposed a way of dealing with it (Mayfield 1960:192-204; 1961). Since that time many field students have used the method, and it has proved es- pecially helpful in combining fragments of data from many sources, as in the North American Nest-record Program at Cornell University. However, not every published report shows awareness of the problem, and letters of in- quiry have shown that some people are deterred from dealing with it because of difficulty with details. Therefore, I offer these further suggestions to sim- plify the procedure as much as possible. THE PROBLEM All nests are not found at the very start. Indeed, most nests of small open- nesting birds are not found until incubation is well under way or until the young have hatched. The observed success in such a sample will be greater than the true nesting success of the species. The shorter the time span of observations, the less the observed losses; that is, nest mortality-loss by destruction or desertion-is a function of time. Since nearly all field studies contain a mixture of nests found early and late, as customarily reported they show nesting success higher than real- ity; but the amount of error is indeterminable because the time each nest entered the sample is not reported. For precise analysis of mortality and sur- vival, it is not enough merely to count nests, eggs, and young. The elapsed time of the observations must also be considered. To illustrate the main difficulty, suppose you found a series of nests when incubation was far advanced. Hatching success would be nearly 100%; and in nests containing large young when found, fledging success would be nearly 100%. Yet you would hesitate to present these figures because it is plain that not enough time elapsed for many accidents to befall. In this extreme case the pitfall is obvious, but in a mixed bag of data, this kind of error may slip through unnoticed. What you are trying to determine is the nesting success of a population. Ideally you would like to find all the nests started by the birds in that pop- ulation, watch all these nests from their beginnings, and observe everything that happened up to the fledging of young. Usually this is impossible and you have to settle for a good deal less, namely, a sample that is anything but 456
This paper presents how weather conditions affect survival of White Stork Ciconia ciconia nestlings. The main goals of the present study are to determine the most critical period for breeding output and to investigate factors influencing reproductive efficiency of the studied population. The mean survival rate of the whole nesting period (day 52 from egg laying to day 20 of nestlings life) was 0.668 (95% CL: 0.611–0.725) and did not differ between years, while mean survival for incubation period was 0.721 (0.681–0.761) and also was not significantly different between years. Finally, the mean survival rate for the nestling period was 0.903 (0.869–0.937) and was different between years.This study shows that the most critical period in the breeding cycle is the time of incubation and the first days of the nestling's life. The period from egg laying to day 20 of the nestling's life is characterised by the highest hazard ratio. Finally, the study demonstrates that, like many other bird species, White Stork nestlings' survival is affected by low temperatures and a high level of precipitation.
In recent years the use of species distribution models by ecologists and conservation managers has increased considerably, along with an awareness of the need to provide accuracy assessment for predictions of such models. The kappa statistic is the most widely used measure for the performance of models generating presence–absence predictions, but several studies have criticized it for being inherently dependent on prevalence, and argued that this dependency introduces statistical artefacts to estimates of predictive accuracy. This criticism has been supported recently by computer simulations showing that kappa responds to the prevalence of the modelled species in a unimodal fashion.
In this paper we provide a theoretical explanation for the observed dependence of kappa on prevalence, and introduce into ecology an alternative measure of accuracy, the true skill statistic (TSS), which corrects for this dependence while still keeping all the advantages of kappa. We also compare the responses of kappa and TSS to prevalence using empirical data, by modelling distribution patterns of 128 species of woody plant in Israel.
The theoretical analysis shows that kappa responds in a unimodal fashion to variation in prevalence and that the level of prevalence that maximizes kappa depends on the ratio between sensitivity (the proportion of correctly predicted presences) and specificity (the proportion of correctly predicted absences). In contrast, TSS is independent of prevalence.
When the two measures of accuracy were compared using empirical data, kappa showed a unimodal response to prevalence, in agreement with the theoretical analysis. TSS showed a decreasing linear response to prevalence, a result we interpret as reflecting true ecological phenomena rather than a statistical artefact. This interpretation is supported by the fact that a similar pattern was found for the area under the ROC curve, a measure known to be independent of prevalence.
Synthesis and applications . Our results provide theoretical and empirical evidence that kappa, one of the most widely used measures of model performance in ecology, has serious limitations that make it unsuitable for such applications. The alternative we suggest, TSS, compensates for the shortcomings of kappa while keeping all of its advantages. We therefore recommend the TSS as a simple and intuitive measure for the performance of species distribution models when predictions are expressed as presence–absence maps.
Accurate modeling of geographic distributions of species is crucial to various applications in ecology and conservation. The best performing techniques often require some parameter tuning, which may be prohibitively time-consuming to do separately for each species, or unreliable for small or biased datasets. Additionally, even with the abundance of good quality data, users interested in the application of species models need not have the statistical knowledge required for detailed tuning. In such cases, it is desirable to use ‘‘default settings’’, tuned and validated on diverse datasets. Maxent is a recently introduced modeling technique, achieving high predictive accuracy and enjoying several additional attractive properties. The performance of Maxent is influenced by a moderate number of parameters. The first contribution of this paper is the empirical tuning of these parameters. Since many datasets lack information about species absence, we present a tuning method that uses presence-only data. We evaluate our method on independently collected high-quality presenceabsence data. In addition to tuning, we introduce several concepts that improve the predictive accuracy and running time of Maxent. We introduce ‘‘hinge features’ ’ that model more complex relationships in the training data; we describe a new logistic output format that gives an estimate of probability of presence; finally we explore ‘‘background sampling’’ strategies that cope with sample selection bias and decrease model-building time. Our evaluation, based on a diverse dataset of 226 species from 6 regions, shows: 1) default settings tuned on presence-only data achieve performance which is almost as good as if they had been tuned on the evaluation data itself; 2) hinge features substantially improve model
We study the problem of modeling species geographic distributions, a critical problem in conservation biology. We propose the use of maximum-entropy techniques for this problem, specifically, sequential-update algorithms that can handle a very large number of features. We describe experiments comparing maxent with a standard distribution-modeling tool, called GARP, on a dataset containing observation data for North American breeding birds. We also study how well maxent performs as a function of the number of training examples and training time, analyze the use of regularization to avoid overfitting when the number of examples is small, and explore the interpretability of models constructed using maxent.
The IUCN Red List of Threatened Species
BirdLife International. (2020). Ciconia episcopus (Asian Woollyneck). The IUCN Red List of
Threatened Species 2020:E.T22727255A175530482. https://www.iucnredlist.org/species/
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National population and housing census. National Planning Commission
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