Aggregations Of Birds Research Articles

Documentation of Avian Species Composition and Assemblage in Agricultural Landscapes of Karnal, Haryana

Avian communities maintain ecological balance by eliminating pests, providing ecosystem services, and acting as biological indicators, thereby playing a pivotal role in conserving agricultural landscapes’ integrity and stability; thus from an environmental monitoring standpoint, assessment of bird aggregations in various landscapes is necessary. A three-year (2021, 2022 and 2023) bird survey was conducted to document the checklist, density, and diversity of bird species assemblage of agricultural landscapes in the Karnal district of Haryana, India, to obtain the richness of birds in different agricultural habitats. A total of 79 bird species from 36 families and 14 orders were recorded; two bird species (Alexandrine Parakeet and Black Headed Ibis) are listed as Near Threatened in the ‘IUCN’ (2010) category. Seventeen avian species with global declining population trends are present in the study area. The Passeriformes order, with 44 species, is the most diverse in the study area. In all habitats, analysis of food and feeding guilds, as well as perching activity, revealed that the insectivorous guild (29) is dominant, followed by Omnivore (25), Carnivore (11), Granivore (7), Frugivore (5), and Nectarivore (2). The results of this study indicate that, in order to enhance the quality of bird habitat in agricultural landscapes, biodiversity friendly farming practices should be adopted.

Documentation of Avian Species Composition and Assemblage in Agricultural Landscapes of Sirsa, Haryana

Avian communities maintain ecological balance by eliminating pests, providing ecosystem services, and acting as biological indicators, thereby playing a pivotal role in conserving agricultural landscapes’ integrity and stability; thus from an environmental monitoring standpoint, assessment of bird aggregations in various landscapes is necessary. A two-year bird survey was conducted from May 2020 and 2021 to October 2020 to 2021 to document the checklist, density, and diversity of bird species assemblage of agricultural landscapes in the Sirsa district of Haryana, India, to obtain the richness of birds in two different agricultural habitats. A total of 87 bird species from 39 families and 16 orders were recorded; four bird species (Alexandrine Parakeet, Asian Woollyneck, Black-Headed Ibis, and Painted Stork) are listed as Near Threatened in the ‘IUCN’ (2010) category. Surprisingly, 13 species with global declining population trends are rare in the study area. The Passeriformes order, with 44 species, is the most diverse in the study area. In all habitats, analysis of food and feeding guilds, as well as perching activity, revealed that the insectivorous guild (32) is dominant, followed by Omnivore (29), Carnivore (13), Granivore (7), Frugivore (5), and Nectarivore (2). The findings from this study suggest that biodiversity-friendly agricultural practices should be implemented to improve bird habitat quality in agricultural landscapes.

Население птиц Охотского моря и сопредельных вод Тихого океана и Японского моря в зимне-весенний период 2020 г.

The transect surveys were carried out in February–May 2020 from ships during the pollock and herring fisheries in the Sea of Okhotsk. We counted 27.4 thousands of 28 seabird species. In comparison with the results of the previous studies in 2015, the species diversity was higher since the observations covered not only the wintering period but also the beginning of the spring migration; therefore, there were waterfowl returning from the south (sea ducks, loons, cormorants) and some larids and alcids. During the winter period (until mid-April) only 19 seabird species were recorded on the survey transects. In addition, we observed three more species of rare gulls in bird aggregations around vessels during trawling. Due to more difficult ice conditions in 2020, the northern boundary of the distribution of some wintering species (Laysan albatross, short-tailed shearwater, pigeon guillemot, and tufted puffin) was located further south than in 2015.

Continental-scale dynamics of avian influenza in U.S. waterfowl are driven by demography, migration, and temperature.

Emerging diseases of wildlife origin are increasingly spilling over into humans and domestic animals. Surveillance and risk assessments for transmission between these populations are informed by a mechanistic understanding of the pathogens in wildlife reservoirs. For avian influenza viruses (AIV), much observational and experimental work in wildlife has been conducted at local scales, yet fully understanding their spread and distribution requires assessing the mechanisms acting at both local, (e.g., intrinsic epidemic dynamics), and continental scales, (e.g., long‐distance migration). Here, we combined a large, continental‐scale data set on low pathogenic, Type A AIV in the United States with a novel network‐based application of bird banding/recovery data to investigate the migration‐based drivers of AIV and their relative importance compared to well‐characterized local drivers (e.g., demography, environmental persistence). We compared among regression models reflecting hypothesized ecological processes and evaluated their ability to predict AIV in space and time using within and out‐of‐sample validation. We found that predictors of AIV were associated with multiple mechanisms at local and continental scales. Hypotheses characterizing local epidemic dynamics were strongly supported, with age, the age‐specific aggregation of migratory birds in an area and temperature being the best predictors of infection. Hypotheses defining larger, network‐based features of the migration processes, such as clustering or between‐cluster mixing explained less variation but were also supported. Therefore, our results support a role for local processes in driving the continental distribution of AIV.

Analysing age structure, residency and relatedness uncovers social network structure in aggregations of young birds

Animal sociality arises from the cumulative effects of both individual social decisions and environmental factors. While juveniles' social interactions with parents prior to independence shape later life sociality, in most bird and mammal species at least one sex undergoes an early life dispersal before first-year reproduction. The social associations from this period could also have implications for later life yet are rarely characterized. Here, we derived predictions from available examples of juvenile groups in the literature (mobile ‘flocks’, spatially stable ‘gangs’ or adult-associated ‘crèches’) and then used three cohorts of juvenile hihi, Notiomystis cincta , a threatened New Zealand passerine, to demonstrate how multistate modelling and social network analysis approaches can be used to characterize group type based on residency, movement, relatedness and social associations. At sites where hihi congregated, we found that juveniles were resighted at a higher frequency than adults and associated predominantly with unrelated juveniles rather than siblings or parents. Movement between group sites occurred, but associations developed predominantly within the sites. We suggest therefore that juvenile hihi social structure is most similar to a ‘gang’, a group structure in which juveniles congregate without adults at predictable sites. Such gangs have previously only been described formally in ravens, Corvus corax . By combining spatial and social network analyses, our study demonstrates how social group structures can be described and therefore facilitate broader comparisons and discussion about the form and function of juvenile groups across taxa. • Early life social behaviour once young leave parents is poorly understood. • We characterize group structure and social associations in a passerine bird. • Juveniles associated with unrelated juvenile peers rather than siblings or parents. • Social structure resembled ‘gangs’ which have few empirical examples. • Describing social structure can help us understand early life social environment.

Effects of bird aggregation on the soil properties and microbial community diversity of urban forest fragments

Forest fragments in urban parks provide important habitat for birds. However, the guano deposited by large aggregations of birds in such fragments can dramatically change soil properties, which in turn, can alter soil microbial community composition, potentially affecting the forests' composition and survival. To investigate the effects of bird aggregations on the soil of fragmented urban forests, we compared the soil properties and microbial communities of two forested islands, one in Liuhuahu park and the other in Wanzuitou park, Guangzhou, where large numbers of birds aggregate yearly to nest. Comparison to sites without bird aggregations suggests that decades of guano deposition appears to have caused soil acidification and an increase in soil nutrients. The relative abundance of the soil bacterial phylum Actinobacteria and the soil fungal phylum Ascomycota were significantly lower in soil under bird aggregations. The aerobic nitrite oxidation, nitrate reduction and cellulolysis bacterial guilds were significantly less abundant under bird aggregations in Liuhuahu park. The wood saprotroph fungi guild was significantly less abundant under the bird aggregation in Liuhuahua park and the pathogenic fungi guild significantly more abundant in Wanzuitou park. Soil properties, including TN, NO3−-N, TOC and pH, explained the variation in Ascomycota and Basidiomycota abundance, and the alpha-diversity of the fungal community. Microbial community variation could potentially slow the rate of decomposition and disease resistance of plant in these forests. We suggest that sufficient contiguous forest should be maintained in urban areas to reduce the density of bird aggregations in isolated forest fragments.

Separate seasons of infection and reproduction can lead to multi-year population cycles

Many host–pathogen systems are characterized by a temporal order of disease transmission and host reproduction. For example, this can be due to pathogens infecting certain life cycle stages of insect hosts; transmission occurring during the aggregation of migratory birds; or plant diseases spreading between planting seasons. We develop a simple discrete-time epidemic model with density-dependent transmission and disease affecting host fecundity and survival. The model shows sustained multi-annual cycles in host population abundance and disease prevalence, both in the presence and absence of density dependence in host reproduction, for large horizontal transmissibility, imperfect vertical transmission, high virulence, and high reproductive capability. The multi-annual cycles emerge as invariant curves in a Neimark–Sacker bifurcation. They are caused by a carry-over effect, because the reproductive fitness of an individual can be reduced by virulent effects due to infection in an earlier season. As the infection process is density-dependent but shows an effect only in a later season, this produces delayed density dependence typical for second-order oscillations. The temporal separation between the infection and reproduction season is crucial in driving the cycles; if these processes occur simultaneously as in differential equation models, there are no sustained oscillations. Our model highlights the destabilizing effects of inter-seasonal feedbacks and is one of the simplest epidemic models that can generate population cycles.

Avian influenza overview August - November 2018.

Between 16 August and 15 November 2018, 14 highly pathogenic avian influenza (HPAI) A(H5N8) outbreaks in poultry establishments in Bulgaria and seven HPAI A(H5N6) outbreaks, one in captive birds in Germany and six in wild birds in Denmark and the Netherlands were reported in the European Union (EU). No human infection due to HPAI A(H5N8) and A(H5N6) viruses have been reported in Europe so far. Seroconversion of people exposed during outbreaks in Russia has been reported in one study. Although the risk of zoonotic transmission to the general public in Europe is considered to be very low, appropriate personal protection measures of people exposed will reduce any potential risk. Genetic clustering of the viruses isolated from poultry in Bulgaria suggests three separate introductions in 2016 and a continuing circulation and transmission of these viruses within domestic ducks. Recent data from Bulgaria provides further indication that the sensitivity of passive surveillance of HPAI A(H5N8) in domestic ducks may be significantly compromised. Increased vigilance is needed especially during the periods of cold spells in winter when aggregations of wild birds and their movements towards areas with more favourable weather conditions may be encouraged. Two HPAI outbreaks in poultry were reported during this period from western Russia. Low numbers of HPAI outbreaks were observed in Africa and Asia, no HPAI cases were detected in wild birds in the time period relevant for this report. Although a few HPAI outbreaks were reported in Africa and Asia during the reporting period, the probability of HPAI virus introductions from non‐EU countries via wild birds particularly via the north‐eastern route from Russia is increasing, as the fall migration of wild birds from breeding and moulting sites to the wintering sites continues. Furthermore, the lower temperatures and ultraviolet radiation in winter can facilitate the environmental survival of any potential AI viruses introduced to Europe.

Automated detection of bird roosts using NEXRAD radar data and Convolutional Neural Networks

AbstractAlthough NEXRAD radars have proven to be an effective tool for detecting airborne animals, detecting biological phenomena in radar images often involves a manual, time‐ consuming data‐extraction process. This paper focuses on applying machine learning to automatically find radar data that snapshots large aggregations of birds (specifically Purple Martins and Tree Swallows) as they depart en masse from roosting sites. These aggregations are evident in radar images as rings of elevated reflectivity that appear early in the morning as birds depart from roost sites. Our goal was to develop an algorithm that could determine whether an individual radar image contained at least one Purple Martin or Tree Swallow roost. We use a dataset of known roost locations to train three machine learning algorithms that employed (1) a traditional Artificial Neural Network (ANN), (2) a sophisticated preexisting Convolutional Neural Network (CNN) called Inception‐v3, and (3) a shallow CNN built from scratch. The resulting programs were all effective at finding bird roosts, with both the shallow CNN and the Inception‐v3 network making correct determinations about 90 per cent of the time with an AUC above .9. To the best of our knowledge, this study is the first to apply neural networks in the analysis of bird roosts in radar imagery, and these analytical tools offer new avenues of research into the ecology and behavior of flying animals, with practical applications to wind farm placement, air traffic administration and wildlife conservation. The NEXRAD radar network offers a tremendous archive of continental‐scale data and has the potential to capture entire vertebrate populations. We apply existing machine learning models to a new dataset which constitutes a valuable approach to extracting information from this archive.

Social information cascades influence the formation of mixed-species foraging aggregations of ant-following birds in the Neotropics

Animals frequently make decisions based on social information obtained from other animals, which can influence interspecific interactions and affect individual fitness. For example, animals eavesdrop on other animals to find profitable food resources, yet the types of cues they use and how these cues influence decisions to approach a resource remain poorly understood. In tropical systems, arthropods inadvertently flushed by army ant, Eciton burchellii, swarms are an important food resource for many bird species, which form mixed-species foraging aggregations at swarms. Competition at swarms is intense and birds vocalize to defend foraging areas, inadvertently producing acoustic social information about the swarm's location. Eavesdropping birds may use these acoustic cues, which provide information about the bird aggregation (i.e. species participating in the aggregation, the size of the aggregation and/or diversity of the aggregation) to assess potential benefits (food resources) and costs (competition for food) of joining an aggregation. To test this hypothesis, we used an acoustic playback experiment to simulate aggregations of birds foraging at ant swarms and we measured community-wide and guild-specific responses of forest birds to playbacks. We included three types of acoustic social information in playbacks that potentially interact to affect an eavesdropping bird's probability of attraction to a swarm: (1) aggregation size, (2) aggregation species richness and (3) degree of specialization on ant swarms for food of birds vocalizing in the aggregation (hereafter ‘dependency’). Using Bayesian generalized linear mixed models, we found that playbacks of obligate ant-following species elicited greater community-wide responses (i.e. attracted more individuals and species) to simulated aggregations compared to playbacks of other, less dependent guilds. We also found that interactions between dependency, species richness and aggregation size influenced the overall community response to playbacks and that species from one guild generally responded to the guild above them (i.e. from less to more specialized). Our results suggest that species evaluate multiple types of acoustic cues representing the costs and benefits of foraging in a mixed-species aggregation at a swarm. We hypothesize that species change from information receivers to information producers upon joining a swarm, ultimately producing an information cascade that further affects the dynamics of feeding aggregations at swarms.

Estimation of the Spatial and Habitat Distribution of Anseriformes in the Yamal-Nenets and Khanty-Mansi Autonomous Regions (Experience from the Use of Ultralight Aircrafts)

In Russia, the conservation of anseriformes is possible through the creation of temporary huntingfree zones during hunting season, especially in spring. A justification for creating such zones and outlining their boundaries (by analogy with the experience derived from the countries on North America) each season must be based on data on annual waterfowl monitoring. The present paper describes census experience drawn from the use of ultralight aviation for further delineating the key staging sites of waterfowl in western Siberia. To refine the duration of monitoring, observation data were combined with those derived from geese equipped with GSM-GPS transmitters. In the spring and autumn of 2012–2014, we covered over 50000 km of aerial surveys of 25 waterfowl species. A new method is advanced for assessing their numbers based on visual observations, flock photography, and modern statistics. We estimated the species densities in 16 habitat types delineated on the basis of Landsat imagery. In terms of this, a system is proposed for extrapolating the survey data on 25 waterfowl species onto model sites in western Siberia. Drops in the numbers of several mass game species were noted. Based on an evaluation of the habitat quality, ten waterfowl hunting-free zones were suggested and delineated. A GIS project was launched that incorporated the main migration routes, boundaries of the key sites, places of mass bird aggregations, and sites for the observation of rare, Red Data Book. A program of long-term monitoring and sustainable use of waterfowl in the study region is offered. Such an approach must also be applied to other regions of Russia.

The role of breeding phenology and aggregation of waterfowl on avian influenza dynamics in southern Africa

Recent outbreaks of highly pathogenic avian influenza virus (AIV) in birds, humans and other mammalian species calls for a better understanding of virus dynamics in wild bird species and populations that act as maintenance hosts. Host ecology influences the transmission of pathogens and can be used to explore and infer pathogen dynamics. Most of the ecological processes proposed to explain AIV transmission in wild birds have been derived from studies conducted in the temperate and boreal regions of the northern hemisphere. We evaluate the role of two key drivers of AIV dynamics in a waterfowl community in Zimbabwe (southern Africa): (1) the recruitment of young birds and (2) the seasonal aggregation of birds. We analyse the seasonal variation of AIV prevalence in waterfowl and overlay these data with the phenology of reproduction and the seasonal variation in the local abundance of these species. We find that the breeding period of southern Afrotropical waterfowl species is more extended and somewhat less synchronized among species in the community than is the case in temperate and boreal waterfowl communities. Young birds are recorded at most times of the year, and these immunologically naïve individuals can therefore act as new hosts for AIV throughout the year within the wild bird population. Although host aggregation peaks in the cold‐dry to hot‐dry season, birds still aggregate throughout the year and this potentially spreads the opportunities for first infection of juveniles and other naïve birds temporally. We did not find a relationship between season, AIV prevalence in waterfowl, the influx of juveniles or the gradual aggregation of birds during the dry season. Therefore, the main drivers of AIV dynamics (juvenile influx and host abundance/aggregation), although present in Afrotropical regions, could not explain the AIV seasonal patterns in our study in contrast to results reported from temperate and boreal regions. These differences imply variation in the risk of AIV circulation in waterfowl and in the risk of spread to poultry, other animals or humans.

Biologically inspired trajectory generation for swarming UAVs using topological distances

This paper presents a trajectory generation logic for a swarm of unmanned aerial vehicles which uses topological distances instead of metric values. Biologically inspired, this method evades exploiting distance measurements in the absence of such capabilities, as it happens in swarming birds. This newly developed trajectory generation logic provides a stable swarming logic which resembles a large aggregation of birds. The hypothesis of this work is that without depth perception, swarming birds rely primarily on their perception of other birds to estimate proximity and adjust repulsive and attractive forces in real-time. From previous biological behavior studies, it is known that a homogeneous and orderly aggregation is exhibited by swarming birds locating themselves side by side rather than in front or behind each other. This behavior, which is based on the relative spatial proximity perception to their nearest neighbors in the flock, allows birds to converge into a highly cohesive and coordinated formation without explicit control of inter-agent distances. Inspired by this biological pattern, a trajectory generation logic is designed and tested in controlling a multi-agent unmanned aerial systems without the use of inter-distances. A six degrees of freedom nonlinear dynamic model for an unmanned aircraft is used for simulation purposes. Each vehicle is provided with a decentralized agent-based robust nonlinear model predictive controller and a set of nonlinear guidance laws for trajectory tracking. The formulation of the proposed trajectory generation, as well as the selected aircraft control, constitute a truly decentralized technique, that allows for an unlimited number of agents within the swarm, as no centralized computations are made.

Supplementary feeding and endangered avian scavengers: benefits, caveats, and controversies

Large avian scavengers are among the most vulnerable vertebrates, and many of their populations have declined severely in recent decades. To help mitigate this marked reduction in abundance, supplementary feeding stations (SFS; colloquially termed “vulture restaurants”) have been created worldwide, often without consideration of the scientific evidence supporting the suitability of the practice. SFS have been effective and important tools for conservation and reintroduction of avian scavengers. However, negative consequences can result from large aggregations of individual birds, disrupting intraguild processes and promoting density‐dependent decreases in productivity. At the community level, SFS favor the congregation of predators (ie facultative scavengers), increasing predation risk on small‐ and medium‐sized vertebrates in the vicinity of the SFS. These feeding stations might also affect processes of natural selection and even render populations maladapted to their natural environments. We also examine future scenarios for avian scavengers in relation to ecosystem services, to changes in agro‐grazing economies and in land uses, and ultimately to rewilding landscapes where SFS play a controversial role.

Migration front of post-moult emperor penguins

The moult is arguably the most critical period in the life of emperor penguins (Aptenodytes forsteri). Birds from western Ross Sea colonies travel yearly to and from the pack ice of the eastern Ross Sea to moult. Despite the suspected large numbers of penguins involved, this migration had never been directly observed. Here, we provide the first description of a migratory front of penguins travelling east to west between their moulting habitat and to the breeding colonies. Early autumn ship-bound visual surveys showed density of birds increased significantly as we approached the eastern Ross Sea and was not related to ice type, per cent ice cover or primary productivity. This supports the hypothesis of a dense “source” of post-moult birds in the eastern Ross Sea migrating in near-synchrony and gradually dispersing towards breeding colonies in the southwest and northwest Ross Sea. Emperor penguins travelled alone or in small groups of up to 8 individuals, concentrating around narrow leads or isolated water holes, and were occasionally seen far from open water, suggesting they move primarily by swimming, complemented by tobogganing. Their new coats indicated they had completed the moult. Aggregations of birds and guano stains suggested they were feeding while migrating.

Spatiotemporal mutualistic model of mistletoes and birds

A mathematical model which incorporates the spatial dispersal and interaction dynamics of mistletoes and birds is derived and studied to gain insights of the spatial heterogeneity in abundance of mistletoes. Fickian diffusion and chemotaxis are used to model the random movement of birds and the aggregation of birds due to the attraction of mistletoes, respectively. The spread of mistletoes by birds is expressed by a dispersal operator, which is typically a convolution integral with a dispersal kernel. Two different types of kernel functions are used to study the model, one is a Dirac delta function which reflects the special case that the spread behavior is local, and the other one is a general non-negative symmetric function which describes the nonlocal spread of mistletoes. When the kernel function is taken as the Dirac delta function, the threshold condition for the existence of mistletoes is given and explored in terms of parameters. For the general non-negative symmetric kernel case, we prove the existence and stability of spatially nonhomogeneous equilibria. Numerical simulations are conducted by taking specific forms of kernel functions. Our study shows that the spatial heterogeneous patterns of mistletoes are related to the specific dispersal pattern of birds which carry mistletoe seeds.

Marine bird aggregations associated with the tidally-driven plume and plume fronts of the Columbia River

Freshwater discharge from large rivers into the coastal ocean creates tidally-driven frontal systems known to enhance mixing, primary production, and secondary production. Many authors suggest that tidal plume fronts increase energy flow to fish-eating predators by attracting planktivorous fishes to feed on plankton aggregated by the fronts. However, few studies of plume fronts directly examine piscivorous predator response to plume fronts. Our work examined densities of piscivorous seabirds relative to the plume region and plume fronts of the Columbia River, USA. Common murres (Uria aalge) and sooty shearwaters (Puffinus griseus) composed 83% of all birds detected on mesoscale surveys of the Washington and Oregon coasts (June 2003–2006), and 91.3% of all birds detected on fine scale surveys of the plume region less than 40km from the river mouth (May 2003 and 2006). Mesoscale comparisons showed consistently more predators in the central plume area compared to the surrounding marine area (murres: 10.1–21.5 vs. 3.4–8.2birdskm−2; shearwaters: 24.2–75.1 vs. 11.8–25.9birdskm−2). Fine scale comparisons showed that murre density in 2003 and shearwater density in both 2003 and 2006 were significantly elevated in the tidal plume region composed of the most recently discharged river water. Murres tended to be more abundant on the north face of the plume. In May 2003, more murres and shearwaters were found within 3km of the front on any given transect, although maximum bird density was not necessarily found in the same location as the front itself. Predator density on a given transect was not correlated with frontal strength in either year. The high bird densities we observed associated with the tidal plume demonstrate that the turbid Columbia River plume does not necessarily provide fish with refuge from visual predators. Bird predation in the plume region may therefore impact early marine survival of Pacific salmon (Oncorhynchus spp.), which must migrate through the tidal plume and plume front to enter the ocean. Because murres and shearwaters eat primarily planktivorous fish such as the northern anchovy (Engraulis mordax), aggregation of these birds in the plume supports the hypothesis that it is the plume region as a whole, and not just the plume fronts, which enhances trophic transfer to piscivorous predators via planktivorous fishes.

An automatic counter for aerial images of aggregations of large birds

Capsule Counts with precision comparable to those of an expert observer can be achieved automatically. Aims To develop an open-source freeware program that automatically extracts and counts the number of birds in aerial images of dense aggregations. Methods Software was developed and validated using aerial photographs of Greater Flamingo colonies from France, Turkey and Mauritania. We used a stochastic approach based on object processes. The objects representing flamingos were defined as ellipses, and the software detected these and produced a count. Details of the procedure are provided in electronic supplementary material. The energy is extracted by a birth-and-death algorithm, leading to the total number of birds. Results This procedure gave counts with precision comparable to manual counts of the aerial photographs by an expert (<5% difference). The procedure does not need any supervision of the extraction by an operator, thus reducing the processing time required to get the estimate of bird numbers in the image from >4 h to 20 min on average. Conclusion This open-source freeware should be useful for ornithologists and wildlife managers.

Stopover habitats of spring migrating surf scoters in southeast Alaska

AbstractHabitat conditions and nutrient reserve levels during spring migration have been suggested as important factors affecting population declines in waterfowl, emphasizing the need to identify key sites used during spring and understand habitat features and resource availability at stopover sites. We used satellite telemetry to identify stopover sites used by surf scoters migrating through southeast Alaska during spring. We then contrasted habitat features of these sites to those of random sites to determine habitat attributes corresponding to use by migrating scoters. We identified 14 stopover sites based on use by satellite tagged surf scoters from several wintering sites. We identified Lynn Canal as a particularly important stopover site for surf scoters originating throughout the Pacific winter range; approximately half of tagged coastally migrating surf scoters used this site, many for extended periods. Stopover sites were farther from the mainland coast and closer to herring spawn sites than random sites, whereas physical shoreline habitat attributes were generally poor predictors of site use. The geography and resource availability within southeast Alaska provides unique and potentially critical stopover habitat for spring migrating surf scoters. Our work identifies specific sites and habitat resources that deserve conservation and management consideration. Aggregations of birds are vulnerable to human activity impacts such as contaminant spills and resource management decisions. This information is of value to agencies and organizations responsible for emergency response planning, herring fisheries management, and bird and ecosystem conservation. © 2010 The Wildlife Society

Larval trematode communities in Radix auricularia and Lymnaea stagnalis in a reservoir system of the Ruhr River

BackgroundAnalysis of the data available from traditional faunistic approaches to mollusc-trematode systems covering large spatial and/or temporal scales in Europe convinced us that a parasite community approach in well-defined aquatic ecosystems is essential for the substantial advancement of our understanding of the parasite response to anthropogenic pressures in urbanised areas which are typical on a European scale. Here we describe communities of larval trematodes in two lymnaeid species, Radix auricularia and Lymnaea stagnalis in four man-made interconnected reservoirs of the Ruhr River (Germany) focusing on among- and within-reservoir variations in parasite prevalence and component community composition and structure.ResultsThe mature reservoir system on the Ruhr River provides an excellent environment for the development of species-rich and abundant trematode communities in Radix auricularia (12 species) and Lymnaea stagnalis (6 species). The lake-adapted R. auricularia dominated numerically over L. stagnalis and played a major role in the trematode transmission in the reservoir system. Both host-parasite systems were dominated by bird parasites (13 out of 15 species) characteristic for eutrophic water bodies. In addition to snail size, two environmental variables, the oxygen content and pH of the water, were identified as important determinants of the probability of infection. Between-reservoir comparisons indicated an advanced eutrophication at Baldeneysee and Hengsteysee and the small-scale within-reservoir variations of component communities provided evidence that larval trematodes may have reflected spatial bird aggregations (infection 'hot spots'). Two life history groupings of dominant species, the 'cyprinid' and 'anatid' parasites, that depict two aspects of progressive eutrophication in this mature reservoir system, were identified.ConclusionsWe conclude that trematode communities in the lake-adapted R. auricularia are better suited for monitoring the effect of environmental change on host-parasite associations in the reservoir system on the Ruhr River and other similar systems due to the important role of this host in trematode transmission in lakes. Whereas variations in trematode community diversity and abundance may indicate the degree of eutrophication on a larger scale (among reservoirs), the infection rates of the two life history groups of dominant species, the 'cyprinid' and 'anatid' assemblages, may be particularly useful in depicting environmental variability, eutrophication effects and infection 'hot spots' on smaller spatial scales.