Important Stopover Site Research Articles

Importance of the 2014 Colorado River Delta pulse flow for migratory songbirds: Insights from foraging behavior

The Lower Colorado River provides critical riparian areas in an otherwise arid region and is an important stopover site for migrating landbirds. In order to reverse ongoing habitat degradation due to drought and human-altered hydrology, a pulse flow was released from Morelos Dam in spring of 2014, which brought surface flow to dry stretches of the Colorado River in Mexico. To assess the potential effects of habitat modification resulting from the pulse flow, we used foraging behavior of spring migrants from past and current studies to assess the relative importance of different riparian habitats. We observed foraging birds in 2000 and 2014 at five riparian sites along the Lower Colorado River in Mexico to quantify prey attack rates, prey attack maneuvers, vegetation use patterns, and degree of preference for fully leafed-out or flowering plants. Prey attack rate was highest in mesquite (Prosopis spp.) in 2000 and in willow (Salix gooddingii) in 2014; correspondingly, migrants predominantly used mesquite in 2000 and willow in 2014 and showed a preference for willows in flower or fruit in 2014. Wilson’s warbler (Cardellina pusilla) used relatively more low-energy foraging maneuvers in willow than in tamarisk (Tamarix spp.) or mesquite. Those patterns in foraging behavior suggest native riparian vegetation, and especially willow, are important resources for spring migrants along the lower Colorado River. Willow is a relatively short-lived tree dependent on spring floods for dispersal and establishment and thus spring migrants are likely to benefit from controlled pulse flows.

Influenza A Viruses from Overwintering and Spring-Migrating Waterfowl in the Lake Erie Basin, United States.

Influenza A virus (IAV) surveillance in migratory waterfowl in the United States has primarily occurred during late summer and the autumn southern migration. Data concerning the presence and ecology of IAVs in waterfowl during winter and spring seasons in the U.S. northern latitudes have been limited, mainly due to limited access to waterfowl for sampling. The southwestern Lake Erie Basin is an important stopover site for waterfowl during migration periods, and over the past 28 years, 8.72% of waterfowl sampled in this geographic location have been positive for IAV recovery during summer and autumn (June-December). To gain a better understanding of influenza A viral dynamics in waterfowl populations during winter and spring migration (February through April), cloacal swabs were collected from overwintering and spring-migrating waterfowl in Ohio and Michigan in 2006, 2007, 2013, and 2014. A total of 740 cloacal swabs were collected and tested using virus isolation in embryonating chicken eggs, resulting in the recovery of 33 (4.5%) IAV isolates. The influenza A isolates were recovered from eight waterfowl species in the order Anseriformes. Antigenically, the IAV isolates represent 15 distinct hemagglutinin (HA) and neuraminidase (NA) combinations, with seven (21%) of the isolates reported as mixed infections based on antigenic HA subtyping, NA subtyping, or both. This effort demonstrates the presence of antigenically diverse IAV in waterfowl during overwintering and spring migration at northern latitudes in the United States, thereby contributing to the understanding of the maintenance of diversity among waterfowl-origin IAVs.

GUIDELINES FOR MANAGING SEABIRDS IN THE ARVOREDO MARINE BIOLOGICAL RESERVE, SOUTHERN BRAZIL

Seabirds usually need productive waters and respond differently to environmental changes according to the oceanographic domain where they occur. The Arvoredo Marine Biological Reserve protects part of an important ecological region in Brazil and shelters substantial marine biodiversity. Here we studied seabird richness and abundance at this protected area to verify what kind of monitoring and managing protocols are needed for future conservation actions. We surveyed the Reserve’s islands and surrounding sea from the autumn 2010 to the autumn 2012. We also considered historical data from literature on seabird colonies to access specific issues related to management actions. Most of 14 surveyed species were migratory, rare, and recorded during winter. The Kelp Gull ( Larus dominicanus ) was dominant and its abundance pattern alternated with those of the other species along seasons. Deserta Island is an important breeding site and Gale Islets is an important stopover site at the Reserve. Few places along the Brazilian coastline support breeding colonies such as the ones in the Arvoredo Marine Biological Reserve. However, the Reserve needs seabird active management to fulfill its purpose of protecting marine biodiversity. Breeding success must be considered as an indicator for intervention and control of predators in the Reserve. The effects of climate changes and overfishing near the Reserve affect the seabirds therefore managers should join a large-scale integrated coastal management and marine spatial planning. A long-term monitoring protocol at-sea and in the colonies using new technologies also can help in this process.

Evolution of the Jiuduansha wetland and the impact of navigation works in the Yangtze Estuary, China

The estuarine wetlands in the Yangtze Estuary face increasing threats due to large-scale engineering projects and huge land requirements. As a Wetland National Nature Reserve and important stopover site for migratory shorebirds of the East Asian–Australasian Flyway, the Jiuduansha wetland, one of four main islands in the estuary, is of both national and international importance. Since 1998 the previously undisturbed wetland has been considerably modified by the adjacent Deep-water Navigation Channel project (DNC). In order to understand the role of the DNC for the evolution of the Jiuduansha wetland, we performed a diagnostic study from multiple perspectives, including deposition rate, area change, evolution track, geometric characteristics, and geomorphological change. By coupling GIS, geostatistics, and remote sensing techniques, this study demonstrates the impact of the DNC on the Jiuduansha wetland in a spatially explicit way. Multi-temporal bathymetric maps and Landsat images from before and after the DNC was constructed were adopted to conduct our study. We find that deposition has occurred in most parts of the wetland over the past almost 30years, accounting for 67.3% of the total area. However, over 40% of the study area shows a decreasing trend in deposition rate. The spatial distribution of deposition–erosion patterns is closely linked to the DNC. We also find that the DNC has substantial effects on the evolution of the Jiuduansha wetland. The 0, 2, and 5m isobaths in the Jiuduansha Shoal (JDS), as well as in the Jiangya Shoal (JYS), the Upper Shoal (US) and the Middle-Lower Shoal (MLS), show different response patterns to the DNC. Specifically, the south training jetty of the DNC has an “adsorption effect” on the JDS above the 2m isobaths intersecting with it. As a result, the evolution track, geometric and geomorphological characteristics of the JDS were markedly altered in the short term. Our comprehensive analysis suggests that in the future, the JDS will become more elongated in both the upstream and downstream direction along the south training jetty, and that the south side of the JDS will be eroded.

The role of phylogeny and life history of migratory waterbirds in designing fishpond management plans

The acceleration of wetland loss on a global scale has frequently been reported in the past decades which is in correspondence with serious declines of migratory waterbirds. Indeed, the spatial distribution of waterbirds during migration has been shown to be associated with various predictors, ranging from feeding behaviours and migratory strategies to physical attributes of wetlands and spatial effects related to human disturbance. These results demonstrate that different constraints of ecology and life history may shape the effects of human disturbance on migratory water bird populations. In this work we analyse the role of ecological predictors and life history traits in shaping avian responsiveness to spatial attributes of artificial constructions in a phylogenetic context, using an extensive dataset of migratory water birds in Hortobágy, one of the most important stop-over sites in a major Afro-Eurasian flyway. Our study revealed that response to human disturbance factors such as the density and distance of public roads on larger spatial scales is predominantly related to life-history predictors such as the age of maturity, migration strategy and constrained by phylogenetic relatedness. Therefore we recommend that phylogenetic relatedness and life-history traits are considered when designing management plans for larger water bodies used by staging waterbirds.

Local site variation in stopover physiology of migrating songbirds near the south shore of Lake Ontario is linked to fruit availability and quality.

Birds that migrate long distances between breeding and wintering grounds are challenged to find adequate stopover sites that can provide a high-quality source of nutrition in order to refuel quickly and continue on their migratory journeys. Wild fruits are a well-documented component in the diets of many passerines during autumn migration. Thus, fruit availability and the proliferation of shrubs that bear low-quality fruits at important stopover sites may dictate the quality of food resources available for refuelling birds and present a conservation concern. We profiled plasma metabolites of two migratory passerine species at two different stopover sites near the south shore of Lake Ontario during the peak of autumn migration. We also measured diversity, availability and nutritional quality of fruits present at these sites. Site explained most of the variation in plasma triglyceride for both bird species, but was less important than other confounding variables for explaining concentrations of plasma β-hydroxybutyrate and plasma uric acid concentrations. Site differences in fat deposition, as indicated by plasma triglyceride, may in part be explained by the large differences in diversity and availability of high-quality fruits between the two sites. Our results suggest that abundant, lipid-rich native fruits with high-energy density are associated with increased fat deposition during autumn stopovers for some species, although other factors, such as proximity to the Lake Ontario shoreline and the opportunities to refuel in the surrounding landscape, are likely to play a role in stopover site use by birds. It is possible that local site characteristics that influence growing conditions may impact the quality of fruits produced by a plant species, altering the availability of critical nutrients for avian consumers.

Shorebird Response to Post-Flood Drawdowns on Tennessee National Wildlife Refuge

Mudflats are important stopover sites for shorebirds during migration, but management plans typically do not provide mudflat habitat in the reservoirs of the Tennessee River Valley (TRV) during May—July. In May 2010, flooding delayed drawdowns on Tennessee National Wildlife Refuge and created wetlands for shorebirds from May—August. We studied wetland use and behavior of shorebirds during delayed drawdowns in 2010, and we compared shorebird abundance between years with delayed and typical drawdowns using International Shorebird Survey data. We found that shorebirds consistently used wetlands for foraging throughout summer during 2010. In addition, abundance of 43% of species tested was greater in years with delayed than typical drawdowns. Our results suggest extending availability of mudflats throughout summer in the TRV may provide important habitat for migrating shorebirds.

Seasonal inundation monitoring and vegetation pattern mapping of the Erguna floodplain by means of a RADARSAT-2 fully polarimetric time series

The Erguna floodplain, located on the boundary of China, Russia, and Mongolia, is a globally important breeding and stop-over site for many migratory bird species. However, it has a fragile ecosystem and is facing severe impacts from climate change and human activities. Motivated by the high demand for spatial and temporal information about flooding dynamics and vegetation patterns, six fully polarimetric RADARSAT-2 images acquired with the same configuration were explored to reveal the characteristics of the floodplain. The evaluation of a set of polarimetric observables derived from the series of polarimetric synthetic aperture radar (PolSAR) data was used to investigate the characteristics of the typical land-cover types in the floodplain. The behaviors of the polarimetric features highlight the benefits of interpreting the scattering mechanism evolutions at different phenological and inundation stages. The vegetation and inundation patterns were mapped by a random forest (RF) classifier with the input of these polarimetric observations. The results show that a multi-temporal classification can better capture the spatial distribution of the vegetation pattern than single-temporal classifications, which often show a large variability due to the effect of phenology and flooding. A hydroperiod map, which was generated by the time-series classification results of open water, illustrates the flooding temporal dynamics and the hydrological regime. The two main environmental factors that induced the changes in the backscattering – phenology and flooding – were identified based on the aggregated classification results of different phenological intervals. The spatial and temporal characteristics of the phenology- and flooding-induced changes were documented by the changes in the trajectories of three patch metrics at the class level. The polarimetric features' importance scores derived from the RF classifier indicate that the intensity-related features are important for land-cover mapping. The HV intensity, in particular, achieves the highest importance score. In addition, the volume scattering component shows a better performance among the composite features, revealing the importance of the quad-polarimetric information for floodplain interpretation and monitoring.

Optimal management of a multispecies shorebird flyway under sea-level rise.

Every year, millions of migratory shorebirds fly through the East Asian-Australasian Flyway between their arctic breeding grounds and Australasia. This flyway includes numerous coastal wetlands in Asia and the Pacific that are used as stopover sites where birds rest and feed. Loss of a few important stopover sites through sea-level rise (SLR) could cause sudden population declines. We formulated and solved mathematically the problem of how to identify the most important stopover sites to minimize losses of bird populations across flyways by conserving land that facilitates upshore shifts of tidal flats in response to SLR. To guide conservation investment that minimizes losses of migratory bird populations during migration, we developed a spatially explicit flyway model coupled with a maximum flow algorithm. Migratory routes of 10 shorebird taxa were modeled in a graph theoretic framework by representing clusters of important wetlands as nodes and the number of birds flying between 2 nodes as edges. We also evaluated several resource allocation algorithms that required only partial information on flyway connectivity (node strategy, based on the impacts of SLR at nodes; habitat strategy, based on habitat change at sites; population strategy, based on population change at sites; and random investment). The resource allocation algorithms based on flyway information performed on average 15% better than simpler allocations based on patterns of habitat loss or local bird counts. The Yellow Sea region stood out as the most important priority for effective conservation of migratory shorebirds, but investment in this area alone will not ensure the persistence of species across the flyway. The spatial distribution of conservation investments differed enormously according to the severity of SLR and whether information about flyway connectivity was used to guide the prioritizations. With the rapid ongoing loss of coastal wetlands globally, our method provides insight into efficient conservation planning for migratory species.

Ecology of Aquatic WarblersAcrocephalus paludicolain a Fall Stopover Area on the Atlantic Coast of France

The Aquatic Warbler Acrocephalus paludicola is the only endangered songbird in continental Europe. This trans-Saharan migratory bird significantly transits along the French Atlantic coastline during post-breeding migration and the right bank of the Gironde estuary has been identified as an important stopover site. We studied the spatial occupancy strategies of stationing individuals during August of three successive years (2010–2012). We characterized habitat use by radio-tracking individuals revealing relatively small foraging ranges (6.6 ± 2.6 ha on average) with only 1 ha actually exploited (core area), and a relatively high habitat fragmentation rate. Capture-mark-recapture analyses assessed the average stopover duration of individuals and body-mass variations during their stopover. The estimated average stopover duration was 6.46 ± 0.46 days (95% confidence interval: 4.4–9.6). Lean birds tended to forage significantly more than stout birds: on average, they gain 2.81 ± 0.89% of their initial mass each day whereas stout birds only gain 0.12 ± 0.56%. Analyses of droppings characterized the local diet. We noticed that Aquatic Warbler preferentially used partially-flooded or flooded habitats with heterogeneous and rather low vegetation, such as bulrush beds or bulrush beds mixed with reed beds. Orthoptera, Araneae and Hymenoptera represented the largest contributions to the consumed biomass (64.7%, 13.4% and 8.9% respectively). The importance of the fuel deposition rate of lean birds reflects the importance of the estuary as a stopover site for the species. It means that the available resources allow birds to replenish and continue their migration route. However, the sustainability of the site's functionality is questioned because of the evolution of habitats (erosion, rise in water levels and changes in food web).

Age and Sex Differences in Fuel Load and Biometrics of Aquatic WarblersAcrocephalus paludicolaat an Autumn Stopover Site in the Loire Estuary (NW France)

The aquatic warbler Acrocephalus paludicola is the only globally threatened passerine breeding in Europe. We studied morphometric traits of 176 individuals captured at one of the key European autumn stopover sites, the Loire estuary on the Atlantic coast of France, in relation to age (first-year and older) and sex (based on molecular determination). We found significant sex differences in wing length, third primary feather length and body mass, with males being longer-winged and heavier than females; adult females also had deeper bills. However, high overlap in all measurements between the sexes meant the best discriminant functions based on wing length and bill depth (adults) and wing length (inmatures) correctly classified only 87% and 75% of individuals, respectively. The mean potential non-stop flight range of autumn staging birds at the Loire estuary with high fuel load was estimated at 1,178 km for adults and 926 km for immatures. We conclude that in autumn migrant aquatic warblers probably do not fly directly to wintering grounds in west Africa. Instead they gain significant body mass for onward migration at a few key stopover sites in western Europe and the southern Mediterranean region. Conservation of a series of important refuelling stopover sites, especially wet grassland habitats, along the migration route is therefore essential for effective protection of the aquatic warbler.

Long-term variation in influenza A virus prevalence and subtype diversity in migratory mallards in northern Europe

Data on long-term circulation of pathogens in wildlife populations are seldom collected, and hence understanding of spatial-temporal variation in prevalence and genotypes is limited. Here, we analysed a long-term surveillance series on influenza A virus (IAV) in mallards collected at an important migratory stopover site from 2002 to 2010, and characterized seasonal dynamics in virus prevalence and subtype diversity. Prevalence dynamics were influenced by year, but retained a common pattern for all years whereby prevalence was low in spring and summer, but increased in early autumn with a first peak in August, and a second more pronounced peak during October-November. A total of 74 haemagglutinin (HA)/neuraminidase (NA) combinations were isolated, including all NA and most HA (H1-H12) subtypes. The most common subtype combinations were H4N6, H1N1, H2N3, H5N2, H6N2 and H11N9, and showed a clear linkage between specific HA and NA subtypes. Furthermore, there was a temporal structuring of subtypes within seasons based on HA phylogenetic relatedness. Dissimilar HA subtypes tended to have different temporal occurrence within seasons, where the subtypes that dominated in early autumn were rare in late autumn, and vice versa. This suggests that build-up of herd immunity affected IAV dynamics in this system.

Radar analysis of fall bird migration stopover sites in the northeastern U.S.

ABSTRACT The national network of weather surveillance radars (WSR-88D) detects flying birds and is a useful remote-sensing tool for ornithological study. We used data collected during fall 2008 and 2009 by 16 WSR-88D radars in the northeastern U.S. to quantify the spatial distribution of landbirds during migratory stopover. We geo-referenced estimates based on radar reflectivity, of the density of migrants aloft at their abrupt evening exodus from daytime stopover sites, to the approximate locations from which they emerged. We classified bird stopover use by the magnitude and variation of radar reflectivity across nights; areas were considered “important” stopover sites for conservation if bird density was consistently high. We developed statistical models that predict potentially important stopover sites across the region, based on land cover, ground elevation, and geographic location. Large areas of regionally important stopover sites were located along the coastlines of Long Island Sound, throughout th...

Prevalence of Anaplasma phagocytophilum in ticks collected from migratory birds in Danube Delta, Romania

Wild birds are hosts for several species of ticks, contributing to the maintenance of their local populations in delimited geographic areas. migratory birds play important roles as distributors of ticks within and between distant territories, including continents. Ticks collected from birds are responsible for hosting a significant number of human pathogens. The extensive wetland complex of the Danube Delta provides an internationally important stopover site for millions of birds, belonging to 300 different species, travelling annually. The aim of this study was to detect Anaplasma phagocytophilum in feeding ticks collected from migratory birds along four migratory seasons. Ticks were collected from the birds with forceps and preserved in 96% ethanol for later examination using a separate vial for each bird. A total of 1436 birds in 56 species (15 families) of Passeriformes and 3 non-Passeriformes bird species were captured. A total of 400 ticks were collected and identified as larvae (n = 191; 47.75%), nymphs (n = 201; 50.25%) or adult females (n = 8; 2%). No adult males were found. The ticks belonged to four species (Ixodes ricinus, I. arboricola, I. redikorzevi and Haemaphysalis punctata). Ixodes ricinus was the most common tick (369/400 ticks, 92.25% of the total collected), with a total of 181 larvae, 180 nymphs and 8 females. For detection of Anaplasma phagocytophilum all 400 ticks were examined by PCR, targeting the msp2 gene. Anaplasma phagocytophilum specific DNA was detected in 2 larvae and 2 nymphs of, I. ricinus, from 3 birds prevalence 1.08-%. The infection was absent from the other species of collected ticks The bird species that carried ticks infected with A. phagocytophilum were Turdus merula, Erithacus rubecula and Fringilla coelebs. Several other studies have demonstrated the presence of A. phagocytophilum in ticks collected from birds. Comparing our data with these results, we confirm the low prevalence of A. phagocytophilum, showingthat migratory birds, despite being without reservoir competencemight be important hosts for the dispersal of infected ticks.

Do migrants influence the foraging behaviour of the insectivorous Cyprus Wheatear, Oenanthe cypriaca, at a stopover site? (Aves: Passeriformes)

During their staging at stopover sites, migrants may compete with resident species over food resources (“resource competition hypothesis”), or migrants feed on surplus that is not utilised by the residents. Here, I studied foraging behaviour of the Cyprus Wheatear, Oenanthe cypriaca, a ubiquitous and common species with a broad niche range, on Cyprus, which is an important stopover site during intercontinental spring migration. During adverse weather conditions, perch height and aerial sallying were lower and perch/pounce activity was higher. Average perch height and sallying increased over the season, while perch-pounce foraging decreased. There was no influence of clock time. Bivariate correlations suggested an influence of migrants on perch height but not on other variables. Using a series of regression analyses with sex, time of day, date, weather conditions and number of migrants as independent variables revealed no influence of the number of migrants on the foraging behaviour of the Cyprus Wheatear. This suggests that the abundance of migrants does not lead to a change in the behaviour of the Cyprus Wheatear.

Towards a Solution to the Goose-Agriculture Conflict in North Norway, 1988–2012: The Interplay between Policy, Stakeholder Influence and Goose Population Dynamics

This paper presents results from a multidisciplinary study of a negotiation process between farmers and wildlife authorities which led to an agricultural subsidy scheme to alleviate conflicts between agriculture and geese in Norway. The Svalbard-breeding population of pink-footed geese Anser brachyrhynchus has increased considerably over the last decades and conflicts with farmers have escalated, especially at stopover sites in spring when geese feed on newly sprouted pasture grass. In Vesterålen, an important stopover site for geese in North Norway, farmers deployed scaring of geese at varying intensity dependent on the level of conflict during 1988–2012. We assessed the efficiency of a subsidy scheme established in 2006, in terms of its conflict mitigation, reflected in a near discontinuation of scaring activities. The presence of pink-footed geese was analysed in relation to scaring intensity, the total goose population size and the increasing occurrence of another goose species, the barnacle goose Branta leucopsis. Scaring significantly affected the number of geese staging in Vesterålen, both in absolute and relative terms (controlling for total population size). The geese responded immediately to an increased, and reduced, level of scaring. Despite the establishment of the subsidy scheme, the number of pink-footed geese has recently declined which is probably caused by the increasing number of barnacle geese. For the farmers, the subsidy scheme provides funding that reduces the economic costs caused by the geese. Sustaining a low level of conflict will require close monitoring, dialogue and adaptation of the subsidy scheme to cater for changes in goose population dynamics.

Fine-scale biophysical interactions drive prey availability at a migratory stopover site for Phalaropus spp. in the Bay of Fundy, Canada

We examined the role of biophysical interactions in structuring the foraging habitat of phalaropes Phalaropus spp. at an important migratory stopover site in the Bay of Fundy. We sampled both biological and physical aspects of the environment and integrated these observa- tions into generalized additive models (GAMs). Strong tidal currents interact with steep bathy- metric gradients at the Brier Island ledges to enhance vertical mixing, creating dense surface aggregations of Calanus finmarchicus copepods at fine temporal and spatial scales. The resulting spatial variation in copepod density in near-surface waters creates a highly heterogeneous foraging environment for phalaropes, which are obligate surface feeders. Models of phalarope abundance over the ledges suggested that phalaropes forage on upwelled zooplankton aggrega- tions as they drifted downstream. Our results highlight the importance of considering underlying physical processes when assessing hotspots of prey aggregations for marine species, particularly within highly dynamic systems such as the Bay of Fundy. This is particularly relevant to consider- ations of the conservation status of red-necked phalaropes Phalaropus lobatus, which have aban- doned a long-time migratory stopover area previously used by more than one million birds during the mid-1980s.

A Physiological Assessment of Seasonal Differences in Spring and Autumn Migration Stopover at Braddock Bay, Lake Ontario

Abstract. This study investigated seasonal differences in fat deposition and nutritional status of migrating passerine birds at an important stopover site on the south shore of Lake Ontario. Birds were captured during spring and autumn stopovers, and their plasma metabolites were measured as indicators of refueling rates (plasma triglyceride) and nutritional state (plasma uric acid). Catharus thrushes had higher plasma triglyceride and lower plasma uric acid in autumn than in spring, whereas Red-eyed Vireos had higher plasma triglyceride in spring than in autumn, but no seasonal differences in plasma uric acid. There were no seasonal differences in plasma triglyceride concentrations in White-throated Sparrows (Zonotrichia albicollis) and Blackpoll Warblers (Setophaga striata), although White-throated Sparrows had plasma uric acid higher in spring than in autumn, suggesting they were consuming more protein than were those captured during autumn migration. These data suggest that songbirds use this site for...

Birds Select Fruits with More Anthocyanins and Phenolic Compounds During Autumn Migration

We evaluated whether fruit selection by autumn-migrating birds at an important stopover site in southern New England was related to water-soluble antioxidant content of fruits. We measured total anthocyanins, total phenolics, and total antioxidant capacity in fruits from common native and non-native plant species and related this to estimates of fruit selection by free-living birds. Birds selected certain fruits over others, with arrowwood (Viburnum recognitum, V. dentatum) consumed at the highest rate, followed by Virginia creeper (Parthenocissus quinquefolia) with much lower consumption of other fruits (e.g., oriental bittersweet (Celastrus orbiculatus), multiflora rose (Rosa multiflora), winterberry (Ilex verticillata)). Antioxidant concentrations primarily differed by shrub species and less so between sites. Arrowwood spp. had the highest total antioxidants, followed by Virginia creeper, northern bayberry (Myrica pennsylvanica), chokeberry spp. (Aronia prunifolia, A. melanocarpa), multiflora rose, winterberry, and oriental bittersweet. These results are consistent with the hypothesis that free-living birds select fruits based, in part, on antioxidant content. We suggest birds may actively select polyphenol/anthocyanin-rich fruits during autumn migration to protect themselves against the potentially damaging effects of oxidative stress caused by long-distance fasting flight. Received 4 April 2012. Accepted 29 June 2012.

The keystone role of anostracans and copepods in European soda pans during the spring migration of waterbirds

Summary1. The European soda pans of the Carpathian Basin provide important stopover sites for several waterbird species. We studied the effect of different invertebrate food types and other characteristics on the habitat choice and distribution of birds on 82 pans (in Hungary, Austria and Serbia) during spring migration.2. Only three environmental variables proved to be significant determinants of the waterbird communities: pan density (spatial effect) along with the density of Arctodiaptomus spp. and anostracans (local effect). Variance partitioning of the data revealed that aquatic invertebrate food supply (Arctodiaptomus and anostracans) had a greater effect than pan density on the 10 investigated bird species, suggesting a dominant role of species sorting in structuring the communities. Pied avocets (Recurvirostra avosetta) and northern shovelers (Anas clypeata) differed from the other species in their strong association with densities of anostracans (avocet) and Arctodiaptomus (shoveler).3. Anostracans and microcrustaceans, especially the most frequent Branchinecta orientalis, Arctodiaptomus spinosus and Arctodiaptomus bacillifer, can be regarded as keystone elements of this soda pan habitat because of their bottom‐up role in structuring waterbird assemblages during spring migration.