Wintering Sites Research Articles

Water level affects availability of optimal feeding habitats for threatened migratory waterbirds.

Extensive ephemeral wetlands at Poyang Lake, created by dramatic seasonal changes in water level, constitute the main wintering site for migratory Anatidae in China. Reductions in wetland area during the last 15 years have led to proposals to build a Poyang Dam to retain high winter water levels within the lake. Changing the natural hydrological system will affect waterbirds dependent on water level changes for food availability and accessibility. We tracked two goose species with different feeding behaviors (greater white‐fronted geese Anser albifrons [grazing species] and swan geese Anser cygnoides [tuber‐feeding species]) during two winters with contrasting water levels (continuous recession in 2015; sustained high water in 2016, similar to those predicted post‐Poyang Dam), investigating the effects of water level change on their habitat selection based on vegetation and elevation. In 2015, white‐fronted geese extensively exploited sequentially created mudflats, feeding on short nutritious graminoid swards, while swan geese excavated substrates along the water edge for tubers. This critical dynamic ecotone successively exposes subaquatic food and supports early‐stage graminoid growth during water level recession. During sustained high water levels in 2016, both species selected mudflats, but also to a greater degree of habitats with longer established seasonal graminoid swards because access to tubers and new graminoid growth was restricted under high‐water conditions. Longer established graminoid swards offer less energetically profitable forage for both species. Substantial reduction in suitable habitat and confinement to less profitable forage by higher water levels is likely to reduce the ability of geese to accumulate sufficient fat stores for migration, with potential carryover effects on subsequent survival and reproduction. Our results suggest that high water levels in Poyang Lake should be retained during summer, but permitted to gradually recede, exposing new areas throughout winter to provide access for waterbirds from all feeding guilds.

Cambios temporales de la avifauna acuática en el sitio Ramsar “Presa de Valsequillo”, Puebla, México

La Convención de Ramsar busca promover la conservación y el uso sostenible de los humedales de importancia internacional y sus recursos biológicos. En 2012, la Presa de Valsequillo (Puebla, México) fue aceptada como sitio Ramsar, pero se desconocen aún aspectos de la ecología de su avifauna. Con este estudio se incrementó el conocimiento sobre la importancia ornitológica de este sitio Ramsar en el que evaluamos la variación temporal de la estructura de la comunidad de aves acuáticas. Primero, desde febrero de 2014 a enero de 2015, estimamos mensualmente la riqueza y abundancia de aves acuáticas de la Presa desde una embarcación con motor fuera borda, y se usó esta información para analizar los cambios en la riqueza y la diversidad. Después, mediante técnicas de análisis multivariante, obtuvimos grupos de meses con base en su similitud y comprobamos su significación estadística. Finalmente, identificamos las especies responsables de tales cambios. En total, observamos 30 especies de aves acuáticas, pero la riqueza mensual (estandarizada a 768 individuos) varió entre 12 y 20. En ‘primavera-verano’, la comunidad de aves acuáticas fue más sencilla (i.e., con menores valores de abundancia, riqueza y diversidad) que en ‘otoño-invierno’. Los principales cambios en la estructura de la comunidad se debieron a variaciones en la abundancia de unas pocas especies: la gallareta americana (Fulica americana), el pato cucharón (Anas clypeata) y el pato tepalcate (Oxyura jamaicensis). Sin excluir otras posibilidades para estos cambios, nuestro estudio sugiere que los patos (Anatidae) utilizan principalmente la Presa de Valsequillo como un sitio de invernada, mientras que las garzas (Ardeidae) la utilizan como una escala en sus movimientos migratorios otoñales. Nuestros datos pueden aplicarse en programas de ecoturismo (observación de aves), buscando las fechas que permitan maximizar el número de especies observadas, su diversidad o su abundancia.

Cold weather increases winter site fidelity in a group-living passerine

Site fidelity during the non-breeding season is beneficial if habitat quality and environmental predictability are high. In group-living species, the costs and benefits of site fidelity may be linked to the non-social (weather) and social (dominance hierarchy) environments, but little is known about factors influencing movements during the non-breeding season. We studied both within- and between-winter site fidelity of the great tit (Parus major), a partial migrant in northern Finland. We collected mark-resight data on wintering great tits across two winters at multiple sites, and tested for the effects of age, sex, season, temperature and day length on site fidelity. Within-winter movement was lower during mid-winter and decreased during cold periods. This pattern is probably linked to energy saving and predator escaping strategies during these demanding periods when energy expenditure is high and birds have limited daylight hours to forage. Site fidelity was lower for juveniles than adults within a winter, but it was unaffected by sex. These results agree with an age related dominance structure and site-specific dominance found in great tits, but they can also be related to prior experience as young individuals still collect information during their first winter. In contrast, between-winter site fidelity was not affected by age or sex, suggesting equal benefits from site fidelity. Juveniles probably gather information on resource abundance and distribution in their first winter, and thereby gain the same benefits as adults from returning the next winter.

Reproductive outcomes determine the timing of arrival and settlement of a single-brooded Nearctic–Neotropical migrant songbird (Catharus fuscescens) in South America

ABSTRACT The breeding seasons of Nearctic–Neotropical migratory songbirds are thought to be constrained by the temporal demands of subsequent seasons. In any population, a subset of adults may fail to fledge young despite repeated attempts, which may prolong reproductive effort. We used geolocators to track the single-brooded Veery (Catharus fuscescens) from a Delaware, USA, breeding site to South America and back, to examine how reproductive failure and the timing of reproduction affected the spatiotemporal aspects of the nonbreeding season. We also considered the effect of additional variables: age, sex, time in population (i.e. experience), productivity, and nutrition via ptilochronology. We found that clutch completion date and reproductive success were significant predictors of South American entry and arrival date at first winter sites, respectively. Reproductive success also influenced the latitude of winter sites. For females only, there was a consequence of reproductive failure: unsuccessful fema...

Use of cluster photographs to estimate overwintering monarch butterfly, Danaus plexippus Linnaeus, 1758 (Lepidoptera: Danaidae), populations at selected California overwinter sites

Conducting a population estimate of overwintering monarch butterflies, Danaus plexippus Linnaeus, 1758, at California winter sites traditionally involves many early morning hours of using binoculars to count the insects as they cluster in tight aggregations among the high foliage of trees. This study investigates the effectiveness of counting the butterflies by using photographs of specifically selected clusters. Counts based on photographs of ten clusters from each of three overwintering sites were compared to counts of the same clusters using binoculars. The data were analyzed using mixed model analysis of variance (ANOVA). The results show that the photograph-based counts were equivalent to the binocular counts within ±10%.

Can collective memories shape fish distributions? A test, linking space‐time occurrence models and population demographics

Social learning can be fundamental to cohesive group living, and schooling fishes have proven ideal test subjects for recent work in this field. For many species, both demographic factors, and inter‐ (and intra‐) generational information exchange are considered vital ingredients in how movement decisions are reached. Yet key information is often missing on the spatial outcomes of such decisions, and questions concerning how migratory traditions are influenced by collective memory, density‐dependent and density‐independent processes remain open. To explore these issues, we focused on Atlantic herring Clupea harengus, a long‐lived, dense‐schooling species of high commercial importance, noted for its unpredictable shifts in winter distribution, and developed a series of Bayesian space‐time occurrence models to investigate wintering dynamics over 23 yr, using point‐referenced fishery and survey records from Icelandic waters. We included covariates reflecting local‐scale environmental factors, temporally‐lagged prey biomass and recent fishing activity, and through an index capturing distributional persistence over time, derived two proxies for spatial memory of past wintering sites. The previous winter's occurrence pattern was a strong predictor of the present pattern, its influence increasing with adult population size. Although the mechanistic underpinnings of this result remain uncertain, we suggest that a ‘wisdom of the crowd’ dynamic may be at play, by which navigational accuracy towards traditional wintering sites improves in larger and/or denser, better synchronized schools. Wintering herring also preferred warmer, fresher, moderately stratified waters of lower velocity, close to hotspots of summer zooplankton biomass, our results indicative of heightened environmental sensitivity in younger cohorts. Incorporating spatiotemporal correlation structure and time‐varying regression coefficients improved model performance, and validation tests on independent observations one‐year ahead illustrate the potential of uniting demographic information and non‐stationary models to quantify both the strength of collective memory in animal groups and its relevance for the spatial management of populations.

Apparent survival of an Arctic‐breeding migratory bird over 44 years of fluctuating population size

Following increases in numbers during the second half of the 20th century, several Arctic‐breeding migrant bird species are now undergoing sustained population declines. These include the northwest European population of Bewick's SwanCygnus columbianus bewickii, which declined fromc. 29 000 birds on the wintering grounds in 1995 to 18 000 in 2010. It is unclear whether this decrease reflects reduced survival, emigration to a different area, or a combination of both. Furthermore, the environmental drivers of any demographic changes are also unknown. We therefore used an information‐theoretic approach inRMarkto analyse a dataset of 3929 individually marked and resighted Bewick's Swans to assess temporal trends and drivers of survival between the winters of 1970/71 and 2014/2015, while accounting for effects of age, sex and different marker types. The temporal trend in apparent survival rates over our study period was best explained by different survival rates for each decade, with geometric mean survival rates highest in the 1980s (leg‐ring marked birds = 0.853, 95% confidence interval (CI) 0.830–0.873) and lowest in the 2010s (leg‐ring = 0.773, 95%CI0.738–0.805; neck‐collar = 0.725, 95%CI0.681–0.764). Mean (±95%CI) resighting probabilities over the study period were higher for birds marked with neck‐collars (0.91 ± 0.01) than for those marked with leg‐rings (0.70 ± 0.02). Weather conditions in different areas across the flyway, food resources on the winter grounds, density‐dependence and the growth of numbers at a relatively new wintering site (the Evros Delta in Greece) all performed poorly as explanatory variables of apparent survival. None of our 18 covariates accounted for more than 7.2% of the deviance associated with our survival models, with a mean of only 2.2% of deviance explained. Our results provide long‐term demographic information needed to help conservationists understand the population dynamics of Bewick's Swans in northwest Europe.

No apparent gain from continuing migration for more than 3000\xa0kilometres: willow warblers breeding in Denmark winter across the entire northern Savannah as revealed by geolocators

BackgroundFor most Afro-Palearctic migrants, particularly small songbirds, spatiotemporal migration schedules and migratory connectivity remain poorly understood. We mapped migration from breeding through winter of one of the smallest Afro-Palearctic migrants, the willow warbler Phylloscopus trochilus, using geolocators (n = 15).ResultsBirds migrated from North European breeding grounds to West Africa via the Iberian Peninsula following a narrow corridor along the West Coast of Africa. Birds then dispersed across the northern Savannah with termination of migration highly variable among individuals. The termination of migration appeared not to be related to timing, current and previous years’ vegetation conditions or biometrics. During winter, most birds moved southwards to improved vegetation.ConclusionThe willow warblers showed a large, unexpected longitudinal spread in winter sites of more than 3000 km between individuals breeding within a 500 m range resulting in a low degree of connectivity. The large wintering area may well be related to generalist behaviour in the species. Our findings contribute to understanding the link between breeding and wintering ecology in long-distance migratory birds.

Seasonal changes of the Hazel Grouse Tetrastes bonasia habitat requirements in managed mountain forests (Western Carpathians)

We studied the differences between spring and winter sites of Hazel Grouse Tetrastes bonasia in a managed, temperate forest in the Beskid Mountains (Western Carpathians, Poland). The study of seasonal requirements of this species in this type of habitat was innovatory. Spring territories must provide birds with appropriate conditions for breeding and winter ones must give good habitat for wintering. The environmental variables of spring and winter sites were collected in three layers in a 100 m radius from the place of recording of the Hazel Grouse: canopy, understory and undergrowth. According to our study, the proportion of deciduous trees was greater in spring territories in comparison to winter territories in all studied layers. Conversely, greater species richness in the undergrowth and understory in spring sites of Hazel Grouse was found in comparison to winter sites. Moreover, a greater proportion of birch, poplar, willow, wild cherry and bird cherry were found in the spring sites of Hazel Grouse in comparison to winter sites. Generalized Linear Model models showed that the occurrence of overgrown clearings, clearfellings with deadwood and higher richness of grass and herbs and their cover in the forest were important habitat factors for Hazel Grouse in both spring and winter sites. Sites of Hazel Grouse were strongly affected by the proportions of beech, sycamore, fir, spruce and larch in the canopy layer in both seasons. Moreover, a greater proportion of tree species producing nuts, drupes or winged seeds was important in both spring and winter sites. Bush cover was important for winter sites of the Hazel Grouse. Food resources, mainly in winter sites are important factors for habitat selection. Summarizing, we found habitat differences between spring territory and winter sites of Hazel Grouse. In both seasons, higher habitat heterogeneity was an important factor for occurrence of this species.

Diet and feeding ecology of the wintering shorebird assemblage in the Bijagós archipelago, Guinea-Bissau

Detailed data on shorebird feeding ecology is mostly lacking for tropical wintering sites, limiting our understanding of trophic interactions among shorebird species and their prey. Using dropping analysis and video recordings we compared the diet of eight shorebird species wintering in the Bijagós archipelago, Guinea-Bissau, one of the most important but also least known coastal sites for shorebirds in Africa. We also calculated niche width and foraging niche overlap among these eight species.Whimbrel, grey plover and redshank fed mainly on fiddler crabs, confirming previous observations made in the Bijagós. A large proportion of the diet of bar-tailed godwit, curlew sandpiper, sanderling and ringed plover was composed of polychaetes, particularly Nereis and Glycera, and also Marphysa in the case of larger shorebirds. Red knots fed mainly on the bivalve Dosinia isocardia. All species showed narrow trophic niches, but particularly so whimbrel, red knot, grey plover and redshank. Niche overlap among shorebird species was mostly insignificant, with the exception of species that fed mainly on fiddler crab.Low levels of niche overlap suggest that shorebirds are able to partition the available food resources in the Bijagós despite the reported low macrobenthic densities in the area. In fact, observational data for bar-tailed godwit suggests resource partitioning even occurs within species, with dietary differences among sexes.

Habitat use and movements of common eiders wintering in southern New England

ABSTRACTLittle is known about the habitat use patterns and movement ecology of American common eiders (Somateria mollissima dresseri) despite potential negative impacts on habitat and eider populations from anthropogenic sources (e.g., oil spills, hunting, offshore wind energy facilities). We used satellite telemetry to quantify migratory phenology, home range size, winter site fidelity, and resource selection of adult female eiders (n = 24) from December 2011 to July 2013 that were captured during winter in southern New England, USA. Eiders spent 39% of their annual cycle in southern New England. In spring, eiders took an average of 16 days (range = 2–47) in 2012 and 20 days (range = 1–61) in 2013 to migrate from wintering grounds to summer areas, whereas the duration of fall migration averaged 47 days (range = 7–115). Eiders exhibited high site fidelity to wintering areas, with 83% of birds with active transmitters (n = 23) returning to the study area the following winter (2012–2013). Mean individual core use home ranges on wintering grounds averaged 38.5 km2 and 95% utilization distributions were 199.3 km2. Based on habitat selection models, eiders preferred shallow, nearshore waters that had relatively fine sediments and a high probability of hard bottom. We estimated that only 3% of our 6,212‐km2 study area had a high relative probability of use by eiders. Future development (e.g., offshore wind energy developments) should avoid shallow, nearshore waters with hard bottoms preferred by eiders to minimize potential impacts. © 2017 The Wildlife Society.

Low level exposure to crude oil impacts avian flight performance: The Deepwater Horizon oil spill effect on migratory birds

In 2010, the Deepwater Horizon oil spill released 134 million gallons of crude oil into the Gulf of Mexico making it the largest oil spill in US history. The three month oil spill left tens of thousands of birds dead; however, the fate of tens of thousands of other migratory birds that were affected but did not immediately die is unknown. We used the homing pigeon as a surrogate species for migratory birds to investigate the effects of a single external oiling event on the flight performance of birds. Data from GPS data loggers revealed that lightly oiled pigeons took significantly longer to return home and spent more time stopped en route than unoiled birds. This suggests that migratory birds affected by the oil spill could have experienced long term flight impairment and delayed arrival to breeding, wintering, or crucial stopover sites and subsequently suffered reductions in survival and reproductive success.

Evaluating the impact of man-made disasters on imperiled species: Piping plovers and the Deepwater Horizon oil spill

Even in the presence of environmental safeguards, catastrophic accidents related to anthropogenic activities occur that can result in both immediate and chronic impacts on local biota. However, due to the unplanned nature of catastrophes, studies aimed to identify the effects of these accidents on an ecosystem and its inhabitants often have imperfect study designs that are reactive rather than proactive, resulting in methodological and analytical challenges. On 20 April 2010, following an explosion on the Deepwater Horizon oil rig, a well blowout occurred on the seafloor approximately 80km off the Louisiana coast in the Gulf of Mexico. This blowout resulted in the largest marine oil spill in United States history, which impacted critical migratory stopover and overwintering habitat for many seabird and shorebird species, including species of high conservation concern such as the piping plover (Charadrius melodus). Here, we assessed the potential longer-term demographic impacts of the Deepwater Horizon oil spill on piping plovers in a capture-mark-recapture framework. We examined whether a series of demographic processes, including probabilities of remaining at a specific wintering site, over-winter and annual apparent survival, winter stopover duration, and abundance varied among oiled and unoiled habitats. We found that the perceived amount of oiling on land, in water, and on individual birds, as well as numerous demographic processes, were spatially or temporally variable. However, we found little support that piping plover demography was negatively influenced by the magnitude of oil observed at an impacted area, or that demographic rates substantially varied between reference and oil impacted areas. Nor did we find that piping plovers that were observed to be oiled had lower survival probabilities following the DWH oil spill relative to non-oiled individuals from the same winter population. Although we did not find that the Deepwater Horizon oil spill substantially influenced piping plovers, our methods provide an analytical framework to more appropriately address both the near or long-term impacts of an anthropogenic disturbance on a species.

Greater Flamingo (Phoenicopterus roseus): Important wintering sites and breeding records in the United Arab Emirates

Greater Flamingo (Phoenicopterus roseus) monitoring was undertaken in the United Arab Emirates from 2003 to 2015 at 36 permanent sites to find key wintering and breeding sites. Bul Syayeef Marine Protected Area with monthly mean of 6553 (±3594) flamingos followed by Al Wathba Wetland Reserve with 1228 (±1190) flamingos topped the list. In addition, Shahama Wetland and Al Aryam Mudflats in Abu Dhabi Emirate form a complex of four nearby sites that hold the majority of nearly 15,000–20,000 birds wintering in the country. Lagoons (Khors) in the northern emirates are the other key wintering sites, that suffer habitat destruction and high disturbance. Breeding has been sporadic and infrequent since the first breeding attempt in 1993. Greater Flamingos have bred successfully only in the Abu Dhabi Emirate on 10 occasions at three sites with the highest eight breeding attempts at Al Wathba and one each at Shahama and Bul Syayeef. A total of 1,972 young have fledged with a high overall breeding success of 43%. The highest number of 801 young fledged at Bul Syayeef in 2009 followed by 420 at Al Wathba in 2015 and 350 at Shahama in 2007. Successful breeding occurred both in summer and winter seasons, breeding attempts were more (58%) in summer compared to winter. Flamingos have bred regularly at Al Wathba Wetland Reserve since 2011, this was made possible due to the provision of an artificial island to aid nesting and better control of predators. Breeding is successful at sites that maintain higher bird numbers and are free from disturbance.

Survey of avifauna of the Gharana wetland reserve: implications for conservation in a semi-arid agricultural setting on the Indo-Pakistan border

BackgroundThe Gharana wetland conservation reserve (GWCR) is a semi-arid wetland adjacent to agricultural areas on the Indo-Pakistani border. Despite being declared an Important Bird Area (IBA) by Birdlife International, the occurrence and distribution of birds has not been well-documented in this area. Our aims were to systematically document the composition, relative abundance and feeding guilds of all avian fauna in order to form a baseline to monitor changes from—and to underwrite—future conservation actions.ResultsFrom 24 surveys over 1 year, we recorded 151 species from 45 families and 15 orders. 41% of species were listed as ‘rare’ and only 22% were ‘very common’. The largest number of families belonged to the order Passeriformes (40%), followed by Charadriiformes (14%) and Coraciiformes (11%). The most species (12%), were found in the family Anatidae (Anseriformes—widely recognized as bio-indicators), followed by Accipitridae (Falconiformes;12%) and Muscicapidae (Passeriformes; 6%). Carnivores and insectivores were the feeding guilds most frequently observed. Indeed, more than 50% of all species fed on the abundant fish, mollusks and insects and larvae. Bark-feeders and nectarivores were the least common.ConclusionsWinter visitors were frequently found, while summer visitors were rare, reinforcing the importance of GWCR as a wintering site for high-altitude species. The conservation of this wetland is especially crucial for nine globally-threatened species. We have provided baseline documentation to help future monitoring efforts for this region, and a template to initiate the implementation of conservation plans for other remote IBAs.

Diet selection by wintering Lesser White-fronted GooseAnser erythropusand the role of food availability

SummaryThe Fennoscandian population of the Lesser White-fronted GooseAnser erythropus(LWfG) is on the verge of extinction and migrates from northern Fennoscandia to Greece on a regular seasonal basis. For the first time, diet selection was investigated during two years at Kerkini Lake, a wintering site in Greece. The relative use of LWfG’s feeding habitats was systematically recorded by visual observations of the LWfG flocks. Food availability was measured by the relative cover of available vegetation types while the diet composition was determined by the microhistological analysis of droppings. In addition, we determined crude protein, neutral detergent fibre, acid detergent fibre and acid detergent lignin content of the most preferred plant species by LWfG and all vegetation categories that contributed to LWfG diet in the middle of the duration of their stay at Kerkini Lake and after their departure from the lake. LWfG feeding habitat was exclusively marshy grassland in water less than 5 cm deep up to 300–400 m away from the shore. LWfG selected a diverse number of plant species (33), however, grass made up the 58% of their diets. The most preferred plant species wereEchinochloa crus-galli,Cyperus esculentus,Scirpus lacustrisandRanunculus sceleratus. LWfG departed from Kerkini Lake in mid-December to the Evros Delta (Thrace, eastern Greece), when either food availability falls in very low levels or flooding occurred in their main feeding habitat. Consequently, as long as food and habitat resources are available for LWfG, it is very likely that the birds will winter mainly at Kerkini Lake and not at the Evros Delta, which will contribute to further minimisation of the theoretical risk of accidental shooting of LWfG at the latter wintering habitat. Thus, future conservation actions should primarily focus on the grassland improvement at Kerkini Lake enhancing the availability of food resources for LWfG (mainly grasses) and the protection of the feeding habitat from flooding.

Migratory connectivity of Semipalmated Sandpipers and implications for conservation

ABSTRACT Semipalmated Sandpiper (Calidris pusilla) populations have undergone significant declines at core nonbreeding sites in northeastern South America. Breeding populations have also declined in the eastern North American Arctic, but appear to be stable or increasing in the central and western Arctic. To identify vulnerable populations and sites, we documented the migratory connectivity of Semipalmated Sandpipers using light-level geolocators, deploying 250 at 8 Arctic sites across the species' breeding range from 2011 to 2015, plus 87 at a single wintering site in northeastern Brazil in 2013 and 2014. We recovered 59 units and resighted 7 more (26% return rate) on the breeding grounds, but none at the nonbreeding site. We recovered only ∼3% of units deployed in 2013 at eastern Arctic breeding sites, but recovered 33% of those deployed in 2015. Overall, birds with geolocators were 57% as likely to return as those carrying alphanumeric flags. Stopover durations at prairie sites (mean: 8.7 days southbou...

Modeling the spread of avian influenza viruses in aquatic reservoirs: A novel hydrodynamic approach applied to the Rhône delta (southern France)

Wild aquatic birds represent a natural reservoir of avian influenza viruses (AIV) that can be spread to poultry. AIV epizootics were associated with huge economic impacts during the last decades and are still of major concern. Within aquatic bird populations AIV are transmitted either by direct contact or through the ingestion of water that has been contaminated by infected individuals. This second route involving environmental transmission is of utmost importance in AIV dynamics, yet it has received far less attention than direct bird-to-bird contamination. Our objective was to combine a hydrodynamic model with data on mallard abundance and AIV infection rate within the population, so as to characterize virus dissemination within a complex wetland network. We chose the Vaccarès hydrosystem as a wetland model since it represents a large part of the Camargue region, which is a major wintering site for a large diversity of aquatic birds including AIV hosts. We aimed to identify the environmental parameters that drive AIV dynamics within this system and the spatio-temporal pattern of dispersion and persistence of viruses. Our results show that in a complex hydrosystem we can expect a great heterogeneity in AIV risk among wetlands. Our simulations underline how a simple “homogeneous box” approach could in the case of deltaic ecosystems minimize the expected risk by diluting it in the whole system. Moreover, such undermining of the risk perception could affect the predictions relative to risk duration. We present a new approach to identify hotspots of virus concentrations within deltaic areas that could take advantage of the duck count data, AIV surveys and hydrodynamic models that may already be available in several major duck wintering areas comprised of complex hydrosystems, such as the large European deltas. Our method could be of particular interest to optimize surveillance strategies in the current context of highly pathogenic AIV diffusion within wild bird populations.

A global evaluation of apple flowering phenology models for climate adaptation

This study presents the first evaluation of apple flowering phenology models using data from 14 sites across the globe. The dataset includes large variability in growing climates, a prerequisite to investigate phenology models for use in climate change applications. Two flowering stages, early and full, were investigated allowing for unique model evaluation based on both statistical performance and biological assumptions. Two overarching phenology models (Sequential and Chill Overlap) and two sub-models of chill (Dynamic and Triangular) and heat (GDH and Sigmoidal) were tested. Flowering times from the different sites illustrated the differing effects of contrasting winter and spring temperatures. Sites with similar springtime temperatures, but different winter temperatures, had different flowering patterns (warmer winter sites flowered later). Across all analyses, results from the Chill Overlap model were better than those from the Sequential model. Of the Chill Overlap models, those fitted with the Triangular or Dynamic chill model and the GDH heat sub-model performed well statistically and met the assumptions of the model across both flowering stages. The mild sites in the analysis were least well represented, regardless of model selection. This global evaluation demonstrated that flowering modelling in temperate fruit trees would progress through appropriate choices of overarching model, sub-models and parameters.

Barr Al Hikman, a major shorebird hotspot within the Asian–East African Flyway: results of three winter surveys

Barr Al Hikman, a large intact coastal wetland in the Sultanate of Oman, is an important wintering site for migratory waterbirds in the Asian–East African Flyway. The last reported systematic survey of the area is from 1990. Here, we present results of three surveys in 2007/2008, 2013/2014 and 2015/2016. Up to half a million waterbirds of 42 species were counted. Shorebirds were by far the most numerous group (>410,000). For 18 shorebird species, numbers wintering at Barr Al Hikman exceeded 1% of their flyway population. Therefore, our results confirm that Barr Al Hikman is still an important wintering ground, not only with respect to the number of birds, but also in terms of species diversity. Furthermore, a comparison with past surveys shows that numbers have tripled since the 1990s. We argue that, taking into account methodological issues, habitat degradation at other wintering sites in the Gulf region of the flyway may be an important factor leading birds to shift to Barr Al Hikman. However, the future of Barr Al Hikman is uncertain: recent rapid urban growth and road construction have drastically changed the Oman coast, and potentially threatening developments are being planned in the area. Therefore, to preserve the Barr Al Hikman area, clear conservation guidelines and actions are needed, and the site deserves to be designated as a Ramsar site.