Flyway connectivity and exchange primarily driven by moult migration in geese.

BACKGROUND: For the conservation and management of migratory species that strongly decrease or increase due to anthropological impacts, a clear delineation of populations and quantification of possible mixing (migratory connectivity) is crucial. Usually, population exchange in migratory species is only studied in breeding or wintering sites, but we considered the whole annual cycle in order to determine important stages and sites for population mixing in an Arctic migrant. METHODS: We used 91 high resolution GPS tracks of Western Palearctic greater white-fronted geese (Anser A. albifrons) from the North Sea and Pannonic populations to extract details of where and when populations overlapped and exchange was possible. Overlap areas were calculated as dynamic Brownian bridges of stopover, nest and moulting sites. RESULTS: Utilisation areas of the two populations overlapped only somewhat during spring and autumn migration stopovers, but much during moult. During this stage, non-breeders and failed breeders of the North Sea population intermixed with geese from the Pannonic population in the Pyasina delta on Taimyr peninsula. The timing of use of overlap areas was highly consistent between populations, making exchange possible. Two of our tracked geese switched from the North Sea population flyway to the Pannonic flyway during moult on Taimyr peninsula or early during the subsequent autumn migration. Because we could follow one of them during the next year, where it stayed in the Pannonic flyway, we suggest that the exchange was long-term or permanent. CONCLUSIONS: We have identified long-distance moult migration of failed or non-breeders as a key phenomenon creating overlap between two flyway populations of geese. This supports the notion of previously suggested population exchange and migratory connectivity, but outside of classically suggested wintering or breeding sites. Our results call for consideration of moult migration and population exchange in conservation and management of our greater white-fronted geese as well as other waterfowl populations.

Wild bird surveillance around outbreaks of highly pathogenic avian influenza A(H5N8) virus in the Netherlands, 2014, within the context of global flyways.

Highly pathogenic avian influenza (HPAI) A(H5N8) viruses that emerged in poultry in east Asia since 2010 spread to Europe and North America by late 2014. Despite detections in migrating birds, the role of free-living wild birds in the global dispersal of H5N8 virus is unclear. Here, wild bird sampling activities in response to the H5N8 virus outbreaks in poultry in the Netherlands are summarised along with a review on ring recoveries. HPAI H5N8 virus was detected exclusively in two samples from ducks of the Eurasian wigeon species, among 4,018 birds sampled within a three months period from mid-November 2014. The H5N8 viruses isolated from wild birds in the Netherlands were genetically closely related to and had the same gene constellation as H5N8 viruses detected elsewhere in Europe, in Asia and in North America, suggesting a common origin. Ring recoveries of migratory duck species from which H5N8 viruses have been isolated overall provide evidence for indirect migratory connections between East Asia and Western Europe and between East Asia and North America. This study is useful for better understanding the role of wild birds in the global epidemiology of H5N8 viruses. The need for sampling large numbers of wild birds for the detection of H5N8 virus and H5N8-virus-specific antibodies in a variety of species globally is highlighted, with specific emphasis in north-eastern Europe, Russia and northern China.

Cadmium in beavers translocated from the Elbe River to the Rhine/Meuse estuary, and the possible effect on population growth rate.

Beavers (Castor fiber) from the Middle Elbe region were re-introduced in the Biesbosch, The Netherlands, and estuary contaminated with cadmium (Cd) by the rivers Rhine and Meuse. The Middle Elbe region was also polluted with Cd, but the beavers released in the Biesbosch originated from two relatively clean habitats within this region. The Biesbosch population grew slower than other released beaver populations in Europe, and it was hypothesized that Cd intoxication was responsible for this. The beavers fed primarily on the bark and leaves of willow and poplar trees, which contained great concentrations of Cd. The average Cd concentration in the food (6.9 micrograms/g(dry)) was above the maximum tolerable concentration for large domestic herbivores. The Cd concentrations of the kidneys and hair of the beavers were correlated with those in the bark of the trees. The Cd concentration in the hair increased threefold after the release in the Biesbosch, and the geometric mean Cd kidney concentration was 55 micrograms/g(dry). Using three different models, an average Cd kidney concentration in the beavers of > 100 micrograms/g(dry) was predicted in the Biesbosch in the near future. Such a concentration causes kidney damage in some other mammals. Beaver kidneys fro the Mulde, a tributary of the Elbe, contained on average 467 micrograms Cd/g(dry), the greatest concentration reported in herbivores. Nevertheless, the fertility along the Mulde was high, due to the fact that it is an otherwise optimal beaver habitat. Furthermore, the low fertility in the Biesbosch was due to a small fraction of successful breeding pairs. We conclude that the initial low population growth rate in the Biesbosch was probably not caused by contamination with Cd. However, future effects on the individual (reproductive) life span cannot be ruled out.

Costs of swimming measured at optimum speed: scale effects, differences between swimming styles, taxonomic groups and submerged and surface swimming.

1. Data on swimming energy expenditure of 30 submerged and nine surface swimmers, covering different swimming styles and taxonomic groups, are selected from the literature. 2. The costs of transport at the optimum speed are compared and related to body mass and Re numbers. 3. Fish and turtles use relatively less and most surface swimmers slightly more energy than the other submerged swimmers; man and mink are poorly adapted to swimming. 4. The metabolic rate in W at optimum speed is approximately equal to the body mass in kg for fish and turtles and three times the mass figure for the other submerged swimmers.