Thomas Eske Holm

Effects of Water Level Management on Autumn Staging Waterbird and Macrophyte Diversity in Three Danish Coastal Lagoons

Many Danish wetlands frequently experience algae blooms and oxygen deficiencies because of eutrophication caused by enhanced nitrogen and phosphorous levels. As a consequence, wetland managers have focused on improving water quality, but often without considering the suitability of wetlands for waterbirds. In this study, managers improved water quality in two Danish lagoons by opening a floodgate to the sea. We studied the responses of autumn staging waterbirds and submerged vegetation, to resultant higher water replacement rates and water levels. A third lagoon with no change in management was studied for comparisons. Lagoons with rise in water levels experienced declines in bird species diversity, a decline in benthivore species abundances and an increase in herbivore species abundances. Macrophyte biomass increased but seagrass diversity was low due to high salinity. The lagoon with no changes in management control had high and stable waterbird diversity and bird-days spent was increasing during the study period. Explanations for this were diverse typography and low water levels. Furthermore, the macrophyte community was more diverse due to low salinity. In order to improve both water quality and to increase waterbird diversity in the managed lagoons, we suggest water levels should be managed actively during peak migration in autumn. This could secure more shallow-water areas to waders and create better congruence between appropriate water levels and timing of peak bird migration in autumn. The rest of the year the floodgate should be left open in order to secure a high water quality.

Effects of climate change on European ducks: what do we know and what do we need to know?

The consequences of climate change for bird populations have received much attention in recent decades, especially amongst cavity-nesting songbirds, yet little has been written on ducks (Anatidae) despite these being major elements of wetland diversity and important quarry species. This paper reviews the major known consequences of climate change for birds in general, and relates these to the limited information available specifically for ducks. Climate change can influence migration distance and phenology, potentially affecting patterns of mortality, as well as distribution and reproductive success in ducks. Studies addressing effects of climate change are, however, restricted to very few duck species, including mallard Anas platyrhynchos and common eider Somateria mollissima. Shifts in winter duck distributions have been observed, whereas the mismatch hypothesis (mistiming between the periods of peak energy requirements for young and the peak of seasonal food availability) has received limited support with regard to ducks. We propose a range of monitoring initiatives, including population surveys, breeding success monitoring schemes and individual duck marking, which should later be integrated through population modelling and adaptive management to fill these gaps.

Current and Potential Threats to Nordic Duck Populations — A Horizon Scanning Exercise

We review the current and future threats to duck populations that breed, stage, moult and/or winter in the Nordic countries. Migratory duck species are sensitive indicators of their changing environment, and their societal value confirms the need to translate signals from changes in their distribution, status and abundance into a better understanding of changes occurring in their wetland environments. We used expert opinion to highlight 25 major areas of anthropogenic change (and touch briefly on potential mitigation measures through nature restoration and reserve management projects) that we consider key issues likely to influence Nordic duck populations now and in the near future to stimulate debate, discussion and further research. We believe such reviews are essential in contributing to development of successful management policy as well as stimulating specific research to support the maintenance of duck species in favourable future conservation status in the face of multiple population pressures and drivers.

Car traffic along hedgerows affects breeding success of Great Tits Parus major

Capsule In hedgerows near roads with fast and frequent traffic, the mortality of Great Tit Parus major broods was higher than in hedgerows with less traffic and hedgerows with no disturbance.

Prevalence of embedded shotgun pellets in protected and in legally hunted medium-sized carnivores in Denmark

Illegal killings of protected species may significantly affect their population status or lower recovery rates after protection. Poaching is difficult to monitor directly, hence indirect methods are required to document poaching incidences and levels. The use of shotguns inevitably results in wounding some animals that are not killed. Inefficient hunting methods may result in high annual infliction rates in game species. To reduce wounding of game species, an action plan was implemented in Denmark. Using X-ray analysis, we monitor trends in prevalence of embedded shotgun pellets in the legally hunted red fox (Vulpes vulpes) after the implementation of the action plan, and assess poaching levels of two protected species, the otter (Lutra lutra) and the badger (Meles meles) in Denmark. Overall, 13.8% of the red foxes and 6.9% of the otters carried embedded shotgun pellets, while none were recorded in badgers. The prevalence of embedded shotgun pellets in red foxes declined from 24.9% to 8.5% from the late 1990s to the late 2000s, while no change was recorded in otters. Prevalence of embedded shotgun pellets was similar in otters and red foxes collected in the late 2000s. The decline in wounded red foxes suggests that the hunting methods have changed after the action plan was implemented in Denmark. The high proportion of otters carrying embedded shotgun pellets shows that there is a significant poaching of this protected species in Denmark, possibly by hunters and fish farmers that cannot distinguish between otter and non-native American mink (Neovison vison).

The feeding ecology and distribution of Common Coots Fulica atra are affected by hunting taking place in adjacent areas

Capsule Birds using a shooting-free area are markedly influenced by close-by shooting. Aims To examine changes in distribution, feeding ecology and food supply of Common Coots before and after the beginning of hunting on adjacent salt marshes. Methods Common Coots were counted and mapped in October and November, i.e. before and after the start of hunting. In both months, activity budgets for the Coots were determined. To quantify the food supply, macrophyte biomass samples and depth measures were taken along four parallel transects in the areas used by the birds for foraging. Results Before the start of hunting in October, 45% of all Coots were observed within 400 m of the hunting area. In November (when hunting had started) the birds redistributed themselves away from the hunting area, reducing the number of birds within 400 m to 5%. Because of this redistribution, Coots were observed in deeper-water areas of the lagoon during November compared to October, and foraging by diving increased significantly from 14 to 35%. The average biomass of submerged macrophytes in the lagoon was 155.01 g dry weight/m2, which corresponds to a total of 302 250 kg in the whole lagoon. The food requirement of each Coot is 52.3 g/day, which is equivalent to 104 kg/day for the autumn peak number at this lagoon (1989 Coots). Conclusion Hunting disturbance outside the shooting-free area displaced Coots from their preferred feeding grounds inside the reserve, causing their redistribution into sub-optimal habitat at greater water depths where Coot feeding costs were higher. Submerged macrophyte biomass showed that food was abundant in the area and therefore unlikely to be a limiting factor that influenced the redistribution of Coots during the shooting season. We suggest that at this particular site the feeding ecology of Coots could be improved by incorporating an appropriate buffer zone between the protected area and the hunted area. This may be of value not only to Coots, but also for other bird species that exploit shallow water.

Effects of a Danish action plan on reducing shotgun wounding of Common Eider Somateria mollissima

Capsule The incidence of embedded shotgun pellets in Common Eider females declined from 34.1% to 5.5% from 1997 to 2009–2011 after the implementation of an action plan to reduce wounding. Males, which were exposed to hunting outwith the area of the action plan, showed a lower rate of decline.