Opvang van Ganzen op de Klei: evaluatie van experimenten in drie winters

Conform het Beleidskader Faunabeheer zijn opvanggebieden voor overwinterende ganzen aangewezen. In akkerbouwgebieden met zware klei zijn de mogelijkheden voor beheerspakketten voor opvang beperkt. Gedurende drie winters (2005-'08) zijn in Zeeuws- Vlaanderen en West Brabant een vijftal experimentele beheerspakketten op hun geschiktheid onderzocht. Het pakketgebruik door ganzen is gemonitord door ganzentellingen en keuteltellingen. Resultaten van onderzoek van: CLM, SOVON en Alterra, op verzoek van LNV, Faunafonds en LT

The effect of the application of mono-lauric acid with glycerol mono-laurate in weaned piglets, on the use of antimicrobials in sow herds

The Dutch government has obliged the pig industry to reduce the use of antimicrobials at farm level with 50% by 2013. The search for alternatives for antimicrobials and other tools which can improve the health status of the farm is intensified. One example of an alternative for antimicrobials is Daafit, a combination of lauric acid and glycerol-mono-laurate, produced by the firm Daavision B.V.

Agricultural pastures challenge the attractiveness of natural saltmarsh for a migratory goose

Broad-scale land conversions and fertilizer use have dramatically altered the available staging area for herbivorous long-distance migrants. Instead of natural land, these birds rely increasingly on pastures for migratory fuelling and stopover, often conflicting with farming practices. To predict and manage birds’ future habitat use, the relative advantages and disadvantages of natural (e.g. saltmarsh, intertidal) versus anthropogenic staging sites for foraging need to be understood. We compared the migratory staging of brent geese on saltmarsh and pasture sites in spring. Food quality (nitrogen and fibre content), antagonistic behaviour, and body weight were quantified at nearby sites in simultaneous seasons. Individuals were tracked with high-resolution GPS and accelerometers to compare timing of migration and time budgets during fuelling. On pastures, birds rested more and experienced higher ingestion rates, similar or superior food quality and reduced antagonistic interactions than on saltmarsh. Brent geese using fertilized grasslands advanced their fuelling and migration schedules compared to those using saltmarsh. Pasture birds reached heavy weights earlier, departed sooner, and arrived in the Arctic earlier. Intertidal mudflats were frequently visited by saltmarsh birds during the day, and available food there (algae, some seagrass) was of higher quality than terrestrial resources. Availability of intertidal resources was an important factor balancing the otherwise more favourable conditions on pastures relative to saltmarsh. Synthesis and applications. Disadvantages of longer foraging effort, more antagonistic interactions and delayed fuelling schedules on traditional saltmarshes may cause geese to exchange this traditional niche in favour of pastures, especially in a warming climate that requires advancement of migratory schedules. However, due to its high quality, intertidal forage can complement terrestrial foraging, potentially removing the incentive for habitat switches to pastures. The relatively high quality of green algae and seagrass, and birds’ remarkable preference for these resources when available, provides a key for managers to create landscapes that can sustain this specialist’s intertidal lifestyle. To keep natural habitats attractive to staging geese with the purpose of preventing conflicts with farming practices, management actions should focus on conservation and restoration of saltmarsh and especially intertidal habitat.</p

Flexibility in faithfulness of Dark-bellied Brent Geese, Branta b. bernicla to moulting sites

The distribution of Dark-bellied Brent Geese Branta b. bernicla moulting on the Taimyr Peninsula, in the Russian arctic, varies between years depending on whether the birds had a successful breeding season. Counts made of moulting flocks show that major shifts in numbers occur, particularly in non-breeding years, when in line with Salomonsen’s (1968) hypothesis a higher proportion of the population moults further north. For instance, the delta of the Lower Taimyr River in the northern part of the Taimyr Peninsula held 10-times more moulting Dark-bellied Brent Geese in 1989, a non-breeding year, than it did in the good 1990 breeding season. At a more local scale, in good breeding years family groups with small goslings tend to move away from breeding islands in the Pyasina Delta, western Taimyr, to avoid gosling predation by Taimyr Gulls Larus taimyrensis which nest in colonies on the same islands, whereas in poor breeding years adult geese concentrate on these same islands to moult and avoid the mainland sites used for moulting in good breeding years. Failed breeders have greater freedom than parent birds to choose where to moult as successful breeders remain with their goslings to protect and guide them to the safest nursery and moult areas. Re-captures of ringed Darkbellied Brent Geese at a moulting site in the Pyasina Delta found that, in poor breeding years, up to one-fifth the birds had moulted at the site previously, but that the majority of ringed birds known to be still alive were not site-faithful to their moulting grounds

Contrasting consequences of climate change for migratory geese:Predation, density dependence and carryover effects offset benefits of high-arctic warming

Climate change is most rapid in the Arctic, posing both benefits and challenges for migratory herbivores. However, population-dynamic responses to climate change are generally difficult to predict, due to concurrent changes in other trophic levels. Migratory species are also exposed to contrasting climate trends and density regimes over the annual cycle. Thus, determining how climate change impacts their population dynamics requires an understanding of how weather directly or indirectly (through trophic interactions and carryover effects) affects reproduction and survival across migratory stages, while accounting for density dependence. Here, we analyse the overall implications of climate change for a local non-hunted population of high-arctic Svalbard barnacle geese, Branta leucopsis, using 28 years of individual-based data. By identifying the main drivers of reproductive stages (egg production, hatching and fledging) and age-specific survival rates, we quantify their impact on population growth. Recent climate change in Svalbard enhanced egg production and hatching success through positive effects of advanced spring onset (snow melt) and warmer summers (i.e. earlier vegetation green-up) respectively. Contrastingly, there was a strong temporal decline in fledging probability due to increased local abundance of the Arctic fox, the main predator. While weather during the non-breeding season influenced geese through a positive effect of temperature (UK wintering grounds) on adult survival and a positive carryover effect of rainfall (spring stopover site in Norway) on egg production, these covariates showed no temporal trends. However, density-dependent effects occurred throughout the annual cycle, and the steadily increasing total flyway population size caused negative trends in overwinter survival and carryover effects on egg production. The combination of density-dependent processes and direct and indirect climate change effects across life history stages appeared to stabilize local population size. Our study emphasizes the need for holistic approaches when studying population-dynamic responses to global change in migratory species.</p