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The Ministry of Agriculture, Nature and Food Quality requires that the Dutch population of European hamster is surveyed each year. This consists of a census of inhabited burrows in the various known habitats patches. The European hamster is present only in the southern part of the province of Limburg and has a preference for arable farmland where cereals or alfalfa are grown. In 2002 the hamster was reintroduced into areas with a specially adapted cropland management regime. In recent years attempts have been made to find new forms of hamster friendly land management practices which can be easily integrated into the farm management and are cheaper to carry out. The area of hamster friendly arable land with suitable habitat is currently more than 700 hectares. Monitoring of the hamster population by means of burrow counts and tagged animals shows that in practice hamsters struggle to survive long enough to produce sufficient litters to enable the population to grow. The latest censuses indicate that there are fewer than 200 inhabited burrows spread over approx. 20 kilometre grids. The hamster population is therefore still critically endangered and restocking remains necessary. Jaarlijks wordt in opdracht van het ministerie van Landbouw, Natuur en Voedselkwaliteit de Nederlandse hamsterpopulatie gemonitord. Dit bestaat uit een telling van bewoonde burchten in de verschillende leefgebieden. De hamster komt alleen voor in het zuiden van Limburg en heeft een voorkeur voor (winter)- graanakkers of akkers met luzerne. De hamster is in 2002 geherintroduceerd in gebieden met een aangepast agrarisch akkerbeheer. De laatste jaren is met het zogenaamde HOEB-project (Hamster op Eigen Benen, 2015-2018) getracht nieuwe vormen van hamstervriendelijk beheer te vinden die enerzijds goed inpasbaar zijn in de agrarische bedrijfsvoering en anderzijds minder kosten qua beheer. Dankzij het HOEB-project is het totaal areaal hamstervriendelijk beheerde akkers met geschikt habitat uitgebreid met ruim 200 ha tot ruim 700 ha. Het is nog afwachten wanneer deze uitbreiding ook een effect gaat laten zien op de hamsterpopulatie. Ondanks alle inspanningen is het tot op heden nog niet gelukt een robuuste populatie te creëren die zelfstandig kan overleven. De monitoring van hamsters, aan de hand van burchttellingen en door middel van gezenderde dieren, laat zien dat het in de praktijk nog steeds erg lastig is voor hamsters om voldoende lang te overleven en voldoende worpen te krijgen om de populatie te laten groeien. De laatste tellingen wijzen op een aantal van minder dan 200 bewoonde burchten, verdeeld over ca. 20 kilometerhokken. Daarmee is de hamster nog steeds ernstig bedreigd en bijplaatsingen blijven vooralsnog noodzakelijk om de populatie te ondersteunen.

In the past decades, large-scale conservation programs have been implemented to halt the decline of farmland species. The mechanisms explaining the effectiveness of these programs remain poorly understood. Here we test the recent hypothesis that the effects of conservation management are determined by the ecological contrasts in limiting resources they create relative to the baseline situation. We examine responses of wintering seed-eating farmland birds to the experimental establishment of winter food plots in areas with contrasting food availability. We found that farmland bird abundance and species richness were strongly positively related to seed availability, regardless of compositional differences between agricultural landscapes. In line with the ecological contrast hypothesis, the responses of wintering farmland birds increased with increasing conservation induced contrast in a key limiting resource. Both contrasts and relative responses were negatively related to baseline food availability, but the absolute bird density in food plots was unrelated to baseline food availability. This indicates that both relative and absolute effects of conservation management need to be considered to properly evaluate the effectiveness of conservation management.

Low pathogenic avian influenza virus can mutate to a highly pathogenic strain that causes severe clinical signs in birds and humans. Migratory waterfowl, especially ducks, are considered the main hosts of low pathogenic avian influenza virus, but the role of geese in dispersing the virus over long-distances is still unclear. We collected throat and cloaca samples from three goose species, Bean goose (Anser fabalis), Barnacle goose (Branta leucopsis) and Greater white-fronted goose (Anser albifrons), from their breeding grounds, spring stopover sites, and wintering grounds. We tested if the geese were infected with low pathogenic avian influenza virus outside of their wintering grounds, and analysed the spatial and temporal patterns of infection prevalence on their wintering grounds. Our results show that geese were not infected before their arrival on wintering grounds. Barnacle geese and Greater white-fronted geese had low prevalence of infection just after their arrival on wintering grounds in the Netherlands, but the prevalence increased in successive months, and peaked after December. This suggests that migratory geese are exposed to the virus after their arrival on wintering grounds, indicating that migratory geese might not disperse low pathogenic avian influenza virus during autumn migration.

A key issue in conservation is where and how much management should be implemented to obtain optimal biodiversity benefits. Cost-effective conservation requires knowledge on whether biodiversity benefits are higher when management is concentrated in a few core areas or scattered across the landscape, and how these effects vary between species. To address these questions, we examined species-specific behavioural responses of over-wintering farmland birds to enhanced seed availability. In a two-year experiment we first examined the relationship between landscape-scale seed availability and farmland bird density. Then we investigated the relative resource delivery (difference in bird densities between landscapes with and without additional management) and the efficiency (number of individuals supported per unit management) of conservation actions, both at the landscape-scale (ca 100 ha) and at the scale of the conservation measures (3.6 ha). The conservation actions were targeted towards ten seed-eating farmland bird species, but we also considered the responses of seven non-targeted and more generalist seed-eating species, seven species that are less dependent on seeds and three species of birds of prey. We found a positive relationship between bird density and landscape-scale seed availability for eleven species and, for four of these species, the slope of this relationship changed before and after a threshold seed density. For two seed-eating specialists, the number of individuals using conservation patches declined with landscape-scale seed availability. In addition, we found that the relative resource delivery declined with landscape scale seed availability for three seed-eating specialists and was independent of landscape-scale seed availability in four other species. Our results suggest that farmland specialists may benefit most from winter food additions if conservation actions result in high landscape-scale seed availability. This may be achieved by concentrating conservation measures or by establishing measures in areas with high baseline seed availability. By contrast, species that can utilize a wider range of habitats and resources may benefit more from scattering measures across larger areas. Therefore, optimal management for the full range of farmland birds in wintertime may require a combination of core areas with concentrated management and more widely distributed smaller patches of conservation measures.