C. van Turnhout

Long-term population developments in typical marshland birds in the netherlands

In this paper long-term developments in the breeding populations of 23 typical marshland bird species in The Netherlands are reconstructed, using data of several monitoring schemes and atlas studies, as well as published sources. Twelve species increased in numbers since the 1950s: Great Cormorant Phalacrocorax carbo, Great Egret Casmerodius alba, Little Egret Egretta garzetta, Eurasian Spoonbill Platalea leucorodia, Greylag Goose Anser anser, Red-crested Pochard Netta rufina, Western Marsh Harrier Circus aeruginosus, Bluethroat Luscinia svecica, Common Grasshopper Warbler Locustella naevia, European Reed Warbler Acrocephalus scirpaceus, Penduline Tit Remiz pendulinus and Common Reed Bunting Emberiza schoeniclus. Nine species declined: Great Bittern Botaurus stellaris, Little Bittern Ixobrychus minutus, Black-crowned Night Heron Nycticorax nycticorax, Purple Heron Ardea purpurea, Black Tern Chlidonias niger, Savis Warbler Locustella luscinioides, Sedge Warbler Acrocephalus schoenobaenus, Great Reed Warbler Acrocephalus arundinaceus and Bearded Reedling Panurus biarmicus. For Water Rail Rallus aquaticus and Spotted Crake Porzana porzana numbers fluctuated without a clear trend. Species typical of uncut reedbeds over standing water declined most strongly, whereas the majority of species preferring drier marshlands with shrubs and bushes, and species with a rather broad habitat choice, on average Increased. Possible causes of long-term population developments are discussed. At present, changes in water table management, falling water tables, terrestrialization and eutrophication have the highest impact on trends of marshland birds in The Netherlands.

Analysis of population development and effectiveness of management in resident greylag geese anser anser in the Netherlands

The resident Greylag goose population in the Netherlands has strongly increased in number which led to conflict with agricultural interests, public concern on goose hunting and legal debate on the need to regulate geese. Such a debate can be facilitated by insight in population development and the effectiveness of management options. In this paper we analyse the historic population development and apply density independent and density dependent models to investigate possible future population development and the impact of management on this development. We explored the influence of density dependence by applying the amount of gosling rearing habitat as the first limiting factor. The models were parameterised with life-history data of two well studied populations during their exponential growth phase as a proxy for the total Dutch population for which life-history data are unavailable. The effectiveness of two management options aimed to reduce population growth: culling birds and egg reduction are assessed with these models. The developed models can be used as a management tool to evaluate the consequences of different measures in advance of their implementation. The results show significant positive growth rates which approximate the growth rate of the total Dutch population based on census data. With density dependence in the amount of gosling rearing habitat the population will grow for another one or two decades before it stabilizes. Of the two considered management options culling birds is more effective in reducing bird numbers than egg reduction. This conclusion holds both under density independent and density dependent conditions.

Assessing the degree of preservation of landscape, natural and cultural–historical values in river dike reinforcement planning in the Netherlands

The Dutch river district is highly valued for its landscape, natural and cultural–historical elements (also called LNC values). According to the current Dutch policy on river dike reinforcements, these values should be safeguarded in planning and executing river dike reinforcement projects by following the ‘selective smart design strategy’. This paper presents an audit model, consisting of 20 modules, assessing the extent to which LNC values are taken into account in the planning process. The model was tested on eight projects and appeared to fit the objectives very well. The assignment of weighting constants used to interconnect the individual modules, however, would be improved if all parties involved could achieve consensus on this issue. The test results showed that in five of the eight projects examined, LNC values were sufficiently taken into consideration. Aspects that were insufficiently taken into account concerned, in particular, fauna surveys, valuation of LNC elements and effects valuation. Moreover, LNC values were often restored or compensated for, rather than preserved. Large differences were found between individual river dike reinforcement projects. The method can also be applied in river dike reinforcement plans in other countries. Copyright