Analysis of population development and effectiveness of mnagement 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