Bijdrage aan geïntegreerde broedvogelmonitoring in Vlaanderen: ringwerk in het kader van het ‘Constant Effort Site’-programma, een case-studie in Essen

Constant Effort Site ringing: towards an integrated breeding bird monitoring system in Flanders, a case study in Essen near Antwerp One of the goals of (breeding) bird research at the Research Institute for Nature and Forest is to develop an integrated population monitoring system. Both monitoring and inventory projects on the one hand and projects that account for breeding success, survival of adults and condition on the other hand should be further promoted. This integrated system should fulfil our national and international obligations. Variables such as breeding success, condition and survival of adults are hard to estimate based on conventional monitoring or inventory studies. Abroad so-called ‘Constant Effort Site’-studies have shown good results. Therefore, in 2004 a pilot CES-study was initiated in Essen in the northern part of Flanders, Belgium. This report describes four consecutive years of CES-mistnetting and makes recommendations for the future. A future increase of the number of CES-sites in Flanders will be necessary in order to obtain a large enough sample to calculate breeding success and survival rates. This increase will only be feasible when professional and financial governmental support is guaranteed. The pilot study shows encouraging results on timing of the breeding season, condition and age distribution of several marsh- and scrub-dwelling passerines. We also compared the CES-results with a parallel territory mapping in the same study area. This comparison results in a more detailed understanding of the true numbers of each species of breeding bird in the study area.