Récék fészkelő-állományának becslése földi számlálással = Assessing the breeding population of ducks by ground counts

Barabás, Lilla (2008) Récék fészkelő-állományának becslése földi számlálással = Assessing the breeding population of ducks by ground counts. MAGYAR VÍZIVAD KÖZLEMÉNYEK, 16. pp. 267-286. ISSN 1416-1389

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Abstract

Efforts of bird counts date back to several decades and are focused primarly on two problems. One is often to study the population dynamics, which knowladge could be important for both scientifique and practical population management points of view. Secondly, birds are usually good indicators of environmental changes, which is especially true for the mobile group of waterbirds. The diversity of bird count methods reflects the complexity of this problem varying by species, habitats, human approach and possibilities. This explains that within the group of a relatively compact bird group like the ducks (Anatidae), many different ways have been developed to estimate the size of breeding populations. Choosing the optimal method for one’s purpose is a difficult question indeed. We must keep in mind that through these estimation and monitoring efforts the main aim is to be able to interpret these data biologically, meaning to detect cause and effect relationship behind the observed changes. With this last statement in view this paper aims to review the different methods that have been used to assess breeeding population of ducks, while exploring the theoretical and practical background of them. Finally, this study presents a recommendation for a national duck breeding population survey in Hungary. The presented recommendation is in accordance with the guidelines of the Wetlands International (Boyd, 1993) suggesting both pair counts and brood counts during the reproduction period. Pair counts consist of recording pairs, lone drakes and small groups of drakes (2-5 individuals) for dabbling ducks and pairs plus lone drakes for diving ducks. In an avarage year I propose that the ideal would be to count pairs min. 4 times throughout the season, but to intervene at least one count in late March-early April for early breeders and another one in May for late breeders, however the final compromise could be to held at least one count in late April. For brood counts I propose to count the ducklings at least once a week determining not only the numbers but their approximate age as well. I trust that this review paper could be a useful summary for laying the theoretical foundation for a long-missed, well-grounded breeding duck survey adopted to Hungary.

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