Michał Jantarski
Ornis Polonica 2017, 58: 117–139
https://doi.org/10.12657/ornis.2017.2.3
Abstract: In this paper I review all methods of counts of the breeding diving ducks Aythyini and dabbling ducks Anatini, and describe their major methodological problems. The most important difficulties in duck counts constitute the overlapping of timing of spring migration and breeding, as well as breeding and after-breeding movements. Other problems include the lack of territorial behaviour, brood parasitism, variable sex ratio and strong habitat preferences in the Common Teal Anas crecca, Garganey A. querquedula and Northern Shoveler A. clypeata. This paper provides evidence that using only one method of duck counts may lead to strongly biased results. The author recommends using a narrow time window for counts of each species, considering their timing of breeding and migration. Large-area counts, combined with surveys of nests and distressed birds at key breeding sites, have been found the most effective survey method for the diving ducks and the Gadwall. This study has revealed that meadow ducks can be successfully counted at carefully selected study plots of 5–10 km2 in the flooded river valleys within a very short time window. In the diving ducks and Gadwall the number of females is equivalent to the number of breeding pairs. However, in the Garganey and Northern Shoveler counts have to rely on the number of males, whose numbers (due to sex ratio) cannot be equated with the number of breeding pairs. The paper draws attention to the need of duck monitoring in the valleys of most valuable, flooded river valleys, and surveys of the Common Teal in its optimal habitats. The author underlines that studies analysing numbers and temporal trends of the diving and dabbling ducks should describe in detail the methods of counts to allow for their future replication and obtaining comparative data.
Keywords: dabbling ducks, diving ducks, habitat selection, methods of estimation of numbers, sex structure
