Wintering water rails Rallus aquaticus in Aust-Agder county, South Norway

Abstract

We report the results from censuses of wintering Water Rails along the coast of Aust-Agder county, South Norway, carried out during seven consecutive seasons by using play-back calls. The species is regularly found during mid-winter in this part of the country, with up to 103 birds found in a single season. However, the number fluctuated considerably between years, and there was a positive correlation between total rail numbers and the average autumn temperature (October – December) each year. Data from one of the years showed that the number of birds declined before early spring, but it is not known whether this reduction was caused by mortality, emigration or other factors. The rails generally responded strongly to play-back, most often by replying with the «pig squealing call». Even so, some birds hardly vocalized at all, and a few were totally silent. Hence, the number of birds recorded in this kind of study must be regarded as minimum counts.