Nest site location and breeding success of Common kingfisher ( Alcedo atthis ) in the Danube river system

Abstract

Common kingfisher, Alcedo atthis is a fish-eating species that preferentially breeds alongside natural watercourses or smaller water bodies. During the seasons 2012, 2014 and 2015, we monitored the density of kingfisher population, nest site location and its breeding success in the Danube river system from Bratislava to Gabčíkovo (Slovakia). Population density was estimated on 23–27 pairs/55 km of the length of river branches. Average distance between nesting holes occupied by different breeding pairs was 816 m ± 421 SD. Kingfishers used river banks and wind throws to dig a burrow. The nest site location, but not nest parameters, was affected by the maximal height of the suitable area of the wall. As wind throws had larger suitable area, the location of nests in wind throws differed from the location in riverbanks. Breeding attempts were successful in 86% cases. The reason of unsuccessful breeding was mainly predation. Almost 72% of pairs bred two times per season, 17.9% of pairs three times and 10.7% of pairs four times per season. The most successful were the second and the third breeding attempts. Breeding pairs produced on average 6.43 young per successful breeding and 14.95 young per season. In total, 58% of pairs alternated breeding attempts. The rest of pairs overlapped attempts using different holes. Average distance between the holes concurrently used by a pair was 113.73 m (min = 0.3 m; max = 372 m). Neither this parameter nor the date of the first egg-lying in previous attempt affected the duration of the overlapping.