Artur Goławski, Emilia Mróz, Zbigniew Kasprzykowski, Katarzyna Słupska, Ewa Droś, Paweł Żmińczuk
Ornis Polonica 2014, 55: 162–172
https://doi.org/10.12657/ornis.2014.3.1
Abstract: This paper presents basic breeding parameters of the Black Tern Chlidonias niger studied in 2007–2008 in the valley of lower Bug river in central-eastern Poland. About 240 pairs nested in colonies located at three old river-beds, and 122 clutches were followed and described. The average distance between neighbouring nests was 3.3 m. Outer nest diameter was on average 14.2 cm, the inner one – 8.1 cm, nest depth – 14.7 mm, and nest height above water level – 30.8 mm. First eggs were laid between 13 May and 17 June (mean 22 May). Most clutches contained three eggs. The average egg length was 34.8 mm, width 25.2 mm, while the volume 11.0 cm3. At least one nestling hatched in 75% of nests. The mean number of hatched young per nest was 2.1 and for successful nest – 2.6. Nestlings hatched between 4 June and 9 July. Main reasons for nest failures were nest desertion (55%), nest flooding (28%) and predation (17%). The studied population of the Black Tern, inhabiting natural habitats in the Bug Valley, had relatively high breeding densities compared to other populations in Europe, Asia and North America. Birds started to breed relatively early and hatching success was high. All these data indicate good breeding conditions in the valley of lower Bug river.
Keywords: Black Tern, breeding ecology, Chlidonias niger, tern colony
