Katarzyna Żółkoś, Włodzimierz Meissner, Marek Kalisiński, Ewa Górska, Maria Mellin, Iwona Ibron, Dariusz Wysocki
Ornis Polonica 2010, 51: 30–42
https://doi.org/10.12657/ornis.2010.1.3
Abstract: The present paper discusses the results of the censuses updating the information about the colonies of the Grey Heron Ardea cinerea in northern Poland for the period 1999–2009. In the decade mentioned, 76 heronries were noted: most of them in the western part (29 colonies), slightly fewer in the eastern (26 colonies) and central (21) section of northern Poland. The colonies under analysis comprised a total of 4654 nests of the Grey Heron, their number was evenly distributed in the three distinguished regions. The average size of the colonies (the median) in northern Poland amounted to 37 nests. Among the 76 colonies recorded, 16 were established on islands on lakes, and their proportion differed significantly between the regions: the highest was noted for the eastern region (50%), and a clearly lower in the western and central (10% each). Of the16 colonies situated on islands, as many as 15 (94%) represented mixed colonies of the Grey Heron and the Cormorant Phalacrocorax carbo. Among the colonies situated on the land, merely 4 out of 60 were mixed (7%). All the heronries were established in trees, the greatest number of them in pine stands (43%). The highest number of the colonies were found in tree-stands aged 81–100 years, yet, quite a substantial share (9%) of the youngest stands category (21–40 years) is worth noting. Of the 76 colonies, 10 (13%) have been taken under protection within nature reserves. In those reserves 2 of the 4 largest colonies, grouping over 200 nests, are situated.
