Current state of the Grey Heron Ardea cinerea and Cormorant Phalacrocorax carbo populations in the Silesian Ornithological Region

The Grey Heron Ardea cinerea bred in Silesia on 24 sites concentrating a total of 1860 breeding pairs. The number of occupied nests per site varied from 1 to 240 (average 77.5; median 33.5). The largest colony was located in downtown Wrocław (240 pairs). 55% of the colonies were situated entirely on the mainland, 25% on islands, 20% in willow beds and reedbeds. 23 colonies were built on trees or bushes and one (on Przemkowskie sh ponds) in a reedbed. The 19 tree colonies were located on a total of 439 trees from 13 genera. e average number of nesting trees in a colony was 25.7 (8–57), and the most commonly used were pines Pinus sp. (35%), alders Alnus sp. (17%) and oaks Quercus sp. (15%). The largest number of nests were recorded on alders (24.3%), pines (21%), willows Salix sp. (16.2%) and oaks (15.2%). The distance from the nearest human settlement ranged from 40 m to 3000 m (average 509 m, median 295 m). As many as 92% of sites were located less than 500 m from nearest buildings. The Silesian Grey Heron population probably keeps growing slowly, while also expanding into the new areas – Upper Silesia and Sudetes. In 2020 it accounted for over 16.6% of the national Grey Heron population. The breeding population of Cormorant Phalacrocorax carbo in Silesia remained stable over the years 2015–2020 and amounted to 744–1056 breeding pairs in 10 sites (which constituted 3.8% of the national population). The clear majority was concentrated in this period on four most regularly occupied sites – Stawno and Radziądz ponds, Dzierżno Duże and Goczałkowicki Reservoirs, the last one being currently the most important colony in the region (accounting in 2020 for over 53% of the Silesian population)