Colonies of herons and other allied waterbirds breeding in Sicily, 2007-2022

We describe the results of the first regional census of herons and other colonial water- birds, including Great Cormorants Phalacrocorax carbo, Little Bitterns Ixobrychus min- utus, Black-crowned Night Herons Nycticorax nycticorax, Squacco Herons Ardeola ralloides, Western Cattle Herons Bubulcus ibis, Grey Herons Ardea cinerea, Purple Herons Ardea purpurea and Little Egrets Egretta garzetta, carried out throughout Sicily from 2007 to 2022. We also collected data about Great Egrets Casmerodius alba and other waterbird species in Ardeidae colonies without any breeding evidence, as Eurasian Spoonbills Platalea leucorodia and Glossy Ibis Plegadis falcinellus. Collected data highlighted a regional widespread increase of the numbers in known colonies and nests of each species, especially of Bubulcus ibis that showed a sharp increase in number from 30 nests recorded for the whole region in 2007 up to 530 nests in 2022, mainly concen- trated in eastern Sicily, in the province of Catania. Also A. ralloides, N. nycticorax and E. garzetta showed a positive trend with an increase in the number of colonized locations and nests recorded, with A. ralloides occupying the most of the Sicilian colonies with at least few pairs. On the other hand, A. cinerea showed a slight negative trend, with 45 nests recorded in 2007 and only 31 in 2022, at the end of the study; A. purpurea is an irregular breeder with an oscillating and unpredictable trend related to only 1–4 ascer- tained pairs maximum for the whole region. Despite the P. carbo is a regular breeding species in Sicily, it has not showed any sign of expansion in the last decade, remaining confined to a few historical locations near the Simeto River and Lentini Lake. All data here presented are related to the minimum and ascertained numbers of colonies and counted nests. Small colonies may not have been counted in some unmonitored loca- tions, often inaccessible. It is highly recommended, in the near future, the creation of a coordinated survey network that would improve and make the census more in-depth and better standardized