Population and distribution of breeding heron species (Ardeidae) in Euskadi (period 2022–2024)

The Lertxuntxo program, launched in 2022, was created to monitor the breeding populations of herons (Ardeidae) in Euskadi by means of biennial censuses. It aims to generate reliable data on the distribution and abundance of herons breeding within this region. In 2022 and 2024, a total of 26 and 23 breeding points were monitored, respectively, and results show an overall population decline of 7.4% between these two census years. However, if the Cattle Egret Ardea ibis, with a population that declined by 36%, is excluded, an increase in abundance of 32.6% was observed. The large wetland sites of the Álava Plains (Salburua and Uribarri-Ganboa) are the most important breeding localities for herons in Euskadi. Natural and unpredictable factors including drought and predation can lead to the complete disappearance of colonies, which highlights their vulnerability. Thus, it is important not only to preserve the wetlands that currently host heron colonies but also those that could potentially support future colonies, especially if restoration work is performed. In the future the Lertxuntxo program aims to act as a benchmark for assessing the conservation status of herons in the region and guiding policy and action designed to protect their populations.