Birds nesting on pylons of transmission lines in Portugal: results of the first national-scale survey with proposal of measures to promote and protect species of conservation concern

This study, conducted within a Portuguese TSO-Academia partnership, comprised (i) a general survey of birds nesting on pylons of transmission lines in Portugal, between 2021 and 2023; and (ii) an annual monitoring programme, launched in 2021, targeting nationally threatened species nesting on pylons to assess nest occupation and breeding success.

In the general survey, from nearly 2000 pylons inspected by ground observation, nests were found on 1,056 pylons, occupied by 14 bird species. White stork was the most frequent species, with 4,227 nests on 1,030 pylons. Other nesting species included three sparrows, one starling, one myna, three corvids, four diurnal raptors and one owl. The annual monitoring programme covered: four nests of Bonelli’s eagle Aquila fasciata, two of which with consistent occupation and breeding success in 2021-2025 period; and one nest of Osprey Pandion haliaetus, detected in 2025, also with breeding success, representing an important contribution for the population recovery after a decade of extinction and a reintroduction programme.

This study shows a remarkable diversity of bird species nesting on the Portuguese transmission pylons, extending well beyond the emblematic White stork. Recommendations for TSOs are proposed to improve nest management and safeguard threatened and sensitive species.