The increase in energy consumption by the Man in the last decades has led to a massive power line grid expansion. Power lines cause negative impacts on biodiversity, including habitat loss and fragmentation, and bird mortality through collision or electrocution. Bird collision with cables is, for some species, the major cause of non-natural mortality and the main direct impact associated with transmission power lines (150-400kV).

Many knowledge gaps remain in this thematic area, including a better understanding of the drivers of collision risk, or of the effectiveness of mitigation measures (e.g. anti-collision devices). Even for particularly sensitive species, little is known on the impacts of collision fatality on population-level viability. Additionally, the occurrence of indirect negative impacts, such as exclusion effects, is barely known.

On another hand, transmission power lines can have some positive impacts on birds; examples include the use of pylons as roosts or nesting structures, or the creation of favourable habitat due to the management of rights-of-way.

Thus, there is an obvious need to further increase our knowledge on the interaction between birds and transmission power lines, through state-of-the-art scientific research, as well as boosting knowledge transfer activities to Transmission System Operators (TSO) and other relevant stakeholders.

REN, the Portuguese TSO, is subjected to Environmental Impacts Assessment procedures focused on its infrastructures, including a need for evaluating the negative impacts caused by transmission power lines on biodiversity. Standardization and adequacy of methodologies used in impact assessment studies should be therefore improved so that outcomes and management responses can be based on better scientific support. Additionally, REN also has a historical record (more than 15 years) of bird fatality, outages, and white stork nests monitoring data information, which have a high potential for scientific purposes.