Effectiveness of bird flight diverters

Bird flight diverters are used around the world both for high-voltage and extra-high voltage power lines in order to prevent birds colliding with overhead power lines and to reduce the associated mortality. Studies on the effectiveness of different diverters confirm a degree of effectiveness by bird flight diverters, but also show that there are considerable differences in terms of the different models of diverters, the bird species group and environmental variables. The aim of this research concept is therefore to analyse and assess the species-specific effectiveness of different bird flight diverters, to describe and evaluate the effect of boundary conditions and to prepare recommendations and the draft of an expert agreement for the next steps.

Methods

The first step involved a literature review focused on the topics of bird collisions and bird flight diverters. Current literature including national and international publications was summarised and analysed. The analysis of the available literature in terms of type of overhead power lines, type of diverter, bird species and bird behaviour, environmental variables and research methods will be presented as a meta-analysis in a database of the results.

Following this, the results and evaluations obtained from the literature survey will be assessed in terms of their factual reliability through surveys of national and international experts. A convention proposal will be developed on the species-specific effectiveness of different bird flight diverters. The aim of the first expert workshop is to discuss and further develop this draft proposal; the second will present and if necessary adapt the draft of the expert agreement.

The aim of the project was to compile information about the effectiveness of bird flight diverters including particular species. This was based on an international literature review, expert consultations using questionnaires and running an expert workshop.

The focus of the project was to develop a coordinated proposal for an agreement to evaluate the species-specific effectiveness of bird flight diverters. From the review of literature sources on the topic of bird collisions with overhead power lines and their prevention through the use of power line markers it was shown that the collision reduction effect of bird flight diverters shows very large species-specific differences, and reliable results only exist for a very few species to date.

Despite this, it was possible to obtain results on mortality reduction figures from studies on different species of birds (=reference species). In a second step, following specific rules, the results from these reference species were applied by means of analogous conclusions to species for which there is so far no proof of the effectiveness of bird flight diverters. This enabled statements on the effectiveness of diverters for a large number of bird species.

The resulting convention proposal will be agreed in an expert consultation.

In view of the expansion of the high voltage and extra-high voltage network required for the energy transition, there is a need in the impending approval procedures to fulfil the legal requirements of species and site protection in terms of the mortality risk in a technically reliable and legally secure manner. The aim of the research project is to develop an expert convention proposal on the species-specific effectiveness of bird flight diverters. This will require a rational classification of the reduction effect of bird flight diverters for bird species at risk from collisions. This applies in particular to species for which there are no studies on reducing collisions at power lines.

The expert convention proposal aims for an evaluation of the species-specific collision risk for birds resulting from the construction of new high-voltage and extra-high voltage power lines and forms the basis for evaluating the species-specific reduction effect of bird flight diverters (reduction of the project-related mortality risk). It will be used depending on the range of bird species at the site and the local conditions.

• Liesenjohann, Monique et al. (2020) Wirksamkeit von Vogelschutzmarkern – Ein Fachkonventionsvorschlag zur Minderungswirkung an Freileitungen, Natur- und Landschaftsplanung 04/2020, page 184 (includes a summary in English)

• www.bioconsult-sh.de

• www.bioconsult-sh.de/de/projekte/bfn-geforderte-projekte/