Visual markers applied to power lines can help to attract flying birds’ attention earlier and avoid collision. Thus, grid operators apply “wire markers” (or bird flight diverters - BFDs) to lines in high-risk areas.

There are many products on the market, provided by different developers. Quantifying their effectiveness is no easy task: it is influenced by many contextual factors. However, scientists generally agree that wire markers can indeed reduce collision risk. For grid operators, factors like durability, cost, and technical implications are important considerations.

All things considered, it can be difficult for grid operators to decide which wire marker is best suited to their specific case.

The purpose of this brochure is to provide a visual summary of available research on wire marker effectiveness and the factors influencing collision risk, to help inform the decision basis for collision-risk mitigation measures.

The initiative consists of several documents, namely:

1. Brochure - to give an abridged, user-friendly overview on the topic and available research.
2. Methodology Report - a more comprehensive overview of the current state of research regarding the susceptibility of birds to collision.
3. Study Summary Table - a review of 50 studies into the effectiveness of wire markers.
4. Annex I - Translated summary of relevant German studies and guidelines on wire marker effectiveness and evaluation of bird susceptibility to power line collision.
5. Annex II - Translated 'Similarity Index' on the effectiveness of wire markers for bird species which have not yet been subject to study (from Liesenjohann et al., 2019).