Scottish Marine and Freshwater Science Volume 5 Number 16:The Avoidance Rates of Collision Between Birds and Offshore Turbines

Recommendations and Limitations

Definitions ( Section 3)

• Micro avoidance should be defined as 'last-second' action taken to avoid collision, occurring within 10 m of the rotor blades.
• Meso-response should be defined as all behavioural responses, including attraction, in flight deflection and functional habitat loss, to the presence of a turbine occurring more than 10 m from the rotor blades and within the perimeter of the windfarm (500 m from the base of the outermost turbines).
• Macro-response should be defined as all behavioural responses, including attraction, displacement, and barrier effects, to the presence of a windfarm occurring beyond its perimeter (> 500 m from the base of the outermost turbines).
• Where an avoidance rate has been derived by comparing observed collisions to those expected in the absence of avoidance, this should be referred to as within-windfarm avoidance, it is a combination of meso-responses and micro-avoidance.

Recommended avoidance rates

• A macro-avoidance rate of 0.64 is recommended for northern gannet ( section 5.4). However, no data were available to derive a within-windfarm avoidance rate for this species ( section 5.3). Based on the evidence available, there is no reason to suppose that the total avoidance rates for northern gannet should be less than those for all gulls. A total avoidance rate of 0.989 is thus recommended for use with the basic Band (2012) collision risk model. This would reflect a within windfarm avoidance rate of 0.970. We acknowledge that this is precautionary, but in the absence of more species-specific data, we feel it is appropriate. It was not possible to recommend an avoidance rate for use with the extended Band (2012) collision risk model based on the evidence available at present.
• No consistent evidence of macro-avoidance was found for black-legged kittiwake ( section 5.4). As it was not possible to derive species-specific within-windfarm avoidance rates for black-legged kittiwake, the within-windfarm rates derived for the small gulls group were considered appropriate for use for this species ( section 5.3). A total avoidance rate of 0.992 is thus recommended for the basic Band model. It was not possible to recommend an avoidance rate for use with the extended Band (2012) collision risk model based on the evidence available at present.
• No consistent evidence of macro-avoidance was found for lesser black-backed gull ( section 5.4). Whilst it was possible to derive species-specific within-windfarm avoidance rates for lesser black-backed gull, these were based on limited data and thus the within-windfarm avoidance rates for large gulls were considered more appropriate for use for this species ( section 5.3). A total avoidance rate of 0.995 is thus recommended for use with the basic Band model and a total avoidance rate of 0.989 for use with the extended Band model ( section 7).
• No consistent evidence of macro-avoidance was found for herring gull ( section 5.4) and thus total avoidance rates reflect species-specific within-windfarm avoidance rates. A species-specific total avoidance rate of 0.995 is thus recommended for use with the basic Band model and a total avoidance rate of 0.990 for use with the extended Band model ( section 7).
• No consistent evidence of macro-avoidance was found for great black-backed gull ( section 5.4). As it was not possible to derive species-specific within-windfarm avoidance rates for great black-backed gull, the within-windfarm rates derived for the large gulls group were considered appropriate for use for this species ( section 5.3). A total avoidance rate of 0.995 is thus recommended for the basic Band model and a total avoidance rate of 0.989 for use with the extended Band model ( section 7).
• Given the multiple ways in which data can be interpreted, it is vital that future studies in which avoidance rates are derived are completely transparent and present their workings as a step-by-step process. Appendix 7 enables the reader to go back to the original source material and fully understand how the values presented in this report have been derived. This also offers an indication of the uncertainty present in the derived values.
• Based on the available data, it was not possible to derive species-specific avoidance rates for three of the five priority species. Of particular concern is the lack of within-windfarm avoidance data for northern gannet given that it is taxonomically distinct from the other four species, all of which are gulls. Future projects should focus on collecting data for northern gannet as a priority. Given the limitations in the data we identified for macro-responses, especially for gulls, there is also a need to collect further data on barrier effects and displacement/attraction rates.