Offshore wind energy - sectoral marine plan: seabird tagging feasibility

Conclusion and Recommendations

Data from tagging projects offer the potential to significantly reduce the uncertainty associated with assessments of the impacts of offshore wind farms on seabird populations. This relates to both a better understanding of the distribution of the species concerned, and a better understanding of how birds may interact with wind farms, and therefore the potential risks posed by collision and displacement. Consequently, new tracking data, both from the breeding and non-breeding seasons, will be valuable for helping to determine whether projects proposed for Plan Options NE2-NE6 and E3 can be released from the highest levels of ornithological constraint, as well as improving the evidence base available for impact assessments in these and other regions.

Extensive tracking data have been collected from colonies on the Scottish East coast of relevance to the ScotWind Plan Options. However, since the FAME and STAR projects were carried out between 2010 and 2015, the focus for much of this work has been colonies in and around the Firth of Forth in support of offshore wind farm developments proposed for that region. A key exception to this has been a geolocator study carried out at multiple sites between 2017 and 2020 on guillemots and razorbills (Buckingham et al., 2021). Consequently, there is a lack of more recent data for SPAs further north, which are of more relevance to the projects proposed as part of ScotWind.

Work proposed for Fowlsheugh and Buchan Ness to Collieston Coast SPAs in the 2023 breeding season will help to fill some of the data gaps, though additional data are required from sites further to the North. However, additional visits are required to these sites during the 2023 breeding season, both to confirm the availability of accessible nests, and to assess the feasibility of tagging work following the 2022 HPAI outbreak and any subsequent outbreaks in 2023. Following an initial assessment of sites in autumn 2022, colonies within East Caithness Cliffs and Copinsay SPAs should be prioritised for these assessments, with a view to carrying out tagging at these sites in the 2024 breeding season. Tagging work at Troup, Pennan and Lion’s Heads SPA may be less feasible, though viewing the site from the sea during the 2023 breeding season would be valuable to confirm this. Similarly, a visit to Stroma, within the North Caithness Cliffs SPA, would also be valuable.

Any future projects, in addition to those planned for the 2023 breeding season, will require substantial planning time. Tag orders should be placed by December in the year before planned summer deployment in order to allow sufficient time for the delivery, testing and programming of any devices. This will require discussion of key study objectives (e.g. purely distribution data, or behavioural data such as flight heights in addition) well in advance of this so that an optimal solution can be agreed between the contractor(s) and their funder(s). Careful consultation and collaboration with other researchers carrying out related tracking work should be strongly encouraged to ensure the greatest value can be obtained from any data.

Of the species considered in this review, substantial GPS tracking work is already taking place on gannets at the Bass Rock. Capturing gannets within either the Troup, Pennan and Lion’s Heads SPA, or the Fair Isle SPA does not appear feasible. Consequently, it is recommended that no additional tracking work at either site is planned at the current time. Similarly, questions remain about the potential for device effects on both puffins and great black-backed gulls. Unless, and until, these questions can be satisfactorily addressed, it is concluded that GPS tracking data on these are unlikely to be available to support the ScotWind process. For future work, as set out in the Roadmap of Actions, exploring appropriate attachment methodologies for great black-backed gulls should be a priority.

For the remaining species, ensuring sufficient data are collected to characterize colony home ranges during the breeding season should be a priority. Sample size analysis suggests that increasing deployment duration is a key part of generating sufficient power to enable this. Consequently, archival GPS tags are not recommended and, given the patchiness of GSM Network coverage at many of the proposed field sites, tags that download data remotely to a base station are recommended. Such tags can potentially collect data for periods ranging from one month to in excess of a year (Figure 49). However, possible attachment methodologies for kittiwake, guillemot and razorbill mean that generating sufficient data to characterize home ranges in a single year is likely to be extremely challenging (Figure 49). This is not necessarily a problem given that recent analyses have highlighted that data collected across multiple years can provide a robust assessment of a species home range in relation to its breeding colony (Beal et al., 2023). Recommendations for GPS deployment on each species are as follows:

• Herring gull – GPS VHF with body harness
• Kittiwake – GPS VHF with tail mount and further trials of glue-mounting to birds’ back to facilitate longer deployment
• Guillemot – GPS VHF back-mounted with Tesa tape
• Razorbill – GPS VHF back-mounted with Tesa tape

Tags should be deployed in the late incubation/early chick-rearing stage (Figure 49) to minimise the risk of desertion. Careful consideration should be given to deploying devices such as Time-Depth Recorders and altimeters alongside the GPS tags to collect additional behavioural data.

For geolocators, estimated wintering distributions did not reach a plateau, although analyses suggested they were levelling off when in excess of 30 geolocators were retrieved. Previous studies highlight that retrieval rates can vary between species, and may be lower for razorbills than is the case for guillemots (Buckingham et al., 2021). Such differences should be taken into account when planning geolocator studies. Whilst additional geolocator data for guillemots and razorbills would be valuable, the lack of a large-scale geolocator study to determine kittiwake non-breeding season distributions for Scottish breeding colonies mean this species should be prioritised. Tags should be mounted on leg rings and, as with GPS tags, deployed during the chick rearing period to minimise the risk of desertion. Tags should then be retrieved the following breeding seasons.

All existing and future tagging studies must be licensed by the SMTP and secure licences and permissions from NatureScot and local landowners where appropriate. All guidance put in place in response to HPAI must be followed and due consideration given to all aspects of Health & Safety during fieldwork.