Guidance Note 4: Guidance to Support Offshore Wind Applications: Ornithology - Determining Connectivity of Marine Birds with Marine Special Protection Areas and Breeding Seabirds from Colony SPAs in the Non-Breeding Season

Published: 2023
Version 1: January 2023

This document is part of a series of guidance notes available on Advice on marine renewables development - marine ornithology.

This guidance note sets out our advice on determining connectivity of marine birds with marine Special Protection Areas and breeding seabirds from colony SPAs in the non-breeding season.  Please see Guidance Note 1 - Guidance to support Offshore Wind Applications: Marine Ornithology which provides the context within which this guidance note is provided. Check the log of updates in guidance note 1 to ensure the most current version is being followed. We expect each and every developer to adhere to this guidance, including the recommended parameters to provide consistent and comparable results for all Scottish projects to be assessed as an individual project and cumulatively.  This guidance note should be used in conjunction with the Cumulative Effects Framework (CEF).

Please note this guidance was written prior to the development of a NatureScot position on how to account for the ongoing Highly Pathogenic Avian Influenza (HPAI) mortality event within an impact assessment. We are currently developing this advice and will provide updates and guidance when they are available. In the interim please contact [email protected]  should you have any specific queries.

1. Introduction

A key initial stage of a Habitats Regulations Appraisal (HRA) for a proposed offshore wind project is screening for Likely Significant Effect (LSE), which requires identifying potential connectivity between the qualifying marine bird features of Special Protection Areas (SPAs) and the project site. Please see NatureScot’s HRA guidance for further information. 

If connectivity is established, an HRA will, generally, need to be undertaken to ascertain whether there is Likely Significant Effect (LSE) and, if so, the potential for adverse effects on site integrity (AEOSI) of the SPA(s) concerned. Typically, this will require consideration of site characterisation survey results, information on impact pathways, and the sensitivity of the species to potential impacts. Further information on feature sensitivity, can be found at Marine Scotland’s Feature Activity Sensitivity Tool (FeAST). Please note the marine bird assessments are awaiting publication.

Marine SPAs have been classified in Scottish waters for inshore wintering waterfowl (divers, sea ducks and grebes); foraging areas for breeding terns; foraging areas for breeding red-throated divers; important areas for European shags, foraging aggregations of true seabirds (both breeding and non-breeding) and wintering gulls. The purpose of these marine SPAs is to protect the birds when in these sites as well as the rich feeding grounds and habitats that they and their prey species depend upon.

The approach to determining connectivity during the breeding season with a colony SPA(s) and/or breeding territory for red throated divers is straightforward as both breeding seabirds and red throated divers are regarded as centrally-placed foragers (as they commute from their nest location/colony to foraging grounds) and have a maximum foraging distance they will travel from their nest/ colony. Our advice relating to connectivity to breeding colony SPAs is addressed in Guidance note 3: Marine Birds - Identifying theoretical connectivity with Breeding Site Special Protection Areas using breeding season foraging ranges. However, during the non-breeding season, when species are not spatially restricted by breeding constraints, determining connectivity is more complex. 

This guidance note first sets out key considerations for connectivity between offshore wind farm development areas and marine SPAs, then sets out how we advise connectivity is assessed for marine SPAs.  We also include advice on connectivity for seabirds from colony SPAs in the non-breeding season.

2. Key considerations for assessment for marine SPAs

In contrast with how we approach HRA for seabirds in breeding season (where theoretical connectivity, based on species-specific foraging ranges, is considered first and then refined to determine Likely Significant Effect (LSE) based on development specific information and impact pathways), for marine SPAs, the impact pathways underpin potential connectivity and LSE. We therefore set out some of these specific impact pathways considerations below. Please also see Guidance note 6: Marine Ornithology Impact Pathways for Offshore Wind Developments for other marine ornithology impact pathways.

When a European site, such as a marine SPA, is classified there is a requirement to provide site specific Conservation and Advice Management (CMA) documents which include the Conservation Objectives for the site. These can be found on SiteLink.  As part of the application process should an HRA be required this will require the development project impacts to be assessed against the site’s conservation objectives.

For all marine SPA qualifying features, we advise that the following points are considered with regard to impact pathways and determining LSE:

Key considerations:

1. Will the development cause any injury or mortality to the qualifying features either within or outwith the marine SPA?
2. Will disturbance/displacement result in a redistribution of birds within the marine SPA? It is important to consider all aspects of the development including associated works and activities, e.g. wet storage locations, cable routes or vessel movements associated with construction, operation including maintenance and repair or decommissioning works.
3. Will the development provide a barrier in terms of access to birds flying to or from the marine SPA (e.g. commuting to roosts off-site, breeding locations)? Flight direction data or tracking studies may be helpful in determining if there are any important commuting routes.
4. Are there any direct impacts on prey or supporting habitat within the marine SPA? For example a cabling route within or directly adjacent to a marine SPA or barriers to fish movement that may impact on prey populations and habitats within the SPA.
5. Are there any indirect impacts on supporting habitats and supporting processes e.g. water flow or quality that may alter the foraging resource? Consideration is required for when there is an impact pathway which affects the ability of the marine SPA to maintain the current extent, quality and distribution of supporting habitats, as well as ensuring a sufficient food supply within the site.

3. Overview of connectivity to marine SPAs

For inshore wintering waterfowl, little gull, Manx shearwater and non-breeding seabirds, we have applied a generic 15km buffer within our GIS tool.  This should be applied to all elements of proposed developments, including  cable routes, wet storage locations, and routes for related vessel traffic (if known) to inform inclusion of marine SPA qualifying features within the long list.  This allows for an audit trail for screening LSE, however, it is important that impact pathways that can affect features or habitat within the marine SPA even though they are more than 15km from the SPA boundary relevant at project level are considered even where these fall outside of the 15km buffer.  Further details on each of the species groupings are considered separately below in sections 3-7.

We advise that the key considerations outlined above are taken into account across all species groupings.

4. Determining connectivity for inshore wintering waterfowl qualifying features of marine SPAs

For all inshore wintering waterfowl qualifying features of marine SPAs to determine LSE impact pathways need to be considered within 15km of the marine SPA.  

In addition to this, the proximity to migratory flyways should be considered qualitatively in relation to the offshore wind development. There is an ongoing Marine Scotland project to include an updated review of flyways and provision of a migratory collision risk modelling tool. Prior to this being published the WWT and MacArthur Green. 2014. Strategic assessment of collision risk of Scottish offshore wind farms to migrating birds. Scottish Marine and Freshwater Science Report: 5(12). review should be used.

In addition, when assessing the impacts from land-based activities (i.e. cable landfall, grid connection) connectivity to marine SPAs for inshore wintering waterfowl may require consideration. In these cases, further discussion may be required with NatureScot.

5. Determining connectivity for wintering gull qualifying features of marine SPAs

Marine SPAs with wintering gulls as qualifying features are designated primarily due to their importance as a roosting site. During the winter months gulls use roosts with a similar centrally-placed foraging behaviour to breeding seabirds. As well as assessments on impact pathways within the marine SPA, connectivity to functionally linked foraging habitats on land (including adjacent shorelines and inland sites) and sea outwith the SPA should also be considered. Wintering gulls will also use the marine SPA itself for foraging.

In the absence of specific gull wintering foraging ranges, we currently recommend that connectivity for wintering gulls using the marine SPAs is determined using the recommended breeding foraging range distance, as per Woodward et al. 2019 (with the exception of Little Gull – see below). We acknowledge more recent tracking studies of gull species during the non-breeding season are currently being undertaken. As and when data is published from these studies, we will review and update this guidance as necessary.

There is currently no foraging range information for little gull.  As for inshore wintering waterfowl features, our GIS tool applies a generic 15km buffer for little gull.       

In addition when assessing the impacts from land-based activities (i.e. cable landfall, grid connection etc.) connectivity to marine SPAs for wintering gulls may require consideration. In these cases further discussion may be required with NatureScot. 

6. Determining connectivity for breeding seabird qualifying features of marine SPAs

We recognise that seabird populations using the marine SPAs during the breeding season likely includes breeders from multiple colonies within foraging range as well as non-breeders and juveniles.  For breeding seabirds within marine SPAs, the population level consequences will be addressed through consideration of connectivity from functionally linked seabird colony SPAs i.e. using the recommended ‘at sea’ foraging ranges, as defined by Woodward et al. 2019 (see Guidance note 3: Marine Birds - Identifying theoretical connectivity with breeding site Special Protection Areas using breeding season foraging ranges).

Information on extent of potential connectivity for non-breeders, sabbatical and juveniles during the breeding season is currently not available. Non-breeders, sabbaticals and juvenile connectivity should therefore be assessed as for breeding adult seabird qualifying features.

The exception for breeding seabird connectivity is Manx shearwater within the Outer Firth of Forth and St Andrews Bay Complex SPA, which may be a mixture of breeding birds from several colonies, sabbaticals, pre-breeding birds and possibly failed breeders.  Further research is required to assess which colonies the Manx shearwaters using the Outer Firth of Forth and St Andrews Bay Complex SPA originate from.

7. Determining connectivity for non-breeding seabirds

This includes non-breeding seabirds that are qualifying features of the marine SPAs and breeding seabirds from colony SPAs during the non-breeding season.

For all non-breeding seabird qualifying features of marine SPAs to determine LSE, impact pathways need to be considered within 15km of the marine SPA. 

For breeding seabirds from colony SPAs during the non-breeding season, to determine which colony SPAs have connectivity with a marine energy development site the BDMPS Report, Furness, R.W. 2015. Non-breeding season populations of seabirds in UK waters: Population sizes for Biologically Defined Minimum Population Scales (BDMPS). Natural England Commissioned Report: 164 should be used. The exception to this is common guillemot as more recent studies show they largely remain in the broad vicinity of their breeding colonies during the non-breeding season (Buckingham et al. 2022). For this species, we advise the non-breeding season population comprises the breeding population found within the MMFR+1SD (mean max foraging range) of the development + age classes, (refer to our breeding season advice Guidance note 3: Marine Birds - Identifying theoretical connectivity with breeding site Special Protection Areas using breeding season foraging ranges for mean max foraging range).

We acknowledge more recent tracking studies during the non-breeding season are being undertaken. As and when data is published from these studies, we will continue to review and update this guidance as necessary.

8.  Determining connectivity for breeding red-throated diver qualifying features of Marine SPAs

For breeding red-throated diver the marine SPA is designed to protect foraging areas for breeding red-throated diver, therefore covers inshore waters most likely to be used by red-throated diver. The marine SPA population is estimated as the numbers of breeding pairs within a 10km range of the marine SPA, and may include red throated divers from breeding SPAs on land, as well as from non-SPA sites.

For breeding red-throated divers within marine SPAs population level consequences will be addressed through consideration of connectivity from functionally linked breeding sites within 10km (refer to the relevant marine SPA CMA documents for the list of relevant SPA(s)), noting that any SSSIs and non-designated breeding sites should be listed too. As with all other marine SPA features, additional consideration may be required for red-throated diver using the marine SPA, where there are impact pathways affecting the ability of the site to maintain the current extent, quality and distribution of supporting habitats within the site as well as ensuring a sufficient food supply within the site.

9. Identification of long list of connected SPAs

Once the initial list of SPA qualifying features with theoretical connectivity is produced, it can be refined further. Agreement on the refinement of the long list should be discussed as part of pre-application discussions with NatureScot.

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