Seabirds: strategic ornithological compensatory measures: review

1 Results summary

The following pages summarise the key findings of this report using tables, figures, and fact sheets. This starts with a table summarising high-level evaluations for several general aspects across all measures, followed by more detailed summaries of key sections. For detailed information please refer to the corresponding sections of the report.

1.1 Summary for all compensatory measures considered in the review

Table 1 provides an overview of all compensatory measures considered within the report with very high-level findings presented. Note that these measures are being considered specifically within the context of strategic compensatory measures and with current knowledge. We have not evaluated the measures in terms of their use for wider conservation purposes which would require consideration of different criteria with consequent changes in scoring.

Table 1. Summary findings across all potential compensatory measures considered in the report. Measures are ordered as per Table 4. Costs are a very high-level relative estimate of direct costs of implementing measures only and have high uncertainty (i.e. these do not include any indirect costs, e.g. to loss of earnings etc resulting from the implementation of a measure). For measures not considered in the practical feasibility assessments (section 7), overall feasibility was not assessed, however we score these qualitatively in terms of their potential as compensatory measures.

This table can be viewed in Excel format.

1.2 Systematic literature reviews assessing ecological feasibility summary

Compensatory measures that corresponded to clearly defined and specific conservation actions were assessed through systematic literature reviews. All compensatory measures were scored on ecological efficacy and confidence in the evidence. Results are summarised below in Table 2 and in Figure 1.

Table 2. Summary of the ecological feasibility for those compensatory measures assessed via systematic literature reviews. Links are provided to the corresponding document sections providing the underlying detailed information. It is also noted whether the measures were assessed for practical feasibility. Measures are in reverse order of ecological efficacy scores, from highest to lowest. For colour coding, see key below table.

This table can be viewed in Excel format.

1.3 Scoping and targeted reviews summary

For compensatory measures that did not correspond to clearly defined and specific conservation actions, scoping reviews were used to identify conservation actions that may have potential as compensatory measures. In one case (bycatch mitigation in longline fisheries) a targeted review was used to summarise the evidence for a measure that had recently been reviewed outwith this study. Table 3 provides a qualitative assessment of the potential of the conservation actions identified.

Table 3. Summary of conservation actions identified for the five compensatory measures assessed through scoping or targeted reviews. Potential was assessed qualitatively only (colour scale is as for Table 2, though scoring is not directly comparable).

This table can be viewed in Excel format.

1.4 Practical feasibility summary fact sheets

Compensatory measures deemed ecologically feasible and potentially practically feasible, were assessed for practical feasibility. The following fact sheets provide a summary of the findings. However, we strongly encourage readers to refer to the corresponding report sections to gain a full understanding of how these conclusions were reached and to understand the caveats around these.

The ‘type of measure’ section (at bottom of fact sheets) uses the following classification:

• General: actions that act over a wide area, and
• Site: actions applied at one or more sites;
• Direct: where action benefits the species directly (e.g. predator management), and
• Indirect: actions that are some steps removed from seabird population response (e.g. reducing fishing may increase prey abundance which may then lead to population level responses in seabird populations).

Sandeel fishery closure

Action: Sandeel fishery closure

Ecological aspects (WP1 and WP2)

Species that may benefit

With low certainty: Kittiwake, Guillemot, Razorbill, and Puffin.

Increased:

• foraging efficiency,
• diet quality,
• chick provisioning and parental care,
• productivity, and
• survival

in a mid- to long-term.

Scalable?

No. Would apply to a wide geographical area.

Scale and degree of population benefit

Over several years prey-base could increase. Subsequently, increases in seabird productivity and survival may be observable.

Effects will be observable at local, regional, and national levels, especially in the east and north-east of Scotland, where fisheries are active (beyond the previously closed area covering a large part of the east region).

Other ecological benefits

• Enhance ecosystem resilience, and overall ecosystem stability.
• Increase in populations of other species foraging on Sandeel.

Risk of not doing

Risk assessed as low–medium, as fishery pressure is low compared to historical levels.

Practical aspects (WP2)

Other benefits

• Increase of tourism and recreational opportunities.
• Benefit to pelagic fisheries.

Implementation time

Implementation could take a few years.

Government intervention? Yes (lead).

Key considerations

• International political opposition, as quota is shared with other countries.
• Displacement of fisheries to other fish species and/or regions.
• Socio-economic impacts to those involved with affected fisheries.
• Lag effects for seabird population responses from changes in fisheries management may limit ability to detect a subsequent population level response.
• Increase of tourism and recreational opportunities.
• Benefit to pelagic fisheries.

*This measure was evaluated prior to the announcement of a Sandeel fishery closure in Scottish Waters in early 2024.

Uncertainties

The abundance of Sandeel is not only regulated by industrial fisheries, but also by predatory fish populations, competition for food sources, and changes in environmental conditions. Consequently, predicting the response of Sandeel populations to fishery closures, is highly challenging. It is even more challenging to quantify and predict the broader effects of fishery closures on the demography of the predator species themselves (i.e. seabirds).

Implementation could take a few years.

Type of measure: General – indirect

Ecological efficacy: Low–medium

Overall feasibility: Low–medium

Fishery closure or enhanced management of prey fisheries

Action: Fishery closure or enhanced management of prey fisheries, focused on Sprat and Herring

Ecological aspects (WP1 and WP2)

Species that may benefit

With low certainty, but likely:

Kittiwake, Guillemot, Razorbill, Puffin, terns, Red-throated Diver, Fulmar, Shag, skuas.

Likely minimal benefit: Large gulls and Gannet.

Increased:

• foraging efficiency,
• diet quality,
• chick provisioning and parental care,
• productivity, and
• survival

in a mid- to long-term.

Scale and degree of population benefit

Over several years prey-base could increase. Subsequently, increases in seabird productivity and survival may be observable. Effects will be observable at local, regional, and national levels, especially in the North Sea. There is considerable uncertainty in the scale of benefits, but these could be moderate.

Other ecological benefits

• Enhance ecosystem resilience, and overall ecosystem stability.
• Increased populations of species feeding on Sprat and Herring.

Risk of not doing

Risk assessed as low–medium, as fishery pressure is low compared to historical levels.

Practical aspects (WP2)

Other benefits

• Increase of tourism and recreational opportunities.
• Benefit to other fishing industries.

Potential management options

• Total Allowable Catches (TAC)
• Limits of time at sea
• Full and/or regional closures
• Partial and/or temporal closures
• Fishing gear restrictions

Government intervention? Yes (lead).

Key considerations

• International political opposition, as quota is shared with other countries.
• Displacement of fisheries to other fish species and/or regions.
• Socio-economic impacts to those involved with affected fisheries.
• Lag effects for seabird population responses from changes in fisheries management may limit ability to detect a subsequent population level response.

Implementation time

Evidence base and existing preparatory work is limited compared to Sandeel, so likely to take several years.

Uncertainties

The abundance of prey fish is not only regulated by industrial fisheries, but also by predatory fish populations, competition for food sources, and changes in environmental conditions.

Consequently, predicting the response of prey fish populations to fisheries management interventions, is highly challenging. It is even more challenging to quantify and predict the broader effects of changes in fisheries management on the demography of the predator species themselves (i.e. seabirds).

Type of measure: General – indirect

Ecological efficacy: Low–medium

Overall feasibility: Low–medium

End of the Gannet harvest at Sula Sgeir

Action: End the harvest of Gannet chicks (‘guga’) at Sula Sgeir

Ecological aspects (WP1 and WP2)

Species that may benefit

With high certainty: Gannet.

With very low certainty: Fulmar, Leach’s Petrel, and European Storm Petrel.

Increased:

• productivity in the short-term;
• population size in the mid-term; and
• natal dispersal increasing populations at other colonies long-term.

Scale and degree of population benefit

Benefits would primarily be for Gannet from North Rona and Sula Sgeir SPA, with medium to high responses in the shortto mid-term, but lower benefit in the long-term (once the population approaches carrying capacity). Low to moderate benefits may accrue to other colonies in north-west Scotland. No significant benefit is expected to Gannet more widely in Scotland.

Other ecological benefits

• Overall decrease in disturbance on the island.

Risk of not doing

• Risk appears to be low. However,
• recent impacts of HPAI are not fully
• accounted for in this assessment.

Practical aspects (WP2)

Loss of cultural heritage

The Gannet harvest has been a longlasting tradition dating back several centuries. As such, it holds significant cultural value for the Ness community. If the harvest were to stop completely, there is a possibility that this practice could not resume due to loss of traditional knowledge.

Government intervention? Likely (not lead).

Key considerations

• Lack of community support could make it politically and logistically difficult to implement.
• Long-term ecological benefits may be overestimated if harvest rates were to continue to decline.
• Ending the harvest without community support could undermine existing community goodwill and trust that took years to develop, this is essential to other ongoing and future conservation schemes.

Uncertainties

The effects on other species may be limited but is not known. There is potential for both positive and negative impacts. Positive from reduced disturbance (e.g. petrels) and negative if Gannet expansion displaces other breeding birds (e.g. Fulmar).

Implementation time

Ending the harvest can, theoretically, be implemented immediately, as long as community has been consulted and an agreement has been reached. Dialogue with the community from the outset is imperative.

Type of measure: Site – direct

Ecological efficacy: Low–medium

Overall feasibility: Low–medium

Mammalian predator eradication and/or management

Actions: Predator eradication (islands) and predator control or exclusion (mainland colonies and islands)

Ecological aspects (WP1 and WP2)

Species that may benefit

With high certainty: Puffin, burrow-(e.g. Manx Shearwater and storm petrels) and ground-nesting species (e.g. terns and waders).

With low certainty/localised cases only: Guillemot, Razorbill, large gulls.

Increased:

• productivity,
• survival (some cases) in the short-term;
• recruitment rates,
• population recovery,
• reestablishment, and
• distribution expansion in the mid- to long-term.

Main mammalian predators in Scotland

• Rodents; Brown and Black Rat – Eradication.
• Medium-sized mammals; Mink, Fox, and feral/domestic Cat – Control and/or exclusion.

Scale and degree of population benefit

Most candidate sites are to the north and west of Scotland with fewer potential sites to the east.

Population level responses can be significant, but this will be site-, predator- and species-specific.

Evidence

There is more evidence to show higher success rates on uninhabited islands, followed by inhabited islands, and then at mainland sites.

Scalable? Yes.

Other ecological benefits

• Enhance ecosystem recovery, resilience, and stability.
• Increase populations of other animal and plant species, especially those native or endemic.

Risk of not doing

Risk is high – without eradication, population declines are likely to continue. Risk for further spread of predators to other sites.

Practical aspects (WP2)

Biosecurity

Eradication must be supported by longterm biosecurity. This will involve:

• conducting preventative measures to minimise risk of reinvasion;
• regular monitoring at sites; and
• rapid response in the case of predator detection.

Government intervention? No, but could be beneficial.

Key considerations

• A forthcoming ban on the most widely used rodenticides may pose significant risk to the viability of future eradication projects.
• The costs of eradication attempts are significant and could increase where initial eradication/control is unsuccessful. Long-term funding is required to maintain biosecurity, and for control/exclusion for ongoing action/maintenance.
• Unintended ecological consequences from poisoning and trapping of non-targeted species. Potential for pesticide-resistance to develop.
• At inhabited sites, support from resident communities is crucial.
• Potential for opposition by animal rights groups in some cases.

Uncertainties

The potential gains for individualspecies cannot by predicted withconfidence.

Highest uncertainty where species are absent with reestablishment not guaranteed post-eradication.

Implementation time

It will take several years to initialise and plan successful programmes. Biosecurity is required in perpetuity.

Type of measure: Site – direct

Ecological efficacy: Medium

Overall feasibility: High

Avian predator management

Actions: Diversionary feeding, removal of targeted or non-targeted nests, eggs, or individuals, and deterrence.

Ecological aspects (WP1 and WP2)

Species that may benefit

With high certainty: groundnesting species, like terns.

With low certainty: Guillemot, Razorbill, Puffin, large gulls, Kittiwake, Fulmar.

Decreased

• disturbance, and
• predation rates in the short-term.

Increased:

• body condition,
• productivity, and
• survival in theshort- to mid-term.

Scale and degree of population benefit

The degree of benefit will range from no to moderate effects depending on species, site, management intervention and whether predation occurs on eggs, chicks, or adults.

Risk of not doing

Risk is medium – impacts of avian predators may increase in absence of management.

Main avian predators in Scotland

• White-tailed Eagle
• Golden Eagle
• Peregrine Falcon
• Large gulls
• Great skua
• Corvids

Other ecological benefits

• Potential for increasing populations of other species also affected by avian predation.

Practical aspects (WP2)

Benefits of each management action

• Diversionary feeding – useful when both prey and predator are of conservation concern. Adaptable as can be stopped at any time.
• Removal – targeted removal is more efficient than large scale culling.
• Deterrence – non-lethal method. Quick and easy to implement at low costs.

Government intervention? No, but could be beneficial.

Key considerations

• Good baseline knowledge on existing predator impacts is required to design measures effectively, which is lacking for most sites.
• Certain actions will only be feasible at more accessible sites.
• Essential to consider the conservation status of predators.
• Ethical concerns and opposition by animal welfare groups could increase difficulty of implementing management.
• Managements could cause undesired ecological effects.
• A combination of different management types could result in an increase in effectiveness.

Uncertainties

The level of avian predation and/or disturbance at seabird colonies has not been well studied in Scotland. The potential management interventions have rarely been trialled for seabirds. Consequently, there is uncertainty regarding their potential benefits. The effects are likely to be highly site- and context-specific.

Implementation time

A few years of preparatory work but could then be put in place quickly (depending on the specific management action).

Type of measure: Site – direct

Ecological efficacy: Low–medium

Overall feasibility: Low

Reduction of disturbance (at colony)

Actions: Reduction of disturbance at colony on land, at sea, and by Unmanned Aerial Vehicles (UAVs)

Ecological aspects (WP1 and WP2)

Species that may benefit

Depends on source of disturbance.

Decreased:

• stress,
• predation, and
• flush rates in a shortterm.

Increased:

• parental care,
• body condition,
• energy allocation efficiency,
• productivity, and
• survival, in shortterm. And
• survival, and
• population size in mid- to -long term.

Scale and degree of population benefit

As a site-based measure, benefits will primarily be to the sites with high existing disturbance.

Effects will range from negligible to moderate, dependent on the effectiveness of management actions.

Scalable? Yes, though management will need to be specific for each site.

Other ecological benefits

• Decreased disturbance on most species at the colonies.
• Increased populations of other animal and plant species impacted by disturbance.

Risk of not doing

Risk is low–medium, most for colonies with existing high disturbance.

Practical aspects (WP2)

List of potential management actions

• Minimum approach distances to seabirds
• Reduce number of visitors
• Provide paths and signage
• Wardening
• Fences
• Educational programmes
• UAV regulation

Key considerations

• Need to consider additionality issues given existing laws and guidance on minimising disturbance to wildlife.
• Effectiveness of reducing disturbance is difficult to quantify.
• Enforcing certain management measures may not be politically feasible and may only act as guidance.
• Risk of affecting local conservation efforts, education, local economy, and reduce appreciation for wildlife.

Implementation time

Will depend on specific action, but likely a few years.

Government intervention? No, but could be beneficial.

Type of measure: Site – direct

Ecological efficacy: Low–medium

Overall feasibility: Low–medium

Bycatch mitigation in longline fisheries

Action: Applying mitigation measures in the floated demersal longline fleet operating in Scottish Waters

Ecological aspects (WP1 and WP2)

Species that may benefit

With high certainty: Fulmar.

With medium certainty: Gannet.

With low certainty: Great Shearwater and Great Skua.

Increased:

• survival,
• population size, and
• potential to arrest population declines in a medium- to longterm.

Scale and degree of population benefit

Benefits are most likely to Gannet and Fulmar populations to the west and north of Scotland, with no significant benefits likely to east coast populations.

For Gannet there may be small to moderate benefits.

For Fulmar there are likely to be strong effects.

Other ecological benefits

• Reduction bycatch of other bird species.
• Enhanced ecosystem resilience.

Risk of not doing

Risk is medium–high, bycatch is one of the biggest threats to certain seabird populations (especially Fulmar).

Practical aspects (WP2)

List of potential bycatch mitigation options

• Operational adaptations: changing timing of gear deployment.
• Gear adaptations: bird-scaring lines, increasing sink-rates, and use of swivel-hooks.
• Management changes: spatial and seasonal closures.

Government intervention? Yes (lead).

Key considerations

• Bycatch could only be significantly reduced if non-UK registered vessels were included as this is a large component of the fleet.
• Need to consider additionality issues, given existing commitments around bycatch minimisation.
• Apportioning benefits to individual SPAs would be difficult.
• Quantifying population level benefits is not possible with high confidence due to wide confidence intervals around bycatch rates (arising from currently low monitoring effort).
• Compliance and monitoring arrangements would need to be put in place to ensure compliance with mitigation requirements.

Implementation time

Full implementation could take a few years, but bycatch mitigation programme could likely be put into place within a year.

Uncertainties

There is high uncertainty in current bycatch estimates, so benefits cannot be quantified with confidence. Several potential mitigation options have been identified. However, few have been trialled within the fishery, leading to uncertainty on which would be most effective.

The UK registered fleet is in the minority, so overall bycatch rates cannot be significantly reduced by targeting UK registered vessels alone.

Type of measure: General – direct

Ecological efficacy: Medium

Overall feasibility: Medium