Displacement Assessment: ASSESSMENT DURING THE NON BREEDING SEASON - - PowerPoint PPT Presentation

Displacement Assessment: ASSESSMENT DURING THE NON‐BREEDING SEASON Francis Daunt Marine bird impact assessment guidance workshop 20 February 2020

Displacement in the breeding and non-breeding seasons

• Marked differences in the ecology of seabirds during the breeding

and non-breeding season

• Data quality is much poorer in non-breeding season, but this is

improving

• Non-breeding season is of critical importance:
• Important populations of most key species in most regions
• Most mortality occurs in winter

Breeding season

• Operating out of a central place
• High energy demands of breeding
• Spatially constrained
• Temporally constrained
• Life history theory: trade-off between current and future reproduction
• Marked variation in productivity

Non-breeding season

• Adult birds are independent of offspring and mates
• Not typically operating out of a central place
• Partial or full migration in winter
• High energetic costs in midwinter
• Spatially constrained e.g. flight costs
• Temporally constrained e.g. day length
• Birds are less constrained than breeding season
• Less marked variation in survival than productivity in most seabirds

Current approach

Joint Statutory Nature Conservation Bodies (SNCB) Interim Displacement Advice Note (2017)

• Density from at-sea survey data
• Apportioning and seasonal

definitions from BDMPS

• Mortality rates from

Displacement Matrix

Density in footprint x Displacement rate x Mortality rate

Limitations of current approach

Apportioning to SPAs Expert judgement

Limitations of current approach

• Summer and winter effects are estimated separately and then summed
• Summer effects on survival mediated by changes in body mass
• Subsequent mortality in the non-breeding season
• Potential for double counting winter mortality
• Relevant to:
• Summer Displacement Matrix / Winter Displacement Matrix
• Summer SeabORD / Winter Displacement Matrix

3 4 5 6 7 8 Sep Oct Nov Dec Jan Feb Mar Apr

Daily foraging time (h)

Laying date Laying date Breedmg success Winter foraging effort

Daunt et al (2014) Ecology

Limitations of current approach

• Subsequent effects on productivity ignored

Potential approaches

• Key priorities:
• Interaction between birds of known provenance and footprints during the

non-breeding season

• Defensible estimates of mortality rate of displaced birds
• Avoidance of double counting in assessments
• Incorporation of carry-over effects on subsequent breeding
• Potential solution:
• Improved estimates of apportioning
• Year-round model of behaviour, energetics and demography

Improved estimates of Apportioning

Lila Buckingham

Year-round model of displacement

• Year-round model of daily intake rate and energy expenditure
• Factor in key constraints arising from habitat loss:
• Spatial: flight costs
• Temporal: seasonal daylength and energetic costs
• Estimate effects on demography:
• Survival
• Subsequent breeding performance

Population-level approach

• Population-level approach:
• Distributions of species
• % time in an area without needing to account for turnover
• % habitat loss
• Effects of mortality
• Potential advantages:
• Where there are limited individual data on year-round activity and energetic

constraints

• More rapid than individual-based approaches
• Likely to provide justification for IBMs in cases where effects may be occurring

Individual-based approach

• IBM is more powerful but data hungry.

Current potential in guillemots where there are year-round data on:

• Distribution
• Activity/energetics
• Body mass
• Good understanding of requirements to plug data gaps:
• GLS deployments in new species to build baseline IBMs
• GPS deployments in new species to estimate interactions with developments

Conclusions on future assessments

• Current approaches lack biological realism
• Non-breeding season effects are occurring at a critical time
• Need empirical studies to fill data gaps
• Need year-round models of behaviour, energetics and demography to estimate:
• Interactions between birds and developments
• Effects on survival
• Effects on subsequent breeding