Quantifying the role of oceanic storminess in determining the survival and recruitment of long-distance, migratory birds

Abstract

The trans-Atlantic migratory seabird, the Manx shearwater (Puffinus puffinus), is an Amber-listed species in the UK and a conservation priority under the EU Birds Directive. This highly pelagic species spends most of its annual cycle at sea, facing severe ocean storms. An extensive capture-mark-recapture ringing project on Manx shearwaters has been ongoing from the only breeding colony in Northern Ireland, Old Lighthouse Island, since 1952 by the Copeland Bird Observatory providing a rare opportunity to assess the long-term impacts of environmental variability on life histories.

The capture-mark-recapture records indicate that the Manx shearwater breeding population at Copeland increased by 33% from 1952 to 2020, reaching approximately 2,900 adults in 2020, which aligns with estimates from tape playback surveys. The oldest Manx shearwater recorded was over 50 years old. Annual survival rates were high (89%), and climatic variability described by the North Atlantic Oscillation (NAO) predicted significant negative impacts, especially during the outbound migratory journey. Recruitment was generally low (17%) and best predicted by the NAO during southern migration. Population estimates suggest stable growth (λ=1.05). Migration phenology showed shifts, with fledglings departing two to three weeks later and juveniles arriving seven weeks later than seven decades ago. Recovery data suggest that winter NAO from two years prior reduced fledgling survival past one year. Metagenomic sequencing on a puffinosed shearwater found no viral infection, indicating an environmental cause, likely caustic faecal ammonia in damp nesting burrows leading to opportunistic infections by soil bacteria.

The thesis underscores the importance of ongoing monitoring and research. Continued capture-mark recapture ringing for population estimation, survival, and recruitment rates is recommended, along with vegetation control to support rabbit and Manx shearwater breeding. This research highlights the complex relationships between environmental variability, migration, breeding, and survival, emphasisng targeted conservation efforts for the resilience of seabirds in a changing climate.

Date of Award	Jul 2024
Original language	English
Awarding Institution	Queen's University Belfast
Sponsors	UK Research and Innovation & NERC QUADRAT
Supervisor	Neil Reid (Supervisor) & Paul Caplat (Supervisor)