Climate oscillations drive millennial-scale changes in seabird colony size

Area of Science:

• Paleoceanography
• Marine Ecology
• Avian Biology

Background:

• Seabird populations are closely tied to oceanographic conditions, but long-term impacts of ocean dynamics on colonies are poorly understood.
• Reconstructing past seabird population dynamics is crucial for understanding ecological responses to climate change.

Purpose of the Study:

• To reconstruct ~10,000 years of seabird dynamics using lake sediments.
• To determine the influence of Holocene climatic oscillations and North Atlantic Oscillation (NAO) on seabird colony size.
• To investigate the role of ocean circulation and pycnocline depth in controlling seabird prey accessibility.

Main Methods:

• Analysis of dated lake sediments to reconstruct seabird population history.
• Correlation of seabird population trends with paleoclimate data (Holocene Thermal Maximum, Little Ice Age) and North Atlantic Oscillation (NAO) variations.
• Comparative analysis of seabird dynamics between Baccalieu Island and Grand Colombier Island to infer basin-wide oceanographic influences.

Main Results:

• Seabird colony growth on Baccalieu Island tracked warming during the Holocene Thermal Maximum.
• Colony size changes from ~5200 BP to the Little Ice Age correlated with North Atlantic Oscillation (NAO) variations.
• Post-Little Ice Age, Baccalieu Island's colony experienced unprecedented growth due to climate warming, increased nesting habitat, and anthropogenic influences.

Conclusions:

• Ocean dynamics, particularly NAO-driven changes in pycnocline depth affecting prey accessibility, significantly influenced seabird colony size over millennial timescales.
• Recent seabird population dynamics, while still influenced by ocean conditions, have been increasingly modified by anthropogenic impacts.
• Holocene climate oscillations and contemporary human activities are key drivers of seabird population changes in the Northwest Atlantic.