Abstract
Understanding physical mechanisms underlying seabird foraging is fundamental to predict responses to coastal change. For instance, turbulence in the water arising from natural or anthropogenic structures can affect foraging opportunities in tidal seas. Yet, identifying ecologically important localized turbulence features (e.g. upwellings approximately 10–100 m) is limited by observational scale, and this knowledge gap is magnified in volatile predators. Here, using a drone-based approach, we present the tracking of surface-foraging terns (143 trajectories belonging to three tern species) and dynamic turbulent surface flow features in synchrony. We thereby provide the earliest evidence that localized turbulence features can present physical foraging cues. Incorporating evolving vorticity and upwelling features within a hidden Markov model, we show that terns were more likely to actively forage as the strength of the underlying vorticity feature increased, while conspicuous upwellings ahead of the flight path presented a strong physical cue to stay in transit behaviour. This clearly encapsulates the importance of prevalent turbulence features as localized foraging cues. Our quantitative approach therefore offers the opportunity to unlock knowledge gaps in seabird sensory and foraging ecology on hitherto unobtainable scales. Finally, it lays the foundation to predict responses to coastal change to inform sustainable ocean development.
Highlights
Understanding how physical processes in our oceans shape the foraging distributions of marine predators is critical to predict responses to environmental change [1,2]
Using a drone-based approach, we present the tracking of surfaceforaging terns (143 trajectories belonging to three tern species) and dynamic turbulent surface flow features in synchrony
We thereby provide the earliest evidence that localized turbulence features can present physical foraging cues
Summary
Understanding how physical processes in our oceans shape the foraging distributions of marine predators is critical to predict responses to environmental change [1,2]. After erupting at the surface, boils will increase in size, decrease in intensity and may evolve into vortical structures before dissipating Volant predators, such as seabirds, must be able to locate such physical cues for prey across a highly dynamic range of flow features. We predicted that state transition probabilities would be affected by the strength of the underlying turbulent feature as well as its distance, as perceived by the terns This allowed us to quantify the influence of prevalent oceanographic features on a surface-foraging marine predator on hitherto unobtainable scales This allowed us to quantify the influence of prevalent oceanographic features on a surface-foraging marine predator on hitherto unobtainable scales (approx. 10–100 m)
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