All procedures were in full compliance with guidelines of the President's Committee on Animal Care at Memorial University of Newfoundland. This research was supported by the following grants (to WAM): NSERC Discovery Grant, Newfoundland and Labrador Murre Conservation Fund, and the Government of Canada's Program for International Polar Year Program. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.įunding: PMR benefited from the following: Natural Sciences and Engineering Research Council of Canada (NSERC) postgraduate scholarship, George Weston Graduate Scholarship, Leslie Tuck Avian Ecology Award, and Maritime Awards Society of Canada (MASC) Maritime Studies Scholarship. Received: JAccepted: OctoPublished: October 26, 2011Ĭopyright: © 2011 Regular et al. PLoS ONE 6(10):Įditor: Howard Browman, Institute of Marine Research, Norway This research highlights the flexibility of breeding common murres and raises questions about the strategies and mechanisms birds use to find prey under very low light conditions.Ĭitation: Regular PM, Hedd A, Montevecchi WA (2011) Fishing in the Dark: A Pursuit-Diving Seabird Modifies Foraging Behaviour in Response to Nocturnal Light Levels. We hypothesise that murres foraging through starlit periods rely either on close-range visual or possibly nonvisual cues to acquire randomly encountered prey. Given the dense prey landscape available, random-walk simulations suggest that murres could benefit from random prey encounters. Whether visually guided foraging is possible during starlit periods is less clear. At night, murres readily foraged during both moonlit and starlit periods, and diving depth and efficiency increased with nocturnal light intensity, suggesting that night diving is at least partially visually guided. Through these periods, they readily dived under conditions equivalent to ambient moonlight (∼10 −4 Wm −2) but rarely under conditions equivalent to starlight (∼10 −8 Wm −2). During diurnal and crepuscular periods, murres used a wide range of the water column (2–177 m), foraging across light intensities that spanned several orders of magnitude (10 3–10 −10 Wm −2). To study foraging of murres under different light conditions, we used a combination of archival tagging methods and astronomical models to assess relationships between diving behaviour and light availability. Yet common murres, a species considered a diurnal visual predator, frequently dive at night. Visual predators tend not to hunt during periods when efficiency is compromised by low light levels.