Impact of Time and Tidal Current Speed on Alcid Abundance and Behavior in San Juan Channel

Abstract

Understanding daily abundance and behavior of animals is an important part of conservation research, as changes in these factors cannot be considered without a baseline to reference. Our study is focused on providing this information about the population of alcids in San Juan Channel in relation to different times of day and different tidal currents. The Pigeon Guillemot (Cepphus columba), Rhinoceros Auklet (Cerorhinca monocerata), Common Murre (Uria aalge), and Marbled Murrelet (Brachyramphus marmoratus) are all species of the family Alcidae, or alcids, which are commonly found in the San Juan Island area. In this study we conducted observations from the shoreline of Hunt’s Point, observing abundance of each species, and categorizing the birds’ behavior into three categories: diving, flying and swimming. Trends in data indicate that abundance and behavior were distinct between species and differed with tidal current speeds. We found that Pigeon Guillemots were most abundant during fast ebb currents, Rhinoceros Auklets during slow ebb currents and slack high currents, Common Murres during slack high currents, and Marbled Murrelets during ebb currents and slack high currents. While observing Rhinoceros Auklets, we found distinct feeding patterns throughout the day that shifted at 16:00. We also found consistent patterns in flight direction of Rhinoceros Auklets, where flying north to south was more common during flood currents than during ebb currents. Understanding patterns of abundance and behavior is critical for designing regulations and maintaining healthy populations of these species. Research should be continued over a longer period of time to provide more data and information about these species throughout a wider range of conditions.