Rapid-response recorders reveal interplay between marine physics and seabird behaviour

In the marine environment, the distribution of primary producers and higher trophic levels is strongly dictated by the physical characteristics of the water column. Typically, life concentrates in regions where there are strong horizontal or vertical gradients in temperature or density ('frontal regions'). Top predators, such as diving mammals and birds, target fronts and their associated high biomass of prey. Until now, the study of the interaction between diving predators and the physical environment has been hindered by the lack of adequate instrumentation. The response times of the available animal-borne temperature-depth recorders have been too slow to accurately measure the external environment where the animals are foraging. This limitation has been overcome by the development of a lightweight, rapidly responding temperature-depth logger. The instrument was successfully deployed on 2 diving seabird species (the common guillemot Uria aalge and the European shag Phalacrocorax [Stictocarbo] aristotelis) in the North Sea. A method for correcting temperature data for the time lag in the response of the temperature sensor is presented. The findings show the potential of this technology in 2 important ways: in providing unparalleled information on the interaction between predators and the marine environment, and as a low-cost method of obtaining high-quality oceanographic data.