MARINE ENVIRONMENT OF BIRDS
[Long-term Climatic and Oceanographic Cycles Regulating Seabird Distributions and Numbers]
by
M. T. Myres
Department of Biology, University of Calgary
Calgary, Alberta, Canada T2N 1N4
Abstract
Seabird ornithologists have generally paid little attention to the possible roles played by long-term climatic cycles or air-ocean interactions on population changes at established colonies or on the processes of colony establishment or extinction. Yet, a rapidly expanding literature in the physical sciences suggests that seabird numbers are not naturally stable at particular colonies for any great length of time. It is suggested that the establishment of new colonies at one end of the range may counter the decline of colonies at the other end. Perhaps these changes in small marginal colonies are important, and they may be more indicative and significant (when detected and explained) than are much larger changes in numbers in bigger reproductive units in the center of a species' range. Fluctuations in seabird numbers must in future be first considered as possible responses either to short-term, or turnarounds in longer term, natural climatic or oceanographic cycles, or to trends ranging in length from a few years to at least several decades.
During the last 30 years extensive literature in the fields of physical and biological oceanography has accumulated that is not readily accessible to the nonprofessional student of seabirds and not as widely understood by career seabird ornithologists as it should be. This literature in oceanography and marine fisheries is as extensive in Russian and Japanese together as in the main languages of Western Europe combined; this abundance compounds the problem of becoming familiar with it if, as a student of seabirds, one's interest in the literature is initially somewhat marginal. Nevertheless, to achieve the best possible appreciation of the oceanographic influences affecting seabirds, particularly in the north Pacific Ocean and its adjacent embayment seas, it is necessary to make the effort.