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 indica- 

 tive and significant (when detected and explained) than are much larger changes 

 in numbers in bigger reproductive units in the center of a species' range. Fluctua- 

 tions in seabird numbers must in future be first considered as possible responses 

 either to short-term, or turnarounds in longer term, natural climatic or oceano- 

 graphic cycles, or to trends ranging in length from a few years to at least several 

 decades. 



During the last 30 years extensive litera- 

 ture in the fields of physical and biological 

 oceanography has accumulated that is not 

 readily accessible to the nonprofessional stu- 

 dent 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 in- 

 terest in the literature is initially somewhat 

 marginal. Nevertheless, to achieve the best 

 possible appreciation of the oceanographic in- 

 fluences affecting seabirds, particularly in the 

 north Pacific Ocean and its adjacent embay- 

 ment seas, it is necessary to make the effort. 



Because of the rigor of carrying out their 

 primary duties while at sea, only a very few 

 North American and European oceanog- 

 raphers or fishery biologists have found time 

 to interest themselves in seabirds and then, 



with a few notable individual exceptions, only 

 as an off-duty pastime. The reason is not far 

 to seek. It is far less important to examine the 

 ecology of organisms at the next highest level 

 of the food chain to the ones that are the pri- 

 mary concern than it is to examine the next 

 lowest level (the food of the fishes or, in the 

 case of phytoplankton, the physical and 

 chemical environment in which the organisms 

 grow best). 



Seabirds are at the very top of the marine 

 food chain, and they are not wholly aquatic in 

 any case since they mainly travel through the 

 air rather than the water and reproduce on 

 land rather than in the sea. Only with the rela- 

 tively recent recognition that seabirds con- 

 tribute to the recycling of nutrients back into 

 the ocean to an important degree, have sea- 

 birds gained a new scientific constituency. 



At about the same time, governments have 

 begun to recognize that seabirds are rela- 

 tively easily examined indicators of the pres- 

 ence of unseen chemical pollutants in coastal 



