Abstract
MOST ocean travellers must have noticed the very irregular distribution of birds on the open sea on different days, notwithstanding the apparently similar conditions of air and ocean. Censuses made during the crossing of the Atlantic record statistically these differences, but little attempt has been made to suggest a satisfactory reason for them. It seems very likely, however, that the presence or absence of pelagic birds is regulated by the oceanic currents, as S. C. Brooks suggests in the Condor (September 1934, p. 185). Oceanographers have shown that where the Arctic Current meets the North Atlantic Drift, there arise complexes of eddies and upwelling of the under waters, and that at the margin of contact there is a surface display of abundant organisms which attract fishes and other predators. This congregation of plenteous foodstuffs in limited areas may well attract pelagic birds, and Jesperson has already shown that there is a general connexion between the numbers of birds seen in a particular area at sea, and the quantity of macro-plankton in the surface waters. Pushing the probabilities further, it is likely that the migrations of oceanic birds may be related to the movements of plankton, by whatever determined, and tentatively Brooks makes the very interesting (but quite untested) suggestion that one of the factors which guided the homing terns of Bird Key from Cape Hatteras, to which they had been conveyed, back to the Tortugas, may have been the rich feeding grounds along the margin of the Gulf Stream. He adds that perhaps other factors too must be considered, such as the density of the air, which has been regarded as determining the northern limit of the distribution of the southern Atlantic wandering albatross.
Article PDF
Rights and permissions
About this article
Cite this article
Distribution of Birds at Sea. Nature 135, 62 (1935). https://doi.org/10.1038/135062b0
Issue Date:
DOI: https://doi.org/10.1038/135062b0