The Eastern Bering Sea Shelf : oceanography and resources / edited by Donald W. Hood and John A. Calder easternberingsea00hood Year: 1981 Pe lagic d is I rib ution 697 Shuntov added the interesting observation that the distribution of shearwaters shifts from the continen- tal shelf areas in the first half of the summer to the deeper waters between the Pribilof Islands and Unimak Pass in the second half. Bartonek and Gibson (1972) found large numbers of shearwaters throughout the areas of Bristol Bay surveyed in July, but noticed a considerable reduction of these num- bers in August. This was
The Eastern Bering Sea Shelf : oceanography and resources / edited by Donald W. Hood and John A. Calder easternberingsea00hood Year: 1981 Pe lagic d is I rib ution 697 Shuntov added the interesting observation that the distribution of shearwaters shifts from the continen- tal shelf areas in the first half of the summer to the deeper waters between the Pribilof Islands and Unimak Pass in the second half. Bartonek and Gibson (1972) found large numbers of shearwaters throughout the areas of Bristol Bay surveyed in July, but noticed a considerable reduction of these num- bers in August. This was about one month later than reported by Shuntov (1961), who estimated that five to seven million Short-tailed Shearwaters gathered to molt in the southeastern Bering Sea in June of 1960, but that by July, molt was essentially completed and the birds were leaving that area. On the average, shipboard surveys produced higher density estimates of shearwaters than surveys from fixed-wing aircraft. Both survey types appeared to produce inflated density estimates because of the dif- ficulty observers have in obtaining instantaneous counts of birds vdthin a transect when birds are in large, often rapidly moving flocks. At the level of an- alysis used for this chapter, however, the two meth- ods produced remarkably similar distribution and density patterns. We have thus chosen to combine shipboard and aerial surveys in order to display the broadest level of perspective available. We have no winter records of shearwaters in the Bering Sea. Our earliest records are of one bird on 24 April and eight birds on 27 April. Our latest rec- ords are of one bird on 21 November and two birds on 22 November. All four records were from waters immediately north of the Aleutian Islands. Spring, summer, and fall distributions of shearwaters are shown in Figs. 40-15 to 40-17. The majority of these birds move into the Bering Sea in May and June and leave in September and October. A fair number move into A
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