EAC 2, Shearwater, January 1967
Page 30
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Transcription
Eastern Grid Cruise No. 2 and Eastern Grid Survey No. 1 -January 1967 This report is a summary of observations and collections made by TURSP personnel in the eastern Pacific Ocean from January 18 through January 28, 1967. (See map #1.) Participating Smithsonian personnel included Brian Harrington (Biologist-in-Charge), Robert DeLong, and David Burckhalter. Superior cooperation was received from the officers and crew of the U.S.N.S. SHEARWATER (T-AG 177), particularly from Captain Gibson, Mr. Webber, and Mr. Wyatt. The grid cruise track is considered to have been as closely followed as conditions permitted, and all positions are considered accurate within five miles. Hourly LORAN fixes demonstrated that an accurate grid track was followed. As no equipment for taking bathythermographs was available, this phase of the survey was not possible. This report is divided into two sections: the first deals with the eastern grid, and the second summarizes the non-grid observations. Eastern Grid Survey No. 1 The Eastern Grid Survey was conducted from 0100 January 19 to 07h8 January 27; 72.9 hours of diurnal observations were conducted for 690 linear miles. Diurnal observations are summarized in Table 1. In addition 3h.6 hours of nocturnal observations were conducted. Nocturnal observations are of little significance and should be regarded lightly as weather and moonlight conditions seemed to cause great variations in bird activity around the ship. These observations are briefly summarized in Table 3, and occasional reference is also made in the species accounts. Weather during this cruise was variable throughout the survey. A relatively stationary high pressure system in the southern part of the grid greatly influenced weather during the last four days; a passing low center during the first three days also brought weather changes. What influence these pressure centers have on pelagic birds is not known at present; thusly remarks on distribution of birds in the species accounts were made without consideration of weather effects. In reference to flocking, groups of five or more birds seen in one sighting (fitting the PORSP definition of a flock) were noted. But flocking in the sense of birds travelling and/or feeding together did not seem to occur along the grid at this time of the year. The closest equivalent to flocking occurred on the 21st of January when a large number of fulmars were observed feeding in a small area. Other sightings of five or more birds together were almost entirely of following birds, particularly gulls, storm petrels, and albatross, or of birds following the ship. The latter group, of course, are not in association with each other, but with the ship. Thus at this stage, flocking activity appears insignificant, and hence is not included in the tables. For purposes of discussion, the grid has been divided into three sections. As will be seen in Table 2, significant differences in