EAC 22, Hall, August-September 1967
Page 90
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Transcription
Storm Petrels WRSP 94 DRSP 15 Storm Petrel sp. 90 All birds observed, with one exception, are believed to be Leach's- type Storm Petrels; the exception being a small, all-dark bird observed on 31 August at 32°30' N, 123°19' W. This bird represents the first pos- sible record of a Leach Petrel (Halocyptena microsoma) in the Grid. The distribution of storm petrels during the survey did not appear random. Densities were high in the north and southern sections of the Grid. Density in the central section appears low; however, these data may be misleading. Seas were choppy during the survey of the central portion and generally smooth during the survey on the northern and southerly sections of the Grid. It is possible that sea conditions such as encountered in the central section reduce the radius of visibility evenough to explain the low numbers recorded. It is well known among field observers that storm petrels are difficult to see in choppy seas (6-8 ft.), but it is not possible to assign a quantitative adjustment factor to these data to account for environment changes. The high linear density of storm petrels in sector 7 is discussed earlier in the report. In summary of that discussion the recorded den- sity is higher than actual densities due to smooth seas and observations from the skiff. Both factors increased the radius of visibility yielding greater numbers of birds recorded. Red-billed Tropicbird Two birds were recorded in sector 9 of the Grid. Red Phalarope Sixty-nine percent of the phalaropes were recorded in the northern section of the Grid. Birds were again recorded in the vicinity of slicks believed to be indicative of oceanographic fronts. These slicks were found in the east side of sector 2, as was the case on EGS 11. The nocturnal abundance of phalaropes in the central section is of interest. On the night of 3 August, after seeing no phalaropes during day, ca. 25 birds were recorded during 2-1/2 hours of nocturnal ob- ervation. The birds are attracted to the ship at night given proper overcast conditions. But on this night the ship was drifting (essentially remaining in one area) and such high numbers are difficult to explain. Do the birds move primarily at night and stay on the water during the day, or is there another explanation? Jaegers Parasitic Jaeger 1 Long-tailed Jaeger 1 Jaeger sp. 21