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NORTHERN PELAGIC: 895 miles and 86.2 hours of observations were completed
in this area. Twenty-one species were recorded, of which Juan Fernandez
petrels were the most abundant. Average density was 0.56 BSM, but most of
these birds were found within the warmer waters in the southeastern part.
Only Black-winged Petrel, Soccorro Petrel, and Red-tailed Tropicbird were
more common in the western part (111°-119°W). TABLE 3 shows the species
present and their comparative abundance.
TABLE 3
DISTRIBUTION AND ABUNDANCE OF BIRDS IN NORTHERN PELAGIC WATERS
Species No. Birds Birds/Hour Area of greatest Abundance
Wedge-tailed Shearwater 80 0.93 13-15° N - 101-103° W
Sooty Shearwater 4 0.05 -
Manx Shearwater 21 0.24 13-15° N - 098-103° W
Herald Petrel 1? 0.01 -
Kermadec Petrel 3 0.03 -
Phoenix/Tahiti Petrel 1 0.01 -
Murphy Petrel 2 0.02 -
Dark-rumped Petrel 1? 0.01 -
Juan Fernandez Petrel 349 4.05 13-15° N - 101-103° W
Black-winged Petrel 7 0.08 12° N - 118° W
Leach Petrel 61 0.71 Random ?
Soccorro Petrel 7 0.08 25° N - 118° W
Least Petrel 5 0.06 -
Sooty Petrel 5 0.06 13° N - 097° W
Red-tailed Tropicbird 6 0.07 12° N - 118° W
Red-billed Tropicbird 6 0.07 13° N - 097° W
Blue-faced Booby 10 0.12 13° N - 097° W
Brown Booby 8 0.09 15° N - 101° W
Red-footed Booby 5 0.06 15° N - 101° W
Pomarine Jaeger. 5 0.06 13#17° N - 101-106° W
Sooty Tern 1 0.01 -
COUNTERCURRENT: 899 miles and 85.7 hours of observations were completed
in this area. Twenty-five plus species were recorded with Juan Fernandez
Petrels outnumbering all others. Average density was 1.71 BSM. In the
western section birds were concentrated at the southern boundary, whereas
in the eastern section they were concentrated at the northern boundary.
This, plus the fact that some species (eg. Manx Shearwaters, Boobies,
Frigatebirds) were found only in the eastern section, and that the Counter-
current was not detectable in the eastern section, shows the effect
that water masses may have on the distribution of pelagic birds. TABLE
4 shows the distribution and comparative abundance of birds within this
area.