Marime Ornithology 19, 117-129, 1992
Diving patterns and performance in male and female blue-eyed cormorants Phalacrocorax atriceps at South Georgia
Kato, A., J.P. Croxall, Y. Watanuki and Y. Naito 1992
Diving pattern and performance in male and female Blue-eyed Cormorants Phalacrocorax atricepes were recorded with continuous-recording time-depth recorders for 10-13 days during the 1990 breeding season. For the female only data on time and depth were retrieved; diving was distributed through the day (including 31% at night); mean dive depth was 63 m. Male dived mainly in the afternoon and evening. Their mean dive depths were 61.4 and 83.9 m; mean dive durations 3.4 and 4.6 min; time at maximum depth (bottom time) averaged 28 and 44% of time submerged; descent time (0.4 and 0.5 min) was shorter than ascent time (1.6 and 2.9 min); dive/pause rations were 0.4 and 0.5 and surface interval was with preceding dive duration. The incubating male making one long dive bout per day, made fewer, longer dives, with less overall bottom time, than the chick-rearing male, which made at least two bouts per day. Most characteristics of diving in 1990 (a year of diving breeding success) were similar to data from 1989 (a year of breeding failure). However there were more, shorter dive bouts in 1989 and shallow (travelling) dives were more frequent; both consistent with lower prey avalibility in 1989 necesstating frequent changes of forging sites.
BD92-1
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