CCAMLR

Forty stomach contents of the blue eyed shag Phalacrocorax bransfieldensis were sampled at Nelson Island, South Shetland Islands, in January 1994. The analysis of the diet showed that fish were by far the main component, followed by octopods, polychaetes and gammarids. Notothenia coriiceps, predominated in frequency (58%) and in weight (65%), whereas Nototheniops nudifrons was the most important by number (47%) . The comparison with data published on pellets analysis of shags from the same colony gave similar results. However, although the methodology used in the present study requires more time in the field, it reduces the errors arose from the examination of regurgitated casts, like erosion by digestion or loss of the otoliths through the gastrointestinal tract. The analysis of the stomach contents is complemented with information on shags’ foraging trips, obtained in the field by film records.

Local fish species were used to feed a captive blue-eyed shag Phalacrocorax atriceps bransfieldensis during 45 days of the austral summer at Jubany Station, King George Island, South Shetland Islands. The otoliths identified in pellets were affected by the digestive process and consequently the fish species were differentialy underrepresented in number and size (length/mass). Except Gobionotothen gibberifrons and Nototheniops nudifrons all the species were underestimated in number (N. rossii fully). G. gibberifrons was also the less affected is size, being Pagothenia bernachii, N. nudifrons, Trematomus newnesi and Notothenia coriiceps largely underestimated. Thus, preliminary correction factors were obtained to improve the accuracy of weight estimations of fish ingested, calculated y means of equations based on otolith-lengths. The shag produced a total of 16 pellets, with a frequency of 1 every 2.5 days. It ingested willingly a mean ration equivalent to 31% of its mass, which is a higher energy requirement than that experimentally observed in other not antarctic shag species. Algae and ploychaetes were found in the casts and came from the fish stomachs. Therefore, their importance in the diet of the blue-eyed shag could have been overestimated in previous studies.

Water temperature and krill abundance in Maxwell Bay, Antarctica, were examined using Pygoscelid penguins carrying appropriate sensors linked to position-determining devices. Fifty-three foraging trips from 49 penguins indicated that during December 1991 and January 1992 the temperature in the top 100 m of the water column was highest in the western section of the Bay which concurred with higher krill abundance as determined by a catch per unit effort index. This work demonstrates that abiotic and biotic features of the environment can be studied using animals to transport probes to the study site, provided information is given on the position of the animals when measurements are made.

Published in Journal of Animal Ecology (1994) 63, 000-000

The suggestion that sex of Adélie penguins, Pygoscelis adeliae, might be assigned by observing which member of the pair (the male) takes the first long incubation shift (Anon. 1991) was examined for each of the 1990–91, 1991–92 and 1992–93 breeding seasons. There was an 8- or 9-day period when more than 90% of the incubating birds were male and a 6- or 7-day period when more than 90% of the birds were female. The dates of these peak periods of male or female presence overlapped by only 2–5 days between the three seasons but were constant to within 2 days relative to the commencement of egg laying. Peak presence of males occurred 15–21 days after the appearance of the first egg in the colony and peak presence of females after 33–36 days from this date. In all three seasons male birds could be identified with 91∙8–98∙6% accuracy within 15–21 days after the first sighting of an egg. The method provides, therefore, a means of identifying the sex of Adélie penguins with an accuracy greater than 90% and is applicable to whole colonies containing several hundred pairs without recourse to continuous observations or capturing the birds.