Foraging behaviour and feeding locations of Rock Shags Phalacrocorax magellanicus from a colony of Patagonia, Argentina

QUINTANA, F.

IBIS

Año: 2001 vol. 143 p. 547 - 553

0019-1019

During 1996 and 1997, foraging Rock Shags Phalacrocorax magellanicus were studied at Punta Loma, Argentina using radio-transmitters deployed on ten adults Shags during the chick-rearing period. Rock Shags undertook 2.6 ± 0.6 sd trips per day. The mean duration of a feeding trip was 2.6 ± 0.7 hours.  A bird spent 36% of daylight hours away from the colony on feeding trips, diving for 92% of the foraging trip, and made a mean of 106 dives per foraging trips. Foraging trip duration was strongly correlated with the total number of dives made in one foraging trip. Rock Shags fed mainly in water less than 10 m deep with a gravelly sand bottom and within 5 km of shore. Mean foraging range was 3.8 ± 2.6 km and 2.6 ± 2.3 km for 1996 and 1997, respectively. These results suggest a high foraging effort (diving time per foraging trip) for Rock Shags, presumably associated with poor food conditions close to the colony. Comparison is made with other Phalacrocorax species.