|Albatross Foraging Biology
Since 1995 we have conducted satellite tracking studies of albatrosses breeding in the Galapagos Islands, Ecuador and in the Hawaiian Islands, USA. We mount small radio transmitters on the back feathers of breeding birds and use the satellites of the Argos system to follow the birds as they move during foraging trips. The distances that they cover are astonishing: waved albatrosses from Espanola Island, Galapagos fly to the Peruvian upwelling zone during the incubation period, with round trips approaching 3000km. Breeding Laysan albatrosses regularly travel to the Gulf of Alaska and back while their nestling waits on Tern Island in the Northwest Hawaiian Islands. Black-footed albatrosses travel to the west coast of the United States and British Columbia, over the continental shelf, where they dramatically slow their flight speed and turn more frequently than when flying between Tern Island, their breeding site, and North America. We suspect that this change in behavior indicates a change from commuting flight to a foraging search mode. If this is true, it means that black-foots fly from the remotest island group to a continental shelf area to find food for their young. During the non-breeding season we have tracked Hawaiian Laysan albatrosses moving from the vicinity of their nests on Tern and Kauai Islands far to the east, reaching the coast of Japan.
Laysan albatross movements during
the 1999 non-breeding season
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|Small immersion monitors
used in conjunction with satellite tags have shown where the albatrosses actually
forage, as opposed to where they fly in a commuting mode. They also show that
the two Hawaiian species spend more time active on the water during daylight hours.
The figure below shows the rate of immersions during a particular daylight period
and the immersion rate during the subsequent night. During periods of very active
feeding (immersion rates > 4/hr), the birds ere active primarily during the day and not
during the subsequent night, when they were presumably in the same food-rich area. A
bias toward daytime feeding has important implications for mitigation of bycatch in
fisheries, an important source of mortality.