Wednesday, November 18, 2009

The Realm of Albatrosses

What is it about oceanic islands that exerts such a siren call? What comprises the allure of farflung bits of volcanic rock and mounds of sand ringed by coral reefs, where seabirds nest in clamorous multitudes?

To name just one marvel, the flight of albatrosses takes my breath away.

Buller's Albatross south of New Zealand (Photo by Narca)

Albatrosses occupy my thoughts, as I gaze over a sea of Chihuahuan Desert, preparing for next spring's WINGS tours to Hawaii and Midway Atoll. To place ourselves in the albatross's world, we must shift our mindset drastically, from the upland's rhyolitic cliffs and coniferous forest, from grassland and desert scrub stretching to the blue-gray horizon. We must enter a waterworld driven by wind and temperature to form currents, convergences, and plankton blooms.

Earth's vast oceans can be grouped, at the roughest scale, into the cold, productive polar waters at high latitudes both north and south, separated by the warm waters of the tropics, where winds falter then die for weeks on end, becalming sailing ships and albatrosses alike. The great albatrosses must have wind.

They also must have food, abundant only in certain regions of the ocean where currents and upwellings create the right conditions for plankton and the food web it supports. Albatrosses also must have nesting grounds, and within the vast oceans, protected islands suitable for nesting are scarce indeed.

Warm seas form a barrier for many oceanic organisms that is as great a challenge as the Himalaya and the Amazon River pose for land-based creatures. On rare occasions an albatross may cross that warm-ocean barrier, but for the most part northern and southern albatrosses have followed their own evolutionary paths. In part due to the immense size of the Southern Ocean––more than 10 times as large as the North Pacific––many more species of albatross soar in southern seas.

Here in northern seas we have three species: the Laysan, the Black-footed, and the endangered Short-tailed Albatross. The Hawaiian Islands are prime nesting grounds for the Laysan and Black-footeds, and among the 18 Hawaiian Islands, Midway Atoll's stupendous colony of nesting albatrosses eclipses all the others.

Satellite tracking of Midway's Laysan Albatrosses has revealed that they shuttle continually between the Hawaiian Islands and the Gulf of Alaska, flying as far as 500 km a day between their nesting islands and their foraging waters, where they find squid to feed their chicks.

In addition to the albatross nesting extravaganza, Midway Atoll has hosted one or two wintering Short-tailed Albatrosses in recent years. A former victim of the feather trade, the Short-tailed population was reduced to only 50 individuals, but is recovering with protection and now numbers over 2300 birds.

In 1912 Robert Cushman Murphy, the great seabird biologist, wrote, "I now belong to a higher cult of mortals, for I have seen the albatross!"

No comments:

Post a Comment