Migrators face a broad array of perils. Their winter home may be under seige or their nesting habitat at risk. Other hazards may ensue at any stage of their travels, as key stopover sites fall victim to urban sprawl and other incursions. For a small shorebird called the red knot, the danger lies in man's heightened consumption of horseshoe crabs.
Each May, thousands of red knots—coming from Tierra del Fuego, by way of Brazil—arrive at Delaware Bay beaches to feast on horseshoe crab eggs. Gobbling more than 10,000 tiny eggs a day, the birds double their weight in two weeks, gaining sufficient stores to fuel their nonstop, 2,500-mile flight to the Canadian Arctic, where they mate. The schedule for red knots is unforgiving: They must quickly put on weight, reach the Arctic by the first week of June, hatch their eggs a week later, and hatch their chicks a few weeks later still, or breeding will fail and the whole 20,000-mile exercise will have been for naught.
Red knots are now jeopardized by the dramatic drop in horseshoe crab populations over the past 15 or so years, as the crabs have been increasingly used for biomedical purposes and as bait for eels and snails. Red knots have declined in turn—a six-fold plunge since 1989 that has some researchers predicting extinction within a decade. Although federal and regional authorities have recently limited crab harvesting, ecologists are not sure the measures are sufficient to save the red knot.
Countless other creatures—from tiny hummingbirds to antelopes and whales—need protection at critical junctures along their migratory pathways. Many observers believe our best hope for preserving these odysseys lies in establishing a network of national and transnational migration corridors that reconnect the land and sea. A full global network of this sort may be impractical. But by starting with a few vital corridors and building from there, we can promote the safe passage of a growing number of animals as they embark on their epoch journeys.
Efforts to save whooping cranes, the most endangered of the world's 15 crane subspecies, offer a rare instance of animals learning about migration by watching what human do. Starting in 2001, humans flying ultralight aircraft have led whooping crane chicks on their first migratory flight south from a wildlife refuge in Wisconsin to a newly-created wintering habitat in a Florida preserve--a 1,200-mile journey.