The plovers and curlew lingered on the savannahs of the Orinoco for two weeks, rapidly growing fat again. There were thousands of other shorebirds flocking the great grasslands—golden plovers that had come down the long oceanic migration route as the curlew′s flock had done, and a dozen other species that had followed the land route of the central plains and the Panama isthmus to rendezvous here on the Venezuelan prairies. There were brilliant tropical birds too, now in the middle of their nesting time and busily feeding young. White egrets had covered acres of riverside swamp with their big nests, the nests often so numerous that they touched one another. Flocks of scarlet ibis, the gems of tropical bird life, followed the riverbanks in their food hunts, approaching first as silhouettes of colorless grey, then flaming into a vivid scarlet as they came nearer, and fading to grey again when they passed.
Food was limitless on the llanos, and many of the arctic shorebirds would migrate no farther, but after two weeks of feeding had fattened them once more the curlew and plover felt the old restless torment calling them again to a more distant southland. The other plover flocks had already gone. As in Labrador, the curlew′s flock was the last to depart.
They took off on a bright moonlit night early in October, followed a tributary valley of the Orinoco until it lost itself in the mountain range that separated the Orinoco and Amazon watersheds, then dropped into a deep valley of one of the Amazon′s tributaries beyond. They followed the slender thread of water southward, and by dawn they had reached the broad Amazon itself. The next night, to take advantage of an eastward shift in the wind, they turned southwest, and another five hundred miles of flying put them, at dawn, within sight of the Peruvian Andes′ snowcapped peaks. The wind died, and now for three nights following they flew southeast along the Andean flanks. On the fifth dawn, gaunt and wing-worn again, they dropped to the grassy flatlands of the Argentine pampas, twenty-five hundred miles south of the Venezuelan llanos.
Spring was greening the pampas grass and giant thistle. Grasshoppers were emerging. For days the birds did little but gorge on the insect life of the short grass plains, flying at intervals to the lower levels where the grass grew denser in brackish marshes and swarms of aquatic insects provided a change of diet. They were always moving, but never moving far. Their worn wing feathers were molted one by one and replaced, giving them full flight power again. Here, they were eight thousand miles from the arctic nesting grounds and of all the tundra shorebird species only the yellowlegs, knot, buff-breasted sandpiper and one or two others had migrated so far, yet at times the restless migration urge still pressed the curlew and plovers southward. On clear nights when the prevailing westerlies swept strongly across the prairies, giving them a good beam wind, the flock would take off again. Hours later, another one or two hundred miles southward, the restlessness would be temporarily appeased and the curlew would lead them down to a moonlit knoll to await the dawn.
In this manner they straggled slowly southward. By the time the hot December sun had burned the giant thistles, and the pampas grass was silver with its nodding panicles of flowers, they were deep down into the stony undulating plains of Patagonia, within a single night′s flight of the Antarctic Sea. The herculean thrust of the migratory impulse had carried them from the very northernmost to the southernmost reaches of the mainland of the Americas. Yet even here there were still great flocks of shorebirds. The days were long and hot, the brief night cool. Of all the world′s living creatures, none but the similarly far-flying arctic tern sees as much sunlight as the shorebirds that spend each year chasing, almost pole to pole, the lands of the midnight sun.
For almost five months the curlew and plovers had been goaded by an insatiable drive that had relaxed at times but never fully disappeared. Now the urge of the migration time was dead. A peculiar lethargy gripped the plovers and they were content to fly back and forth between two salt lagoons —feeding, dozing, flying listlessly, waiting like an actor who has forgotten his lines for the prompting of instinct to tell them what to do next.
But within the curlew, as fast as the pressure of the migratory urge relaxed a new tormenting pressure replaced it. It was the old vague hunger and loneliness. Suddenly the curlew remembered again that he lived alone in a world to which other members of his own species never came. A restlessness of a different sort beset him. He tried to lead the plovers farther afield but they would not follow. Finally the restlessness became irresistible. The curlew spiraled high, circled and re-circled the lagoon where the plovers were feeding. He called loudly and repeatedly, but the plovers gave no sign of hearing. Then the curlew turned eastward toward the coastal tide flats that he knew were there, many hours of flight away. He was flying alone again.
Patagonia had none of the deep rich soil of the pampas. Much of it was gravelly shingle, cut by sharp ridges of volcanic rock, and the vegetation was scanty. Even where the coarse grass and thistles grew, they were burned brown now by the fierce summer sun. Out of this arid land the shorebirds were drifting eastward toward the cool, food-rich mudflats of the seacoast.
Here one of the highest tides of the world leaves miles of beach exposed at every ebb, and the stranded flotsam of the sea replenished twice daily was a food supply that never waned. Vast flocks followed each low tide outward. Most of them were golden plover, but there were yellowlegs too, flashing their white rumps, while buff-breasts and sander-lings daintily dodged the breakers as though afraid to get their feet wet.
The curlew wandered from flock to flock, seeking restlessly he was not sure what. His long, downcurved bill and wide spread of wing made him stand out prominently among the thousands of other smaller shorebirds.
It was January, and the tundra nine thousand miles to the north would remain for months yet a sleeping, lifeless land of blizzard and unending night, but the curlew began to feel the arctic′s first faint call. It was a feeble stirring deep within, a signal that dormant sex glands were awakening again to another year′s breeding cycle. It was barely perceptible at first. It strengthened slowly. And it was a sensation vastly different from the autumn migratory urge. The call to migrate south had been a vague, restless yearning for movement in which the goal was only dimly defined, but in this new call the goal was everything and the migration itself would be incidental. The essence of what the curlew felt now was a nostalgic yearning for home. And the goal was explicit—not merely the arctic, not the tundra, but that same tiny ridge of cobblestone by the S twist of the river where the female would come and the nest would be.
The curlew started home. Drifting slowly from mudflat to mudflat, he didn′t move far each day, but the aimlessness was gone. The movement was always northward.
The other shorebirds had felt it too. They were constantly moving and the bird population of the mudflats changed with every hour. In a week the curlew was two hundred miles northward.