Friday, 18 February 2011

A Moveable Feast

The ants are coming! The ants are coming! Far from striking fear into the hearts of birders, army ant swarms are longed-for events because they bring out the antbirds. Army ants, contrary to the 50's adventure and horror movies of my youth, do not consume everything in their path, such as cows, horses and the occasional tourist. They are out for insects,larvae and invertibrates, although if the odd egg or infant bird falls into their path, well...that's another matter. Their prey will naturally try to escape, leaping, flying or running as fast as it can, only to fall victim to the various antbirds that specialize in following the swarms.

Last week, my friend, Martha, and I, along with six other birders and our guides, encountered one of these ant swarms crossing our trail. Within a few minutes, we went from seeing a few columns marching across the mud to a generalized melee spreading across the rain forest floor. In their midst, dozens of bicolored and ocellated antbirds were dancing about, swooping down on caterpillers and other, many-legged creatures trying to escape the enslaught. The bicolored antbirds' strategy was to perch horzontally about a foot off the ground on twigs and vines, scouting out the ground below, and then diving for the scurrying insects. They would flare their tails in excitement before they dropped like raptors onto the kill. The ocellated antbirds had a different and more methodical approach; they poked at the leaf litter, tossing it aside ruthlessly to expose the fleeing bugs and pounced on them. Occasionally, there would be a brisk exchange of territoriality and the ocellated antbird, a weightier opponent, would chase the bicolored antbird away.

We watched the show in fascination. The antbirds were beautiful and terrible and innocent. They blindly addressed their own need. Once, a plain brown woodcreeper appeared opportunistically to take advantage of the harvest. The ants spread out across the trail like water spreading from an overflowing tub. Then, slowly, the swarm moved off into the deep brush and the streams became trickles. The antbirds followed like pilot fish snatching morsels of food from the mouth of the shark.

We always think of Nature with a capital "N" as motherly, benign and all-knowing. Seeing the ant swarm and the camp-following antbirds reminded me that it's small "n" nature, clever, thrifty and unsentimental. Nothing is wasted. Nothing is safe. Nothing is predictible.

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