Natalie Angier in The New York Times:
BARRO COLORADO ISLAND, Panama — Here in the exuberantly dour understory of the Panamanian rain forest, the best way to find the elusive and evolutionarily revealing spotted antbird is to stare at your boots. For one thing, if you don’t tuck in your pant legs to protect against chiggers and ticks, you will end up a color plate in “Rook’s Textbook of Dermatology.” For another, sooner or later — O.K., much later, many, many hiking hours later — you will finally step into a swarm of army ants boiling out across the forest floor. At that point you should step right back out of the swarm and start looking for the characteristic flitting and hopping of the thrush-size antbird, listening for its vibrato “peee-ti peee-it” call. Because wherever there are army ants out on a hunting raid, peckish antbirds are almost sure to follow. The birds are not foolish enough to try to eat them: Army ants are fiercely mandibled and militantly cohesive. Instead, they hope to skim off a percentage of the ants’ labor, by snatching up any grasshoppers, beetles, spiders or small lizards that may jump to the side in a frantic attempt to elude the oncoming avalanche of predatory ants. It’s a gleeful reversal of the conventional notion of parasites as little, ticky things that plague large, poorly dressed hosts. Here the big vertebrates are the parasites, freeloading off insects a fraction of their size. And the parasitic strategy is so irresistible that according to recent research in the journal Ecology, the spotted antbirds on Barro Colorado Island just may be taking it professional. Whereas the species has traditionally opted for a mixed approach — filching from ant swarms but also finding food on its own — the island-bound antbirds appear to increasingly depend on army ants to scare up their every meal. Janeene M. Touchton a researcher associated with the Smithsonian Tropical Research Institute and Princeton, and the principal author of the report, is now trying to identify the personality traits that may facilitate a spotted antbird’s leap from amateur to polished parasite. Is it boldness, aggressiveness, a love of novelty? Or maybe a lack of aggressiveness, a nonchalance about territory and a refusal to pick a fight? She is collaborating on the project with Martin Wikelski of the Max Planck Institute for Ornithology.
Dr. Touchton, who is 37, looks as if she could be Keira Knightley’s sister and has the field-hardiness of a Dr. Livingstone. In her view, studying spotted antbirds offers an extraordinary opportunity to catch evolution on the wing, to identify the precise steps behind the great mystery of how new species arise from old ones.