The Genius of Birds

by Jennifer Ackerman

To see if birds are truly navigating, scientists put them on boats and planes and drive them around in cars (like those hostage sparrows) to land them in a distant, unfamiliar place with no clue of distance or direction. Then they release the birds and watch how they reorient. It’s called a displacement study, and it’s a powerful tool to investigate true navigation. Scientists suspect that pigeons and other birds navigate using a two-step “map-and-compass” strategy. First, they determine where they are at the point of release and which way they need to travel to get home. (This is the map step: In human terms, it’s the spatial coordinate system that suggests “I’m south of home, so I need to travel north.”) Then they use landmarks or celestial or environmental directional cues as a compass to keep them on the straight and narrow. The whole system, including both map and compass, appears to consist of multiple elements involving different types of information—sun, stars, magnetic fields, landscape features, wind, and weather. The compass part is fairly well understood, due in large part to thousands of studies depriving birds (often pigeons) of one sense or another, displacing them, and then seeing whether they’re thrown off course. Pigeons, like humans, are eye-minded creatures. It would be surprising if they didn’t use that grove of gnarled oak trees, that oxbow curve in the river, that hedgerow or weird triangular skyscraper, to home in on their lofts. And, it turns out, ...