For the Birds Radio Program: White-crowned Sparrow
How do we know so much about White-crowned Sparrows?
Ornithologists have amassed a tremendous amount of information about North American birds, but most people never think about how this information is gathered. The White-crowned Sparrow is one of the most heavily researched of all birds, in part because different subspecies live within an easy distance of a few California universities, and in part because it’s easy to provide an adequate diet to keep these seed-eaters alive for long periods in captivity.
The flight of white-crowns has been measured in wind tunnels. These birds normally fly 5.15 meters per second in still air, which translates to about 11 1/2 miles per hour. To maintain a constant ground position as the wind tunnel air speeds changed, the birds could speed up to almost 40 miles per hour, or could slow down to [negative] –2 miles per hour, actually flying backward!
White-crowned Sparrows have also been the star performers in studies designed to unravel some of the mysteries of bird migration. They were first studied for nocturnal restlessness. Like many migratory birds, white-crowns sleep soundly at night during summer and winter, but after a short nap at sunset in spring and fall, they awaken and flutter about their cage. In spring, the activity peaks between sunset and midnight, and in fall between midnight and dawn.
When placed in large enclosures under the open California night sky, white-crowns were found to collect on the north side of the enclosure in spring and the south side in autumn. Using 8 specially wired perches, ornithologists learned that during spring days, a white-crown chose perches randomly, but throughout the night, they chose the north perch 73 percent of the time, the northeast perch 15 percekt of the time, the northwest perch 6 percet of the time, and each of the remaining 5 perches, oriented east, west, southeast, southwest, and south, 2 percent or less of the time.
The closely related White-throated Sparrow helped scientists to understand exactly how birds use stars to find their direction. Apparently they aren’t born with a tiny star map embedded in their brain—rather, the slow but steady rotation of stars around the north star is the critical factor. When they were kept inside a planetarium during the spring migration period, White-throats oriented southerly when the north star was projected incorrectly to the south. When the birds were presented with a completely fictitious sky pattern, in which stars rotated around Betelgeuse of Orion instead of the north star, they used Betelgeuse to orient.
Although scientists haven’t unraveled all the mysteries of birds’ homing abilities, White-crowned Sparrows have proven that they can find their way home from quite a distance. In October, 1962, 574 of them were trapped and banded around San Jose, California, and shipped to the Patuxent Wildlife Research Station in Maryland, where they were released, thousands of miles from their normal north-south migration route. A year later, 8 of these banded birds were re-trapped all the way back in San Jose, not one carrying a map or a Triple A trip plan. Others probably also found their way back to San Jose but steered clear of nets and traps after their first unfortunate encounter with curious ornithologists. And my guess is that at least one lost little white-crown asked Burt Bacharach for directions.
Recording from Carpenters, “Do you know the way to San Jose?”