Every evening, near an old shopping mall north of downtown Austin, thousands of migrating purple martins roost in just a few small live oak trees. Starting at dusk, the birds began to congregate over the parking lot, first just a few, then more and more. After about thirty minutes, there were thousands flying around the parking lot, clouds of birds wheeling and turning and chirruping. The whole canopy of sky above us was filled with birds. Then, on some unheard signal, they all dove towards the trees and jostled for roosting spots, chirruping madly at each other until everybody eventually found a spot. One person described it as a "tornado of birds," which is a pretty accurate description, as large clumps of them spiral in ever tightening circles before diving for the tree. It's really quite an amazing spectacle, more exciting even than our famous bats. It's difficult to convey in photographs, but hopefully, you'll get some idea of it.