Purple martins blacken sky

AUSTIN (KXAN) - It starts an hour or so before sunset. Careful observers looking up can pick out a few soaring dots in the sky. Within minutes, the dots begin to multiply, slowly at first, then more quickly. In no time, the dots are recognizable as birds, small at first, then larger and larger as they descend.

The pattern is helter skelter, but as the number of birds continues to balloon, its direction begins to take on a more circular track. Then, just before dark, the flock grows thick, dark and loud, reminiscent of a NASCAR race as the cars thunder around an oval track.

Welcome to the annual premigration gathering of purple martins in a grove of trees just across the street from the north side of Highland Mall.

"These are the parents and the young of all the purple martins around Austin and all points north, we think," said Julia Balinsky, purple martin monitor for the Travis Audubon Society .

Glancing skyward, Balinsky breaks into the proud smile of a mother. She and her husband, Andy Balinsky, spend months every year, starting in January, caring for a host of human made martin nests at the Hornsby Bend Bird Observatory just southeast of Austin. The birds bear their young in those nests, contained in hanging gourds and elevated houses. The Balinskys chase away invading sparrows and starlings, gently pick bits of eggshell off the wee ones and hoist the nests back in place, far above the ground.

"These are my babies!" Balinsky beams.

Now grown and ready to migrate with their elders, the young birds join in the ritualistic dance in the sky before settling into a grove of oak trees for the night. Within weeks, they will all be gone, bound first for the Lake Pontchartrain area near New Orleans, and then on to Brazil.

It's impossible to know just how many birds congregate in this area every night.

"There are some numbers floating around and I haven't personally counted every bird," said Balinsky. "Three hundred thousand, maybe a half a million."

Whatever the number, as the sky darkens, not so much from the setting sun as from the growing flock, more and more people arrive on the scene, as well. Some sit in lawn chairs they've brought from home. All worry somewhat about being hit by falling poop. They take the chance because this natural phenomenon is a glory to behold.

"It's an awesome spectacle; it's a spectacular show," said spectator Tom Loomis, who brought along his grown children and one of their friends. "It's astonishingly abundant with birds."

The attraction is evidently mutual.

"Purple martins are birds that need humans around them and they need to be near water," Balinsky said. "In the south, they nest around humans. If you put up a purple martin gourd rack in the middle of nowhere and there's plenty of water and plenty of everything they need, they're not likely to nest there. They just like it when there are humans around."

Some say that may be not so much because humans are around as it is because other critters are not. According to Rob Fergus, who co-wrote The Purple Martin , a book about the birds, with UT professor Robin Doughty, purple martins choose "islands of green space surrounded by asphalt."

Experts speculate that such environments reduce the risk of being eaten out of house and home by such predators as great horned owls, screech owls, rat snakes and raccoons.

Whatever the reason, the setting sun casts the swirling martins in a kaleidoscope of silhouettes. They seem to pick up speed, dizzily racing round and round the trees that will become their beds. The late arrivals flap their wings furiously and almost hover, as they desperately seek out an unused bit of branch on which to settle. Their chatter is incessant, almost like the sound of a waterfall cascading into a pool.

The mesmerized spectators give in to the gathering darkness, gather up their lawn chairs and fly off to beds of their own.