BROWNSVILLE, TEXAS — ON a sweltering June morning dense with mosquitoes, a National Audubon Society official pilots a shallow-draft motorboat across the Laguna Madre. The hypersaline bay lies between the south Texas coast and Padre Island, the barrier island that stretches 100 miles from Corpus Christi almost to Brownsville on the Mexican border.
Rising modestly from Laguna Madre's southern end is Green Island, whose 12 acres are home to the world's largest colony of reddish egrets - currently some 600 pairs, although the number varies from 500 to 1,000.
At the turn of the century, hunters supplying plumes for women's hats almost wiped out the reddish egret. Today it is a ``candidate 2'' species - thought to be suitable for listing as endangered or threatened. Seventy years after plume hunting was outlawed, the beautiful shorebird has not returned in any numbers to its former habitat in Florida.
Fortunately, plume hunters never discovered Texas's Green Island, the reddish egret's last holdout early in the century. The National Audubon Society did, though, and in 1923 leased the island from the state of Texas for $1 a year.
Texas has more species of birds - 579 - than any other state or Canadian province, so the society's presence has grown accordingly. Audubon now owns or leases 34 Texas islands totaling 13,000 acres. The society raises $100,000 a year to have five wardens keep them free of human and natural predators.
That duty is especially important at the beginning of the spring and summer fledging season. The islands are more active than usual, with parents feeding their newly hatched young.
Mike Farmer, the society's Texas Coastal Sanctuaries manager, docks the boat at Green Island and walks to shore. ``Right under this board was a five-and-a-half-foot rattlesnake a few months ago,'' he says. He cheerfully offers other warnings as he follows a brush-lined trail up a slight rise. ``Watch out for these things. They'll really stick you,'' he says, indicating an agave plant. It resembles a giant pincushion with the sharp ends outward.
Then he pauses. ``You hear that underlying `chick chick chick'? That's all young. Whereas that `wah wah' are adults.''
Farmer arrives at a rarely used cabin built by John Larson, who held the warden's job in 1928 and actually lived there with his wife and three children during the crucial March-August nesting season.
Still useful is the tree-top platform nearby. Farmer creeps to the top. Suddenly the bird sounds are connected to their origin. In every direction, roosting birds bob and flap among the branches as if afloat on a leafy sea.
The reddish egret is only one of Green Island's species. Farmer ticks off the others: sooty, Caspian, sandwich, and royal terns; little-blue, great-blue, black-crown-night, yellow-crown-night, and tri-colored herons; great and snowy egrets; white and white-faced ibis; and roseate spoonbills - 5,000 pairs in all, making Green Island one of the largest nesting places for wading birds in the United States.
Birds constantly glide in or flap away. A reddish egret soars overhead with nesting material in its beak. ``Now watch these ibis come in,'' Farmer says. ``They come in as a group, but they split and go to their own nests.''
As breathtaking as the view is, Farmer has a bigger surprise in store. He returns to ground level and leads down another trail, a virtual tunnel through the undergrowth. He's now in a forest of granjeno, a type of hackberry bush whose spidery limbs offer ample nest-building sites. It's like a grocery store aisle with fledglings stacked as thick as soup cans on the left and right. At his approach, smaller birds stay put, while older ones sidestep away warily.
``Look at all these hatched eggs. This is great,'' Farmer says, pointing to shells that have been neatly pecked in two. Other shells have a punched-in look. Those were eaten by grackles, he says.
Four-legged predators from the mainland also swim or wade across the two-foot-deep Laguna Madre.
``Raccoons are worse than coyotes,'' Farmer says. ``Coyotes can't climb trees.''
Protecting Green Island helps its inhabitants survive, but now scientists understand that the wetlands that supply their food must be protected also. ``That's what we've lost so much of,'' Farmer says. When the US Army Corps of Engineers dredged the intercoastal canal, it dumped the spoil on an important tidal flat. Some 60 percent of area tidal flats have been lost, and some of the remainder are threatened by potential development.
``Right now, we're dodging bullets,'' Farmer says.