The time has come, perhaps inevitably, when man and nature have collided on South Padre, a spit of sand on the southwest tip of the Gulf Coast. The conflict pits the free flight of birds against man's need for power -- the type of power measured by kilovolts and also the kind measured by dollar bills.

As in most Texas environmental issues, state and federal officials have lined up on opposite sides. But there is an unusual twist to this one. Texas is on the side of the birds and the naturalists, and they might win.

South Padre is considered the gem of Texas beaches, which to some critics of its tarred sand and littered dunes only means that the other beaches from Galveston on down must be costume jewelry. Still, this is the Gulf of Mexico; the sunrise is gorgeous and the weather is almost tropical.

That South Padre is for the birds is irrefutable.

Roger Tory Peterson, renowned ornithologist and author of field guides, ranks it among the top birding regions in North America, with "an incredibly rich and diverse bird life." Naturalists last year counted 12 million waterfowl using the nearby Laguna Atascosa Wildlife Refuge, including the endangered Texas brown pelican. It also is a funneling point for two migratory flyways, the Central and Mississippi, bringing an array of songbirds and raptors here in spring and fall, among them another protected species, the peregrine falcon.

That South Padre is coveted by man is obvious.

The first condominiums and resort hotels sprouted about 15 years ago and crowd the beach for several miles. Developers such as former governor John Connally and the local Franke brothers consider it some of the prime resort property around. It also is a staging area for two exotic tourist species: college students and wealthy Mexicans from Monterrey. Chamber officials say the number of tourists migrating over the mainland bridge each March has increased from 360,000 in 1980 to an expected 600,000 next month. Electricity use has nearly tripled in a decade.

With the island grown beyond the capacity of its essential services, and another seven miles primed for development after being exempted from the Barrier Island Protection Act in 1982, people here saw a need for more power. The utility that serves the island, Central Power & Light of Corpus Christi, devised a way to provide it.

From a point known as Holly Beach on the mainland, the power company proposed to run a transmission line eight miles across a bay called Laguna Madre to a station on South Padre about four miles north of where development now stops. The line would carry five wires strung out 55 to 90 feet above the water along 70 H-frame wooden poles spaced 600 feet apart.

Aesthetics aside, naturalist groups had problems with the proposed line when the utility first sought Army Corps of Engineers approval in 1982. Birds fly into aerial power lines, and get maimed or killed. To ornithologists, this plan seemed especially dangerous.

"It is generally agreed that there are five things an aerial power line should not be placed near: wildlife refuges, feeding grounds for waterfowl, migratory flyways, nesting grounds and areas populated by endangered species," said Cyndy Chapman, an officer of Bird Rescue Inc., a group that rehabilitates injured birds in South Texas. "Incredibly, the Laguna Madre power line would contradict all five precautions."

The utility company had reasons for its proposal. The first was practical. Since South Padre is open to violent storms and hurricanes that can knock out the power supply, it seemed to make sense to place the new line as far away as possible from the old one, which is several miles south of the Port Isabel bridge.

If CP&L is afraid of storm damage, naturalists asked, why not bury the line in a cable across the bottom of Laguna Madre? That elicted the economic argument. The aerial line was the cheapest alternative. It would cost about $5 million, little more than half the price of an underwater line. CP&L said it felt an obligation to make the best deal for its customers.

The brown pelicans presented a more difficult problem. Because they are protected under the Endangered Species Act, the utility had to demonstrate to the Corps and the Fish and Wildlife Service, which enforces the act, that the aerial lines would not affect brown pelican mortality rates. CP&L hired an environmental consulting firm, Espey-Huston, to do a study.

Chuck Sexton was the staff ecologist in charge of the project, which began in July 1984. Three days each month for six months, Sexton and two assistants observed the airspace above the proposed power-line route from dawn to dusk. In the mornings they took a boat out into the middle of Laguna Madre and counted pelicans. In the afternoons they retreated to a mainland station near the wildlife refuge and did the same thing. They tried to measure the birds' speed, their ages and altitude.

It was tedious work, but Sexton felt he could not rely on past pelican studies elsewhere in the country, because every situation is different. By his count there were perhaps 150 to 200 brown pelicans in the area, out of a total existing population of 500 to 600. In September, during the peak migratory season, he and his assistants also tried to count the numbers and varieties of all birds moving across the water, but that, Sexton said, "got to be overwhelming at times."

The final report, which Sexton did not write (by then he had moved on to another job), was a factual presentation of everything Sexton had observed during his field trips, plus a supplemental review of what experts around the country felt about the dangers of brown pelicans flying into transmission lines.

CP&L called the study the most exhaustive ever conducted on brown pelicans and concluded from it, in the words of David Sullivan, the utility's environmental manager, that "the burden of information shows the impact would be minimal. Perhaps 1 percent of the mortality of migratory waterfowl would be from transmission lines."

Last September the Fish and Wildlife Service, which had expressed serious reservations about the project from the beginning, withdrew them. The directive to stop opposing the line came from the Albuquerque regional office, which got its directive from the Reagan administration in Washington. There were only two caveats -- that the lines be marked with optic yellow tags, known as spoilers, so they would be more visible to the birds, and that the situation be reassessed if, after construction, it is shown that 15 or more pelicans a year are being killed. The Corps of Engineers issued a permit approving the project.

The Sierra Club and Audubon Society then carried the issue to the state, noting CP&L could not build the line without approval from the state's General Land Office.

Sidney Gauthreau, professor of zoology at Clemson University and an expert on bird migratory patterns, said the environmental impact study had a major flaw: It failed to monitor bird activity at night. Gauthreau pioneered the use of radar surveillance techniques to show that birds move at night far more than previously thought.

"There is more avian biomass in the atmosphere at night than you can shake a stick at," said Gauthreau. "The atmosphere is less turbulent at night. It is fine to study pelican movements by day, but by night may be as important. No one has quantified that movement at South Padre. If the night movement is considerable, the danger of the transmission line could be considerable, whether it is marked with yellow spoilers or not."

Sexton, who now works for the city of Austin parks department, said his field study for CP&L was not sophisticated enough in terms of population modeling to conclude whether the potential loss of pelicans from the line would be ecologically significant. If anyone asked his personal opinion on whether the aerial line was worth building, he said, this would be his response:

"One of the things CP&L made clear when arguing against burying the line was that they did not want their customers to absorb the increased cost. If someone asked me, as a customer, whether burying the line was a reasonable expense, whether I would be willing to pay more for electricity to assure that brown pelicans would not be imperiled, I would say yes. In my opinion, it would be worth paying the price."

Although he has not issued a ruling, state Lands Commissioner Garry Mauro has indicated that he will not grant the easement unless the cables are buried under the bay, as another state agency, Texas Parks and Wildlife, has suggested. "I hold the ace," Mauro said. "And I'm not sure this aerial line is in the best interests of Texas. The Corps of Engineers and feds can say whatever they want, but this doesn't appear ecologically sound."

However the issue is resolved, there will be more power on South Padre, and within a few years another seven miles of the beach may be developed. There are plans for a convention center, a golf course and more condominiums. In a few years, perhaps, there might be concern about what this means to the peregrine falcon, the ocelot and the Kemp's ridley sea turtle. But as South Padre Mayor Minnie Solomonson said:

"The world never stands still. People keep multiplying . . . traveling. If you're going to proceed with growth, you need to provide the amenities that people expect at a resort. You can never turn back to the South Padre Island of 1971."