The Cow Trap Lake Project has been a success on multiple levels.
A gull-billed tern wheeled in the stiff south wind raking Cow Trap Lake, pulled up short over one of the 19 low islands staggered along the coastal lake’s northern reaches and hovered on rowing wings for a couple of seconds before plunging like a hawk into a patch of wavewashed oystergrass, where it snatched breakfast.
The tern, its stout bill firmly holding an unlucky fiddler crab vainly clacking its pincers in protest, spun on a white wing, stroked perhaps 50 yards upwind and glided to a landing among scores of its feathered relatives gathered on the gravelcovered ridge of a larger island.
The three-fourths of an acre island and a twin just to its west swarmed with birdlife, mostly gullbilled terns and black skimmers, but also least and Forster’s terns, a handful of loafing brown pelicans and laughing gulls as well as ruddy turnstones. A single pair of American oystercatchers, too — the oystercatchers’ long, coral/ orange bill and flaming yellow eyes making them stand out even among the colorful avian mass surrounding them.
“These birds just began arriving over the past month or so,” Woody Woodrow said as we floated in a boat tucked in the lee of one of the pair of 500-foot-long, gravelly islands on a bright, windy, early-May morning. “They’ll begin nesting soon. It’s pretty obvious they like these islands.”
The pair of islands and the 19 smaller, lower, vegetation-covered “terraces” strung behind them didn’t exist five years ago. Neither did a 2,000-footlong submerged artificial reef created with more than 770 tons of crushed stone that sits between the two larger islands.
All are part of the Cow Trap Lake Project, a collaborative effort between federal and state agencies, private conservation groups, businesses and charitable organizations that is reaping multifaceted benefits for wildlife, coastal fisheries, birders, waterfowlers, anglers and others who enjoy these natural resources. Addresses wetland loss
The project, which has created more than 10 acres of terraces and islands fringed by more than two miles of intertidal estuarine habitat that is prime fish habitat and fishing areas, began as an effort to address what is becoming an increasing issue along coastal Texas: loss of coastal marsh, prairie and wetlands.
“We were seeing severe erosion along the north shoreline of Cow Trap Lake,” said Jennifer Wilson, biologist with the San Bernard National Wildlife Refuge, which includes much of the 1,000-acre estuarine lake and adjacent Cedar Lakes complex near the mouth of the San Bernard River in Brazoria County.
Wind-driven waves pushed across the open fetch of Cow Trap Lake were gnawing away the shoreline, eating into the coastal marsh rimming it. That coastal marsh is crucial habitat for waterfowl and other wildlife, serves as nursery habitat for coastal fisheries and other marine life, and serves as a buffer against storm surge and a sponge for floodwaters.
“We estimated we’d lost 17 acres to erosion,” Wilson said. And the problem was accelerating as sea levels rose.
That loss of crucial wetlands was a concern to Ducks Unlimited, the international conservation organization focused on wetlands and waterfowl. And DU was one of the first of more than a dozen government, public and private organizations that came together to address the issue.
“It’s a project that fits our purpose — protecting and enhancing vegetated coastal marsh, creating and protecting habitat,” said Kevin Hartke, regional biologist with DU’s Texas Conservation Field Office. “We are glad to be a part of it.”
Funding for the project came through grants that have included $626,000 from the Gulf Environmental Benefit Fund, administered by the National Fish and Wildlife Foundation and funded through penalties associated with the Deepwater Horizon oil spill. But several other funding sources contributed to the project, including Houston Endowment, Coastal Conservation Association, ConocoPhillips, NRG, USFWS’s Texas Coastal Program, NOAA and grants associated with the North American Wetlands Conservation Act.
“It’s almost impossible to take on a project of this scope without a major cooperative effort between a lot of groups, public and private,” said Woodrow of the US. Fish and Wildlife Service’s Ecological Services Clear Lake field office.
And it was a huge, logistically challenging project in a shallow, isolated area.
The project focused on building a series of 21 terraces — low islands, each shaped like an elongated “s” — in the open water near Cow Trap Lake’s eroding northern shoreline. The terraces, created by dredging material from the bay bottom, would be planted with hardy vegetation — smooth cordgrass, often called oystergrass — that would hold together the terraces’ soil.
The low islands attenuate the force of winddriven waves, protecting the eroding shoreline and allowing establishment of smooth cordgrass and other aquatic vegetation that protects against erosion.
During the engineering and design planning for the island, planners decided to make two of the terraces into larger, higher islands that could serve as nesting sites for waterbirds, especially colonial nesting species such as black skimmers and terns.
Such birds’ preferred native nesting habitat is naturally occurring islands of oysters or clam shell, where the communal nesting birds gather in large numbers to lay their eggs in shallow depressions and raise their young. The open water surrounding the islands helps protect the highly vulnerable concentrations of ground-nesting birds from predation from raccoons, snakes and other terrestrial predators. Additional nesting sites
With the population of many of Texas’ colonialnesting waterbirds struggling to remain stable and many declining, creating additional nesting habitat out of an island designed as an erosion buffer was a way to enhance the Cow Trap Project’s benefits.
The nesting islands — each 500 feet long, 60 feet wide, and 4.5 feet high and covered with a layer of crushed limestone that mimics natural shell — were built in 2014. In 2015, the first spring after the nesting islands were built, U.S. Fish & Wildlife Service biologists documented 181 nesting pairs of colonial waterbirds nesting on the two islands. In 2016, that number jumped to 1,241 nesting pairs and 1,141 pairs documented in 2017.
The majority of the nesters were gull-billed terns and black skimmers, two species with very limited nesting habitat. Texas hosts about half of all breeding pairs of gull-billed terns found along the Atlantic and Gulf coasts, and the colony on the Cow Trap Lake nesting islands is one of the largest known in Texas. Black skimmers, a strikingly colored waterbird with a singularly identifiable bill, have seen their population in Texas decline by as much as 70 percent over the past 30 years.
The islands also are used as nesting sites by least terns, Forster’s terns, oystercatchers and other waterbirds.
The project has benefited coastal fisheries and anglers as well as avian life. The terraces and nesting islands scattered over the project’s 30-acre footprint total a little more than 6,800 feet in total length, said Scott William of the USFWS Ecological Services office. The total area holding oystergrass and other intertidal vegetation fringing all sides of the terraces and islands is at least double that. And all of it is prime estuarine habitat supporting finfish, crabs, crustaceans and other marine life. Wide range of benefits
Add the considerable marine habitat created by the submerged artificial reef — a reef that will serve as substrate for oysters and clams and other mollusks — and the boost to Cow Trap Lake’s fish and fishing potential is significant.
While the Cow Trap Lake Project has resulted in a wide range of benefits to bird life and fisheries habitat, its primary function is to prevent erosion and loss of coastal marsh. And it is doing that job splendidly. Not only has erosion behind the breakwater of terraces and islands and reef ceased; the shoreline is beginning to repair itself, with oystergrass growing in the shallows. Also, the breakwaters have been a boon to water clarity along the affected shoreline, sifting sediments from the water and aiding in vegetation reestablishment.
“I think it’s been a very successful project,” Wilson, the San Bernard NWR biologist, said as she scanned the nesting islands swarming with skimmers and terns and fringed with a mix of water and oystergrass where mullet and mud minnows swirled. “You can see the benefits.”