Sunday, March 11, 2001

Redheads: Going Where the Sea Grass Grows

David Sikes/Caller-Times

Estimates are that one million redhead ducks, about 80 percent of the world’s population, winter in the 130 mile-long Laguna Madre.

Undulating above the waters of Nighthawk Bay, a dense ribbon of waterfowl streamed from the western horizon.
   The birds just kept coming and coming as our airboat glided onto the backside beach of Padre Island. The notion that these coveted diving ducks, thick as blackbirds in a grain field, represent only a small fraction of the redhead population that winters in the Laguna Madre, was, at that moment, staggering. How could there be more?
   A scene such as this quickens the pulse of most hunters and makes us appreciate the wondrous waterfowling opportunities along the Texas coast. About 80 percent of all redheads in the world visit here each fall.
   Plentiful numbers
   Between October and March, the ebb and flow of redhead ducks flying between the Laguna Madre and the freshwater tanks on the King and Kenedy ranches is as regular as the tide and certainly more frequent. To survive, the birds periodically must purge their bodies of salt, consumed with sea grass from the flats of the Laguna Madre.
   The critical balance of a burgeoning redhead population, sea grass and freshwater could become tenuous, particularly during periods of drought.
   Addressing the problem
   Ducks Unlimited is concerned and proactive enough to look at the situation. Also funding the project is the Rob and Bessie Welder Wildlife Foundation and the Coastal Bend Bays and Estuary Program and several smaller contributors.
   The project will cost between $200,000 and $250,000.
   Bart Ballard, a research scientist at the Caesar Kleberg Wildlife Research Institute at Texas A&M University-Kingsville, heads the DU study to determine whether the habitat can sustain the growing number of redheads, now at about one million birds.
   That's a lot of ducks. And they eat a lot of shoal grass.
   The three-year study is multifaceted. First, the research team must determine the abundance and distribution of sea grass and redheads between Corpus Christi and Mexico. So the five-man team goes into action before the ducks arrive, sampling the submerged vegetation and recording its relative abundance on the Laguna Madre floor.
   Learning more
   Throughout the ducks' stay in South Texas, biologists gather core samples of grass beds at the rate of 840 samples per month. This is backbreaking work, followed by tedium at the lab. Meanwhile, observers from the ground and air - Kingsville pilot Anse Windham does his part - monitor duck movement, abundance and distribution.
   Funny thing about the way redheads eat: They aren't as efficient as you might expect. They will not eat the green leafy grass itself. They don't even eat the roots. These picky eaters will only munch on the rhisomes, or underground runners that propagate new growth.
   Of course, to access the rhisomes, entire plants are uprooted and discarded. That's one reason for the rafts of floating shoal grass cursed by winter anglers on the Laguna Madre.
   But is this wasteful eating habit doing harm to the habitat?
   Depending on which casual observer is asked, shoal grass is either on the decline or more plentiful than ever in the Laguna Madre. Others say the amount of grass hasn't changed much over the years, only the distribution of grass beds is different.
   Chris Onuf, who oversees the U.S. Geological Survey's Texas Gulf Coast Field Station in Corpus Christi, sites a 35 percent overall decline in shoal grass over the past 40 years in the Laguna Madre. Not only do redheads rely on shoal grass, any angler knows that grass beds help to stem erosion, provide cover for baitfish and are used as nurseries for shrimp and a variety of game species.
   Some studies even indicate that shoal grass is the preferred vegetation of young trout and redfish.
   Onuf said that manatee grass has replaced much of the shoal grass in the upper Laguna Madre while turtle grass has taken over many of the shoal grass beds that once blanketed the Lower Laguna Madre.
   He didn't care to speculate on whether redheads have contributed to this shift. Like the rest of us, maybe he's counting on Ballard's biologists to provide some insight.
   Also threatening sea grass in the Lower Laguna Madre, near the Arroyo Colorado, is over enrichment of nutrients. Speculation is that agricultural runoff and storm drainage is killing sea grass. Under certain conditions, nutrient-rich water produces algal blooms such as brown tide, which can smother sea grass.
   And throughout the lagoon, periodic dreading of and traffic on the Gulf Intracoastal Waterway clouds the water with silt at times, robbing sea grass beds of vital sunlight. We're not sure what destructive practices occur across the border.
   Hard work
   Obviously, DU isn't prepared to wait and see where the truth lies regarding the dynamics of shoal grass and redheads.
   Dale James, a doctoral student in waterfowl biology, and John Davis, a research associate, comprise the core of the five-man research team studying the entire 130-mile length of lagoon.
   Considering the amount of fieldwork involved, I can't imagine when these guys sleep.
   Besides sampling and analyzing sea grass, Ballard, James and Davis also will examine the survival and health of wintering redheads.
   To do this, they must harvest eight birds a week. That's right. They use shotguns.
   But that's where the fun ends.
   Once in the lab, the birds are plucked, the feathers are tested, stomach contents are examined, then the birds are pureed so they can be evaluated for fat and protein content.
   You might ask what the practical application of such a study might be. Ballard offers this scenario.
   If the team determines redheads are destroying beyond recovery grass beds adjacent to inland freshwater sources, then DU could focus on coastal conservation measures to alter the feeding and watering habits of the birds. This could result in the creation of more widely distributed wetlands along the coast to take pressure off heavily grazed shoal grass beds. This also might prepare the saltwater and corresponding freshwater habitats for the burgeoning redhead population to come and at the same time offset some of the effects of drought on South Texas waterfowl.
   Makes sense to me.