Text Copyright Gary Clark
I could hardly believe my eyes. I was standing in the center of the huge Dow Chemical Company plant at Freeport. Uncountable miles of big metal pipes formed a surreal steel web that stretched as far as I could see. But in the midst of pipes, towers, and bunker buildings I saw hundreds of elegantly bedecked black skimmers nesting peacefully on a four-acre stretch of barren ground.
Why does a large colony of black skimmers nest every year in the middle of the Dow Chemical plant? One reason is that Dow is next to the Gulf of Mexico, the Brazos River, and nearby marshes where there's ample food sources such as scaled herring and stripped mullet. But perhaps the most important reason the skimmers nest at Dow is because the company protects them.
In the late 1960s Maurice Garner a Dow employee, noticed that black skimmers were nesting in a scruffy parking lot in the chemical complex. Garner convinced Dow to reroute parking and built a fence around the lot. Later, he and other Dow volunteers covered the lot with crushed oyster shell to make it more suitable for nesting skimmers.
In the mid 1970s Douglas Slack, professor and associate department head in the Department of Wildlife and Fisheries Sciences at Texas A & M University, volunteered as a consultant to help Garner with the management of the skimmer colony. When he got to the site, Slack discovered that there were 500 to 600 skimmers nesting on a relatively small scrape of land in the middle of the chemical complex.
"I have to assume," Slack said recently, "that the birds are able to feed their offspring at this site. Therefore, food availability in nearby marshes plays an important [role] in determining colony site location. In addition, the colony is relatively free from predation. Predation in colonial nesting waterbirds is an important determinant of choice of breeding sites."
James Heller, a member of the Wildlife Steering Committee at Dow, knows about predation. He began his volunteer work with the black skimmers in the early 1990s and noticed that skimmer chicks were strangely disappearing. Maurice Garner, who had retired but was still helping with the skimmers, suggested the problem was predation by feral cats. Late one evening, Heller saw a big orange cat sitting on top of a pipe near the fence around the nesting site. Heller installed an electrically charged wire around the fence. End of cat predation.
Heller, along with other Dow volunteers, worked to improve the black skimmer nesting site. They re-covered the area with crushed oyster shell, placed small shelters on the site for shade, and infused the bare land with water that flows down long concrete troughs on either side of the nesting ground.
The introduction of water helped save the skimmer colony. Heller had watched skimmer chicks die off between 1991 and 1993. Necropsies of the dead chicks revealed that they had died primarily from dehydration. Heller and other volunteers installed shelters for shade and diverted water into the troughs. The skimmer chicks have thrived ever since.
"When I talk to groups," Heller says, "I emphasize that the responsible thing is not just setting up a nesting site. It goes beyond that. You have to set it up right and you have to maintain it."
Dow Company volunteers like James Heller, Tom Taroni, and Rose Wagner spend their off-hours maintaining the black skimmer colony. They also share the lessons they've learned with government agencies and conservation organizations. The Brazoria National Wildlife Refuge, for instance, uses the Dow plan for managing nesting black skimmers.
Black skimmers are in a group of birds called colonial waterbirds that include species such as great blue herons, least terns, and snowy egrets. Colonial waterbirds nest in large and often mixed groups probably as a way of defending their nesting sites against predators. Black skimmers nest on sandbars, beaches, and shell banks. They need a nesting site relatively safe from predators and human disturbance. Dow provides such a site.
Professor Slack said, "The Dow Chemical site plays an important role in the conservation of black skimmers on the Upper Texas Coast. We found a significant decline in numbers of black skimmers for the Galveston Bay Estuary for the period 1972-1992. However, the decline in black skimmer numbers was more than offset by the increases at the Dow colony. Apparently, the skimmers moved out of the nesting sites in the Galveston Bay complex into the Dow Chemical Company site."
I enjoyed watching the skimmer mating ritual at the Dow site. The male dances in front of a female, wagging a fish held crosswise in his beak. If the female takes the fish, the male then mates with her. If not, he has to wave his fish in front of another female or two. My wife saw one male wagging a stick in front of a female. The female took it (or as my wife said, fell for it) and allowed the male to mate with her. Sly male.
Many skimmers splay out on the barren ground in a behavior called loafing, which conserves energy during the heat of the day. The hens brood newly laid eggs. From time to time, the skimmers fly off to catch fish by furrowing the surface of the water with an extended lower mandible that's longer than the upper mandible. Once the lower mandible makes contact with a fish, the bill snaps shut and the skimmer eats the fish, feeds it to a chick, or uses it to flirt with a female.
Gary Clark and Kathy Adams Clark - NPN 134
Gary Clark's articles appear each week in the Wonders of Nature column in the Houston Chronicle. Kathy Adams Clark is a professional nature photographer who teaches photography courses and is a member of the Board of Directors of the North American Nature Photography Association. Visit their web site at www.kathyadamsclark.com.
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