Publications

Texas Mottled Ducks

Texas Mottled Ducks

Article by Todd Jay Steele

Photos by David Butler, Larry Ditto, Monte Hensley, Todd Jay Steele

Back in the 1980s, when I was relatively new to duck hunting, I harvested a duck that I could not identify at the mouth of the Brazos River south of Freeport.

“Hey, I think I shot a Black Duck … no; think it’s a Dark-plumage Mallard hen,” I told my hunting buddy Bill as I flipped the bird back and forth in my hand, closely inspecting the speculum feathers and bar patches.

Finally, I declared, “This duck is a Mallard/Black Duck cross!”

There were no cell phones in those days to quickly identify the bird at hand, only an image memory from the Lone Star duck chart pinned in my garage. As a recent transplant from the East Coast to the Texas Coast, I was blissfully ignorant that the bird in hand was a Mottled Duck.

The two of us shot four “hybrids” that morning and decided to call it quits, as Mallard hens were 70-point birds, and we assumed we’d reached our limit under the point system.

When I got home that evening and opened up the Peterson Guide, I realized the species in question was a Mottled Duck. Over the following decade, I would pursue Mottled Ducks from the Barrow Ranch in Anahuac to marshes and inland rice fields along the Mid-Coast.

They were hard to hunt and we mostly jump-shot them. Mottled Ducks isolate themselves from other duck species in small marsh potholes and knee-deep sloughs that required long arduous walks across thigh-high cordgrass. Limits in the 1970s and early 1980s ranged up to five Mottled Ducks per day, but in 1985, Mottled Duck limits dropped to one bird, where they have remained ever since.

Today in coastal Texas, the Mottled Duck is the holy grail, unequivocally the wariest and smartest of all ducks in Texas. A denizen of isolated marshes and backwaters, and introverted as opposed to gregarious, they are thinkers—rarely committing on the first pass—suspicious of anything out of place. And in the hand of a duck hunter, the Mottled Duck is a true trophy.

Where They Nest

The Mottled Duck is the only dabbling duck in the continental U.S. that does not migrate. In Texas, they are most numerous in the marshes east of Houston, with their numbers declining as one goes southwest along the coast. Concurrently, our marsh system narrows going down the coast, showing a direct correlation between the marsh and Mottled Ducks.

In the marsh, they prefer to nest in very dense bunches of Gulf cordgrass and inland in thick stands of grasses. They are secretive ducks and prefer to nest in sites with minimal disturbance, with peak nesting times in March and April. Nesting sites are often a long distance from brooding sites.

According to Bart Ballard, Ph.D., a research scientist with Texas A&M University at Kingsville, Mottled Ducks have been tracked leading their young from a nest to water up to two miles away—a hazardous journey for all.

In the brackish environments, the studies have shown that ducklings reach a threshold of survival in salinities ranging between 9-13 ppm. At 15 ppm, studies have shown that survival drops to only 10 percent, according to David Butler, Texas Parks and Wildlife Department (TPWD) waterfowl specialist.

Very few Mottled Ducks nest in saline marshes, preferring brackish or freshwater marshes. They will frequently re-nest, but their clutches will be smaller. Young fledge in 8 to 10 weeks. A flightless molt period occurs later in the summer for approximately 27 days. Habitat for the molt must have sufficient freshwater and food sources including spikerush, bulrush, widgeon grass and invertebrates to sustain birds during that period of time.

Although Mottled Ducks congregate in small groups, they become gregarious in late summer. According to retired TPWD biologist and Mottled Duck expert, Charles Stutzenbaker, “Flocks upwards of 40,000 birds have been observed in one field.” I have observed on more than one occasion more than 10,000 Mottled Ducks in Brazoria County rice fields in the 1980s during early teal season.

Hybridization

Mottled Ducks belong to the genus Anas and are closely related to mallards, black ducks and Mexican ducks. Ducks within the genus Anas all hybridize to a certain degree, with interbreeding by the mallard species producing viable and fertile offspring. Hybridized Mottled Ducks were found to comprise 10 percent of the population sampled in one study of the Florida population, while the Western Gulf Coast (WGC) hybridization rate was approximately 5 percent. Hybridization of Mottled Ducks with mallards in Florida is a direct result of released mallards over many years, and Florida law now prohibits the release of mallards.

The transplanted South Carolina population from Texas and Louisiana now appears to be all hybrids from interbreeding with mallards. It is unknown if Mottled Ducks hybridize with Mexican ducks, a subspecies of mallard that occupies a narrow range along the Rio Grande River in West Texas. Up until recently, there has been a significant real estate gap between Mexican ducks and Gulf Coast Mottled Ducks, but that gap may be shrinking per recent winter aerial surveys.

Hybridization combined with close similarities in plumage colors often causes confusion in differentiating Mottled Ducks from hen mallards, Black Ducks and Mexican Ducks (see accompanying sidebar for differences). TPWD list in their regulations bag limits of 1 “dusky” duck (including Mottled Duck, Mexican-like duck, Black Duck and their hybrids). In flight, they all have solid dark bodies with solid white on the undersides of their wings. It is very difficult to spot differences in all of these “brown ducks” in aerial surveys that are conducted in areas where species overlap.

A Wild Duck in Decline

Not all is well in the realm of the Mottled Duck. Their numbers have been declining over the past 50 years (1966 and 2015) at a rate of 3.1 percent per year according to the North American Breeding Survey, with a cumulative decline of 78 percent over that period. Their declining numbers are a concern for both state and federal biologists who are working diligently to understand their living requirements and how to protect their environment.

In Texas, efforts are ongoing to improve nesting success and grassland conditions, protecting suitable brooding habitat in close proximity to nesting habitat, minimizing interaction with predators and maintaining optimal habitat sizes. Up until recently, Texas Mottled Ducks have been in decline while the Louisiana birds have remained stable, but within the past three to four years, there has been a reversal. Today, Texas Mottled Duck numbers have become stable, and Louisiana numbers have dropped.

The Past (Loss)

Factors negatively impacting Mottled Ducks include habitat loss by development, conversion of rice fields into row crops, predation, (five times higher than hunting), land erosion, capricious precipitation, spent lead poisoning from the past (pre-1991), encroachment of brush and tallow trees, saltwater intrusion into freshwater ecosystems from channelization and sea level rise, and lack of sediment being deposited on the landscape due to watershed channelization.

“The habitat for Mottled Ducks along the Gulf Coast is becoming increasingly fragmented and the connectivity of nesting and brooding areas is being lost. In addition, they are sensitive to urban sprawl that is swallowing up the landscape such as the Katy prairies west of Houston,” Ballard said.

An ideal ecosystem for a Mottled Duck would be 500 to 1,000 contiguous acres with nesting, brooding and molting habitat. Coastal Texas lost more than 210,000 acres of estuarine and palustrine coastal wetlands between 1955 and 1992. Concurrently, harvest numbers of Mottled Ducks began to drop as well.

Mottled Duck harvest numbers have declined dramatically since the day I held my first one in my hand. Harvest rates in the 1960s and 1970s averaged about 52,000 birds per season. In the 1980s and 1990s, the average harvest declined to approximately 20,000 birds, with bag limits under the point system ranging from five to three to two to one, and closed entirely during the 1975-1976 season.

In 1985, the limit on Mottled Ducks in Texas dropped to one bird where it has remained ever since. (Current regulations do not allow any Mottled Duck to be harvested the first five days of the season). Recorded harvest rates for the past four seasons (2014 through 2017) for Mottled Ducks in Texas were respectively 5,034 birds, 6,187 birds, 4,372 birds and 4,919 birds—a stable but slightly declining harvest.

If Mottled Ducks were struggling, then why an open season at all? For one, much of the money dedicated to the study of Mottled Ducks was funded through duck hunters. Second, with a one-bird bag limit per day, banding studies have shown only a slight decline in harvest rates, while at the same time, adult bird numbers are increasing in Texas. This means hunting harvest is not impacting Mottled Ducks, under current regulations.

Numerous studies and leading experts in Mottled Ducks all agree that recruitment of the young is the limiting factor. Data indicates that Mottled Ducks have one of the lowest survival rates of any dabbler ducks.

The Present (Knowledge)

From the aerial spring survey counts on Mottled Ducks conducted by TPWD, the U.S. Fish and Wildlife Service (USFWS), and the Louisiana Department of Wildlife and Fisheries, biologists are compiling information on breeding populations and locations.

“We now have a tremendous data stream that is beginning to tell us part of the story of the Mottled Duck’s life,” Kraai said. “In addition, life spans of Mottled Ducks are known through the long-running banding program.”

But gaps in knowledge regarding the species’ ecological requirements still need to be studied and understood. Habitat selection by Mottled Duck females is still somewhat of a mystery as they scan the landscape looking for ideal nesting habitat with brooding habitat nearby.

The brood-rearing period is perhaps the least-known aspect of their reproductive ecology. The species’ reclusive nature and preference to nest in remote undisturbed places makes finding those key areas difficult for biologists and research scientists.

Ballard and his associates have implemented a relatively new system to identify key Mottled Duck habitat. The system, called the Mottled Duck Decisive Support Tools, comprises computer-based graphical systems to aid stakeholders in identifying areas on the landscape where conservation actions will have the greatest benefit.

Overlapping various databases such as satellite imagery, national wetlands inventory data and cropland data will help biologists target specific wetlands and grasslands that will benefit nesting and brood-rearing. The 34-layer spatial data, available for download, includes waterfowl breeding and non-breeding layers, objectives layers, social objectives layers, and raster data mixed-model layers.

The Future (Intervention)

Every winter, TPWD partners with USFWS to conduct wintering waterfowl surveys across the Texas. In recent years, “brown ducks” are being observed outside their normal Gulf Coast range and are being counted in increasing numbers in the Blackland Prairies Region and especially the South Texas Brush Country where numerous stock tanks and lakes have been added. This area, for the most part, is remote and isolated from human disturbance—ideal for reclusive Mottled Ducks.

Whether this is an expansion of Mottled Ducks from the north or Mexican Ducks from along the Rio Grande River is unknown at this time, but it appears that this duck of the secretive marsh may be discreetly expanding its range into the wilds of the Brush Country. Plans are underway to expand spring Mottled Duck surveys into this region, and the University of Texas at El Paso will be conducting genetic studies of captured birds to see if these are indeed Mottled Ducks or expanding Mexican ducks.

“If they are indeed Mottled Ducks, this will be exciting news and hope for an expanding population in Texas,” Kraai said. If it is an expansion of the species, this will not come as a total surprise to waterfowl biologists as the Mottled Duck in Florida has for a long time been adapting to new habitat in the northern part of the state. Another new expansion area of Mottled Duck is its urbanization, nesting in freshwater lakes of housing developments, unheard of just a short time ago.

“The Mottled Duck appears to be highly adaptable even with its very specific needs,” Kraai said.

The Gulf Coast Joint Venture (GCJV) is a conservation partnership of 14 groups for protection and enhancement of priority bird habitat along the Gulf Coast. GCJV Coordinator Barry Wilson stated there are two programs now in place to help the Mottled Duck.

The first is the Mottled Duck Program under the Texas Prairies Wetlands Program, a grassroots program that was started three years ago by the GCJV, funded through TPWD, administered by Ducks Unlimited (DU) and designed to provide habitat for Mottled Ducks during their nesting, brooding and molting periods.

“It is similar to the Texas Prairies Wetlands Program which runs from September through March,” said Taylor Abshier, DU biologist. “The Mottled Duck Program is designed to assist landowners in Texas, but later in the season—January through August—and often on different key landscapes. Ideally, the habitat contains all the ingredients needed for a successful raising of ducklings which includes areas for nesting, brooding and molting.” Currently, DU administers four to five projects per year.

The second program through the GCJV that provides financial incentives to private landowners is the Grassland Restoration Incentive Program (C-GRIP). C-GRIP specifically targets the central section of coastal Texas and helps cover brush management, prescribed burning, native seed reseeding and prescribed grazing. Anyone wanting to help Mottled Ducks can contact GCJV or DU under the Texas Prairies Wetlands Program.

Another way to help Mottled Ducks in their recruitment efforts is to not pull the plug on duck ponds at the end of duck season. Leaving water on the landscape not only helps migrating waterfowl refuel and build their fat reserves for the journey north, but it also provides crucial brooding areas for Mottled Ducks.

“Duck ponds late in the duck season are rich in
invertebrates consisting of snails, leeches, copepods, worms, small crawfish, aquatic insects, even freshwater shrimp,” Butler said. “Rather than dump all that biomass down the drainpipe, landowners and waterfowl managers should consider leaving the water on the landscape as long as possible to help Mottled Ducks.”

He continued, “Managers of wetlands should also consider a three-year rotation of a duck pond. The first year the soil is disturbed via disking, shredding or burning to set back succession; the second year, it is left flooded; with the third year being a contingent year to either disk or leave flooded if conditions become wet. Leaving water on the landscape year after year only invites the takeover of undesirable plants such as cattails, lilies, bulrush and tallow trees.”

“What keeps me up at night regarding Mottled Ducks is the urbanization of the coastal areas where the Mottled Duck has lived and thrived for centuries,” Wilson said. “The Mottled Duck is a flagship species, a barometer for determining the health of our coastal wetlands. We are steadily losing important habitat for their survival.”

 

The habitat loss not only affects Mottled Ducks, but a myriad of other species as well that depend on similar habitat to survive. For the waterfowler in Texas, there is no greater satisfaction than being able to harvest a trophy Mottled Duck, imbued with appreciation for all the efforts to protect the habitat and species for future generations to enjoy and gratitude to the tireless biologists, scientists, conservationists and landowners working feverishly behind the scenes to secure a future for one of Texas’ signature species.

Brown Duck – Notable Comparisons in Texas

Drake Mottled Duck - Distinctive black nape at base of bill. Sharp contrast with body and head feathers. Tail mostly dark with blackish markings. Speculum with thin to absent white lower border. Body feathers darker brownish compared to Mexican Duck.

Drake Mexican Duck - Faint or absent black nape at base of bill. Sharp contrast with body and head feathers. Tail mostly dark with blackish markings. Speculum with upper and thinner lower white borders. Body feathers lighter brownish compared to Mottled Duck.

Female Mallard -  No black nape at base of bill. Muted contrast with body and head feathers. Tail mostly whitish to cream with dark markings. Speculum with wider upper and lower white borders. Body feathers orangish brown compared to Mottled Duck and Mexican Duck.



Stay Informed