Texas Waterfowl

Mottled Duck

59 SOURCES introduction: Aldrich and Baer 1970; USFWS 1978; McCracken et al. 2001. texas distribution : Swepston 1979. population status: Rose and Scott 1997; Pérez-Arteaga et al. 2002. range and habitats: Lindsey 1946; Ohlendorf and Patton 1971; Nymeyer 1975; O’Brien 1975; Hubbard 1977; Bellrose 1980; Lockwood and Freeman 2004; Pérez-Arteaga and Gaston 2004. reproduction: Lindsey 1946; O’Brien 1975; Hubbard 1977; Swepston 1979. appearance: Huey 1961; Bellrose 1980; Drilling et al. 2002. MOTTLED DUCK Anas fulvigula Although rates of ingestion of lead pellets (spent lead shot) by Mottled Ducks have declined since regulations were implemented that prohibited hunting waterfowl with toxic shot, their ingestion rate is still among the highest of any North American duck. Ingestion of lead pellets occurs while ducks are foraging ; the shot is either picked up as grit or as a potential food source. From 1998 to 2002, approximately 14 percent of Mottled Ducks harvested on national wildlife refuges and wildlife management areas in Texas contained ingested lead pellets. Lead pellet densities that exceed 600,000 per acre have been found in some Texas coastal wetlands.These estimates are the highest reported in North American wetlands. TEXAS DISTRIBUTION Breeding: Mottled Ducks nest in all coastal counties and in many first-tier inland counties.They nest inland along the Rio Grande to Zapata County and inland along the central coast to Lavaca, Colorado, Austin, and Waller Counties. Their breeding density is fairly light (about one breeding pair per square mile) throughout most of their range. Their highest breeding densities occur in the coastal marshes and prairies between Galveston Bay and Sabine Lake. Small numbers of Mottled Ducks are regularly documented in north central and northeast Texas. Interestingly, attempts were made to establish a breeding population in northeast Texas during the mid-1970s. Although it is doubtful that this propagation attempt is the source of today’s northeastern Mottled Ducks, it cannot be ruled out. Winter: From 2000 to 2008, Mottled Ducks averaged 26,084 during Texas Midwinter Waterfowl Surveys.They are most abundant in the Coastal Prairies, although dabbling ducks they are regularly observed in the South Texas Brush Country and Coastal Sand Plain (TPWD unpublished). TEXAS HARVEST From 1999 to 2006, Mottled Duck harvest in Texas averaged 11,399 annually. This was 20 percent of their estimated annual US harvest. LONGEVITY The longevity record for a wild Mottled Duck is 13 years, five months. It was banded in August 1963 in Jefferson County and recovered in November 1975 at Sea Rim State Park, which is also in Jefferson County. POPULATION STATUS Mottled Duck population estimates and population trends vary across surveys. Estimates derived from banding data suggest the fall population in Texas and Louisiana hovers at about 630,000. In the mid-1990s the estimated spring population in Texas Mottled Duck (male). Photograph byTim Cooper, April 1997, Laguna Atascosa National Wildlife Refuge, Cameron County, Texas. 61 was 220,000. Christmas Bird Counts from 1980 to 2007 suggest the Texas population is stable. However, trend data from several sources, including USFWS harvest surveys , the Breeding Bird Survey, and midwinter waterfowl surveys, suggest Mottled Ducks are declining in Texas. Breeding pair surveys conducted on national wildlife refuges in Texas also suggest sharp declines, particularly since 1995. Hybridization with feral Mallards (semiwild or park ducks with origins from domestic stock) is a major conservation concern. Mottled Ducks in Florida have been so overwhelmed by the introgression of Mallard genes that their continued recognition as Mottled Ducks is in jeopardy. A winter 1998–99 survey of hunterkilled Mottled Ducks in Texas suggested 6 percent have hybrid wing characteristics. The 2007 publication Gulf Coast Joint Venture: Mottled Duck Conservation Plan called for efforts to minimize interactions between Mottled Ducks and feral, resident, and released Mallards. DIET Breeding Mottled Ducks forage heavily on invertebrates, including amphipods, crayfish, dragonfly nymphs, midge larvae, and snails. Estimates of invertebrate consumption during fall and winter vary greatly, ranging from 1 percent to 40 percent. Seeds are heavily consumed during fall and winter, particularly those of rice, barnyard grass, smartweed, and widgeongrass. RANGE AND HABITATS Breeding: Mottled Ducks are found in peninsular Florida and along the northwestern Gulf coast from Alabama west and south to Veracruz. Small numbers breed in northeastern Louisiana and in north central and northeastern Texas. Breeding pairs use depressional wetlands, coastal ponds, irrigation canals, rice fields, and coastal marshes. Pairs tend to select ponds located in fresh...