Estimating Abundance of Breeding Mottled Ducks in Texas

• Published in: Wildlife Society bulletin Vol. 29; no. 4; pp. 1186 - 1192
• Main Authors: Ballard, Bart M., Merendino, M. Todd, Terry, Russel H., Tacha, Thomas C.
• Format: Journal Article
• Language: English
• Published: Bethesda The Wildlife Society 01-12-2001; Blackwell Publishing Ltd
• Subjects: Animal reproduction; Breeding; Breeding of animals; Ducks; Gulfs; Land surveying; Population estimates; Waterfowl; Waterfowl and Wetlands; Wetlands; Wildfowl; Wildlife ecology; Wildlife habitats; Wildlife management; Texas
• ISSN: 0091-7648; 1938-5463

Estimates of abundance of breeding mottled ducks (Anas fulvigula) along the western Gulf Coast are rare, and most information has been based on localized surveys. Current information reporting trends in mottled duck abundance suggests a declining population in Texas. Our objectives were to estimate breeding mottled duck abundance in Texas and evaluate an aerial circling technique. We compared the ability of the aerial circling survey to estimate numbers of breeding mottled ducks to intensive ground surveys of a stratified random sample of approximately 300 wetlands throughout the mottled duck's range in Texas. From ground surveys during peak breeding (April) in 1994 and 1995, we estimated approximately 105,000 breeding pairs of mottled ducks in Texas and a total spring population of approximately 220,000 mottled ducks both years. Aerial circling survey estimates for breeding mottled duck abundance in March 1994 and April 1995 were similar to ground survey estimates. Estimates from aerial circling surveys in May 1994 and March 1995 were higher than ground surveys, partly because certain wetland types were surveyed more readily from aircraft. There were discrepancies in classifying pairing status between aerial circling and ground survey personnel, with aerial circling surveys recording more (P<0.001) lone mottled ducks and ground surveys recording more pairs. The aerial circling method appears more advantageous than ground surveys to estimate breeding mottled duck abundance along the Texas coast. There appear to be considerably more mottled ducks breeding along the Texas Gulf Coast than previously thought. Information on breeding abundance should give managers critical information to interpret midwinter survey tallies and evaluate habitat needs.