Annual Habitat Selection by Mottled Ducks in Coastal South Carolina

Mottled ducks (Anas fulvigula) are endemic to Gulf Coastal United States, Florida, and Mexico. Birds from Florida, Louisiana, and Texas were released in coastal South Carolina from 1975 - 1983, and subsequent banding data suggest a dispersing and increasing population in the state. Because autecology of mottled ducks is little known in South Carolina, we radio-marked 116 females in August 2010 - 2011 in the Ashepoo, Combahee, and Edisto Rivers Basin to assess habitat use throughout the annual cycle. We monitored habitat use by aircraft during fall-winter and via ground reconnaissance during spring-summer. Because of small sample size due to radio-transmitter failure and logistics, we pooled data across years to obtain 1,241 locations from 67 females. Selection ratios (wi) showed that females selected managed tidal impoundments but avoided unmanaged wetlands during fall-winter and spring-summer. In fall-winter, females selected wetlands containing planted corn (wi = 1.96 [1.25, 2.57]) over wetlands with natural vegetation (wi = 0.92 [0.86, 0.98]). Mottled ducks also selected brackish wetlands (wi = 1.87 [1.68, 2.07]) over wetlands that were fresher (wi = 0.18 [0.08, 0.29]) or more saline (wi = 0.65 [0.37, 0.92]). Our study highlights the importance of managed brackish impoundments to mottled ducks in South Carolina and underscores differences between birds' habitat use compared to elsewhere in their range.

Publication date
Starting page
Ending page