Migration routes and chronology of American black ducks

Bowman, Jacob L.Migration influences the ecology, evolution, and conservation of migratory animals (Webster et al. 2002), yet migration routes and timing between breeding and wintering areas is virtually unknown for American black ducks Anas rubripes. We used satellite telemetry to identify migration routes and stopovers, estimate migration chronology, and describe variation among black ducks marked between 2007???2009 in Delaware, New Jersey, New York, Ohio, and Virginia. A total of 31 transmitters provided at least one full data set during spring migrations. Black ducks departed wintering areas March 18???June 7 ( x?? = April 17), averaged 3.35 stopovers (SE = 0.3 stopovers; range = 1???5 stopovers) and 6.44 d at stopovers (SE = 0.8 d; range = 0.54???12.2 d), migrated 1,126 km (SE = 89.5 km; range = 270???1,396 km), and arrived at inferred nesting areas April 16???June 28 ( x?? = May 9). South Atlantic Flyway black ducks migrated almost twice as far and took nearly twice as many stopovers as Mississippi and North Atlantic Flyway black ducks; South and North Atlantic Flyway black ducks arrived at inferred nesting areas approximately 2 and 4 weeks after those from the Mississippi Flyway, respectively. Black ducks south of the 40th parallel migrated more than 50% farther, took nearly twice as many stopovers, and arrived at inferred nesting areas 2 weeks after those to the north. Black ducks east of the 76th meridian migrated nearly 25% farther and arrived at inferred nesting areas 3 weeks after those to the west. Nine black ducks spent all or portions of spring migration along the Atlantic Coast, and 10 used the Hudson and St. Lawrence River valleys. Stopovers included Long Island Sound, NY, Narragansett Bay, RI, Lake Champlain, VT, Merrymeeting Bay, ME, and the Gulf of St. Lawrence, Canada. All 11 black ducks wintering in Ohio stopped at Lake St. Clair, Saginaw Bay, St. Mary???s River, or the Georgian Bay. A total of 13 transmitters provided at least partial data during autumn migrations. Black ducks departed inferred nesting or molting areas October 5???December 1 ( x?? = October 24), averaged 2.0 stopovers (SE = 0.3 stopovers; range = 1???4 stopovers) and spent 12.6 d at stopovers (SE = 3.5 d; range = 0.25???41 d), migrated 993 km (SE = 202.9 km; range = 277???1,485 km), and arrived at wintering areas November 18???December 18 ( x?? = December 1). Our study confirms the importance of known stopovers and emphasizes the continued need for conservation and management of wetland habitats along established migration corridors. Furthermore, migration chronology and stopover duration of stay from our study should be incorporated into energetic carrying capacity models to better inform and direct habitat goals for black ducks in northeastern North America.University of Delaware, Department of Wildlife EcologyM.S