Geographic variation in foraging patterns of pre-incubating female Mallards

Differences in productivity between habitats in different parts of a duck's breeding range may influence how birds allocate time to meet the exogenous nutritional requirements of clutch formation. However, no study has compared activity patterns between birds in different portions of their breeding range. We used focal-bird observations to compare the time-activity patterns of pre-incubating female Mallards (Anas platyrhynchos) in the prairie pothole region of Manitoba and North Dakota with those in eastern forested New Brunswick. Birds in eastern Canada had higher foraging effort (63.7 vs. 41.6%, P < 0.01) and spent less time in comfort (12.2 vs. 7.6%, P = 0.01) and locomotion (12.7 vs. 4.1%) activities than birds on the prairies. Females responded to lower productivity by devoting more time to foraging, which may be why Mallards in eastern Canada are able to lay first clutches that are equal in size to those of prairie Mallards.