Incubation behavior of Northern Shovelers in the subarctic: A contrast to the prairies

We examined patterns of nest attendance of Northern Shovelers (Anas clypeat a) at Minto Flats, Alaska to explore geographic variation in incubation rhy thms between females nesting in Alaska and females nesting in the prairies of North America. Females nesting at Minto Flats exhibited lower incubation constancy than females from the mid-continent. Females nesting at Minto to ok 4.1 +/- 0.1 recesses day(-1), twice as many as other Anas species nestin g in the prairies, but length of recesses was not different than prairie ne sting conspecifics. Timing of recesses was dissimilar to rhythms reported f or Northern Shovelers in the prairies; many recesses were taken at midday, fewer recesses were taken in the morning and evening, and females were on n ests less when ambient temperature increased. Variation in the number of re cesses taken per day was explained by differences among females and day of incubation. Recess length varied both among females and with time of day th e recess was taken. Our data suggest that females at Minto have more diffic ulty obtaining food resources during incubation than females in the prairie s. Differences observed in attentiveness among females at Minto an likely r elated to variation in territory and female quality.