The effects of late-incubation body mass on reproductive success and survival of canvasbacks and redheads / Todd W. Arnold, Michael G. Anderson, Robert B. Emery, Michael D. Sorenson, and Cristina N. de Sobrino.

Includes bibliographical references (pages 961-962).

Intraspecificv ariation in nutrient reserves is believed to affect reproductive
success of female waterfowld uringe gg laying and incubation (the nutrient-limitationh ypothesis).
W e tested the nutrient-limitationh ypothesisi n Canvasbacks( Aythyav alisineria)
and Redheads (A. americana) by relating the body masses of incubating females with subsequent
nest success, brood survival, and adult survival. Our analyses were based on 392
Canvasbacksa nd 76 Redheadsc aptureda nd weighedd uringl ate incubationi n southwestern
Manitobad uring 1983-1993. For Canvasbackst, here was a significanti nteractionb etween
body mass and age; failed adults (ASY) weighed 3 g more than successful adults (P = 0.65),
but failedy earlings( SY) weighed3 7 g less than successfuly earlings( P = 0.03). For Redheads,
nest success was unrelated to body mass. For both species, brood survival and adult survival
(i.e., return rates) were unrelated to female body mass. Thus, future reproductive success
was correlated with body mass in only one out of seven test comparisons (i.e., nest success
of yearling Canvasbacks). Although we had large sample sizes and used similar methods,
our results were notably different from a previous study of prairie dabbling ducks (Anas
spp.),w herel ight-weightf emalesw erem orel ikelyt o experiencen est failure.F orb oth studies,
we believe thati nvestigator-inducedn est abandonmentw as an importantc auseo f conditiondependent
nest failure. We conclude that nutrient reserves were of minor importance in
determining future reproductive success of adult Canvasbacks and Redheads, but may be
important for yearlings.