|SREL Reprint #0610|
Age-specific Changes in the Major Body Components and
Caloric Values of Growing Wood Ducks
L. Clay, I. Lehr Brisbin, Jr., and Kenneth A. Younstrom
Analyses of the major body components of pen-raised
Wood Ducks (Aix sponsa) revealed that body-fat indices (g fat/g
lean dry weight) decreased rapidly during the first week of life from a value of
approximately 0.30 at hatchling. Low
values of about 0.10 were then maintained until an age of 2 weeks, after which a
gradual increase in the fat index occurred until a value of 0.39 was reached at
about 6 weeks. A slight decrease in
body fat then occurred as asymptotic weight was approached.
Body-water indices (g water/g lean dry weight) were low at hatching and
increased rapidly to a maximum value of about 3.14 at 1 week, declining
gradually thereafter throughout the remainder of the growing period.
Ash indices (g ash/g lean dry weight) and the caloric values of lean dry
and ash-free lean dry biomass did not change significantly throughout the
growing period. Live-weight caloric
values, however, varied in a pattern similar to that of the fat index.
The abrupt increases in body water and decreases in body fat during the
first week of life seem to typify growing waterfowl and clearly differentiate
them from other precocial species of birds such as Japanese Quail.
Whole-body counting of potassium-40 was not successful in accurately
predicting the total body fat of growing Wood Ducks.
Received 25 September 1978, accepted 1 December 1978.
SREL Reprint #0610
Clay, D.L., I.L. Brisbin Jr., and K.A. Youngstrom. 1979.
Age specific changes in the major body components and caloric
values of growing wood ducks. Auk 96:296-305.