Wl. Hohman et al., FOOD AVAILABILITY AND FEEDING PREFERENCES OF BREEDING FULVOUS WHISTLING-DUCKS IN LOUISIANA RICEFIELDS, The Wilson bulletin, 108(1), 1996, pp. 137-150
Expansion of the breeding distribution of the Fulvous whistling-duck (
Dendrocygna bicolor) into the southeastern United States after the mid
-1800s coincided with the establishment of rice (Oryza sativa) culture
s in Texas, Louisiana, and Florida. In southern Louisiana, where appro
ximately 80% of rice is aerially seeded in water Fulvous whistling duc
ks are suspected of feeding extensively on planted rice and are consid
ered a nuisance. To determine the extent of rice utilization by ducks
nesting in southwestern Louisiana, we estimated food availability in r
icefields and assessed feeding preferences. We also examined effects o
f sex and stage of reproduction on food selection. Feeding sites in Lo
uisiana ricefields that were tilled and hooded in preparation for spri
ng planting, contained abundant foods (mean +/- SE = 109.0 +/- 18.0 g/
m(2)), especially seeds of moist soil plants such as signalgrass (Brac
hiaria extensa), beakrush (Rhynchospora sp.), and flatsedge (Cyperus i
ria). Diets of males and females were similar (P = 0.080), but varied
through the reproductive cycle (P = 0.008). Consumption of plant mater
ial was slightly reduced during the period of rapid ovarian follicle g
rowth in females; however, ingestion of animal foods never exceeded 4%
. Fulvous whistling-ducks exhibited feeding preferences (P < 0.001) wi
th aquatic earthworms (Oligochaeta) and wild millet seeds (Echinochloa
sp.) being preferred over other food taxa. Rice made up <4% of the di
et and was selected in proportion to its availability before and durin
g period of rapid follicle development. Almost 25% of the diet of incu
bating females consisted of rice; however, we concluded that crop depr
edation by Fulvous whistling-ducks (less than or equal to 0.1%) was of
minor importance relative to other potential sources of crop loss. In
deed, use of ricefields by whistling-ducks may actually benefit farmer
s if ingestion of seeds of undesirable plants reduces the need for cos
tly herbicide treatments.