BIOLOGICAL DATA AND HABITAT REQUIREMENTS
WILDLIFE SPECIES: Aix sponsa | Wood Duck 



TIMING OF MAJOR LIFE HISTORY EVENTS : 
Courting-  before fall migration and again in spring
Age of Maturity-  1 year
Nesting-  late January (South); early March (Midwest); March-April (North)
Clutch-  7 to 15 eggs; average 12; some females deposit eggs in
         another female's nest (called "dumping")
Incubation-  26 to 37 days
Fledging-  56 to 70 days
Migration-  some southern residents are year-round; northern populations
            head south in late September and north in late February [5]


PREFERRED HABITAT : 
Wood ducks prefer wooded wetlands and forests with small lakes, ponds,
or riparian corridors, and flooded forested bottomlands.  They nest in
tree cavities or man-made boxes, usually within 0.6 miles (1 km) from
water [5].  They prefer riparian areas with a large amount of shoreline
per unit area of water, and with the opposite shore at least 100 feet
(30 km) away [13].  In the Mississippi River valleys, chicks prefer water
sites where currents are less than 1 mile per hour (1.6 km/h).  Chicks
less than 2 weeks old use flooded lowland forests, while older chicks
use shrub communities [13].  Breeding and brooding hens prefer sites
with ratios of 50 to 75 percent cover:25 to 50 percent open water.
Detailed habitat suitability index models have been developed for wood
ducks [13].

Wood duck preference for trees used for cavity nesting have been listed
in order of descending importance.  In floodplain forests these are
baldcypress (Taxodium distichum), sycamore (Platanus spp.), silver maple
(Acer saccharinum), black ash (Fraxinus nigra), sourgum (Nyssa spp.),
and black willow (Salix nigra).  On upland areas these are black oak
(Quercus velutina), red oak (Q. rubra), white oak (Q. alba), blackjack
oak (Q. marilandica), bur oak (Q. macrocarpa), and basswood (Tilia
americana) [2].

A study in northcentral Minnesota identified 31 wood duck nest cavities
and found that 21 of these were in mature (60-75 years) quaking aspen
(Populus tremuloides) stands, while the rest were in mature (100-120
years) mixed hardwood stands.  Nest sites were within 1,150 feet (350 m)
of water, and entrance holes were not less than 12 feet (4 m) above
ground [8].


COVER REQUIREMENTS : 
Wood ducks prefer sites with nest cavities within 0.3 miles (0.5 km) of
water, but will nest more than 0.6 miles (1 km) from cover if necessary.
Nest cavity trees must have a d.b.h. of greater than 12 inches (30 cm).
The nest entrance hole should be at least 6 feet (2 m) above ground, and
greater than 3.5 inches (8.9 cm) in diameter.  The interior basal area
should be greater than 40 inches squared (258 cm sq) [5].

Water depths are important in brooding and breeding habitat from
mid-April to late September in the North and mid-January to late
September in the South.  In breeding habitat, depth should be 3 to 18
inches (7.5-45 cm), and banks should be sheltered with shrubs.  In
brooding habitat, chicks need a water depth of less than 12 inches (30
cm) so they can forage for invertebrates [13].

Ideal cover for wood ducks is provided by shrubs that hang in a dense
canopy about 2 feet (6 m) above the water surface.  Downed timber can
provide year-round cover.  Habitat consisting of downed timber, woody
and herbaceous plants, and interspersed water channels provides good
brood cover [13].  Optimum cover for brooding consists of 30 to 50
percent shrubs, 40 to 70 percent emergent plants, up to 10 percent
trees, and 25 percent open water [13].


FOOD HABITS : 
The majority of wood duck food consists of plant material, with a
supplement of invertebrates.  During winter almost 100 percent of the
diet is plants, with an increase in animal protein (35 percent) in early
spring [5].  These percentages remain constant for males during the
summer and fall molts, but increase for females to about 80 percent
animal protein during egg laying.  This percentage drops for females
during incubation, when their diet includes high-energy seeds.  Wood
ducks usually will not forage in agricultural fields as long as their
native food sources are plentiful [13].

Some plant foods of wood ducks include fruits of maples (Acer spp.),
oaks, ash (Franius spp.), sassafras (Sassafras albidum), sweetgum
(Liquidambar styraciflua), baldcypress, water hickory (Carya aquatica),
buttonbush (Cephalanthus occidentalis), Asiatic dayflower (Aneilema
keisak), watershield (Brassenia schreberi), barnyard grass (Echinochloa
spp.), rice cutgrass (Leersia oryzoides), primrose willow (Ludwigia
leptocarpa), white waterlily (Nymphaea odorata), panicum (Panicum spp.),
smartweeds (Polygonum spp.), pondweeds (Potamogeton spp.), water bulrush
(Scirpus subterminalis), and slough grass (Sclera reticularis).
Invertebrate foods include spiders, crayfish, midges, scuds, water
boatmen, sowbugs, damselflies, dragonflies, caddis flies, and orb snails
[5,13].


PREDATORS : 
Wood duck predators include humans, mink (Mustela vison), raccoon
(Procyon lotor), fox squirrel (Sciurus niger), bullfrog (Rana
catesbeiana), snapping turtle (Chelydra serpentina), largemouth bass
(Micropterus floridanus), crows (Corvidae spp.), and starling (Sturnus
vulgaris) [2,5].


MANAGEMENT CONSIDERATIONS : 
Overmature trees and snags should be left on logging sites for wood duck
nesting cavities.  Mixed stands of trees, including those producing mast
and/or providing nesting cavities, should be left on these sites.  Elm
(Ulmus spp.) and maple are an important component of wood dick habitat
because they provide both [5].  Nest boxes constructed of wood, metal,
or plastic can be used in areas where cavities are limited.  If placed
in direct sunlight, however, plastic or metal may reach internal
temperatures high enough to kill embryos.  For detailed information on
constructing nest boxes, refer to the U.S. Fish and Wildlife Service
[14].

In bottomland hardwood sites where flooding is controlled, it is
important to maintain a flooding regime that promotes oaks that bear
small acorns.  Overcup oak (Quercus lyrata) produces large acorns which
are usually unsuitable as wood duck food [5].  Water depths in foraging
areas should be maintained at levels less than 8 inches (20 cm), but can
be deeper in resting and roosting sites.  Detailed information for
managing flood-controlled wetlands for wildlife habitat across the
United States is available [4].

Bottomland hardwood sites need openings to increase the growth of mast-
producing oaks.  Their growth is stunted under closed canopies [11].
Openings can be created by thinning or select cutting.

Long-term studies indicate that growth of trees on greentree reservoir
sites (GTRs) is reduced by several years of flooding.  However, there
is no indication that this poses any threat to wildlife, such as
wintering wood ducks, that use GTRs.  Flooding GTRs is recommended from
mid-September in the North and continuing through mid- to late October in
the South.  Drawdown should begin in mid-February [11].


REFERENCES : 
NO-ENTRY

Related categories for Wildlife Species: Aix sponsa | Wood Duck