Ecology of Red Maple Swamps in the Glaciated Northeast: A ...

et al. (1984) hypothesized that, given similar vegetation
struh, avian richness and abundance
would increase at sites with deeper organic soils
and water seasonal surface-water coverage. Merrow
(1990) verified this hypothesis, to some extent,
in his study of 12 mature, relatively homogeneous
red maple swamps. Of 20 habitat variables examined,
only peat depth was significantly correlated
with avian abundance. Surface-water coverage
was not an important variable in Merrow's
study, most likely because water levels in southern
Rhode Island were unusually low during his
census period.
Red Mapk Swamps a'
Habitat
swamp immediately adjacent to the impoundment.
Nest densities in the green-timber impoundment
were also higher than those in flooded dead timber
and cattail marshes within the refuge (see
Cowardin et al. 1967). Mallards accounted for
nearly 8094 of the 355 nests found (Kivisalu et al.
1970). Other nesting species included wood duck,
black duck, Canada goose (Bnznta canadensis),
blue-winged teal (Anas discors), green-winged teal
(A. crecca), hooded merganser, gadwall (A.
strepera), and American wigeon (A. americam).
Stumps and tree cavities with openings less than
1 m above the ground accounted for the majority of
waterfowl nest sites from 1965 to 1967 at Montezuma
(Kivisalu et al. 1970). After a predator-control
program was instituted in 1968, the majority
of waterfowl nests were built on tree mounds. Racpredadofeggs
~ ~ ~ floodplains, t e d bmin swamps, and beaver
flowages of tho Northeast are important feeding coons andminkwemthe~rimar~
snd -as for migrating waterfowl and incubating hens. Nests were placed an average
1959; Stanton 1965; Rockwell 1970; Kirby 1988). In of 70 cm above the water surface; thus, the need for
most years, surface water levels in forested wet- ca~ful water level management in forested waterlands
are highest from late fall through spring, fowl impoundments is clear.
allowing access ta these areas by migrating water- Of all the waterfowl species that breed in the
fowl, Among the species that frequent flooded Northeast, wood ducks (Fig. 7.6) are the most
swamps during migration are the wood duck, highly adapted for life in forested wetlands
American black duck, mallard (Anas platyrhyn- (Johnsgard 1975; Bellrose 1976). Their strong dechs),
ring-necked duck (A~th~a collaris), and pendence on surface water, cavity-nesting habit,
hooded merganser (Lophodytes cucullatus). perching ability, and deft maneuverability in flight
Waterfowl species that breed in northeastern lidfilt bws shruba unique adaptations to
forested wetlands include QK)=~ or stump m~ters this habitat. Throughout the and central
such as American black ducks and mallards, as well united states, wood ducks breed in floodas
cavity-nesting wood ducks, common goldeneyes plain forests and bottomland hardwood
(Buce~hala 'langula), 'Ommon mergansers Wer- maple swamp is the principal forest type used by
@s me~mer), and hooded mergansers @lbse
bmding wood ducks in the Northeast (M&ilvreY
1976). 1968). Upland forest stands within 0.3 krn of sur-
Impoundments in hard- face water bodies also may be used as nesting areas
woods of the southern and central United States
and Rogers McCilvrey 1968).
provide important migration and wintering habitat
Grice and Rogers (1965) and McGilvrey (1968)
for waterfowl (Yeager 1949; Kadlec 1962; Fredrickoutlined
the habitat requirements of breeding wood
son and Taylor 1982). Given the success of this
technique in wintering areas, green-timber im- ducks in detail. Trees at least 40 cm in diameter,
poundments were constructed in the mid-1960$ at with cavities at least 15 cm deep and entraoees
the Montezuma National Wildlife Refuge in central larger than cm in diameter? appear to be the
p+w york. ~h~ pwpose of the impoundments was minimal nesting; requirement. Still or slowly movto
provide both migration and nesting habitat for surface water 8 to 45 cm deep must be present
waterfowl (Thompson et al. 1968). A 120-ha red in Swamps when ducks are seeking nest sites in
maple swamp, which was diked and flooded to a Mmh and April, and areas should remain i .~depth
of 25-30 em from mid-March through June, dated at leasf, halfway thgh
the incubation pewas
wed by 10 species of nesting waterfowl be- riod. Because of the scarcity of natural cavities in
tween 1965 and 1969 (Kivisalu et al. 1970). Water- many swmps and the loss of forested wetland
fowl nest density averaged 0.91 per ha over the habitat, the introduction of artificial nest boxes has
&year period; only six waterfowl nests were found signif~cantly increased wood duck breeding populaduring
the same 5 years in 365 ha of unmanaged tions throughout the eastern United States