|
DELTA MARSH, MANITOBA-Most
of the hen mallards arriving on the prairie breeding
grounds this spring
will set up housekeeping in grass or brush, where
90 percent of their nests will be destroyed by
marauding predators. A few of the lucky ones
will take up residence in predator-proof, high-rise
condominiums known
as Hen Houses.
Hen Houses are three-foot-long wire cylinders
stuffed with straw and grass, and mounted on
posts in small
wetlands. Opportunistic mallards use the tunnels
as secure nesting sites.
Research has shown that
hen mallards nesting in artificial structures
are much more successful
than hens nesting in upland cover, and that's
good
news for ducks and duck hunters.
"
The number of mallards hunters see each fall
is directly related to what happens on
the breeding
grounds each spring," says Jim Fisher,
who heads up Delta Waterfowl's Duck Production
Program. "Unfortunately,
what happens up here isn't always pretty."
Scientists
say fox kill up to 900,000 ducks-mostly
hens-each spring on the prairie breeding
grounds, and egg-eating predators like
skunks and raccoons
destroy 9 out of 10 nests.
"
Mallards and other puddle ducks nest in
upland cover, often far from the nearest
wetland," explains
Fisher. "The hens and their nests
are extremely vulnerable to predators during
the incubation period,
and even if the hen is successful, she
must then lead her brood to the nearest
wetland."
Delta's research has
shown that Hen Houses enjoy up to 80 percent
occupancy rates
and nest success
as high as 80 percent. And when the ducklings
hatch, they just jump off the balcony
and
into the wetland.
"
Hen Houses are likely one of our most cost-efficient
management tools for increasing nest
success," Fisher
says. "That's important, because
research has shown that nest success
accounts for 43 percent
of the annual variation in mallard
numbers."
Fisher says he has erected
2,200 Hen Houses in Manitoba and
another 400
in North Dakota.
Four
more super sites (100 Hen Houses)
are scheduled for Manitoba, Alberta and
North Dakota.
Mallards are the only
upland-nesting ducks that use Hen Houses
consistently, although
Fisher
says he's aware of scaup, canvasback,
blue-winged teal
and even the odd wood duck using
them. "Mallards
are very opportunistic," says
Fisher. "They'll
utilize a man-made structure, presumably
to increase their odds of success."
Hen
Houses are the mallard equivalent
of the popular wood duck boxes
that have been
around
since the
1930s. Nest structures similar
to Hen Houses were first used
in Europe,
and
later in
the eastern United States.
Delta
Waterfowl began experimenting with Hen Houses
on the prairie
breeding grounds
in the
1990s. When
studies conducted by Delta's
Student Research Program showed
how successful
they were
at thwarting predators,
Delta became actively involved
in erecting Hen Houses across
the "duck factory".
Delta chapters have gotten involved
by building and installing
Hen Houses in their areas.
"
One member - Tom Dufour of Baton Rouge,
Louisiana-got so excited about Hen
Houses that each year he and
other members of that chapter
build 100 Hen Houses," says
Fisher, "and each summer
Tom and his wife drive them
all the way from Louisiana
to North
Dakota."
Delta currently
teams with the North Dakota
Game and
Fish Department,
the Alberta Conservation
Association, the Manitoba
Habitat Heritage Corporation,
and
the US Fish and Wildlife
Service
to erect and maintain Hen
Houses on the
prairie
breeding grounds. |
