OBJECTIVE
Wood Ducks are one of the few species
of cavity-nesting waterfowl in Minnesota. They normally nest in
tree cavities produced by woodpeckers, squirrels, or other animals.
Although these cavities usually are near water, Wood Ducks sometimes
nest in areas quite far from water if suitable nesting sites are
not available nearer the water. Female Wood Ducks lay and incubate
their eggs within these cavities, but the young leave the nest
soon after hatching and never return to it.
In response to declining Wood Duck numbers during the past few
decades, many sportsman's groups have installed "artificial
cavities" or nest boxes throughout the species breeding range.
Many designs of nest boxes have been used, and new designs continue
to be tested. Traditional nest boxes have been constructed of
wood, but plastic, composite, and metal boxes also are in use.
This exercise will examine whether Wood Ducks prefer to use either
wood or metal nest boxes, as well as assessing whether nest box
placement (on tree or on pole over water) influences nest box
use.
HYPOTHESIS
Wood Ducks around Winona nest more successfully in metal nest
boxes placed over water.
METHODOLOGY
Wood Duck nest boxes near Lake Winona and Boller Lake will
be opened and use by Wood Ducks during the 2004 nesting season
will be evaluated. We will be walking through snow and on ice
and using a variety of ladders to access the nest boxes, so dress
appropriately. Successful nesting attempts are evidenced by the
fluffy layer of down feathers added to the wood-chip layer by
the female Wood Duck and the presence of eggshells. It is common
for some eggs to remain unhatched within the nest. We will attempt
to estimate the number of hatched versus unhatched eggs within
each nest box. It is also common for some nests to contain only
unhatched eggs, indicating a nest abandoned for some unkown reason
or a "dump" nest used by one or more females to dispose
of eggs with no intention of incubating them. Some "dump"
nests may contain >20 eggs. The instructor will provide you
with a data sheet to facilitate collection of nest box use information.
After each nest box has been examined, we will add additional
wood chips to the box if necessary to prepare it for the 2005
nesting season.
Other organisms also may use the nest boxes intended for Wood
Ducks. Mergansers may use the boxes for nesting, and their eggs
are often larger and more pointed than Wood Duck eggs. During
the winter, Eastern Screech Owls, squirrels, and various mice
often use the nest boxes, so be prepared for a sudden encounter
with a surprised occupant. To be safe, always slap the side of
the nest box a few times to make sure that the occupant knows
you are coming and vacates earlier rather than using your arm
as an escape runway later! If owls have been using the boxes,
we will collect any regurgitated food "pellets" for
analysis in a later lab exercise.
ANALYSIS
After data are collected, display the results in table form (successful
vs. unsuccessful, wood box in tree vs. metal box on pole). Also
use the information gathered to determine hatching success (both
percent of nests that were successful in hatching at least one
egg, as well as percent of total eggs laid that actually hatched)
for both Wood Duck and Mergansers. Compare nest success versus
box type with the aid of a contingency table (Ecology lab manual).
EQUIPMENT
Step ladders
Extension ladder
Wood chips
Hammer and nails
Plastic bag (for owl pellets)
Data sheet
Ecology lab manual
___________________________________________________
Neal D. Mundahl
Department of Biology
Winona State University
Winona, Minnesota
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Synopsis