Winona State University
Lab Exercise



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.


Wood Ducks around Winona nest more successfully in metal nest boxes placed over water.


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.


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).


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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