By Kim Klosterman and Jenny Gainer
At the Cincinnati Zoo, the beginning stages of duck breeding season on Swan Lake are just around the corner. Most people associate spring time with cute little ducklings, but at the Zoo’s bird house we have to start preparing in the winter. In order to promote natural breeding behaviors on our lake there are a few things bird keepers have to do to encourage our feathered friends. We have successfully bred, raised, and released ruddy ducks, bufflehead, goldeneye, wood duck, and several species of merganser over the years. This is due, in part, to the hours of work our keepers spend on making duck boxes, installing them, monitoring them, and rearing chicks.
Cavity nesting bird populations have been in decline in the last few decades due to the loss of mature and old growth in our forests. Mature forests provide larger, dead standing trees, called snags. These snags are typically in various stages of decomposition. Certain species of cavity nesting waterfowl will use abandoned woodpecker holes or natural tree cavities. These same species will also use artificial nest boxes, so providing these sites for our ducks helps increase our captive and wild waterfowl populations.
Nest boxes are installed on posts above the water in mid-February, or as soon as the ice thaws on Swan Lake. This gives the ducks several weeks to get acclimated to seeing the boxes, swimming around them, sitting on top of them, and eventually going inside. It’s around the beginning of April that egg-laying begins. Keepers check the boxes every two weeks for eggs to ensure we do not miss any hatching. Any eggs that are found are pulled for artificial incubation. Eggs are weighed, candled for fertility, numbered, and set up in our incubator.
Eggs cannot be left with the parents for a very important reason. Although our ducks are in a somewhat captive setting on the lake, there is still risk of predators on zoo grounds. Any duckling that hatches is at high risk of predation by raccoons, cats, possums, foxes, and even some of the bigger fish that reside in the lake. So Cincinnati Zoo keepers take over parental duties by incubating, hatching, and rearing the ducklings. Once the ducks are full grown, eating very well on their own, and are acclimated to the outdoors, they are re-introduced to Swan Lake.
So, the next time you are at the Zoo, be sure to look for our ducks and their nest boxes out on Swan Lake.