Smith: Nest boxes help ducks hatch and assist students with lessons of wetland ecology

Leap Day is recognized Feb. 29 about every four years to keep human schedules and solar movements in sync.

But leap days occur annually throughout May in Wisconsin thanks to an army of conservation volunteers who build duck nest boxes.

And these outdoor events are much more fun than anything to do with the Gregorian calendar.

As you might know, wood ducks and a select few other duck species nest in cavities. Historically that would mostly have been natural spaces in trees.

That's still true in some cases today but more than ever these ducks lay their eggs in structures provided by humans called nest boxes.

Once the ducklings hatch the hen waits about one day then flaps out of the temporary housing, lands on the ground or water outside and calls to the brood.

The ducklings show the wisdom of nature in even day-old beings: they follow mom. The tiny ducks use their toe nails to climb a lattice on the inside of the box, stand on the lip of the opening and jump.

No two first flights are the same. Most involve tumbling.

If all goes well the ducklings land uninjured and gather around the hen. When the last peeping youngster is out of the box, the hen leads the troop to water.

Nest boxes have played vital role for wood ducks

The structures are relatively small in size but over the last century have played a substantial role in helping boost the wood duck population.

As hard as it may be to believe today, in the early 1900s some people feared the wood duck would go extinct.

Unregulated hunting, including market hunting, and habitat loss were to blame.

However the Migratory Bird Treaty Act of 1918 prohibited the hunting of wood ducks nationwide. And in the 1930s, the use of artificial nest boxes buoyed the species' recovery.

By 1941 the woodie population was considered sufficiently robust that a hunting season was reopened.

The species has fared well in many Eastern and Midwestern states, including Wisconsin. In 1973, the first year of the state's breeding duck population survey, the Department of Natural Resources reported 9,000 wood ducks in Wisconsin. In 2023 the population was estimated at 102,381 wood ducks, 20% higher than the long-term mean.

The nest boxes also provide nesting sites for buffleheads, common goldeneyes and hooded mergansers. And those are just the ducks. Other birds such as screech owls and great-crested flycatchers commonly use the structures.

Here are tales related to 2024 hooded merganser leap days engineered by some of the state's most dedicated nest box builders and supporters, Jeff Bahls of Beaver Dam and Jessica and Ryan Peterson of Brillion.

Jeff Bahls was taught as a youngster: 'you hunt, you gotta give back'

Bahls grew up in a hunting family and his father taught him early that if "you hunt, you gotta give back." He estimates he has helped hatch about 10,000 ducks over the last three decades, mostly woodies. He maintains about 200 nest boxes on private land and a few public properties, including Horicon Marsh State Wildlife Area where he works as a DNR wildlife technician.

He also serves as president of the Horicon Marsh Bird Club and leads seminars on proper nest box construction.

They might seem to be modest wooden boxes mounted on a pole, but to a cavity-nesting duck in need of a place to lay its eggs they are the waterfowl equivalent of a penthouse suite.

Bahls said the box should be ventilated so it does not overheat, should deter or prevent predators from entering, and must allow ducklings to climb out. The standard duck nest box has a 3-inch diameter entrance hole.

About 30% of his duck boxes are occupied by hooded mergansers, Bahls said. He keeps a calendar and tries to be present at a few leap days each year.

Wood ducks and hooded mergansers incubate their eggs for 30 days, give or take a day.

This year Bahls timed it perfectly for a box near his home. On May 13 he saw the hen hooded merganser poke out of the opening, look around, fly down and start calling. Bahls knew what was next.

He leveled his camera and telephoto lens on the nest box and waited for puff balls to start leaping. Eleven hooded merganser ducklings jumped; Bahls was able to capture images of six of them in the air as well as a group shot of the hen and youngsters waddling to water.

That counts as success on all fronts.

Jessica and Ryan Peterson use next boxes for educational purposes

Jessica and Ryan Peterson of Brillion are avid nest box builders and watchers, too. The married couple monitors and maintains about 30 duck nest boxes on property they own as well as public lands nearby.

They also work as teachers in the Brillion school district and are members of the Wisconsin Waterfowl Association.

When they learned WWA was looking for a curriculum about ducks, Ryan reached out to them and discussed what might be possible.

Jessica, it turned out, was already creating one for an environmental science class she was teaching.

When she finished it a couple years ago she shared it with WWA. It's now being used in 30 Wisconsin schools, Jessica said.

It includes lessons for students in grades 5 to 12.

The curriculum is available free through the WWA. The organization also provides 10 duck nest boxes a year at no cost to teachers in the state who have an appropriate place to erect them.

The goal of the project is to increase awareness of waterfowl, waterfowl habitat and waterfowl conservation. It focuses on wood ducks since they are fairly common in Wisconsin and an easy bird to support with the construction of nest box houses. But the lessons cover a broad range of waterfowl and wetland topics.

A recent review of the course material made me want to be a student again. It includes stunning color photography and duck identification quizzes as well as information on bird migration, habitat needs, nest predators and awareness of the array of cavity nesters in the Wisconsin outdoors from black-capped chickadees to black bears.

It also includes resources for building nest boxes, installing a video camera and a guide to predicting leap day.

The work by Jessica and Ryan to create and distribute the curriculum is drawing accolades. The Wisconsin Wildlife Federation honored the couple with their Wisconsin Wildlife Educator of the Year award in late April and the Wisconsin Conservation Congress presented them with the 2023 Wisconsin Conservation Educator of the Year award in early May.

"We are wood duck enthusiasts," Ryan said. "It was a great chance to bring wildlife into our classrooms."

This spring at Brillion Middle School, for example, students visited a nest box about a 10-minute walk from school. They donned waders and crossed a creek to visit the site to check on egg laying.

As explained in the Petersons' curriculum, the hen will lay an egg a day. Once all the eggs are laid, the hen begins to incubate them.

So when the students determined the hen had started incubating, they stopped visiting the nest box. From there it was monitored entirely via a video camera mounted in the box. This year a hooded merganser nested in the box. And May 5 was leap day.

The exciting event was made into a video and posted to YouTube.

Brillion students also recorded a wood duck leap day May 27.

"We've been trying to get this spread throughout the state," Ryan Peterson said. "We're hoping more schools will take it on."

To learn more, visit www.wisducks.org.

This article originally appeared on Milwaukee Journal Sentinel: Nest boxes help ducks hatch and assist students with lessons of wetland ecology