For the Birds Radio Program: Peregrine Falcon vs. Great Horned Owl

Original Air Date: Jan. 17, 2008 Rerun Dates: Jan. 3, 2014

A Great Horned Owl is nesting on a Peregrine Falcon nest box at the Oak Brook Power Plant in Wisconsin.

Duration: 4′08″


When Minnesota first began its Peregrine Reintroduction Program, one of the worst problems people faced when trying to hack out baby falcons was predation from Great Horned Owls. Baby falcons are fairly easy prey by these large and fierce owls. Of course, in nature the female Peregrine is almost always in the nest with the eggs or tiny nestlings, but the reintroduction involved putting out babies without a nearby parent. In order to make the program succeed during the first stages, some Great Horned Owls had to be removed from hack box areas.

Now that the Peregrine program is a rousing success, baby falcons aren’t on their own anymore. And adults are fiercely protective of their nesting sites. The WE Energies Company in Wisconsin has set out many Peregrine boxes in cities along the Lake Michigan shoreline, and there have been no problems with owls since falcons started nesting there.

But this January, suddenly an adult female Great Horned Owl took over a Peregrine nest box, not to steal the babies but to produce babies of her own. This owl is visible via the nest cam set up at that box at the Oak Creek Power Plant. The owl was first detected on January 4, sitting on the edge of the box. When the peregrines who normally nest in that box started harassing her later in the day, rather than flying off—which would be dangerous for a slow, direct flyer like an owl—she withdrew and cowered in a corner of the box. Peregrines are great at attacking in the air, but if either peregrine landed in the box, the owl would have the advantage.

Nest cam photos for the following four days showed the female owl cowering in the corner all the time, and people observing the nest box saw the peregrine pair buzzing the box, showing lots of defensive, vocal behaviors. But on January 8, a researcher saw an egg in the box. This represents the earliest known date for a Great Horned Owl nesting in Wisconsin.

No one knows how the owl or the peregrines will fare this year. Assuming this is a fertile egg, the male owl must be around somewhere, bringing food to the female at nighttime. If neither owl flies about during daylight, they should be reasonably safe from the falcons, which are in trouble if they actually land in the box. Chances are they’ll have to pick another nest site for themselves this year. If they don’t move on, the baby owls will have problems when they get ready to fly. Baby owls often jump from nests before they’re capable of flight, and if this happens in the daytime, the owlets will be easy prey for the falcons. It’s a dog-eat-dog world out there, and since both species are protected by law, researchers and We Energies personnel are watching but not interfering. I’m hoping the peregrines find a new nest site for the season so both pairs can raise families, but it’s impossible to predict accurately what will happen.

If you’re interested in seeing the day-to-day developments in this dramatic story, go to the We energies website at and go to the drop down menu about environment.