Why this owl raised a duckling as its own

“Oh, we have an owl chick. This is wonderful!”

These were Laurie Wolf’s first thoughts when she noticed something small and fluffy bobbing up and down inside the nest box in her Jupiter, Florida, backyard. An eastern screech owl had taken up residence in the box about one month before, so she suspected it was an owl hatchling.

But the truth was far stranger.

As a storm rolled in and the sky darkened, Wolf and her husband caught a glimpse of the mother owl poking her head out of the nest box. And right beside the owl was a tiny, yellow-and-black duckling.

“The two of them were just sitting there side by side,” says Wolf, a wildlife artist and amateur photographer. “It’s not believable. It’s not believable to me to this day.”

Concerned that the predatory owl might eat the wood duck chick, Wolf contacted a raptor expert, who confirmed the duckling might be in danger. A local wildlife sanctuary agreed to care for the animal if she could catch it.

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But just as Wolf and her husband were about to intervene, the wood duck chick leapt out of the box and “made a beeline” to a nearby pond, and she hasn’t seen the little critter since.

“I don’t think I’ll ever experience anything like that in my life again,” says Wolf.

But it’s possible she might: Wood ducks have been scientifically recorded living with eastern screech owls before.

“It’s not commonly documented, but it certainly happens,” says Christian Artuso, the Manitoba director of Bird Studies Canada, who made a similar observation back in 2005 while he was studying eastern screech owls for his Ph.D.

In that case, the female owl was actually able to incubate and hatch three wood duck chicks, says Artuso, who published the findings in 2007 in the Wilson Journal of Ornithology.

Unlikely nesties

You see, wood ducks are known to practice brood parasitism. This means that parent ducks will sometimes lay an egg or two in someone else’s nest—usually another wood duck or another closely related species. (Read about another famous brood parasite, the cuckoo.)

“You could think of it as not keeping all your eggs in one basket,” says Artuso. “If you spread your eggs out, then your chances of passing on your genes are increased slightly, especially if you lose your own eggs to a predator.”

There are also other recorded examples of birds of prey incubating the eggs of waterfowl, including an American kestrel incubating a bufflehead and an osprey fostering a clutch of Canada geese.

Artuso’s isn’t even the only published record of a wood duck parasitizing an eastern screech owl, he says. (See 25 examples of brood parasites.)

“We know this occurs, but we really don’t know the frequency,” he says. “So I was happy to see another example of this.”

Supernormal stimuli

But shouldn’t the female owl be able to realize she’s sitting on the wrong eggs? After all, wood duck eggs are not only more oblong in shape than owl eggs, they're also about twice the volume. (See stunning photos of birds of prey.)

Artuso says it’s impossible to know what a wild owl is thinking, but that it could be a case of what scientists call supernormal stimuli.

“The parents might be thinking, Oh my god! This egg is huge! We’re going to have the best baby in the world!”

But it’s more likely that the occurrence is just so rare, eastern screech owls simply haven’t evolved a defense against it.

Hitting the ground running

As for the Florida duckling, it may have survived, he adds.

Wood duck chicks are precocial, says Artuso, which means they are pretty independent from the get-go. There are also many documented cases of chicks from one brood joining up with those from another brood. (Read about National Geographic’s very own duck family.)

And even if it was hatched by an owl.