Image by Gus Van Vliet/U.S. Fish and Wildlife Service.

Pictured above is the marbled murrelet, a seabird native to the coasts of the Pacific Ocean.

Marbled murrelets stay mostly around Oregon, Washington, Northern California, British Columbia, and Alaska (although also somewhat in Russia and northern Japan).


They thrive in old-growth forests, and if you're a human it's rare to find one of their nests because they tend to build them hundreds of feet off the ground.

As a species, they're endangered, in part because of logging that has reduced the size of their habitat. But there's another concern as well that is also, but indirectly, human-caused.

This guy:

Image by Noel Reynolds/Flickr.

That's the Steller's jay, another species of bird.

The jay isn't a very picky eater and therefore tends to go to where the food is.

We humans go and visit old-growth forests — that part is OK — and then we toss bread or seeds or other such stuff on the ground, hoping to feed the birds.

Marbled murrelets only lay one egg per year. When jays are around, eating those eggs, it makes it hard for the marbled murrelet population to grow.

That sounds like a very nice idea — birds have to eat, after all! — but there's a downside. The jay population thrives and are attracted to this new abundance of edibles, and while they're in the neighborhood, they find something else to snack on: eggs.

That includes chicken eggs, if there happen to be some laying around, but it also includes marbled murrelet eggs.

To make matters worse, marbled murrelets only lay one egg per year. When jays are around, eating those eggs, it makes it hard for the marbled murrelet population to grow.

The good news is that jays are “really, really smart," as Elena West, a researcher with the University of Wisconsin-Madison, told NPR.

And also per NPR, Portia Halbert, a park scientist at Butano State Park just outside of San Francisco, has used the jays' intelligence against them. How? With a little bit of poison.

Halbert and team take chicken eggs and paint them to look like marbled murrelet eggs. Then they inject these decoy eggs with a little bit of something called Carbocal into the eggs, which, if you're a bird, is a bad thing to eat — it'll likely make you throw up.

The jays learn that the eggs aren't good for them and, over time, learn not to eat them.

The jays learn that the eggs aren't good for them and, over time, learn not to eat them. And as smart as the jays are, they aren't quite smart enough to differentiate between chicken eggs and marbled murrelet eggs.

So eventually, the jays learn to let the marbled murrelet eggs go uneaten.

Hopefully, this will help keep the marbled murrelet population growing.

Although there's one other reason to be concerned. Halbert and her team (and similar teams in other forests) can only place tainted decoys on the ground — the nests of marbled murrelets are simply too high up for humans to reach.

Some researchers are concerned that the jays will realize that the eggs on the ground aren't safe to eat but that the ones up in the nests — and therefore, the ones most likely to hatch — make for perfectly fine snacks.

Dan Lewis runs the popular daily newsletter Now I Know ("Learn Something New Every Day, By Email"). To subscribe to his daily email, click here.

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