Laura Erickson's For the Birds

Tuesday, May 28, 2013

A "retched" solution to a conservation conundrum

Steller's Jay
Steller's Jay
One of my more vivid memories from college was learning how monarch butterflies protect themselves from predation. Their diet is high on the bitter-tasting toxins in milkweed. The moment a bird bites into a monarch, it is repulsed by the bitter taste, and if it actually swallows a monarch, the toxins quickly induce vomiting.


 Birds are intelligent creatures that learn from experiences, and link that horrible reaction to the bright orange and black colors of a monarch, so if a bird does eat one, it never does it again. Another butterfly, the viceroy, is safe from predation because it looks so very much like a monarch, even though viceroys aren’t toxic or bitter tasting at all.


 The classic textbook example that made such a profound impression on me involved an experiment on Blue Jays, and two black-and-white photos of a Blue jay eating a monarch and then vomiting left a vivid impression.

That memory instantly came to mind as I was reading an article about a new approach to saving the endangered Marbled Murrelet, a plump seabird little bigger than a robin who nests in old-growth coniferous forests.

Marbled Murrelet
Marbled Murrelet

The species declined by more than 90 percent since the 1800s, due to over-logging in its nesting areas, over-fishing in its feeding waters, and pollution. Populations are more robust in the northwest, but those nesting in California’s redwood forests are in dire straits. Those forests now get some protection, but the murrelets continue to disappear. Researchers discovered an important contributing cause: egg predation. Marbled Murrelets lay only a single egg per year on a mossy flat branch of a giant redwood, and the worst predation comes from a handsome and intelligent little culprit, Steller’s Jay. Once a jay develops a search pattern for murrelet nests, it becomes a repeat customer, and Steller’s Jay longevity, combined with their intelligence, means that they grow ever more effective, year after year, at finding nests.

Identifying the problem is essential for solving it. Researchers clearly couldn’t get rid of the Steller’s Jays—if they did remove them from one area, others would move in, and it seemed like an unfortunate solution in every way, especially because Steller’s Jays have always shared habitat with Marbled Murrelets. But fortunately, those scientists working on the problem, perhaps remembering those Blue Jay vomiting experiments, came up with a scathingly brilliant idea.  They are training the jays to avoid eggs patterned like Marbled Murrelet eggs by setting out small chicken eggs dyed blue-green and speckled with brown paint, that had been laced with carbachol. Moments after piercing one of these eggs to eat the contents, a jay vomits. And voila—that jay is done with Marbled Murrelet eggs forever. It’s obviously impossible to train every Steller’s Jay to avoid these eggs, but in 2010 and 2011, after researchers zip-tied hundreds of these fake eggs on redwood branches in several California parks, egg-snatching dropped by from 37 percent to more than 70 percent.  Jays are territorial and many remain on their territories for a decade or more, so this learned behavior is likely to reap long-term benefits to the Marbled Murrelets. Who would have guessed that saving a tiny sea-faring bird would involve vomiting jays? 

4 comments :

  1. Amazing, I'm happy they have found a solution! Off to find a picture of a Marbled Murrelet.

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  2. Viceroys are now known to be toxic too. According to the Wiki page on Müllerian mimicry, "The viceroy butterfly appears very similar to the noxious-tasting monarch butterfly. Although it was for a long time purported to be an example of Batesian mimicry, the viceroy has recently been discovered to be actually just as unpalatable as the monarch, making this a case of Müllerian mimicry." The reference cited is to an article in the journal Nature (11 April 1991). Müllerian mimicry by the way is defined as a case where "two or more poisonous species, that may or may not be closely related and share one or more common predators, have come to mimic each other's warning signals."

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  3. We've just returned from to a trip to the California redwoods where we learned a lot about Stellar Jays (and had some personal encounters with these bold birds) and the Marbled Murrelets while visiting Big Basin State Park. We had no idea about this though (the information there talked more about predation by crows, if I'm not mistaken). This is a fascinating twist on the stories of the fragile but extraordinarily beautiful ecosystems we encountered. Thank you!

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