"We see this crazy overlap of jays in campgrounds because of the density of food," Halbert told OurAmazingPlanet. The overpopulation also menaces federally protected species, such as snowy plovers, desert tortoises and California least terns - the jays eat their eggs too.
Steller's jays don't seek out murrelet eggs. But when the birds circle picnic areas near murrelet nests, some discover the chicken-size eggs make a fine treat. The smart, savvy birds will return to the same spot over and over, searching for food. Murrelets, to their misfortune, nest in the same tree every year.
Masters of disguise, the first marbled murrelet nest wasn't discovered by scientists until 1974, in Big Basin Redwoods State Park. The seabird doesn't actually build a nest, instead choosing a flat branch covered in cozy moss and needles, with cover to hide from airborne predators. At dawn and dusk, parents switch roles, flying offshore to dive for fish and invertebrates. [Watch the mysterious marbled murrelet]
"For an animal that lives for some 20 years, losing an egg is a terrible, terrible loss," Bensen said. "They're investing an enormous amount of energy into that one baby."
Killing Steller's jays won't help the murrelets; even more of the marauding birds will invade campgrounds to compete for vacant territory, biologists have concluded. Plus, jays are part of the natural ecosystem, said Richard Golightly, a biologist at Humboldt State University in California. Instead, researchers think aversion training is the cheapest, most effective way to stop Steller's jays from snacking on murrelets.
"It freaks everybody out to train wild animals to do what you want, but it surprised the heck out of all of us how much more feasible it was than we thought," Bensen said.
The plan, the brainchild of Humboldt State graduate student Pia Gabriel, centers on carbachol, an odorless, tasteless chemical that provokes vomiting with just a small swallow. Researchers fine-tuned the correct dose with lab tests at Humboldt State in 2009. Small chicken eggs, dyed blue-green and speckled with brown paint, were offered as meals to jays, with carbachol hidden inside. Wild Steller's jays in this first treatment group usually tried just one taste of the carbachol-filled fake eggs.
"All of a sudden, their wings will droop, and they throw up. That's exactly what you want - a rapid response - so within five minutes, they barf up whatever they ate," Bensen said. The quick action helps the jays link the eggs with the illness.
Some jays wouldn't even touch the eggs - evidence that murrelet egg-nabbing is a learned behavior, Golightly said.
In spring 2010 and spring 2011, a team zip-tied hundreds of the copycat eggs to redwood-tree branches in several parks. Each chicken egg was painstakingly colored (Benjamin Moore Oceanfront 660) and speckled to resemble murrelet eggs. A control batch of red speckled eggs also decorated the forest.
"We've been accused of being the Easter bunny in the woods," Golightly told OurAmazingPlanet.