Here's an unexpected solution to a military problem.

The U.S. military is keen to keep birds away from their airfields, as errant birds can unwittingly down a multimillion-dollar airplane, not to mention endanger the lives of its crew, by flying into an air intake. It fell to the Army Corps of Engineers' Engineer Research and Development Center (ERDC) to come up with a solution.

Take One was robot dogs, using a Boston Dynamics model. The idea was that the dog 'bot could tirelessly patrol runways, scaring birds off.

It didn't work. "What we found out quickly was, because [the robot dog] had such a slow approach speed," explains Dr. Jacob Jung, an ERDC research wildlife biologist, "that it did more of just pushing animals out of the way once it finally got close enough to them, than it did really scaring them off."

They then struck upon the idea of using a chassis from Traxxas X-Maxx, a manufacturer of off-road RC cars.

These can zip around at up to 20 mph.

But birds don't necessarily recognize a miniature monster truck as a predator, so the researchers purchased a plastic coyote figurine from a forestry supplier.

As it turns out, these are two great tastes that taste great together. The resultant "Coyote Rovers" did the trick.

These are categorized as UGVs, for Unmanned Ground Vehicles. The ERDC says the demo system cost was "between $2,500 and $3,000," though it's not clear how many Coyote Rovers that yielded. In any case, they've given demonstrations at airfields in Tennessee and Florida, and say the cost is worth it. The conventional way to reduce bird presence at airfields is to keep the surrounding grass short, so that birds don't have a place to hide. "Even at a small number of airfields, if you can give them one more week between mowing, that ends up being a huge [cost savings]," says Shea Hammond, an ERDC research biologist.

I imagine the next step will be placing the coyote figurines on top of lawn-mowing robots.