Scarecrows keep birds away from crops. And now, according to the Massachusetts Bay Transportation Authority, a cardboard cutout of a police officer is keeping thieves away from bicycles.

The Boston Herald reported last week that a phony figure of a “burly officer watching over the bike racks” at the Alewife MBTA subway and bus station in Cambridge has helped cut bike thefts there by 67 percent.

This “scarecop” apparently looks rather real — if you’re sufficiently distant or unperceptive.

It also looks like MBTA Officer David Silen, thanks to a quite life-like image of his face.

Officer Silen cited this advantage of the law-enforcement innovation: “We’re not tied up taking stolen bike reports here so we are more available to respond to more serious crimes that require a police response.”

MBTA officials are even considering adding more cardboard crime fighters at other stations — and not merely to lower bike larceny. They also think the stand-in police could help counter fare evasion — and smoking.

This trickery sounds reminiscent of practices in these parts to slow down speeders by putting dummies dressed like policemen in patrol cars parked along highways.

It also sounds like a creative way to cut personnel costs — and crime.

Then again, to borrow from the Scarecrow in the glorious 1939 film classic “The Wizard of Oz,” no resolute bike thief, “if he only had a brain,” is likely to long be fooled by a cardboard cop.

And when it comes to the police’s vital duty “to protect and serve,” a real-life “burly officer” still beats any phony stand-in.