The Chicago Sun-Times’ Carol Slezak reports on one of the lamer cases of viral marketing in recent memory.

When six St. Louis Cardinals billboards were vandalized recently, Cardinals fans fingered Cubs fans as the likely culprits. As if Cubs fans don’t have more important things to worry about than stealing a dozen cardinals from St. Louis-area billboards. But no — plenty of folks suspected that a group of Cubs fans took a road trip to St. Louis with one purpose in mind: To climb a half-dozen massive billboards and cut the huge cardinals off the baseball bats they perched on.

The plot thickened when someone calling himself Bird Napper, who said his interests are “stealing birds from billboards” and “watching Cardinals baseball,” claimed responsibility for the thefts, which began on Feb. 17. Bird Napper, who said he was a 23-year-old male, confessed on his Web site at myspace.com.

To prove he took the birds, Bird Napper e-mailed a reporter at the St. Louis Post-Dispatch and said he’d appear outside the Post-Dispatch building with the birds at 4:30 p.m. on Feb. 21. And sure enough, right on time, Bird Napper and a companion ran past the building carrying 8-foot Cardinals cutouts. Then they jumped into a vehicle and drove off before anyone could catch them.

Bird Napper posted an explanation for the thefts on his Web site, saying basically that he and some friends thought it would be funny to steal the birds.

Fingers began pointing in a different direction after Dan Farrell, the Cardinals’ senior vice president of sales and marketing, told the Post-Dispatch on Feb. 21 the missing birds “were not acts of theft or vandalism, as far as we know.” Perhaps the Cardinals organization knew something it wasn’t saying?

Not long after Farrell made his statement, the real perps confessed. The whole thing was a hoax, dreamed up by St. Louis sports radio station KTRS-AM and an advertising agency.