Lincoln Karim was arrested last month after he and several other residents protested the decision by Zahn's husband, head of the co-op board, to move the hawk that had become known as "Pale Male."
Zahn and her husband said Karim harassed them and their children, so they complained to police.
In court Wednesday, prosecutors said Zahn did not want to pursue the charges anymore and a judge dismissed the case, "Celebrity Justice" reported.
"He exercised his first amendment right of protest in an issue of great public interest in this city," said Karim's lawyer, Dino Lombardi. "There's absolutely nothing harassing or threatening about saying 'Bring back the nest.'"
Actress Mary Tyler Moore and other supporters of Karim accompanied him to court.