Bird, a partner, and Cooper joined the New York-based independent last year.
Bird is returning to London, where he will continue working for Anomaly. He joined the company from Sony BMG Entertainment, where he was vice-president, brand partnerships.
Prior to this, he worked as managing director of Soul and group business director at Bartle Bogle Hegarty.
Cooper is rejoining Dare, the Cossette Communications-owned digital shop he left in November 2007 where he spent two years as a creative director after a stint at Agency Republic.
He will reportedly launch Dare's New York office in early 2009.
Anomaly has denied the departures are related to job cuts, pointing to the recent capture of the global Umbro account as a sign of good health.
Anomaly set up its spin-off shop 16 months ago after deciding its headcount had grown too big to manage. It has around 20 employees.