Safety Brian Dawkins ended nearly four months of speculation by announcing his retirement via his Twitter feed on Monday. Dawkins had spent the offseason deliberating over whether to return for a 17th NFL season after missing four of the Broncos' final five games in 2011 because of a pinched nerve in his neck. His contract had expired at the end of last season, but the Broncos had said he could come back if he chose to do so.