WASHINGTON (Reuters) - President Barack Obama celebrated his 51st birthday on Saturday with a round of golf, then helicoptered to the Camp David presidential retreat for a quiet evening off the campaign trail.

Obama, an avid golfer, played with colleagues and friends at the Andrews Air Force Base in hot, muggy weather conditions before taking Marine One to Maryland's Catoctin Mountains in the afternoon.

The White House did not release details of the president's evening plans or share the menu for the birthday meal he was expected to share with wife, Michelle.

Their daughters were at summer camp this week and it was not clear whether they would be present at the rustic getaway that the Obamas have visited less than past White House residents. The president often opts to golf at Andrews or play basketball in downtown Washington to unwind on the weekends.

Obama is set to visit Connecticut and Colorado for campaign events next week, and will host a re-election fundraiser with a birthday theme at his family home in Chicago next weekend.

Vice President Joe Biden said in a campaign email last month that supporters donating $5 or more would be entered into a raffle for a chance to attend that event at the Obama residence.

"Take it from me. You'll have fun at this one," Biden wrote.

(Reporting by Samson Reiny in Washington and Eric Johnson in Chicago; Writing by Laura MacInnis; Editing by Anthony Boadle)