Captains of the District's commercial community sang "Happy Birthday" to Mayor Marion Barry and contributed $1,000 each at a 50th birthday breakfast yesterday that inaugurated fund raising efforts for Barry's still unannounced reelection candidacy.

About 125 persons attended the gathering at the Washington Hilton, although some did not pay $1,000, said Ann R. Kinney, finance chairwoman for the Barry campaign.

"If we had had a $1,000-a-plate breakfast in 1978, we could have had it in a phone booth," said Barry in recalling his first, long-shot campaign for mayor. "Our phone booth has now expanded to the Washington Hilton."

The fund raising birthday party was a good "gimmick," attorney Robert Linowes observed. And former D.C. finance and revenue director Jeffrey Humber, now a New York-based Merrill Lynch executive, said he'd "go anywhere for a great breakfast."

National Bank of Washington President Luther Hodges, seated next to American Security Bank President Daniel J. Callahan, scanned the scene and concluded that if he were Barry, "I would be riding pretty high, and I would be feeling pretty good. And I think that he is."

Barry commented after the breakfast that he wishes "everyone in the city had the socioeconomic position to give $1,000" and added that there will be fund-raising events aimed at less fortunate supporters.

Mattie Taylor, a former school board member who declared her candidacy for mayor Jan. 17, sharply criticized what she called the breakfast's "Queen Marie Antoinette of France mentality."

"I am incensed that the mayor would have a $1,000-a-plate breakfast when our public housing tenants can't get the stoves and refrigerators purchased for them to prepare breakfast on," she said. "It is the height of arrogance and total insensitivity to the needs of the people."

Barry, who raised $1.3 million for his campaign in 1982, has said he hopes to bank more than that this year.

D.C. City Council member Betty Ann Kane (D-At Large), who challenged Barry for mayor in 1982 and is running for reelection this year, said Barry's overwhelming dominance in fund raising all but locks out his competitors.

"It makes it very, very difficult for anybody to mount a serious challenge," she said. Kane said it was "obscene" for Barry to want to raise so much money for a campaign that so far lacks a "serious" challenger.

Council Chairman David A. Clarke and council members John Wilson (D-Ward 2) and Charlene Drew Jarvis (D-Ward 4) are testing the waters for possible mayoral bids, but none has announced any plans.

Wilson said yesterday that Clarke's decision on whether to run for mayor or to seek reelection as chairman is likely to determine his own course. He said that if Clarke runs for mayor, he will stay out of that race and seek the chairman's seat. If he and Clarke were to challenge Barry, Wilson said, they would split the opposition vote and assure the mayor of a third term.

Wilson also said he might stay out of both races and "spend the summer on Long Island."

Dennis Sobin, who publishes sexually oriented material, is the only other announced candidate for mayor.