The leaders of two major District government agencies have announced they are leaving their posts in the near future, the first signs of a “brain drain” for lame-duck Mayor Vincent C. Gray (D).

Gray lost his bid for reelection in last week’s Democratic primary to Council member Muriel Bowser (D-Ward 4), but his term stretches to next January, when the winner of a November general election between Bowser and David A. Catania (I-At Large) will assume the mayoralty.

In the meantime, Gray must run the city as a lame duck for an unprecedented nine months — even as key figures in his administration begin to find new jobs.

The District Department of Transportation announced Tuesday that director Terry Bellamy and chief engineer Ronaldo “Nick” Nicholson will leave their posts before the end of the month. A spokesman for the department, Reggie Sanders, did not have any information on their future plans. The two oversee numerous major projects, including the rollout of the city’s new streetcar network, the reconstruction of the 11th Street Bridge complex and the planning for a new South Capitol Street bridge.

Also departing is Nicholas A. Majett, director of the Department of Consumer and Regulatory Affairs, which handles a variety of permitting and licensing functions. Majett said Tuesday he will assume a “high-level” post for Prince George’s County Executive Rushern L. Baker III in early May. His departure was first reported Monday by Washington City Paper.

“I think I can go to Prince George’s County and make a difference there like I did in the District,” Majett said. “I don’t think I can do much more in D.C. We’ve automated a lot things, the culture has changed, permits are issued faster, licenses are easier to get. I’m not leaving anything undone.”

The move to Prince George’s has been in the works for months, Majett said, and had nothing to do with Gray’s loss in the Democratic primary last week. “That wasn’t one iota of a factor,” he said.

Regardless of the reasons for the exodus, the departures are likely to leave two crucial city departments without stable leaders for months, thanks to the unprecedented nine-month lame-duck period.

Gray said he was “not surprised” by the departures, as he expected his cabinet members to be in high demand for other jobs. Interim leadership will continue to make progress on the city’s top priorities, he said: “We’ve got pretty good bench strength.”

Harry Wingo, chief executive of the D.C. Chamber of Commerce, whose members rely on Majett’s department for licenses and permits, said he was unconcerned about the flux. “I know the mayor will be on top of it,” he said after joining Gray for a bill-signing Tuesday afternoon. “The team has been very effective.”

The threat of nine months of uncertainty is the result of a new election schedule that set the Democratic primary on April 1, five months ahead of the previous date, in September. Although the schedule was intended to comply with federal law requiring new accommodations for absentee and overseas voters, it has been widely criticized for placing the peak of campaign season in winter and attracting historically low turnout.

Word of the departures spread on a day when the D.C. Council met for the first time since the election, with some lawmakers who had previously defended the early primary agreeing that it was a mistake and should be moved to a later date.

Council member Jack Evans (D-Ward 2), introduced legislation to move the city’s primary to the second Tuesday in June. “April 1st did not work. We found ourselves in the harshest winter in many, many years trying to campaign,” he said.

Evans, who trailed in returns far behind Bowser, Gray and fellow Council member Tommy Wells, also proposed making the city’s primary open, with voters of any party able to cast ballots to increase participation.

Even Council member Mary M. Cheh (D-Ward 3) who was a key vote against pushing back this year’s primary, said of the April date: “In retrospect, it was a mistake. I really downplayed in my mind and am now reconsidering as I see the effects, the lame duckery.”

Cheh, who also oversees the sprawling transportation department, said she was disappointed about the departure of Bellamy and Nicholson.

“We’re going to have headless agencies,” she said. “It’s a kind of disruption I was hoping we could avoid. It doesn’t help to have drift in these agencies for half a year. . . . We’re seeing the consequences of a long lame-duck period.”

Bowser said she was not surprised by the departures, noting that other cabinet officials, including city planner Harriet Tregoning and employment services director Lisa M. Mallory, have already left. “They’ve been bleeding people for a while,” she said.

As for how Bowser expects Gray to proceed with his appointments, she said, “I expect that he’ll put somebody competent in acting positions and give the new mayor an opportunity for a fresh start in those agencies.”

Aaron C. Davis contributed to this report.