Dave Morgan, a senior advertising executive at AOL, left the company Monday after three months in the position to pursue unspecified startup opportunities.

AOL described Morgan’s departure as voluntary and said he would continue helping AOL identify startup opportunities strategic to AOL and its emerging Platform A advertising unit, the company’s effort to consolidate its ad operations as it tries to boost advertising sales to offset plummeting subscription revenue.

Morgan, 44, joined AOL with its September purchase of Tacoda, a business he had founded that delivers targeted online ads based on a visitor’s browsing habits. He became AOL’s executive vice president for global advertising strategy on Nov. 9.

Morgan “is an entrepreneur at heart, and so it didn’t really surprise me that he wanted to get back in the startup game again, and we’ll look forward to working with him in the future,” AOL’s chief operating officer, Ron Grant, said in a memo to employees.

The development comes days after AOL’s parent, Time Warner Inc., reported that AOL had its slowest quarter of advertising growth since it started trying to remake itself as an ad-focused Internet business.

Time Warner also said it planned to separate AOL’s ad operations from its dial-up access business. That could lead to a sale of the dial-up business in the U.S. _ as it already has done in Europe _ and in turn make the advertising operations more attractive to potential bidders.