Embattled Internet pioneer Yahoo will announce job cuts when it releases its quarterly earnings report, according to The Wall Street Journal.Yahoo chief executive Marissa Mayer will lay out a cost-cutting plan which includes chopping 15 percent of the work force, an estimated 1,600 positions, the Journal said, citing unnamed people close to the matter.The cuts follow a key investor in Yahoo pressuring the board of directors for a change in management. The activist shareholder, the hedge fund Starboard Value last month said investors in Yahoo appear to "have lost all confidence in management and the board" after the company, led by Silicon Valley star Mayer, has failed to turn around Yahoo's core Internet business.In a letter to the board, Starboard said Yahoo needs to sell off the core business to other investors, but that so far the company has ignored expressions of interest from buyers. Starboard argued that "significant changes are desperately needed."In December, SpringOwl, another sizeable Yahoo investor, demanded the company cut more than 80 percent of its workforce and replace chief executive Mayer.