Twitter's content spans from informal discussions between researchers to the marketing communications of universities research departments, research funders, and other organisations. It is incomplete because it only reflects the outputs of active users. Some people/organisations may not use Twitter, some Twitter accounts are inactive. With that caveat here are some suggestions for the types of content you might look for:
Types of evidence
Description
Comment and discussion between researchers
Experts, academics and researchers comment or discuss research topics.
Researchers talking about their research
Tweeting about their research and recent publications.
News on recent research stories
Twitter is an instant news source extending across all topics from millions of contributors.
Unpublished and never to be published events
Events that before Twitter may never have been reported or published are recorded through "live" tweeting from organizers and participants.
Tweet Chats
Discussions hosted on Twitter.
Signposts to other content on social media
Twitter is integrated with other social media and the web. Twitter signposts other social media and content on the web.
PR, Press Releases, Marketing and Publicity
Twitter is a key tool for public relations announcing new reports, events and courses.