Most first interviews are now behavior interviews, or sometimes called "structural interviews." This is commonplace now. You want to know why? Because those making the hiring decisions generally believe that past behavior and performance are great indicators of future behavior and performance; a lot of the literature supports this view.
So the belief is, when you are interviewing with a company, your behavior on past assignments and at past jobs is the strongest indicator of what you will do for them. So you must have specific examples, and they must be in the form of a story. They must be direct, succinct, organized, and structured.