Bird strikes are usually not a problem, but you need to evaluate what you're seeing at the time, and act accordingly. Returning to land is never a bad idea (unless the place you're returning to is on fire or some other compelling reason to press on). Be conservative.
Before I could mutter a word, my instructor had allready pushed down hard on the yoke but it was too late!
Trying to outmaneuver a bird is usually the wrong choice. There's seldom time to overcome inertia and get the airplane turned away, but birds are very good at getting out of the way, given a chance.
Birds tend to tuck their wings and dive to get clear. Attempting to outdive the bird or to dive to avoid a bird is a great way to cause a bird strike. Don't try to outmaneuver the bird.