A few additional notes:
Cape St. Mary's is a great place, not only for the gannets, but also for kittiwakes. Look also for American pipits on the walk to the gannets. Eat at The Gannet's Nest, which is just at the turnoff to the road to Cape St. Mary's.
In Witless Bay, you can also charter private zodiac tours. Elaine's B&B at very least did this. That way you can decide which places to visit and home in on the birds as much as you want. Lots of puffins, razorbills, etc.
Look for bald eagles anywhere along the coast. We saw them at Cape St. Mary's, in Conception Bay, at Twillingate.
Gros Morne is fabulous for hiking in general, for interesting flora, and for gray jays and boreal chickadees.