One of your first stops should be Sportsmens Migratory Bird Center. Here, you'll be able to find your bearings and get lots of useful information before you set out exploring.
If you're staying a while in Oak Harbor, Sportsmen's Migratory Bird Center is a fine place to kick off your sightseeing. This tourist information center is one of numerous attractions worth checking out here. Magee Marsh Wildlife Area, and Ottawa National Wildlife Refuge are also waiting to be discovered nearby.