William O'Brien State Park, on the banks of the St. Croix River, is home to more than 200 different varieties of birds, including 20 different kinds of warblers.
And that's just the beginning. Robert Janssen spent eleven years surveying birds in Minnesota's state parks and another five compiling the data for the new book "Birds of Minnesota State Parks."
Henderson has been fascinated with birds since his father first showed him a nest in their cornfield in Iowa. That bird was his "portal bird" — a term for the first sighting that gets someone excited about birding.
Listeners shared their own "portal bird" experiences on social media.
Minnesota birders have plenty of species to search for this season. According to Janssen, there are 439 recorded bird species in the state — and he has seen 406 of them.