Is a math professor’s website a weird place to find bird calls? Maybe, but this free site provides song recordings for 25 different bird groups in New York. Many of these birds live outside New York too, so this is a decent general list for the northeastern US.
Our lives are so busy that we rarely slow down to appreciate what's around us. In a five senses hike, you'll slowly walk your trails and stop occasionally to explore what you're seeing, hearing, smelling, feeling, and even tasting. This is a great activity to do with kids.