Sure sign of spring, the mating call of the peeper, a tiny frog with a piercing voice. Heard in wetlands from one end of New York State to the other, and many other states, reportedly. Check out Wikipedia, if you really must know more: http://en.wikipedia.org/wiki/Spring_Peeper
Can remember a spring ride taken last year along route 17 from Sullivan to Chautauqua Counties. Could even hear their piercing croaks from the car, zipping along at 60 miles an hour, windows rolled down.
Amazing creatures. Saw one once, very tiny. My meditative ear locked on to the lilliputian perpetrator a couple of feet away, and let the music bore into my head. It does to the ears what a momentary glance to the sun does to the eyes, temporarily blunting the sense.
This Youtube doesn't do the sound justice. It's taken 10 feet from the lake's edge. Gives an idea, however.