Technically it’s a gray treefrog, Missouri’s most common species of treefrog. I tracked it by sound to this perch on the rip of our above-ground pool. Since it sounded more like “a birdlike, musical trill” than “a buzzer”, I concluded, with the help of the Missouri Department of Conservation’s website that my visitor is an eastern gray treefrog (Hyla Versicolor) and not a Cope’s gray treefrog (Hyla Chrysoscelis). Judging from the evening chorus, the swampy pond just downhill from the house is frequented by hundreds of eastern gray treefrogs.