According to NJDFW, “The Northern Gray Treefrog spend most of its time high in the trees, except during breeding season when they are at the water’s edge. Bare horizontal branches over water are the preferred calling sites during breeding season. They breed in vernal ponds or swamps, and remain in mixed forested uplands during the rest of the year. Like many treefrogs, these species frequently call on warm rainy days outside of breeding season.” The Northern Gray Treefrog has a slow trill (almost bird like) call. Listen for them on hot humid days while walking the trails at MCR in July and August!