Most bogs exist in glaciated areas, but Black Moshannon State Park is on the Allegheny Plateau. This area was not covered by glaciers during the last ice age. The bogs formed here because of the beds of sandstone that lie flat, a short distance below the surface of the earth. The sandstone formations in the park do not absorb water very well, so any depression in them will collect water, as has happened here. The bogs extend the shores of the lake. Migratory shorebirds that visit here include greater and lesser yellowlegs, least sandpiper, solitary sandpiper, and the spotted sandpiper, which has been confirmed as using the IBA as a breeding grounds.