The Black-and-White Warbler (Mniotilta varia) is a small songbird that acts more like a woodpecker or nuthatch than it does a Warbler. Even its breast markings and wing pattern are similar to a Hairy Woodpecker, but its longer bill and head shape can help distinguish it as a warbler.
I spotted the one in the photo above at Idylwild WMA.
Mostly a forest and wooded are bird, this Warbler will breed in Maryland in the spring and summer months.