I wanted to second Walter remarks about the Norther Flicker complex.  Maryland does not have any accepted records of "Red-shafted" Flicker and all reports should be submitted to the MD/DCRC.  I'm not even sure how many records there are for the East.  Presumed intergrades of the yellow and red forms have been documented in Maryland.  Though I have not seen any of these in Maryland myself, Zach Baer and I were treated to several in the Black Hills while visiting friends there this summer.  The underwings of the these flickers can vary from Yellow to Orange to Red and the head pattern shows almost all variations as well.  Many of the flickers we saw had mostly Red underwings (and would surely call attention to themselves in the East) with intermediate head patterns.  The patterns on the head can be quite odd looking and my friends had some great photos of the variation.  If you see a flicker with red underwings, try to get a look at the face pattern and take notes even if it is a hybrid.  The bird is still worth documenting.  
 
Matt Hafner
Bel Air, MD