My favorite bird-subtype reference guide, which I use when assuring myself of an iNat identification or looking for info on behavior and nesting, is the Peterson Ref. Guide to Woodpeckers of North America by Stephen Shunk.

CON:
-Out of print. (Sorry!)

PRO:
-The deep knowledge!
-Doesn't shy away from confusing info, so best reference on sapsucker hybridization I've seen, e.g.
-good selection of beautiful photos of adults and juveniles for most taxa I've read thus far

#FavFieldGuide #birding