Reddit mentions of Carving Award-Winning Songbirds: An Encyclopedia of Carving, Sculpting and Painting Techniques (Fox Chapel Publishing)

Lots of different kinds of carving:

• Carving with knives (not just whittling), usually small things like figurines / characters or wildlife
  
• Carving "in the round" 3D sculptures like the masks you're talking about (done with gouges)
  
• Relief carving, where you carve scenes and whatnot into a flat surface (also done with gouges)
  
• Chip carving, where you carve geometric patterns into surfaces (done with gouges and special chip carving knives)
  
• Power carving, carving 3D stuff with power tools like a dremel, foredom or other micro motor. Good for bird carving.
  
• Chainsaw carving!
  
  If you want to carve in the round (things like those masks) then you'd be best served trying to find some good books to read. I recommend Chris Pye's books, just search on Amazon. This can be expensive to get into as good gouges aren't cheap, but you can start with a few and work your collection up.
  
  If you want to carve with knives a good way to learn is to just go on youtube and there's tons and tons of videos of people carving various things and you can follow along. Look up Gene Messer, he does all kinds of little figures. This is cheap to get into, just need a good knife and a strop with some compound to look after it.
  
  If you want to power carve birds I recommend Lori Corbett's book "Carving Award Winning Songbirds"
  
  I don't know much about relief carving or chip carving so can't help ya there. Chainsaw carving I know absolutely nothing. Don't do that one unless you have a teacher nearby hah!