I have done the best I can to keep the sizes of the birds in proportion to one another.
For A I chose Auks:
Bustards are large plains dwelling birds that make their home in steppe type environments across Europe, Asia, Africa and also Australia. The Great Bustard and the Kori Bustard joust for the status of "largest flying bird", with the Great Bustard being the heavier of the pair. Species include Bustards, Korhaans and Florican.
C was going to be for Corvids - a vast family that contains ravens, crows, jackdaws, jays, magpie-jays, scrub-jays, treepies and magpies.However, I think there are just too many for me to do in one go, and it will be better for me to separate out the Genus Jays under "J" (Jays being more colourful than the others). This means, I'm afraid, no crows or ravens - then again, with them being pretty much black, it's not the most interesting page to colour anyway!
So, for C I think I shall do Cranes instead.