Source : Webster's Revised Unabridged Dictionary (1913)

Avifauna \A`vi*fau"na\, n. [NL., fr. L. avis bird + E. fauna.]
   (Zo["o]l.)
   The birds, or all the kinds of birds, inhabiting a region.

Source : WordNet®

avifauna
     n : the birds of a particular region or period