BIRDS OF A REGION is a term used to describe the birds that inhabit a particular region. The two crossword solutions for this term are ORNIS (5 letters) and AVIFAUNA (8 letters). ORNIS is derived from the Greek word for bird, and it refers to the scientific study of birds. AVIFAUNA is a combination of the Latin words for bird and fauna, and it is used to refer to the bird species that inhabit a particular area.