Complex sentence: The avifauna of Serbia and Montenegro includes a total of 381 species, of which 1 have been introduced by humans, and 6 is rare or accidental in Serbia and Montenegro and are not included in the species count.
Split into simpler sentences: The avifauna of Serbia includes a total of 381 species, one of which has been introduced by humans. Six species are rare or accidental in Serbia and are not included in the species count.