A bird-brained cipher

Today my partner, an avid ornithologist who I swear spends his whole day looking at codes and tables online, left me this cryptic clue when I asked where he had been all day. He complained about a change from 6th to 7th edition of some checklist and how he stuck with 6th edition because he liked it better, but I never understand what he’s on about. He can be a bit of a birdbrain, so hopefully one of you can help me figure out what he’s talking about!

Where has he been?

4540 (2) 0431 (2) 4610 (2) 8506 (2) 3980 (2) 5332 (1)