I'm looking to use "Night bird" as a name or title for something. I don't know which, if any, of the following would be correct:
What rules come into play when this is being used as a name or title of something, and is there more than one correct way to phrase it?
If you want to say "night bird" with the words "night" (nox) and "bird" (avis), you should say "bird of the night", avis noctis. When you decline this expression, noctis (of the night) remains in the genitive case whereas avis takes the required case.
A more Latin way would be to use an adjective. I would go with nocturnus (nightly, nocturnal or nighttime). Thus "night bird" would be avis nocturna (literally "nightly bird"). Here both words are declined, since we have an adjective attribute.
If you want to use it as a title, the nominative (undeclined) case is the best choice. Therefore I suggest avis nocturna.
I second the recommendation of avis nocturna. (It would also be possible to say nocturna avis.)
If you wanted something more poetic, you could also go with something like avis tenebrosa, which would translate to something like "gloomy bird" or "bird of gloom" or "dark bird."
«Noctis avem», in Ovid's Metamorphoses XI 24, about (presumably) an owl.
