Does the speak with animals spell (Basic Rules, pg. 277) or the circle of shepherds druid subclass feature speech of the woods (XGtE, pg. 23) let a player understand Giant Owl the language?
I'm sure a player would be able to communicate with a Giant Owl with said spells & features, Giant Owls understand common for what that's worth, but I want to know if players can conceivably listen in on a conversation between two Giant Owls speaking their native language using these abilities.
Is there some innate property to languages which would exclude their comprehension from these abilities? My instinct is the Comprehend Languages spell would let players understand Giant Owl the language but not a mundane Owl. Whereas speak with animals would do the inverse, or partly the inverse in that they can communicate in mundane owl with a Giant Owl but not in Giant Owl with a Giant Owl.