The Clarinetland Bird just appears in the episodes Squidward in Clarinetland and Ghost Host. Squidward accidentally encounters this bird chasing SpongeBob, who'd recently stolen his clarinet. The Clarinetland Bird, upon seeing Squidward, questions Squidward, who in response says that he is looking for his stolen clarinet. The Bird, who claims to be the "Keeper of the Clarinets", scoffs at Squidward's plight, and tells him that "a clarinet cannot be owned". He then proceeds to eat Squidward due to his lack of respect.
The Clarinetland Bird is simply an eagle head protruding illogically from the ground.
The Clarinetland Bird's stomach is an obvious play on surrealistic dimensions, as it is illogical for him to even have a stomach. Inside leads to several other implausibly placed rooms. The first is a mirrored room, where Squidward's reflections tease him by putting their clarinets into their mouths. The next room is a giant clarinet-cannon with several clarinets above, where Squidward chases SpongeBob through, before landing in a SpongeBob-themed pinball game, played by Patrick. There is a giant vacuum that sucks up Squidward and SpongeBob and blows them into Outer Space where Squidward lands back in the front of the locker.