There's no punch line here, just an entire flock of relatable pigeons singing a relatable song as if they were born to do it. And the panels you see here aren't even half of it. They perform the entire song "Under Presuure" by Queen and David Bowie at Pigeon Comics, as drawn by ProfessorBees (Christian McGowan). See the rest of it here.
This particular comic has become quite popular, and readers are asking for posters to be produced. That might happen. -via Metafilter