The Orioles, with lead singer Sonny Till, had a big crossover hit in 1948 with "It's too Soon to Know," which was a #1 R&B song and made the top 15 in the pop charts. The Orioles are in the Rock & Roll Hall of fame.
The Penguins had only one big hit, "Earth Angel," but it was one of the definitive vocal group songs of the '50s. It's sure to show up in any oldies rotation, and it's been recorded again and again by other artists. Cleveland Duncan sang lead, and he also sings the part on Frank Zappa's "Memories of El Monte." The cover version by the Crew Cuts outsold the Penguins version, but it's the one by the Penguins that I remember.
One of the best and most popular of the "bird groups" was The Flamingos, and they're one of my favorites. Their biggest seller, and the song that most people probably associate with them is "I Only Have Eyes for You," but "Your Other Love" is the one I'll put here. It's just one of a dozen or so great songs I could have picked. Like The Orioles, The Flamingos are in the Rock & Roll Hall of Fame.
There are plenty of other bird groups: The Wrens, Crows, Jayhawks, Falcons, Cardinals, Swallows, and Larks come to mind. Maybe I'll to some of those one of these days.