"Yes. I'm talking to you, Mr. Chubby Beak. You marshmall--[smashes glass wall] Oh!"
— GLaDOS talking to the chicks
Mr. Chubby Beak is one of the Bird's chicks that she must forcefully abandon due to the commands of GLaDOS. The Chicks must be kept at all times within Aperture Science Oviperous Warming Vault until maturity.
While GLaDOS is discouraging the chicks. Mr. Chubby Beak accidentally breaks the glass of the warmer. When GLaDOS realises this, she planned to turn the chicks into killing machines (probably to redeem her failed attempt on humans). After that, the light fades. The fate of these chicks and Mr. Chubby Beak is unknown.
GLaDOS talking to Mr. Chubby Beak and his two unnamed siblings