The birds are minor characters in The Backyardigans.
Birds' calls can be heard whenever the main characters are in the backyard. These birds are never shown, but their twittering can be heard in every episode. The characters rarely acknowledge the birds; one exception is in "Fly Girl", in which Maharani Tasha orders the birds to stop chattering so that she can enjoy some peace and quiet.
Most of the birds have not been seen, so it is unknown what they look like. However, one appears in the book adaptation of "Fly Girl". It is mostly light blue with darker blue wings and an orange beak.
The birds are heard in every episode of The Backyardigans, but never shown. "Fly Girl" is the only episode in which they are mentioned.