das Vögelchen
little bird
The diminutive form of Vogel (bird); a small bird. The expression is often used affectionately or for young birds.
Ein kleines Vögelchen ist aus dem Nest gefallen.
A little bird has fallen out of the nest.

little bird
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little bird
The diminutive form of Vogel (bird); a small bird. The expression is often used affectionately or for young birds.
Ein kleines Vögelchen ist aus dem Nest gefallen.
A little bird has fallen out of the nest.

The ending '-chen' is a diminutive form. It turns 'der Vogel' (bird; o) into 'das Vögelchen' (little bird; ö). Words with '-chen' are always neuter (das) and often have an affectionate or cute meaning.
Schau mal, das kleine Vögelchen auf dem Ast!
Look, the little bird on the branch!
The expression 'Ein Vögelchen hat mir gezwitschert' (a little bird told me) is a fixed idiom. You use it when you pass on information but want to keep the source secret. It is usually followed by a 'dass' clause.
Ein Vögelchen hat mir gezwitschert, dass du eine neue Stelle hast. Stimmt das?
A little bird told me that you have a new job. Is that true?
In its literal meaning, 'Vögelchen' (little bird) is used not only for small birds, but also often in an emotional, affectionate context, for example when speaking with children or when you find an animal cute.
Das arme Vögelchen zittert vor Kälte.
The poor little bird is shivering from the cold.
bird
'der Vogel' and 'das Vögelchen' can both mean an animal with feathers, wings, and a beak. 'Vögelchen' is the diminutive form of 'Vogel' and often sounds small, cute, or affectionate. For a normal-sized or large bird, 'Vogel' is more natural. 'Vögelchen' fits more for a small bird or young bird. The words can be confused because they look very similar. There is also the idiom 'Ein Vögelchen hat mir gezwitschert' (a little bird told me); there, 'Vögelchen' does not necessarily mean a real animal, but a secret source of information.

Vor dem Fenster sitzt ein kleines Vögelchen und pickt an den Körnern.
A little bird is sitting in front of the window and pecking at the grains.
Ein großer Vogel fliegt über den See.
A large bird is flying over the lake.