BirdFont for Windows isn[SQ]t a widely known or established font or font application. There[SQ]s no readily available information about a program or font with that exact name. It[SQ]s possible :

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It[SQ]s a very niche or obscure font:

Many custom fonts exist that aren[SQ]t widely publicized.
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The name is slightly different:

There might be a minor spelling variation or a similar-sounding name.
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It[SQ]s a private or internal font:

Some organizations create fonts for internal use only.
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It[SQ]s a misspelling or a misunderstanding:

The name might be incorrect.

If you encountered this name somewhere, providing more context (where you saw it, what it was used for) would help in identifying what it might be.