How many letters does the top answer for “author of the blue bird” have?

The most common answer is daulnoy (7 letters).

Crossword clue: author of the blue bird

2 answers found in Letterora's clue database (Wikidata facts, Open Trivia DB, WordNet and Webster definitions — all licensed sources).

daulnoy 7 letters wd-fact-v3

maeterlinck 11 letters wd-fact-v3

Belgian playwright (1862-1949)

author of blue 67% similar → mitchell

author of the birds 67% similar → hitchcock

author of blue dragon 50% similar → toriyama

author of blue velvet 50% similar → hopper, lynch

author of the birds of america 50% similar → audubon

author of the blue castle 50% similar → montgomery

author of the painted bird 50% similar → kosinski

author of the thorn birds 50% similar → mccullough