"Legendary bird" would be "densetsu na tori" (den-setsoo nah toh-ree).
In Japanese language, the common word to say 'bird' is 'tori', there could be several variations depending of the kind of bird you are referring to. For instance, if you want to say 'little bird', you can say: 'kotori'.
Tori
You may say 'tori,' written: 鳥
'Tonde iru tori.'
Hachidori (literally: bee bird)
i would say legend Larry Bird
Most say it was or still is but few say it isn't, I think it might be just a legend but some say they saw it but it could just be a rare bird.
It is 'densetsu.'Densetsu, or 伝説 is the most common word for legend.
There isn't one, but you can literally say "blue bird" by combining blue "aoi" and bird "tori" together.
The Japanese word for legend is densetsu.
鳥の島 Tori no shima
赤い鳥 (akai tori)