"I do not know the language of birds."
Translation:Ben kuş dili bilmiyorum.
The use of ben has nothing to do with that sentence. You can also say "Ben kuşların dilini bilmıyorum" an be correct. It is just a different way to say the same thing (in this case using a possessive structure or a noun compound doesn't really change the meaning).
"Ben kuş dilini bilmiyorum" was also not accepted. (The sentence structure is a bit different, but I believe the essential meaning remains the same). Incidentally, I recall reading an article about a type of language (used by villagers in a remote, mountainous part of Turkey?) called "Kuş dili"! If I ever find the link again, I will share it here.
"Kuş Dili" is a language used in the (Kara Deniz) Black Sea Coast Region of Turkey. The Black Sea Region is famous for its cuisine, folk dance and, thanks largely to the Giresun Province, its "bird language". The 400-year-old whistled language is part of the region's cultural heritage and has made its way onto the UN cultural agency's list of endangered languages.
For those who might be interested, here is the link.