Can a Kenku communicate using sign language?

Question

The description for the Kenku race (VGtM, p. 109-111) includes this statement:

You can read and write Common and Auran, but you can speak only by using your Mimicry trait.

In the Kenku origin tale, the description further explains that:

[...] to ensure that the kenku could never divulge any secrets, their master took away their voices.

and

Although unable to speak in their own voices, kenku can perfectly mimic any sound they hear, from a halfling's voice to the noise of rocks clattering down a hillside. However, kenku cannot create new sounds and can communicate only by using sounds they have heard. Most kenku use a combination of overheard phrases and sound effects to convey their ideas and thoughts.

Kenku can't speak except by mimicry.

The Kenku have a voice, but it seems they don't have the ability to vocalize their own words; they have no voice of their own. However, they can form their own words because they can write Common and Auran, so they can form their own words in writing (right?). The Mimicry trait is clearly for speaking only.

As sign language is neither vocalized nor written, I would like to know:

Can a Kenku learn sign language and use it to communicate without mimicry?

Answer 1

While Kenku are unable to form voices of their own, there's nothing to stop them from communicating nonverbally. That being said, there's two issues. Part of the Kenku curse is that they lost the creative spark, so any sign language would have to be made for them by someone from another race. Even if a kenku could have a sign language created for them, they'd run into issues that people with real sign language deal with, so some things to consider would be:

• Having their hands full. It's hard to sign with a weapon in your hands, so there would be no communication in combat.
• Most people won't know sign language, so anyone who wishes to learn the language would have to spend 250 days learning the language and costing 1 gold per day. Your DM can homebrew how long it takes to learn certain individual words or phrases. You can also work with a fellow player to say you've known each other long enough to teach them the sign language.
• Sign language is not audible, so anyone not looking at you would not be listening to you.
• Many spells like Comprehend Languages and Tongues does not help with sign language, as both target spoken languages.

Additionally, it bears repeating that "because their ingenuity and skill had turned toward scheming against their patron, the spark of creativity was torn from their souls." A kenku can learn writing by seeing words, but they cannot create words or write words they've never seen. Their vocabularies, both written and spoken, are done by mimicry and copying.

Answer 2

There's nothing in the rules specific to this. As such, I believe this can be home brewed to be allowed, should the DM be agreeable. It stands to reason that they have the ability to mimic, so they could in theory learn sign language that way. Additionally, they can be rogues, so they learn thieves cant, which contains hands signals, a sign language of sorts.

But ultimately, it falls on the DM to decide.