Blackfeather Woods ultraviolet

He watched the blackbirds devour the meal before squabbling over scraps of fluff and bones.
Naturally, Altar took off with several in his beak.
His sister questioned the noise and he grinned.
"Honestly, it takes practice." He didn't want his sister expecting to do it straight away.

"So you have to fold your tongue up to the roof of your mouth, then make a sound, like a soft growl, and gently blow. I think that's how I do it." He wasn't certain, but it's the best he could describe the sound. He demonstrated the best he could too, causing. Altar to return with an expectant caw. 
"If not, train them to a different sound." He didn't mind if she did. She could probably get her own flock -- or singular companion like Tundra -- but it might help if they have different sounds, so the birds know who is calling them.