Shade
Monster Junkie
Based on this, I'd say they need Bluff ranks, too.Kenku do not speak; although they may give out bird-like squawks, these are gibberish. Kenku apparently communicate with each other telepathically. They are adept at symbols, sign language, and pantomime.
Kenku may appear to be friendly, helpful, and even generous. They freely give treasure to humans and demihumans, but it is rarely genuine and crumbles into dust within a day. They may offer nonverbal advice to humanoids, but this is carefully designed to mislead. It may actually lead the party into dangers and difficulties they might otherwise have avoided. As a rule of thumb, kenku have only a 5% chance of actually helping people.
For the caster level of spell-likes, how about caster level equals HD? Invisibility lasts one minute per level, so that's plenty of time before they use it again "at will" or discharge it. Caster level 5 is the minimum to cast call lightning, so the 5 HD kenku that can use it would already meet this.
I could see no reason to lower the Dex for the top dog, either. I'd make it equal to the others.