Trying to remember a book/storyline. Possibly a StarTrek novel.
Alien bird-like with a beak 'cracks' the skull open and swallows the brain whole. Brain is incorporated into their skull, becoming dual-brained? It's not "Conspiracy" or the Bugs.
I thought that one of the brains could be suppressed with a sedative, allowing one victim to fight back. But I'm foggy after this.