My belief is that people internally have systems of morality. This system doesn't always match what they say, or what they do, but when people see themselves acting in ways that don't match their internal morality, they feel emotions like guilt.

To me, therefore, moral behaviour means behaviour which I think is dictated by the internal sense of morality of the person acting. For instance I consider a lot of what Richard Stallman does to be moral behaviour, because it is motivated by his morality (or appears to be - read what he says) even if the issues involved don't match my sense of right and wrong. I don't consider similar choices on the part of Bob Young to be moral behaviour because his self-described morality is quite different. (He had at one point an excellent talk on why it was in Red Hat's marketing self-interest to act in ways that the FSF considered moral.)

By contrast "practical" means just that, courses of actions that might be indicated because they are doable and not necessarily for any other reason.

As for Polynesian cannibalism, I likewise cannot find any links to what I was thinking of online. My memory, however, is of a series of articles that I had to read once for a philosophy course, in it they described a Polynesian cult on a densely populated island which was highly promiscuous, and then killed the resulting infants as a form of birth control. As you might imagine, the appalling image stuck in my mind...

Cheers,
Ben