Well, I would say there are many different definitions of this. It would all depend on who you ask, as to what is considered a sexual behavior.

Some might say sexual behavior is being very flirty. And I wouldn't say just small flirting. Very Flirtatious behavior.

Others would take the definition a step further in saying that sexual behavior could be any of the sexual actions a human could take. Any action you might take with someone you are in a relationship with, like kissing or anything further than kissing.

While some will argue about the specifics, broadly speaking, sexual behaviors can be defined as all those things we “do” that we consider sexual. Those might be things we do with others, like kissing, erotic touch, intercourse, etc.
http://sexuality.about.com/od/glossary/g/sexual_behavior.htm