It's the perfect medium for them after all -- aside from a stage, that is. It's really focused and quick. And 140 characters is an ideal length for one liners and quirky observations.
They can also use it to announce upcoming gigs, etc. But this seems to be less common than tweeting gags and engaging with other comics and fans.
They use it to promote videos of their standup acts and they are big users of Vine, an intriguing spin-off from Twitter for sharing short video grabs.
People with the same interests or professions will of course tend to follow each other on Twitter (that's what it's there for, after all). But it seems that this tendency is extreme when it comes to comedians. Scroll down a comic's following list and every second profile will have a photo of a guy in a spotlight holding a microphone! So Twitter is obviously going to be a real asset as I develop my website about this subject.
After getting started there I then had a look at Facebook. It was not nearly as useful. Yes, there are heaps of comedians on this site. But they are harder to find. While lots of them have pages that you can discover by searching for words like "comedy" and "comedian", they often just build pages under their own names.
Not surprisingly, comics use Facebook to construct real fan pages in the truest sense of the word. Their posts seem to consist almost solely of news about their upcoming shows, as well as posts about how much fun they had at the last one. They seem not to do nearly as much interaction with their peers as they do on Twitter. And they don't discuss the craft of comedy so much.
Now these tendencies are different to people with a real interest in say, social media itself. They tend to use Twitter and Facebook -- as well as other similar sites -- in pretty much the same way. They're forever sharing information, tips and relevant news and blog articles.
This is interesting. Not only do people in different niches gravitate towards different social networks. They also use each of them differently. This is definitely something to remember when working out which social networks to focus on.