I don't personally 'tweet' - I do have a mobile phone, but use it just for emergencies - but I must confess that I am a daily reader of the Surfbirds Norfolk twitter posts. This is a fabulous resource for Norfolk birders, since one can discover within seconds if something new has turned up, or if a long-stayer is still around.
The majority of posters can be divided into two groups:
* Older birders/photographers who have the time - and, often, resources, to spend two or three days in the field. I am probably in this category, in the 'it's good exercise and provides social interaction now I'm retired' subset.
*Younger, often newly-graduated birders, whose tweets are filled with absorbing accounts of multi-species twitches around the UK and far-flung destinations.
I find it quite interesting to read the thumbnail autobiographies that appear at the top of each page. In the case of subset two, these frequently include some form of statement about protecting the environment and a personal commitment to combat global warming, climate change, carbon dioxide emission and so on.
To me, there's a dichotomy here: how does jetting around the world or driving thousands of miles annually within the UK address these noble aims? Just for fun, have a look at your region's tweets: I bet most of the posters have seen the Dusky and Blue Rock Thrushes, the Eastern Stonechat, the Pacific and White-billed Divers and most of the other recent 'good' birds.
Let me quickly add that I might well have added myself to the crowds at these twitches 20 years ago: I personally think anything that gets people out in the countryside and away from TVs and games consoles is a good thing. But let's not pretend we're saving the planet by doing it!
I attach a photo of a nice little bird that didn't add to my carbon footprint!