JackT,
Do you already have a scope or is this your first scope ? If you already have a scope would you like more of the same, or what would you like to change ? If this is your first scope do you have any preferences on objective size e.g. 50, 60 or 80mm ? Would you like lightweight ? What sort of birding do you do e.g, 10 mile hike and/or sea watching in a gale ? Does your budget include a tripod and head ?
If this is your first scope and you have no idea what you like or dislike, and you can get to a "scope shop", then I strongly recommend you go and try some, because you can often quickly get a better idea of what you like and don't like. However, some scope likes and dislikes only become apparent after several months or years using a scope. In that case it can be better to buy a second hand scope first.