I personally have always thought of this to be quite a 'naff' thing, and certainly not something that's necessary - however it's not something I've ever actually seen at any of the wedding I've been to, I've just known about it - iykwim.
Anyway, after being at a wedding fayre in our venue a couple of weeks ago, there were two doves on 'display' - in all their glory, sitting very cutely in their white bird cages with some pretty ribbon to decorate. It actually really caught my eye and I thought it fitted in with our venue beautifully. I sent the exhibitors an email yesterday asking for a quote and it came back at £180. I told my H2b last night and he just about chocked on his drink - '£180 for two old birds' as he put it - lol.
What's your views, is it naff as I originally thought, or is it quite a nice sentiment?