If the plants were relatively young, slugs could be the problem, in which case I would recommend Nemaslug Slug Killer, which saved my brassicas last year.

However if the plants were established, it sounds like too much damage to be slugs. Rabbits are hugely destructive and likely to be the issue here, pigeons are more likely to strip the tops rather than eating the whole plant. Unfortunately to control rabbit damage you only have two options, fence the whole area (certainly possible with raised beds) or shoot them which may or may not be possible in your location!