I am not aware that the BLP Committee has adopted a policy on this but I am even newer to the Committee than Glenn. And I certainly don't claim to be an expert on the impacts of bird feeding, nor the ethical issues.
Are there perhaps two different but related questions here: the impact of feeding birds generally; and the use of food to attract birds for photographers?
The first is a big question which covers a lot of things. Feeding is probably more widespread in Australia than might at first seem to be the case. Certainly overseas in places like the US and UK feeding seems to be extensive and certainly tolerated and perhaps even actively encouraged by some bird conservation organisations. People feed birds for all sorts of reasons, but I expect at least some of it is for similar reasons to why we have pets - because many people like interacting at a personal level with animals and seeking the companionship and 'approval' of animals. That in itself raises a bunch of ethical issues. I don't know about other places in Australia but here in Canberra the birds that are attracted to feeders tend to be those which are well established in urban areas, very tolerant of humans, dominant and aggressive, and obtain their food from a variety of natural and human sources. These birds are highly adept at scavenging for any and all sources as any outside cafe in green spaces can attest. I am not sure if this makes it OK to feed them, although I expect that small amounts of additional food such as bird seed make relatively little difference to the well being of these birds. However,this is a debate which will continue particularly as urbanisation continues.
The second is more about to what extent is it appropriate (or, perhaps, ethical) for photographers to use artificial means to alter the behaviour of birds for the purpose of improving the photographic outcomes? When you turn the question around like this it takes on a different tone. Of course, one can argue that if someone feeds birds, there is clearly no additional harm in taking incidental pictures of them. However, there may be an argument that the photographer should not disturb birds specifically for photography be it with food, or with the playing of sounds, or similar. BLP's policies say members must not use sounds to attract birds on the basis that to do so has the potential to impact negatively on birds, and a precautionary approach should be taken until proven otherwise. One could also argue that a precautionary approach should also apply for use of other artificial arrangements to disturb bird behaviour in ways which are favourable to the photographer, purely to improve the photographic outcomes.
Does the question change if you replace 'food' with 'water'? I am not sure.
While I don't have a particularly well thought through position on this myself, I tend towards a view that one should try and go to where the birds are, rather than enticing them artificially, and try and capture them behaving as if you weren't there (as much as possible - clearly your presence will always have some impact). This does not mean the birds are free generally of human interference, of course - living in an urban area means that some human interference is always present, even if in a very generalised way. I'd be the first to say its a very grey area, the more so the deeper one digs.
Cheers
Simon