Just a few thoughts on the landscape photography side of the discussion. In my view landscape photography has had a long history of being heavily influenced by the medium and by manipulation of the latter. In the days of black and white film, the medium generally didn't influence results too much to start with (although colour filters were often used to darken skies etc.). But then enthusiasts started mucking around with different film developers to get different looks, and finally Ansell Adams came along with his zone system in which he often wasn't necessarily trying to reproduce the subject faithfully, but rather used a variety of tools in film and print development to get a precisely calibrated look to the final print - some of his most famous images of Half Dome in Yosemite Valley had almost black skies in the print. Later, with colour transparency film we initially had Kodachrome, which produced a reasonably accurate final image on a sunny day, but on an overcast or showery day, quite frankly produced an undersaturated bluish result which often didn't do justice to the colours one had seen with the naked eye. Then came Fujichrome Velvia, a very saturated film which was the mainstay of professional landscape photographers for a decade or more, and which was sometimes over the top in sunny conditions or sunsets/sunrises but much more near accuracy on a wet cloudy day. It was from that background wih Velvia that many photographers first used digital cameras on landscapes, and after finding the ex-camera results didn't have anything like the Velvia 'look', they learnt how to use the RAW conversion software to 'correct' the difference. I think this legacy from the saturated film stocks may still be hanging around to some extent in landscape photography, perhaps reinforced by the stock agencies and magazines etc. which would have felt a need to maintain consistency in the photographic 'look' after digital arrived.
I have my doubts whether the evolution of avian photography has followed exactly the same path, though there are some parallels. I seem to remember that Fujichrome Velvia wasn't always favoured for wildlife, including avian, because it was generally acknowledged that the film was not designed to be colour-precise. You may have found avian photographers more likely using Kodachrome or Ektachrome, the latter being more accurate in overcast conditions than the former (and quicker to get developed). In digital, I get the impression that the oversaturation tendency in processing is not as widespread as seems to have become the case in landscapes (and I have to admit I have to fight the tendency myself - I was a long-time Velvia user in landscape photography). I agree with Ian that processing for submissions to the BLP galleries should aim to have colours as accurate and natural as possible. Mind you, sometimes you get a surprise with some species - I have some recent photos of an Eastern Rosella that look quite oversaturated in the RAW straight out of the camera; put these next to other recent processed images I've produced from other species, and the latter images look a bit flat by comparison.
Cheers, David