The Colour of Buzzards

The old common buzzard seems to come in a variety of shades and hues. I've seen very pale. almost white ones, brown ones, spotted ones and at the moment our neighbourhood is being graced with the darkest coloured one I think I've ever seen. I've seen it several times in the last few days and he or she is dark umber in colour, almost black, on top and charcoal grey under the wings, with a reddish chestnut patch on both shoulders. Seen quickly overhead it resembles a slightly bizarre raven until you get a proper look and then everything about it is unmistakeably buzzard.