A worldwide community photographing and learning about wildlife
Either a hen harrier or a Montagu's harrier, I'm not sure which. When I got closer, it flew away and the shots I took of it in flight were not use for identification at all.
Looking at an enlargement of the eyes in the first picture I am inclined to agree with the Black-shouldered Kite, there is now a healthy population of them in southern Portugal and I have even seen and photographed one here.