One of the Paisley Ravens (presumably the off-duty bird) spent the whole day perched on prominent lookouts near the nest. At one point he (I assume) chased off a Carrion Crow that had strayed too close. At no time did I notice another bird, which makes me think incubation must have started and the female is sitting tight. Interestingly, the perch that the bird seemed to favour the most (an aerial on the top of a six-storey, stone building) was one I have not seen used in any previous years. I wonder if it means this year's male is a new bird.