Flying over Bridge Street at Williton, 0745 this morning, a swift that appeared to be on it's own and not interacting with the others. Looked much like the others appart from a very white partial belly. The white came nowhere near the throat as I would expect from alpine swift and was more of a splodge than a clearly defined patch. Can I presume that this is just a colour aberation of common swift and not a first year alpine?.
Hello Paddy,
Alpine Swift is much larger than Common Swift, which sometimes aerially-mob it because of its falcon like shape and size. What you saw was most probably a Common Swift with pied-plumage, which is variable in the amount of white; I’ve seen one of these types on 3 occasions.