The bird on the image is a young bird. A few weeks after leaving their nest, it becomes tough to distinguish the young from the adults. A relative difference between a young bird and an adult is the facial pattern: a young birds has less contrast and a less pronounced facial mask: adults have a pronounced and continuous white facial disc, and a more contrasting, clearly delineated black mask around their eyes. The juveniles already start to develop these features, but the facial disc and mask are still more diffuse.

Moreover, almost all the adults have started to moult in august and thus the adults have a more worn out plumage. So a bird with a fresh and intact plumage in august on this breeding ground, was very likely to be a young bird. When flying and hunting, one could also notice that the young birds were still a little bit clumsy.