When a young bird is learning to catch fish, refraction can make it difficult for the bird to be successful because it distorts the appearance of objects underwater. The bending of light as it passes from air to water can make the fish appear closer or farther away than they actually are. This can confuse the bird and make it harder for them to accurately judge the distance and position of the fish. It takes practice and experience for the bird to overcome this challenge and develop the skills needed to catch fish effectively.