Sand Martins look very similar to House Martins. The main difference is colour - House Martins appear deep blue, and Sand Martins brown. However when they are flying overhead this will be very difficult to see. A better way to distinguish them is the House Martin has white all over its underside, whereas the Sand Martin has a very clear dark collar. Sand Martins nest in sand banks along the coast, and will occasionally visit Druridge Pools to feed.