Bank nest holes
Many birds nest in holes. Some nest in natural cavities, some in ones they have excavated themselves. Only very few British birds habitually make holes in banks by water bodies, or cliff faces of quarries etc. In fact, there are only two British breeding
SAND MARTIN Sand Martins are colonial nesters and excavate tunnels in vertical banks in soft rock or compacted sand or mud, often next to water. They will return to previously occupied burrows. The tunnels are a few centimetres in diameter and can be up to metre in depth. The are often arranged in rows near the top of a cliff, but may be more ‘randomly’ organised. At the end of the tunnel is a small expanded chamber wherein they lay four or five eggs on the straw and feather lining. Apparently, the males dig the burrows and the females prepare the end chamber, though this would be very tricky to observe! Sand Martin nest banks can be artificially created to attract colonies.
KINGFISHER Kingfishers are solitary nesters (ie the pair will nest a long way from any other pair), excavating a burrow into sandy banks usually next to water. The nest hole is usually about half a metre from the top of the bank, and needs to be clear of the water, and also relatively free of vegetation, for easy access on the wing. Kingfisher burrows are c.6cm in diameter and 60-90cm deep. As with Sand Martins, there is an unseen chamber at the end, but it is unlined. The clutch is usually 6-7 eggs. Occupied nest holes may be betrayed by whitewash (droppings) under the entrance. If you can see this, then sit and wait at a decent distance and eventually an adult Kingfisher will visit the hole.