A few of our birds nest in holes in banks of compacted sand or mud. The most well known bank nesters are the aptly named Sand Martins, which nest colonially, excavating deep, roughly circular holes (and tunnels) in suitable sandy banks, where they can find them. Sand Martin colonies usually consist of several, even scores of holes, most often near the top of a bank. Holes are only a few inches in diameter. The other main bank nesting bird in the UK is the Kingfisher, which has a similar-looking tunnel nest, most often in a bank of a river or lake, often not obvious, as it is tucked out of view.