It's easier than you might think to tell swifts, swallows and martins apart. Try our simple tips!
They're dark, sooty brown all over, but swifts often look black against the sky. If you get a good look, you might see their pale throat.
The wings are long and narrow. The tail is slightly forked, but not as much as a swallow's.
Swifts have a piercing, screaming call, but they aren't noisy at the nest. Swifts nest in holes - often inside old buildings or sometimes in specially-designed swift nestboxes - so you'll never see them building a nest outside. In fact, if you can see an obvious nest, it's definitely not a swift!
You'll see swifts flying low and fast around buildings, screaming loudly, or perhaps swooping fast into a little crevice in a building to their nests. They also hunt for food (insects) over water or sometimes farmland.
You won't see them perching on telegraph wires or fences; they have tiny feet and legs and can hardly walk!
Swallows have dark, glossy blue backs, wings and heads, with a reddish patch under the chin.
Their long, forked tails are distinctive; males have the longest tail 'streamers' to show how fit and strong they are.
Swallows have a twittering song, which they give from a perch on a fence or building, or while they're flying.
They nest in buildings, or sometimes sheds or porches, but not under the eaves like house martins - another name for this species is 'barn swallow'. Swallows build a nest cup from mud, straw and feathers.
You can often see swallows perching on wires, especially around migration time, when they gather in flocks.
Like swifts, house martins often live in built-up areas.
They build their nests under the eaves of houses, gathering mud to make a cup with a small entrance hole at the top.
House martins have glossy blue upperparts, similar to a swallow, but the white rump is distinctive. Their tail is also forked, but much shorter than a swallow's.
Their call is a sharp 'jik, jik' with some twittering.
Like swifts, swallows and sand martins, you could see them over any lake or river, flying around to catch insects.
Sand martins are similar in shape to house martins.
Their backs and wings are brown - perhaps a bit like a swift - but their underside is white with a brown breast-band.
Unlike the other species, they don't nest in or around buildings. As the name suggests, sand martins make burrows in sandy river banks or even heaps of sand at quarries!
They can be seen flying around together at their nesting colonies, and have a buzzing voice.