Swallows and martins have evolved to be specialists at catching insects on the wing. Their streamlined shape and long, thin, tapering wing shape makes them fast and highly manoeuvrable.
How to identify swifts, swallows and martins.
Scientific name: Hirundinidae
Iolo visits the North Pembrokeshire coast near Cardigan to see house martins nesting on sea cliffs.
Iolo visits Pembrokeshire and finds out where house martins nested before they began using the eaves under houses. There are only half a dozen locations where the birds still nest naturally on sea cliffs using mud and grass to attach a ball to the side of the cliff. The nest is then lined with feathers and can take up to two weeks to construct.
The shading illustrates the diversity of this group - the darker the colour the greater the number of species. Data provided by WWF's Wildfinder.