House martins nesting under the roof's eaves

I love all the wonderful summer bird visitors such as swallows, swifts, house and sand martins. As a child  I stayed at my granny's house which had similar mud nests like these in her house which looked out across the Thames Estuary at Thorpe Bay near Southend on Sea.

When I saw these flying in and out of the nest with food for their young I couldn't resist a session with my camera. You can see several generations of nests, the currently active ones are banked with mud right up to the roof, except for a tiny horizontal gap at the top  through which the parents fly in with food for their young. apparently they will return to old nests each year if they can, because it saves them about ten days of work creating a new abode. Here you can see several old abandoned nests in various stages of disintegration. I expect they are progressively older. They seem to fly with abandon which charms me. The sand martins have a different approach needing to find a way to fly up to and into a crack or hole in a 'cliff' face. They all are niches which amaze me wherever they are.