At least since Saturday 2nd April (when I first saw them) there has been about 500 sand martins coming into roost in the reedbed at dusk. The flock appeared about 8 pm this evening and in the fading light appears as a moving smudge - not the impression of a dark cloud that a flock of starlings has as the birds are smaller and fly a lot faster. They perform aerial acrobatics like a starling flock, twisting and turning, and as they drop over the reedbed they dash over the feathery reed heads, rising and falling as they follow the contours. All is still as they seem to have settled in the reeds then the flock will dash across one of the channels to a different roost site. If the birds are close to the footpath their chattering calls can be heard. I can't recall having seen this behaviour in spring before. If the roost continues it will surely attract a hobby, once that migrant raptor has returned.
It was a wonderful evening to sit and watch the daylight fade over the reedbed, with the silver reed heads bathed in a crimson wash from the dusk sky. A few water rails were calling and I heard a woodcock roding - its display flight when the bird emits a squeaky call, but I couldn't see it (sounded as though it was flying over the eastern hedgerow). A bat flying at dusk was probably one of the pipistrelle species that has been recorded on site (common or soprano).