We've been away recently and so just catching up with local bird news. The swift at the Johnston house martin nest on 11 July is intriguing. However, we're a bit confused by the photo.
The dark bird shown is not a swift, which do not have such long outer tail feathers. Swifts also have longer, narrower wings than the bird in the photo, which appears to be a dark (possibly a melanistic) swallow. Was it helping to feed the young? A very interesting observation!
The bird in the photo very much reminded us of a melanistic swallow that we observed in a mixed flock of hirundines, feeding and resting on Stackpole Warren a few years ago.