The roof of the corrugated iron shed that appears in a couple of the earlier photos was covered in mud nests. There would have been a hundred or so. I assume they belonged to swallows but we never saw any birds.
Maybe the birds have migrated or were all away from home having a meal. I don't know about swallows but most birds only use a nest after mating. Then they abandon the nests till breeding season comes around again. Awesome capture!