Loved the picture of the quirky House Martin nest sent in by Liz; I have attached a pic of Red Rumped Swallow nest taken in Corfu for reference, very similar. One possible explanation is; I noticed this year when a nesting pair built a nest attached to one of my double artificial boxes they copied the artificial precisely despite it being probably three times the normal size. I also noted one colony abroad that made really tiny nests with entrances hardly visible on the wall all exactly the same size and spec. Perhaps it was born abroad in a redundant RR Swallow nest ? There again the pair could just as well be very innovative or very bad at calculations :-)
Tony Clark
