’Not very elegant but also least distressing! Juvenile [sand martins/bank swallows] were approx 12-13g, whlist adults were approx 13.5-14.5g.’Personally, I've found a number of other uses for old film canisters. Photo from Salmagundi. There was also a nice article this week in The Telegraph about the successful use of artificial breeding cliffs for sand martins in the UK.
