Martins, in my experience, are fine with strings being hung at this late stage. Bit of trial and error to get the length right, and they will be wary for a very short while. It worked reasonably here in the end, but I am convinced this sparrow issue is the biggest driver in house Martin decline. It is widespread now I know to watch out for it in other villages. Where there were martins, there are now more sparrows. If feeding birds, sparrows are an invasive species. This needs to be publicised by RSPB rather than relentless encouragement of 24x7x365 blanket, untargeted bird feeding. You said martins nested last year, and less have returned. Do you know how well the nests ended up doing? Did they all fledge young?
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