Using citizen science to assess drivers of Common House Martin Delichon urbicum breeding performance

Many hirundine (swallows and martins) species are declining throughout their ranges. The Common House Martin Delichon urbicum is a migratory hirundine that breeds throughout Europe but has shown recent declines in some parts of the UK, particularly in the south. We conducted a large-scale citizen science survey to assess how the breeding performance of House Martins, measured by the number of attempted broods and nest success, is influenced by nest-specific, landscape and weather factors. Pairs in eastern parts of the UK started breeding earlier than those in the west, and breeding performance was higher in eastern regions. There was no effect of latitude on either aspect of breeding performance, so our measures of breeding performance alone do not help to explain differences in population trends across the UK. The probability of attempting multiple broods and producing successful nests was higher in previously used nests than in newly built nests, and in artificial nests than in natural nests. Nests built on plastic soffits of buildings were less likely to be multi-brooded and less likely to be successful compared with other materials. Suggested conservation measures therefore include discouraging the removal of old nests and encouraging the installation of artificial nests, particularly on buildings with plastic soffits. This study provides comprehensive insight into the breeding biology of House Martins, and although our findings do not show conclusively that breeding performance is the sole driver of population trends, they go some way to explain declines in House Martins and ultimately provide information that may help conserve this species.

Automated summary

Many hirundine species, including the Common House Martin, are experiencing declines in their populations. A citizen science survey in the UK found that breeding performance of House Martins is influenced by nest-specific, landscape, and weather factors. Birds in the eastern part of the UK breed earlier and have higher breeding performance compared to the west. Conservation measures should focus on discouraging removal of old nests and installing artificial nests, particularly on buildings with plastic soffits.