Barn swallows have declined across the UK as agricultural intensification reduces insect prey and barn access for nesting. Understanding their requirements guides welfare-positive farm management.
Barn swallows that cannot access traditional nesting buildings because of barn conversion or sealed entry points experience complete breeding failure for the season despite having successfully navigated the journey from sub-Saharan Africa. Pairs that establish territories around converted buildings repeatedly attempt entry, expending energy reserves on unproductive territory defence. Chick survival in years of low insect abundance is directly determined by prey availability, and chicks that do not receive sufficient insects before fledging die of starvation. The cumulative loss of accessible nesting sites and insect food across the landscape means that swallows face compounding welfare challenges at both breeding and wintering grounds.