The barn swallow (Hirundo rustica) is a long-distance migrant breeding across the northern hemisphere and wintering in Sub-Saharan Africa. UK populations have declined by 45% since the 1970s, driven primarily by reduced insect availability on farmland and threats along their 10,000 km migration route.
Barn swallows that fail to find sufficient insects during breeding face a stark welfare choice: extend foraging trips while chicks are left unfed, or reduce clutch size or abandon nests entirely. Chicks that starve before fledging die slowly over 12-24 hours. Adults completing two 10,000 km migrations annually face predation, hunting (in Malta and other Mediterranean countries), and dehydration over the Sahara. Nestlings in late broods that fledge too late face migration without adequate body reserves. The welfare impact of insect decline is experienced across all life stages simultaneously, making this one of the most pervasive welfare threats for a familiar species.