Puffins look like they belong on a postcard, with brightly coloured beaks, comical waddling walks, tucked into dramatic clifftop burrows. Behind that cheerful image, however, puffin colonies across Britain and Ireland have spent decades in serious decline, driven out of their traditional nesting grounds by invasive rats, overgrown vegetation and the general disruption that comes with sharing an island with predators the birds never evolved to handle.