The Brent Goose, which breeds in High Arctic Canada, arrives in Dublin each autumn, gathering in estuaries, parks and green spaces to graze on grass. Ireland is crucial to this far-northern breeder. Ornithologist Kendrew Calhoun explains how public sightings help track populations, migration and breeding success for conservation...

Derek Mooney and guests explore the natural world in all its forms. Listen live every Monday at 10pm on RTÉ Radio 1.