The Urdaibai estuary snakes north of Gernika to kiss the sea at Mundaka, covering around 220 sq km of constantly evolving water flows, mud banks, marshes and forests. The impressive Urdaibai Bird Center, close to the village of Gautegiz-Arteaga, will teach you all about the different feathered friends here.
Even when the centre is closed, you can still visit several bird hides, which overlook marshland and a lagoon. There's also a live bird cam on the website.