Outside the breeding season, goosanders are usually wary birds, liable to take flight at the first inkling of an approaching human threat. Not so the females when they have a raft of dependent ducklings, incapable of flight, in their care: then, all-powerful maternal instinct triumphs. We surprised her as we crossed the narrow footbridge over the River Wear. She had nine ducklings, not long out of their hollow-tree nest, and now they were trapped between us and a low waterfall that tumbled over a rocky ledge. In winter, she would have flown away in an instant, but now she would not even swim her way out of trouble. Her ducklings, as buoyant as corks, could not swim up the waterfall and were constantly swept downstream towards us by the force of its flow. A goosander in a state of high anxiety, swimming in circles with her charges huddled around her, climbing on to her back. Where was the father? Back in the 1980s, it was proven that British goosander drakes, identified by tags and coloured dyes, undertake a long summer moulting migration to Scandinavia. He would have left the nest as soon as she began to incubate eggs, more than a month ago, and may now be loafing around in the Tanafjord in Norway, in the company of 35,000 others from western Europe, moulting out of their dapper bottle green, pink and white breeding plumage into drabber feathers. With luck, he’ll be back in November to father some more ducklings. Why fly so far to moult? Goosanders only colonised Scotland in the 1870s, spreading into the border county rivers and northern England 50 years ago. The drakes’ long summer migration might be a legacy of their earlier, more restricted continental distribution. As for the females, there’s not enough time to join their consorts in Scandinavia after they’ve raised their ducklings here, so they stay on our rivers to moult in winter eclipse plumage. We left our single-parent goosander in peace, crossing the bridge quickly so that she and her flotilla could pass underneath. With danger gone, the family white-water rafted between the boulders, bobbing downriver towards calmer waters.