@gentle lemur I just googled for pictures of Long tailed ducklings and i guess you are correct? The female long-tailed duck is the mother tho. She hatched them.
In the same aviary there was a king eider male that was following the female and showing interests earlier this year. Maybe hybrids? Or if the bird park put other eggs under her.
This does not look like a Long-tail duckling to me, and even less like an Eider. I remember Pintails as having pale faces and above-eye-stripes, but it certainly looks more like an Anas spp.
@Andrew Swales Weird, the female they were following is a Long-tailed duck. In the aviary there is also spectacled eider, king eider, freckled duck, barrows goldeneye and some kind of scaup.
If its not one of these species or hybrids i guess the park must have put other eggs under her.
I contacted a friend who is interested in hybrids, he then contacted another friend who is an experienced waterfowl breeder. He was sure this duckling is a young chestnut teal (Anas castanea) and that the park probably put these eggs under the brooding long-tail female while hatching her own more valuable eggs in an incubator.
