Mystery feather

We went out to a bird location by the sea and what a day, almost no wind and sunny and +4°C. 
I found a feather that neither my husband nor I have been able to figure out which bird it is from. 
As you can see, the stripes run along the spring and not across. 
I know there are a lot of bird-savvy blippers, so I am pinning my hopes on you. 
What bird has lost these striped feathers?