Does 2dn have a “z” or a “s” in it, as the bird can have either?
Is it a “z” because the secretion has a “z”?
Is it a “s” because it is a “sounds like” and so should not have a “z”?
Does it really matter? Really it should!
I used a z . Chambers shows ouzel as the first spelling and ousel as alternative. When looking for ousel in Chambers, it shows "see Ouzel". Owzat ? Zzzzzz ;0)
That reminds me of a story you would appreciate. A friend was staying in Shaftesbury. He went into a pub (as you do) and was chatting to the barman, who said (and you'll have to do the voice):
"I expect you can tell from my accent that I'm not from these parts .................................................................................................................................................................................... I comes from Sturminster Newton".