Hi Phil and welcome to the Community
The absence of any markings on the throat make me think it's a 1st winter bird. As such, I'm not sure you can tell the sex at this stage. If it is a young bird it may not have a mate yet.
A very nice bird to have in your garden and it is obviously at home on your fountain. I've no idea where it would roost - possibly in a nearby tree?
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Tony
My Flickr Photostream
When the bird first appeared in our garden it was as a pair but we have not seen the other one now for at least 3 weeks.
We do keep putting out mealworms and I was thinking about getting some maggots, would I be doing the right thing ?
If the wagtail is taking mealworms I'd stick to those. At least they are easy to handle and clean.
I have a Grey Wagtail that has been visiting our garden every day for just over 3weeks now !!!! Also likes the dried mealworms. Was also wondering where it roosted at night!!
New to forum ,trying to work out how to attach a photo !!!!
I also have wagtails. They are so cute but sorry I can't answer your question