gray wagtail

Hi all

I have just joined this forum and I have a question about a grey wag tail that has just visited my garden!!! My sister lives in scotland and I have seen them before (river tay)  but can not belive I have just had one in the garden. I do my very best to attract birds and recently the patio has flooded making an artificial pool. I live in surrey and there is a river near the house but we are quite urban here. 

Is this unusual will he/she be back?

  many thanks