Juvenile Grey Wagtail?

Juvenile Grey Wagtail?

Observation - Juvenile Grey Wagtail? - UK and Ireland. Description: Beautiful bird with a long thin tail and very distinctive yellow underneath at rear. Seen in a church yard in York. Is this a female as it does not have the black bib, or does thhe black bib only appear when they are breeding? At what age to grey wagt

Beautiful bird with a long thin tail and very distinctive yellow underneath at rear. Seen in a church yard in York. Is this a female as it does not have the black bib, or does thhe black bib only appear when they are breeding? At what age to grey wagtails develop adult plumage?