Grey Wagtails

I had an afternoon to myself today so I took the opportunity to get out with the camera, and headed for the river Kent to explore for good places to photograph Grey Wagtails. After half an hours walk I found a likely place and set up, struck lucky almost straight away, don't you love those days.
When I got home some of the photos show the bird with prey items in it's beak, any ideas what they are ?

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