No interactions present.
I notice that some of the Oystercatchers have all red bills and others have some black on the bill. What, if any significance does that back marking have?
It partly depends on what mud they have been poking around in! Otherwise, juveniles do have a darker distal half to the bill, and generally the colour of the bill intensifies with age and with summer plumage.
My Flickr photos...
Lat/Lng: 50.71861, -1.85226
OS grid ref: SZ105910