Stewart at Boulmer Birder made a comment here some days back regarding the variability of individual birds. Some of the images I took of Common Ringed Plover today struck me as demonstrating his point perfectly.
Images 1&2 are of the same individual and 3&4 of another, both juveniles. The latter with its thin breast band had me checking between the toes, at least until I got home as I just couldn't remember whether Semipalmated Plover had more or less white around the eye and forehead, less being the answer some quick revision provided consigning my aspirations to the recycle bin. Maybe its simply a juvenile female hence the much narrower band. The leg length seems longer too.
Then there was this one, presumably either second calendar year/adult non breeding type rather than an early moulted first year.