This video from Britain says about itself:
BTO Bird ID – Small Breeding Grebes
15 March 2016
Small grebes in summer are gloriously-coloured birds, but two of the three species are unfamiliar to most. Poor light or frequently encountered partially moulted birds can also cause some identification headaches. Let us help you separate these beautiful birds.
The video is about three species: little grebe, black-necked grebe and Slavonian grebe.