Onced aged correctly, most birds are sexed according to the below.
2cy: 2cy males are similar to 3cy+ males (see below) but often show a slightly less distinc pattern in face. Females have no or rather little black on crown, often a dirt grey forhead and some white admixed in the black chin.
3cy+:Males show a pure white foread and a glossy black crown reaching far down the nape and is distinctly demarked towards the pale grey mantle. Black chin lack any white feathers and face pattern is very contrasting in pure white and pure black. Females shows les black on head (not reaching down the nape) sometimes with some grey admixed. Forhead is generally white but with some grey feathers present. Face pattern often les distinct than in males.
2cy female April. Note the lack of black in the crown and nape and the rather sullied face (although the forehead is rather white in this bird). [1ET29449]
2cy female April. Same individual from above. [1ET29449]
3cy+ female April. Rather restricted black crown with some grey feathers in both crown and forhead. [1ES24497]
3cy+ female April. In this female the crown reaches rather far down the nape, but note the grey feathering in crown, nape and forhead. [1ET29450]
3cy+ male May. Note the pure white foread and a glossy black crown and the distinct demarkation towards the pale grey mantle. Face pattern is strongly contrasting in black and white. [1ET28119]
3cy+ male April. Another male showin from above. [1ET29459]