Black-winged or Common Stilts are from Eurasia/Africa. They usually have an all white head/neck but may have a black cap and/or nape seasonally; the black nape does not join the black wings.
Their extremely long, thin legs relative to their body size shows why they are called Stilts.
They are occasional, rare visitors to UK from continental Europe.
Black-necked Stilts are from the Americas and have a black cap and black back of neck at all times. The black nape meets the black wings without a white gap.
For both species, the female (centre) has dark brown on her wings rather than the glossy green-black of the male (left), while the chicks (right) have brownish plumage.