Unlike the hybrids, these birds show an all white foreneck and isolated black nape. Females have slightly longer, more upturned bills than males and duller, less shiny black. I believe this is a female. This species is sometimes called the White-headed Stilt. The name Pied Stilt was adopted by Clements starting with the 6th edition and IOC starting with the current version. This species arrived in New Zealand from Australia in the 19th century and increased through the mid 20th century, but now appears to be declining.
Taxonomy and geographic variation controversial. H&M4 and HBW lump this bird with the Black-necked Stilt of the Americas, the White-backed Stilt of South America and the Black-winged Stilt of Eurasia and Africa. To make matters more confusing OSNZ uses the name Pied Stilt for this entire assemblage. Meanwhile Clements and the IOC split the entire group into four species. If we follow the lumpers, this bird is H. h. leucocephalus, which ranges from Australasia to Philippines through Indonesia. If we follow the splitters, then this species is monotypic.