A photo of a snow-white tūī seen in the wild has Kiwi bird watchers all in a flutter.
The beautiful bird was photographed in a kōwhai tree near Taumarunui by Simon Rapley in 2017, and his image was shared online in a native animals Facebook group on Saturday - to the delight of many.
Mr Rapley, who works in foresty, said he came across a large group of about 40 tūī flocking around a kōwhai tree, and saw what he initially thought was a dove flying among them.
"I just thought ... that doesn't seem right, because tūī are quite aggressive birds and they wouldn't tolerate a dove hanging out with them - so I got a pair of glasses out and had a look, and it was a tūī," Mr Rapley said.
"It's something you don't see every day."
Mr Rapley said the white tūī seemed to be quite aggressive compared to the other birds.
"At one point it was in a tree by itself and any other tūī that came near it, it chased them off ... I just assumed that it might have some kind of weakness due to its colouring, but no, it seems to be a pretty hardy individual," he said.
Mr Rapley said he saw the same bird in the same location both in 2016 and in 2017 during the spring, but had not seen it in 2018, as he had not spent as much time in the area while the kōwhai were flowering.
Guy Tichborne, another photographer and bird watcher, shared a striking image of a pure white fantail he photographed north of Auckland last month.
According to Te Papa's Curator of Vertebrates, Colin Miskelly, the birds have a condition called leucism, which is sometimes confused for albinism.
In leucism, birds can have unusually coloured plumage, with either patches or areas of white feathers, or total white colouration. Their eyes remain dark coloured.
In albinism, the bird is totally white, with pink eyes being the giveaway between the two conditions.
"Causes of aberrant plumage in birds are complex and may be due to genetic, developmental or environmental factors or a combination of these," he said.
"The New Zealand species for which partial or complete leucism is most often reported in is the blackbird, but there are many reports for tūī, kererū, fantail, variable oystercatcher, red-billed gull and Australian magpie among others."
Mr Miskelly said a handful of unusually coloured tūī get reported to the museum each year.
According to the British Trust for Ornithology, leucism is inherited from the parent bird, but the gene can be also be recessive and skip generations.
Leucism is believed to partially weaken the feathers, making them more prone to wear, and leucistic birds' colouration may also make them more vulnerable to predation or less likely to attract a mate.
The opposite to leucism or albinism is known as melanism, where light-coloured plumage is replaced either partially or fully by charcoal shades. This condition has also been observed in a number of New Zealand birds.
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