The "green sparrows" that caused a social media flutter in Castlecliff last month had likely been having dustbaths in a green substance, Birds New Zealand regional representative Peter Frost says.
Sparrows with patches of green colouring had been spotted in the suburb and some speculated they had crossed with greenfinches, and others that they had been in contact with greenish pollen.
But Frost said the birds' green colour was not uniform, either across individuals or across a group. He thinks it's more likely the birds came into contact with the green dye of hydroseed, used to stabilise soil around roadworks, or for new lawn plantings.
They could have been having dustbaths in sand coated with the substance, because their heads and underparts were their greenest parts.
Or they could have bathed in water coloured by copper or chromium substances, or have been sprayed by a dye. It was more likely the green colour was topical, rather than from something they had eaten.
