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Dr Williams said the population of native birds had increased a lot, particularly in the past five years.
''I came to Dunedin from up the Mackenzie country in 1962 and I never saw a tui in the wild in the city until probably five years ago and suddenly they are everywhere.''
He said it was most likely because of the growing popularity of planting a variety of natives like kowhai and flax, which provide food sources at different times of the year.
''Twenty years ago nobody was planting natives.
''Now, things Maori are being looked on a lot more positively and that includes planting native trees and shrubs and stuff.''
Project Gold started two years ago with the aim of increasing the native bird population in Dunedin and that would also provide more food for tuis in coming years, Dr Williams said.
He said species such as flax also needed to be planted to ensure there was a food source to sustain the bird population in the late autumn and early winter when kowhai was not providing food.