Kererū sightings have seen a huge increase across the Bay of Plenty, according to the latest New Zealand Garden Bird Survey.

The survey, released today by Manaaki Whenua – Landcare Research, compiles data from volunteer bird counters across the country and uses the data to estimate how bird counts change in different parts of New Zealand.

Of the districts in the Bay of Plenty, Tauranga saw the largest increase in kererū sightings, increasing 96 per cent in the last five years and 192 per cent in the last 10 years.

Sightings in the last five years increased 57 per cent in the Western Bay, 68 per cent in Rotorua, 88 per cent in Kawerau, 75 per cent in Whakatāne and 47 per cent in Ōpōtiki.

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Manaaki Whenua research associate Dr Eric Spurr, who initiated this nationwide citizen science project in 2007, said the results showed increases in fantails, tūī and kererū counts nationally in the last 10 years, with the rate of change accelerating in the past five years for the latter two species.

Kererū counts have risen rapidly since 2013, particularly in Canterbury and Marlborough, Waikato and Hawke's Bay.

Spurr said the survey was not designed to determine why these changes had occurred, but it was likely due to recent predator control and restoration planting.

"Reducing predator numbers enables birds to breed more successfully and potentially increase in number."

Conversely, numbers of silvereyes noted by survey participants have reduced by 28 per cent, which Spurr said may be a reflection of climate change.

"In warmer winters, fewer silvereyes come into gardens, presumably because more remain in surrounding farmlands and forests."

Despite the decline, this was good news for silvereye counts as the decline appeared to be slowing.

Spurr said the survey's results were important as birds acted as backyard barometers - telling us about the health of the environment we live in.

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Other birds with increased sightings in the Bay of Plenty included the myna, tūī, fantail, blackbird and silvereye.

Decreases were seen in sightings of the chaffinch and goldfinch.

Greenfinch populations were strong across the Bay of Plenty, except the Western Bay, and a similar pattern was recorded with starlings, which were also down in Tauranga and Kawerau.

Fantail, dunnock and song thrush sightings saw little or no change, house sparrows were also stable.

Bellbird sightings were down across the region, except Tauranga and the Western Bay.