Garden birds a 'barometer' of environmental health

Kererū numbers are on the rise in Hawke's Bay, including at Pourerere Beach where resident Sue Nathan snapped this pair earlier this year feeding on Puriri berries.

While greenfinches, kererū, tūī and bellbirds appear to be on the rise in Hawke's Bay, the region is following the rest of the country with declining numbers of silvereyes, according to the 2017 State of NZ Garden Birds report released this week.

The report draws on 31,000 bird counts gathered by volunteers in their backyards since 2007, as part of the New Zealand Garden Bird Survey which was collated and released by Manaaki Whenua Landcare Research.

This year's report showed that counts of one of the most common native garden birds, the silvereye (tauhou), also known as "waxeye", was still declining, prompting researchers to warn it could be a sign something was changing for the species.

NZ Garden Bird Survey founder and Manaaki Whenua Research Associate, Dr Eric Spurr, said the silvereye had declined by 43 per cent nationally, with rapid declines in Southland, West Coast, Otago, Nelson and Gisborne.

In Hawke's Bay this species was reported to be in "shallow" decline, having dropped in numbers by 23 per cent over the last 11 years.

"We don't yet fully understand what is driving these changes but increasingly warmer winters may mean silvereyes are less likely to come into gardens in search of food," Dr Spurr said.

"They come more in cold winters when there's snow on the hills."

On the rise, however, both across the country and in Hawke's Bay, were species such as tūī, bellbird and kererū, although the greatest increase was in greenfinch numbers, which had almost doubled since the surveys began.

Dr Spurr said these increases, particularly among the endemic species, could be a result of improved predator control in urban and rural areas.

Napier Forest and Bird's Neil Eagles, who lived in Taradale, said he was not surprised by the increases.

"Last year for the first time in our backyard we had a bellbird - although we live close to Dolbel Reserve we have usually just heard them but it was after one of our kowhai trees."

He said planting of both native and exotic trees closer to town helped create corridors for the birds, which might in part account for the increase in numbers in people's gardens.

"There's also the riparian planting that's being done by the likes of the Hawke's Bay Regional Council for controlling sediment loss, which has this added benefit as well."

Hawke's Bay Regional Council biosecurity advisor Rod Dickson said the growth in some bird species could in part due to the large amount of pest control that had happened in both rural and some urban areas over the last 10 to 20 years.

"We have done our own targeted bird counts in certain areas and that has also shown an increase in bellbirds, tūī and kererū, and people are increasingly telling us they are seeing more of these birds."

Hawke's Bay Biodiversity Strategy project manager Genevieve Bennett said it was great to see all the efforts that people around the community had made in terms of trapping and habitat restoration starting to pay off.

"We're not there yet - there's still more to do and everyone can play a part in protecting our rare and precious species."

Across the country six of the most common species found in people's gardens (blackbird, dunnock, chaffinch, goldfinch, song thrush, and starling) had experienced shallow to moderate declines (10–31 per cent over 11 years).

Manaaki Whenua ecologist Dr Catriona MacLeod said with birds acting as "backyard barometers" of the health of the environment, such declines should not be ignored.

"It might be tempting to dismiss these declines as unimportant because these species were all introduced to New Zealand from Europe. However, these birds are signalling change in our urban and rural environments that we need to better understand," she said.