Organisers of a nationwide survey are urging people to keep a sharp eye out for feathered visitors to their back gardens from this weekend.

The annual, week-long nationwide garden bird survey, running from this Saturday until next Sunday, is one of New Zealand's largest citizen science projects and aims to keep track of populations of common native species often found around our homes.

Last year, about 138,000 birds were counted nationwide, up 38,000 on the previous year and contributing to the more than one million birds Kiwis have counted in over 25,000 gardens since the effort was launched in 2007.

Its founder, Landcare Research scientist Dr Eric Spurr, said harsh conditions last winter probably forced more birds to move into gardens in search of food.

"So far the weather this autumn has been really mild and Niwa [National Institute of Water and Atmospheric Research] has predicted temperatures to be above average this winter in all regions, so this may have an impact on bird numbers."


Last year, the top 10 birds were similar to the previous year, with the exception that the song thrush dropped out and the goldfinch swooped in, he said.

Over the survey's history, the top two most abundant species have remained the same - the house sparrow and silvereye.

Third and fourth position has been battled out between the blackbird and starling, while fifth and sixth place has typically either been myna or tui - although the myna is not found in the South Island.

"Before the survey we had no idea what was happening to populations of our more common native species, such as tui, bellbird and kereru," Dr Spurr said.

"I didn't want them to become rare like kiwi or kokako. I'm hoping that the survey will act as an early warning system to alert us if their numbers are declining."

Since the survey started, participation rates have doubled, and last year more than 3500 people took part.

"I would love for the number to be a lot higher this year."

Landcare Research ecologist Dr Catriona MacLeod said studying bird populations provided valuable information about the state of the environment.

"Birds not only bring enjoyment to our everyday lives, they also tell us about the health of the environment we live in. To understand our environment we need to build a picture of birdlife across New Zealand."

All that was required was a comfortable chair and a spare hour to record what was seen, then another few minutes of time to submit the results online.

"The more people involved, the more we can learn."

Dr MacLeod has been using the survey as a case study for her building trustworthy biodiversity indicators research, funded by the Ministry for Business, Innovation and Employment.

Full instructions on how to take part in the survey, including the tally sheet and bird identification guide, are available on the Landcare Research website:

The 10 most spotted garden birds of 2015

• House sparrow

• Silvereye

• Blackbird

• Starling

• Tui

• Myna

• Fantail

• Chaffinch

• Greenfinch

• Goldfinch