State of NZ Garden Birds 2025 | Te Āhua o ngā Manu o te Kāri i Aotearoa
What are our garden birds telling us?
Birds act as backyard barometers – telling us about the health of the environment we live in. They are signalling significant changes in our environment over the last 10 years. We should be listening.
The Bioeconomy Science Institute has distilled a substantial information base – bird counts gathered by New Zealanders from more than 51,000 garden surveys since 2015 – into simple but powerful metrics.
Thank you to all the citizen scientists who participated in the survey in 2025. It was a great turnout.
Key findings from the 2025 survey
Key signals continue for five native species:
- Kererū counts again show a slow increase over 10 years (16%), but now show a moderate decline over 5 years (22%), compared to the short-term slow decline seen last year.
- Fantail (pīwakawaka) counts again show a slow increase over 10 years (31%), with moderate long-term increases in two regions. Their counts remain stable over 5 years (-3%), but with slow short term declines in three regions.
- We continue to see a slow increase in tūī (kōkō) counts in the long-term (19%) and short-term (7%). Their regional long-term trends continue to show a rapid increase in Canterbury (198%).
- For the first time, silvereye (tauhou) counts show a slow increase nationally over the long-term (16%) and short-term (15%).
- Bellbird (korimako) counts over 10 years continue to be stable (5%), but for the first time they show a slow increase over 5 years (9%).
Key signals for introduced species that also act as environmental indicators:
- Myna counts remain stable nationally over 10 years (-1%), with some evidence of a stable trend over 5 years as well (-4%). They show evidence of long-term increases in three regions and short-term increases in two regions.
- Goldfinch counts now show a slow decline over 10 years (16%) and a rapid decline over 5 years (37%), compared to the stable long-term trend and moderate short-term decline seen last year.
- For the first time since 2020, dunnock counts are stable nationally over 10 years (1%), with slow to moderate increases in three regions. There is some evidence for a slow increase nationally over 5 years (6%), with moderate short-term increases in three regions.
- Starling and chaffinch counts again show a slow decline over 10 years (11% and 24%, respectively). Similar to last year, chaffinch counts also show a moderate decline over 5 years (18%).
If you’re keen to know more about what’s happening with garden birds in your region, reports for individual regions are available, or check out out the full State of NZ Garden Birds 2025 | Te āhua o ngā manu o te kāri i Aotearoa report.
What more needs to be done to care for birds?
Since 2021 we’ve asked New Zealand Garden Bird Survey participants what more needs to be done to care for the birds in Aotearoa New Zealand. In 2025, 3,503 participants responded to the question. We’ve analysed the responses, and they reflect the five themes below.
How we calculate NZ Garden Bird Survey results
The general idea behind the survey is to convert the individual bird counts people contribute into meaningful estimates of wider population changes over time. Counts from every garden surveyed are linked to their location within a neighbourhood, suburb, district and region to calculate how bird counts change over time at each of these spatial scales.
We expect a species whose population is increasing over time to show an increase in counts and vice versa. While this is simple in principle, because there are different numbers of gardens in different regions, and different people decide to participate in some years, it might appear as though bird count numbers have changed, when it is just the proportion or location of survey returns that have changed.
Cleaning ‘noisy’ data
The type of garden surveyed (rural or urban), whether people feed birds, and the total number of gardens surveyed in a region also add complexity. Statisticians refer to this as ‘noisy data’ because there are so many variables to take into account.
To reduce this noise, we use cutting edge statistical techniques to account for these variables. Following bootstrap analysis and bias-correction of the modelled data, estimated trends in bird populations over the past 5- and 10-year periods are summarised nationally and regionally according to their direction (decline or increase) and size (rapid to slow).
These long-term trends are called ‘signals’ and show a persistent increase or decrease in the abundance of a species. We categorise these signals in the following way:
When using samples to estimate wider populations, we need some way of measuring whether the sample actually reflects the wider population. We used 80% confidence intervals for the average percentage change in each species’ counts to evaluate confidence in our estimates. We generally have more confidence at the regional level than district or suburb.
The easiest way to improve this confidence at the district or suburb level is to increase the number of bird counts done. The more people who participate, the greater the strength of our evidence for what’s happening to garden birds at the local scale.
