How have tūī counts changed across regions?
Across the rest of the motu, tūī numbers show only a shallow increase over 10 years, and little to no change over the previous five years.
That’s nothing to worry about says senior researcher Dr Angela Brandt. “The rate of these increases is generally slowing down, which makes some sense when you think about how percentage increases work. Having four tūī sightings is a 100% increase when you started with only two sightings, but seeing six the next year becomes a 50% increase.”
There are also similar shallow increases nationally over the long-term for both kererū and pīwakawaka (fantails) (except in Canterbury where there has been a rapid increase of these birds over the past 10 years). Not such good news for tauhou (silvereye) whose long-term shallow decline nationally has shifted to a moderate decline in the short term.
When it comes to our introduced species, mynas (maina) are continuing their rapid increase in Wellington (126% over 10 years) and increasingly in the Manawatū-Whanganui region (30% over five years), but numbers show little to no change nationally.
However there have been some declining numbers that Dr Brandt says should trigger an alert with goldfinch (kōurarini) and chaffinch (pahirini) counts showing a rapid decline (30% for both species) over five years.
“We’ve seen some pretty consistent trends for declining observations of the pahirini, and the declining trends for it are bigger in our latest report compared to in 2022 or 2021, and consistent across the country."
Dr Brandt says being able to notice this trend proves the value of the NZ Garden Bird Survey. “Birds are important indicators of the health of New Zealand’s environment, and many perform important ecosystem functions, while others have inherent value as taonga species. If we see birds begin to decline that suggests something has changed in their habitat, perhaps an increase in predators or a decrease in available food and shelter, which could also be affecting other species,” she says.
Other species showing declining numbers were house sparrows (tiu), whose counts showed a decline over both the long and short term for the first time. Starlings (tāringi) and dunnocks also both showed shallow declines over 10 years.
To promote wider use of NZ Garden Bird Survey data for research and monitoring purposes, Manaaki Whenua has begun uploading the yearly data to the Global Biodiversity Information Facility, GBIF. There are now 5 years of data that are publicly available (2018–2022) with the 2023 data to be added soon.
In the 2023 survey, we asked participants, “what more needs to be done to care for birds in New Zealand?”
Of the 3,684 people who answered the question, 43% mentioned cats in their responses. While the answers of what could be done ranged across a spectrum from cats wearing bells all the way to outright bans, New Zealanders are acknowledging a conversation about this polarising issue needs to move forward.
Survey founder Eric Spurr says he is excited that his vision to provide long-term data on New Zealand garden bird trends, when establishing the survey 18 years ago, is now bearing fruit. He is also thrilled at the number of people volunteering to take part in the survey over the years.
“Without these volunteers (citizen scientists) – more than 60,000 since the survey’s inception – none of these data would have been collected,” he says.
2024 survey
This year the survey runs from 29 June – 7 July 2024. There is plenty of bird identification information on the NZ Garden Bird Survey website, so lots of time for everyone to get familiar with the manu that visit our gardens. Get ready to take part, because your contribution matters!
