Bird Monitoring Reserves

Every autumn and spring, our passionate bird enthusiasts head into 31 local reserves to take part in the Five Minute Bird Count. Since 2019, we have followed the same survey method, creating a valuable dataset that allows us to measure changes in bird populations and better understand how our local birdlife is responding over time.

Since monitoring began, 35 bird species have been recorded across the project area. Of the 15 most abundant species, three are endemic, four are native, and eight are introduced, including three species classified as pests under the Regional Pest Management Plan (RPMP).

Encouragingly, the bird monitoring data shows a positive overall trend. Nine species have exhibited statistically significant increases in abundance over the study period, while no species have shown a statistically significant decline. The species demonstrating significant increases are tūī, silvereye, song thrush, blackbird, greenfinch, spur-winged plover, eastern rosella, feral pigeon, and magpie.

These results suggest that bird populations across the project area are generally stable or increasing, with a number of species becoming more abundant over time.

While introduced species remain more abundant than native species across the monitoring area, both groups have shown positive trends over time. Analysis of paired surveys found that introduced birds occurred at significantly higher abundances than native birds (Wilcoxon signed-rank test, W = 23,464, p < 0.001).

This pattern is not unexpected, as many introduced species such as myna, house sparrow, blackbird, and starling are highly adaptable and thrive in urban environments. These species are generally more tolerant of habitat degradation, human disturbance, and predator pressure than many native birds.

Encouragingly, despite the dominance of introduced species, both native and non-native bird populations have increased over the monitoring period, suggesting that overall bird abundance across the project area is improving. This includes positive trends for several native species, indicating that ongoing restoration and pest control efforts are helping to create better conditions for birdlife.

Kepa Bush was the only site to show a significant decline in native bird abundance over the monitoring period. Analysis indicates that native bird numbers decreased by an average of 14.4% per year (95% confidence interval: -25.9% to -1.2%, p = 0.033), demonstrating a consistent downward trend across the study period.

Importantly, this decline was observed in both monitoring seasons. There was no evidence that the rate of change differed between autumn and spring surveys (Year × Season interaction, p = 0.270), suggesting that the reduction in native bird abundance is not driven by seasonal variation but reflects a broader long-term trend at this site.

The reasons for this decline are not immediately clear and may warrant further investigation. Factors such as changes in habitat quality, food availability, predator pressure, disease, or local disturbance could all influence native bird populations. Given that many other monitored sites have shown stable or increasing native bird abundance over the same period, Kepa Bush stands out as an important area for continued monitoring and assessment to better understand the drivers of this decline.