Diversity, abundance and distribution of terrestrial birds in Tāmaki Makaurau / Auckland 2009-2024. State of the environment reporting.

Executive summary

Birds serve as important environmental indicators; closely monitoring them helps us understand their population dynamics and gain insights into the quality of their habitats and the ecological functions essential for their survival. In New Zealand, bird surveys typically employ the standardised five-minute bird count method to collect the monitoring data presented in this report. This report outlines the findings from bird monitoring carried out within the Terrestrial Biodiversity Monitoring Programme (TBMP) covering forest and wetland habitats, which requires five years to complete a full monitoring cycle: forests (2009-2023) and wetlands (2011-2024).

Most birds counted in forest and wetland sites were indigenous species (67.8% and 55.63% respectively), with only a small percentage of these native species being regionally categorised as “Threatened” or “At Risk” (1.3% and 1.6% respectively). Four of the top five bird species monitored in forest plots were indigenous. Tauhou/silvereye (Zosterops lateralis lateralis) was the most common forest species, followed closely by tūī (Prosthemadera novaeseelandiae novaeseelandiae) and then riroriro/grey warbler (Gerygone igata), pīwakawaka/North Island fantail (Rhipidura fuliginosa placabilis) and the Eurasian chaffinch (Fringilla coelebs), all detected in >70% of bird counts. Silvereye was also the most counted species for wetland sites by far, followed by common myna (Acridotheres tristis), grey warbler, house sparrow (Passer domesticus) and tūī , all detected in >60% of counts.

Across both forest and wetland areas, species abundance and richness exhibited similar trends in different land classes. In regional and sub-regional forest and wetland sites, native species were more prevalent in indigenous land classes, while introduced species thrived in modified landscapes. Recent monitoring has shown a notable increase in the abundance and richness of native species over the years in forest and wetland sites, while the numbers of introduced species have remained stable. Further examination revealed that variations in populations of tūī, silvereye, grey warbler and pīwakawaka contributed to this increase in forests. Abundance of kererū (Hemiphaga novaeseelandiae) and kākā (Nestor meridionalis) in forests, and mātātā/fernbirds (Poodytes punctatus) in wetland were strongly linked to habitat quality, indicating their potential as indicators of habitat health. Although bird populations in wetlands displayed a strong preference for indigenous habitats, native species appear to be re-establishing themselves in altered areas. However, the still significant presence of introduced species in many wetland areas (Āwhitu, Inner Gulf Islands) is a sign of low-quality habitats that require management attention. As anticipated, regions surrounding expansive, healthy forests (Hunua and Waitākere Ranges, Aotea/Great Barrier Island) tend to support a greater diversity of native bird species.

This study identifies the importance of protecting the integrity of indigenous habitats to support our native bird populations. It has identified a positive trend in the numbers of native birds in forest and wetland habitats, which is encouraging. However, this trend is limited to habitat generalists, non-threatened species, highlighting the ongoing need for efforts to support native and endemic species that rely on well-managed and preserved habitats for survival, as they remain largely marginalised in more urban and rural areas. It emphasises that well-managed forested areas, along with restored rural and urban environments, all serve as sanctuaries for the restoration and recovery of native biodiversity in forests and wetlands. It is vital to continually highlight the significance of refuge habitats in modified landscapes. The findings of this report illustrate the value of long-term biodiversity monitoring in identifying trends. They also uncover the need to reassess monitoring frameworks and planning to address information gaps, ultimately improving decision-making and management. Given that terrestrial birds serve as indicators of environmental health; their thriving populations reflect a healthier and more resilient Tāmaki Makaurau.

Auckland Council technical report, TR2025/17

September 2025

See also

Te oranga o te taiao o Tāmaki Makaurau. The health of Tāmaki Makaurau / Auckland’s natural environment in 2025. A synthesis of Auckland Council’s state of the environment reporting