Does rat trapping and tree planting work?

Pest Free Hibiscus Coast Project Manager Jenny Hanwell of Forest and Bird says she is often asked what results have come from all the local trapping and planting.

Her answer is a recently published thesis from Massey University student Hayden Pye which shows that, from 2013-20, the numbers of common birds on the Coast were stable or increasing. 

The results were comparable with similar studies from healthy or predator-free environments. 

Hayden analysed eight years of bird count data collected by Hibiscus Coast Forest & Bird. Volunteers carried out 2115 surveys in this time, across 17 sites around Whangaparāoa Peninsula and Ōrewa. 

The results show that 18 bird species remain stable or had significant increases in abundance between 2013 and 2020. In particular, tūī and riroriro (grey warbler) showed significant increases in numbers over the past few years, and most of the common bird species on the peninsula have healthy populations for an urban environment. 

There were far higher numbers of native and endemic species in areas with substantial tree cover – highlighting the importance of natural habitats in supporting birdlife. 

Hibiscus Coast Forest & Bird chair, Pauline Smith says when Pest Free Hibiscus Coast began, she envisaged more fantails and possibly bellbirds and that is now a very real probability. 

“The reward for pest control efforts will appear in all our gardens throughout the peninsula,” she says.

Hayden’s supervising Professor (and Hibiscus Matters’ columnist), James Dale, says the findings contribute to the growing body of scientific research focused on the conservation of native birds in urban environments, as well as providing insight into New Zealand’s Predator Free 2050 goal. 

However, Jenny says there is still much work to do.

“The study shows that sufficient natural habitat must be available to maximise the effect of pest control – so we need to keep planting native trees and rat trapping,” she says. “It is also important to avoid feeding seeds and bread to the birds, which favours introduced species that displace native birds (such as mynas), and attracts rats.”