Urban human-wildlife conflict: North Island kākā (Nestor meridionalis septentrionalis) in Wellington City

Abstract

Human-wildlife conflict is common wherever humans and wildlife coexist and is a growing problem in urban landscapes. Successfully mitigating conflict with wildlife requires an understanding of the ecological and social dimensions of the problem. In Wellington City, New Zealand, a human-wildlife conflict is beginning to emerge with North Island kākā (Nestor meridionalis septentrionalis: Nestoridae), a threatened endemic parrot that was reintroduced to the city in 2002. Kākā damage property but especially damage tree bark while foraging for sap. In this thesis, I investigate the conflict with kākā using ecological, behavioural and social science approaches to understand the problem and recommend ways to mitigate the growing conflict with kākā.

To investigate tree selection for sap foraging by kākā, I sampled the characteristics, microhabitat and distribution (independent variables) of 282 trees at 15 sites across public greenspaces in Wellington City, and used model averaging to determine the relative influence of independent variables on the binary dependant variable – presence/absence of bark damage. Tree size (Σωᵢ [Akaike weight] = 0.859) and site exposure (Σωᵢ = 0.739) had the greatest influence on tree selection for sap feeding. Kākā were found to prefer larger trees ( x ± SE, DBH: x damaged = 64.8 ± 5.2 cm, x undamaged = 32.9 ± 4.5 cm) at more exposed sites. Exotic species were significantly more likely to have been damaged than native species (Fisher’s exact test, p < 0.001). Seven of 10 tree species damaged were exotic, and exotic conifers, such as macrocarpa (Cupressus macrocarpa) and Lawson cypress (Chamaecyparis lawsoniana) were the most commonly damaged species.

I used instantaneous scan sampling to record kākā behaviour during 25 60-100 minute observation periods at Anderson Park, Wellington Botanic Garden, and during 12 opportunistic observations of sap feeding kākā in Wellington City during other research activities. Forty observations of sap feeding were made and 20 sap feeding kākā identified. Based on estimated sex, females were no more likely to sap feed than males (exact binomial test p = 0.916) and both adults and juveniles were observed sap feeding. Kākā were observed displacing sap-feeding conspecifics and defending sap feeding sites from tui (Prosthemadera novaeseelandiae). This indicates that sap is an important resource across sexes and life stages of kākā and is not just a supplementary food for females before breeding as previously hypothesised. Since supplementary food is provided by Karori Wildlife Sanctuary and utilised by the identified kākā, and 34% of Wellington residents provide food and water for birds, it is unlikely that further provision of supplementary food will reduce sap feeding.

To investigate residents’ attitudes and problems with birds, I hand-delivered 1030 questionnaires to households in 10 Wellington City suburbs. I then assessed the relationship between a person’s attitude and their biodiversity knowledge, engagement with birds and greenspaces and experience of bird problems. An extraordinary survey return rate of 61.8% (n = 635) revealed that residents had overwhelmingly positive attitudes towards native birds, despite 25% experiencing a bird problem. Planting trees to attract birds was the only predictor to provide substantial inference for attitude (ωi = 0.873). Experiencing a problem with birds was not an influential predictor of attitude when modelled alone (ΔAIC = 17.50, ωi = 0.000), but when combined additively (ωi = 0.568) and interactively (ωi = 0.400) with planting to attract birds these models comprised the confidence set. Respondents who had planted to attract birds were more likely to have more positive attitudes than the rest of the population even when they reported a bird problem. Hence, attitude to birds and tolerance of problems they cause was most closely associated with a person’s positive engagement with birds rather than their negative experiences.