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Why does the pūkeko cross the road?

Waka Kotahi NZ Transport Agency and sector partners contracted Manaaki Whenua to identify, assess, monitor and manage road edge effects on biodiversity. The research emphasised the vulnerability of larger native birds to roadkill due to behaviour and habitat factors.

The poster below identifies some of the larger native birds recorded as road kill. It proposes why, when and/or where species may be vulnerable, and potential mitigation actions to test. Some threatened native birds are vulnerable to road kill due to their willingness to cross roads (sometimes linked to large home ranges or roads bisecting habitat), unwillingness or inability to fly, freeze behaviour when faced by threats (i.e. vehicles), activity at night, dawn and dusk (making them more difficult to see and avoid), slow breeding rates and/or low natural densities.

Poster: Road kill of native birds

Poster: Road kill of native birds. Click to download.

There are very few studies on road kill of small birds.

The level at which road kill has an effect at the population scale is not known for most native birds. In large, contiguous natural areas most native birds are primarily limited by predation from mammals. However, in most lowland areas populations are probably limited by lack of suitable habitat, as only very small areas of native forest and/or wetlands remain; here roadside vegetation may be beneficial or act as ecological traps.

Studies are needed to identify where road kill effects may threaten nationally vulnerable species and to inform development and testing of avoidance, minimisation and mitigation that works for Aotearoa New Zealand fauna. Examples include embedding alternative designs into capital projects that reduce artifical light at night (seasonally or permanently), reducing access to active lanes and providing ‘safe passage’, or slowing traffic and/or creating habitats in ‘safe’ areas.

The 2023 study highlighted the need for effective assessment, particularly of ‘forever’ road edge-effects which include adverse effects that may increase over time, such as pest plants and effects linked to vehicle movements (light, noise, and road kill).