Urban Oasis: Why more birds are calling Christchurch home this winter

Photo: Christchurch City Council Newsline

As the autumn air cools in Christchurch, a noticeable increase in the local bird population is taking place.

Christchurch City Council ecologist Andrew Crossland said this seasonal phenomenon is quite expected.

"Autumn sees a boost in bird numbers because all the young have fledged which seasonally doubles populations. Then as the weather cools, we have this annual influx of birds, both native and introduced, arriving to over-winter in the city."

Birds from various habitats, including the remnants of forests on the Port Hills and the surrounding countryside, are migrating into the city.

Known as an altitudinal migration, this movement involves species such as fantails descending into more urban environments where they can be easily spotted in locales like Riccarton Bush.

"They disperse into domestic gardens and parks and reserves including Riccarton Bush, the Botanic Gardens, Bottle Lake Forest and wooded riparian zones along city waterways.”

This migration is driven by the city’s diverse and extensive woodland habitats on the Canterbury Plains, which offer a wide range of winter food resources.

The urban environment of Christchurch also provides a thermal advantage.

"The city has a heat island, making it appreciably warmer than bush patches high up on the Port Hills or inland – especially on winter nights.

Birds like fantails move down from the hills, and from the countryside to the west of the city in an an altitudinal migration. They can be spotted in places like Riccarton Bush / Photo: Christchurch City Council Newsline

"In a prolonged winter blizzard with sub-zero temperatures for several days, more than half of native fantails and grey warblers on the Port Hills can die, whereas survival chances in the city’s woodlands, parks and gardens are much higher."

Local residents can play a role in supporting the native bird population through the colder months.

By planting trees and shrubs, particularly those that connect with vegetation over boundary fences, Christchurch inhabitants help create vital "habitat patches."

Native species like kanuka, manuka, koromiko, kaikomako, totara, and matai are especially beneficial, providing critical insect food resources.

This seasonal shift not only enriches the city's biodiversity but also indicates the success of ongoing conservation efforts.

"This is likely due to predator control work on the Port Hills but changing habitat and food availability could also be a factor.

“It's why we’ve seen bellbirds returning to the city landscape, after being largely absent for many decades prior.

There is hope for reintroducing several locally extinct species such as the brown creeper, South Island rifleman, and South Island fernbird, thanks to two decades of habitat restoration and predator control on the Port Hills facilitated by the community and the Council Regional Parks Team.