|Our Environment: Issue Issue 10 - Summer 1997:|
A recent study undertaken for the Parks Unit by one of Christchurch's foremost ornithologists Andrew Crossland, has found that in the 1850's 32 native bird species were recorded in the Port Hills but now, 150 years later, the number has been reduced to 14, two of which are locally rare.
The report, entitled Port Hills Birdlife - Inventory, Analysis and Restoration Potential, covers the entire Port Hills, from Godley Head to Gebbies Pass. Its aim is to investigate the state of birdlife on the Hills and recommend steps that could be taken to improve or restore habitat for native birds.
Of special interest were Andrew Crossland's findings regarding the relationship between the City Council's reserve network and adjoining remnant forest patches, and the influence of Port Hills native forests on native bird populations in Christchurch City. This is interesting because Christchurch, of all New Zealand's major cities, is by far the poorest in terms of numbers and species richness of native bush birds living within the urban area. With the exception of Riccarton Bush, the only significant remnants of indigenous forest within the vicinity of Christchurch are the bush remnants on the Port Hills.
Numbers of the common bush birds in good habitats on the Port Hills do compare favourably however with anywhere on the New Zealand mainland. At few other places in New Zealand can one attract up to ten Bellbirds to a single tree using a 'squeak bottle', as can be done at sites such as Kennedy's Bush, Sugarloaf and Ahuriri Summit. If habitat in other Port Hills remnants were upgraded to this standard then both total bird abundance and species richness would certainly increase.
Currently in autumn and winter varying numbers of four native bush birds move down from the Port Hills and enter Christchurch City. These include large numbers of Silvereyes, Grey Warblers and Fantails which disperse widely to orchards, gardens and parks, as well as much lower numbers of Bellbird which remain around the foot of the hills.
While the bush remnants in best condition (most under Council control) support good populations of native birds, many of the others are still being severely degraded by grazing animals and other influences.
If isolated forest patches were linked to form more continuous forest, grazing animals excluded and more north facing and lower altitude forest allowed to develop then the Port Hills could become one of the best areas for native birds on Banks Peninsula. This is especially significant because of their proximity to Christchurch, the South Island's largest population centre. Provided the indigenous food supply (totara etc) is increased in the City, upgrading of Port Hills forest should lead to much higher numbers of native birds moving to the City from their core habitat areas on the Port Hills.
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