Observations Of New Zealand Native And Non-Native Birds In Relation To Vegetation Type. Abstract
New Zealand’s landscape has changed extensively since the arrival of humans. Now, native and non-native species of both flora and fauna co-exist. People enjoy having wildlife around them and in recent years there has been a great deal of interest in urban wildlife. This study explores the concept of whether native vegetation fosters the presence of native birds and/or non-native vegetation fosters the presence of non-native birds. My working hypothesis is: “there is no difference in the percentage of native and non-native birds between “gardens” having native or non-native vegetation.” Note: the word “garden” for the purposes of this study refers to maintained areas of vegetation and for clarity the term garden has been replaced with the word vegetation.
Key words: Native birds, non-native birds, native vegetation, non-native vegetation INTRODUCTION
Native birds of New Zealand have been subjected to considerable habitat changes over the past 800 years (post human settlement). Deforestation has considerably reduced the original forest cover to 23% (Dawson, 2009). Drainage of nearly 90% of wetland areas (Johnson, 2009) has further diminished natural habitats. Habitat changes compounded by the introduction of mammalian predators (e.g. rats, possums, stoats, cats etc.) have further had significant negative impacts on native bird life. Adaptation by native birds to terrestrial mammalian predation has not occurred at a rate that would have prevented at least some extinctions. By definition a native bird or native plant (vegetation) of New Zealand is a species that occurs naturally in an area and therefore one that has not been introduced by humans either accidentally or intentionally. Many non-Native birds of New Zealand were introduced by early European settlers for “sentimental reasons to help them feel at home with their new surroundings.” (Walrond, 2009) Some 33 bird species have become naturalised to the New Zealand environment and are established and reproducing in the wild (New Zealand Biodiversity, n.d). A contributing factor to non-native bird establishment is the introduction of some 6000 flora species of which some 2000 have become naturalised to the New Zealand environment (New Zealand Biodiversity, n.d). Introduced flora species are referred to in this document as non-native vegetation. The geographic location of this study includes four localities situated on the alluvial and coastal plains of Gisborne, New Zealand. All four areas are within a 15 kilometre radius of Gisborne CBD. The Gisborne area was once part of large forested area made up of wetland swamps with flora species including kahikatia, and free draining areas dominated by matai and rimu (Wilmshurst, Eden & Froggatt, 1999) Through anthropogenic clearing and drainage the area is now dominated by pasture and intensive agricultural land use (Kirkpatrick.2005), with only remnants of the original vegetation still present. METHOD
Bird identification techniques applied
As I was not familiar with bird identification methods, firstly I needed to familiarise myself with distinguishing physical features and recognition of distinctive bird calls of birds I was most likely to encounter during this study. I was able to do this by making reference and studying several illustrated books on New Zealand birds (Heather, Robertson, 2005; Falla, Sibson, Turbott, 1979; Fitter, 2010; Chambers, 2007) and listening to recorded bird calls on a number websites on the internet (Department of Conservation, n.d; Karori Sanctuary Trust, n.d; “Native birds”, n.d). For this study I included all birds sighted including birds that were in flight. Birds that I could positively identify by bird call alone were also included. An exception to these parameters which I considered sufficient to use for a positive identification method was the distinctive wing beat...
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