Bird species on public conservation land

  • Image, Bird species on public conservation land.

    The status of our bird communities is an important indicator of the condition of our ecosystems. Many indigenous birds play key ecological roles, including dispersing seeds and pollinating flowers. In some situations, exotic bird species (not indigenous to New Zealand) can partially fulfil these roles. A reduction in the distribution and/or decline in numbers for common and widespread species can equate to large losses of individuals and ecosystem integrity. It could also indicate increased pressures such as predation or habitat change. By measuring the composition of bird communities across public conservation land (woody and non-woody sites) we can monitor how they change over time.

    We report on the occupancy (presence), abundance and richness (diversity) of indigenous and exotic widespread bird species on public conservation land.

    We classified Bird species on public conservation land as a national indicator.

    Key findings

    Trend not assessed

    More different indigenous bird species were found in woody sites than in non-woody sites (medians of 7.7 and 2.3, respectively) distributed across public conservation land between 2013 and 2016.

    • Indigenous bird species outnumbered exotic bird species in 96 percent (739 of 771) of woody sites.
    • Indigenous bird species richness was highest at sites where the observed land cover was indigenous forest (a median of 7.9).
    • Five indigenous species (grey warbler, silvereye, tomtit, bellbird, and fantail) and two exotic species (chaffinch and blackbird) were detected in more than 50 percent of sites; they were the most widespread species.
    • Of these seven widespread bird species, the estimated abundance of one indigenous bird (silvereye) decreased at woody sites (from an average of 1.7 to 1.3 a site) and non-woody sites (from an average of 1.5 to 0.9 a site).
    Figure 1
    Interactive app

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    Source: Department of Conservation

    Note: Species richness at each monitoring site is defined by:

    • total richness – estimated number of both indigenous and exotic bird species at a site
    • indigenous richness – estimated number of different indigenous bird species at a site
    • exotic richness – estimated number of different exotic bird species at a site
    • indigenous dominance – the proportion of bird species at a site that are indigenous.

    Woody sites include indigenous forest, planted forest, and shrubland. Non-woody sites include a range of habitats (eg bare ground, coastal sands, coastal wetlands, grassland, inland water, inland wetlands). Some bird species are typically found across only some of these non-woody habitats.

    Figure 2

    Graph, Bird richness by cover

    Note: Indigenous richness is the estimated number of different indigenous bird species at a site. Exotic richness is the estimated number of different exotic bird species at a site. Total richness is the estimated number of both indigenous and exotic bird species at a site. Indigenous dominance is the proportion of bird species at a site that are indigenous.

    Note: Woody sites include indigenous forest, planted forest, and shrubland. Non-woody sites include a range of habitats (eg bare ground, coastal sands, coastal wetlands, grassland, inland water, inland wetlands). Some bird species are typically found across only some of these non-woody habitats.

    Figure 3

    Graph, Bird richness by observed land cover

    Note: Indigenous richness is the estimated number of different indigenous bird species at a site. Introduced richness is the estimated number of different exotic bird species at a site. Total richness is the estimated number of both indigenous and exotic bird species at a site. Indigenous dominance is the proportion of bird species at a site that are indigenous.

    Woody sites include indigenous forest, planted forest, and shrubland. Non-woody sites include a range of habitats (eg bare ground, coastal sands, coastal wetlands, grassland, inland water, inland wetlands). Some bird species are typically found across only some of these non-woody habitats.

    Figure 4

    Note: Common species are species having occupancy over half of public conservation land. In 2016 these birds were: bellbird, blackbird, chaffinch, fantail, grey warbler, silvereye, and tomtit.

    Figure 5 

    Note: Common species are species having occupancy over half of public conservation land. In 2016 these birds were: bellbird, blackbird, chaffinch, fantail, grey warbler, silvereye, and tomtit.

    Figure 6

    Graph, Estimated abundance of common indigenous and introduced bird species on woody sites

    Note: Common species are species having occupancy over half of public conservation land. In 2016 these birds were: bellbird, blackbird, chaffinch, fantail, grey warbler, silvereye, and tomtit.

    Estimated abundance is an index measure using the five-minute bird count method. The vertical error bars on each mean represent the 95 percent credible intervals.

    Figure 7

    Graph, Estimated abundance of common indigenous and introduced bird species on non-woody sites

    Note: Common species are species having occupancy over half of public conservation land. In 2016 these birds were: bellbird, blackbird, chaffinch, fantail, grey warbler, silvereye, and tomtit.

    Estimated abundance is an index measure using the five-minute bird count method. The vertical error bars on each mean represent the 95 percent credible intervals.

    Definition and methodology

    The Department of Conservation (DOC) has a national monitoring programme to assess the status and trend of biodiversity across all land managed by DOC, with an emphasis on the land. This monitoring programme provides estimates of priority ecological integrity indicators and measures. The terrestrial monitoring programme operates at approximately 1,400 plot locations that are evenly spaced across public conservation land. Sampling locations are permanently marked, allowing repeated sampling. Approximately 280 plots are measured each year, with every plot being measured on a five-year rotation cycle.

    The information we report on was collected by bird monitoring carried out between 2013 and 2016. The monitoring took place at 1,069 sampling locations (298 non-woody sites and 771 woody sites) distributed across public conservation land. Each location has up to five bird-count stations where standardised five-minute bird counts were carried out – standing at a station and counting the number and species of birds seen or heard within a five-minute period. The sampling periods are for the 12 months ending June.

    The five-minute bird counts are used to estimate bird occupancy (presence), abundance (density) and richness (diversity) of species. For abundance, a linear regression model – conditional on occupancy – was used to calculate species abundance for the most common species only. The data collected each year are compared with all data to compare abundance between years. For species richness, a Bayesian hierarchical multispecies model was used to determine the total number of different species occupying a site. For this measure, we report only on terrestrial birds (52 species), removing non-terrestrial birds (eg gulls or ducks) from our analysis.

    We distinguished woody sites from non-woody sites using the Land Use Map. Forest sites include: indigenous forest, planted forest, and shrubland. Non-woody sites include: bare ground, coastal sands, coastal wetlands, grassland, inland water, inland wetlands. Some bird species are typically found across only some of these non-woody habitats. A small portion of sites have not been displayed on the map for reasons of confidentiality. However, all site data are included in the aggregated graphs and analysis.

    Note that Our land 2018 uses the terms 'forest' and 'non-forest' to refer to 'woody' and 'non-woody' cover, respectively.

    Data quality

    We classified Bird species on public conservation land as a national indicator.

    Relevance

    relevance-direct This national indicator is a direct measure of the ‘Land species, taonga species, and genetic diversity’ topic.

    Accuracy

    Image, High accuracy. The accuracy of the data source is of high quality.

    See Data quality information for more detail.

    Archived pages

    See Bird species on public conservation land (archived April 2018).

     

    Published 19 April 2018

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