{"id":1320,"date":"2022-03-31T15:13:04","date_gmt":"2022-03-31T02:13:04","guid":{"rendered":"https:\/\/gardenbirdsurvey.nz\/?page_id=1320"},"modified":"2024-04-09T12:06:50","modified_gmt":"2024-04-09T00:06:50","slug":"report-2020","status":"publish","type":"page","link":"https:\/\/gardenbirdsurvey.nz\/results\/report-2020\/","title":{"rendered":"2020 NZ Garden Bird Survey results"},"content":{"rendered":"
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State of NZ Garden Birds 2020 | Te \u0100hua o ng\u0101 Manu o te K\u0101ri i Aotearoa<\/h2>\n\n<\/div><\/div>\n\n
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What are our birds telling us?<\/h2>\n\n\n\n

Birds act as backyard barometers \u2013 telling us about the health of the environment we live in. They are signalling significant changes in our environment over the last 10 years. We should be listening.<\/p>\n\n\n\n

Using cutting\u2212edge techniques, Manaaki Whenua \u2013 Landcare Research has distilled a substantial information base \u2013 bird counts gathered by New Zealanders from over 39,000 garden surveys since 2010 \u2013 into simple but powerful metrics.<\/p>\n\n<\/div><\/div><\/div>\n\n

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\"Cover:
Download State of NZ Garden Birds 2021 | Te \u0101hua o ng\u0101 manu o te k\u0101ri i Aotearoa<\/figcaption><\/figure>\n\n<\/div><\/div><\/div>\n<\/div>\n<\/div><\/div><\/div>\n<\/div>\n<\/div><\/div>\n\n
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Key findings from the 2020 survey<\/h2>\n\n<\/div><\/div>\n\n
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Good news for four native species:<\/h3>\n\n\n\n
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  • Kerer\u016b <\/strong>counts have moderately increased (by 79%) over the past 10 years \u2013 a bigger increase than the 2019 results showed (43%).<\/li>\n\n\n\n
  • Fantail <\/strong>(p\u012bwakawaka) counts also show a slightly larger increase over the long-term.<\/li>\n\n\n\n
  • T\u016b\u012b <\/strong>(k\u014dk\u014d) counts still show a shallow increase over the long-term.<\/li>\n\n\n\n
  • Silvereye <\/strong>(tauhou) counts are no longer moderately decline over the long-term \u2013 they now show only a shallow decline over the past 10 years. And, for the first time, silvereye counts show a 5-year increase \u2013 shallowly increasing nationwide and moderately increasing in three regions (Manawat\u016b-Whanganui, Marlborough, and Taranaki).<\/li>\n<\/ul>\n\n<\/div><\/div><\/div>\n\n
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    Introduced species:<\/h3>\n\n\n\n
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    • Myna <\/strong>counts have been increasing in some regions over the past 5 and 10 years, but have been rapidly increasing in Wellington.<\/li>\n\n\n\n
    • Starling <\/strong>counts continue to show a moderate decline nationally over the long term.<\/li>\n\n\n\n
    • The numbers of song thrush<\/strong>, goldfinch <\/strong>and dunnock <\/strong>are no longer showing national declines over either the short or long term.<\/li>\n<\/ul>\n\n<\/div><\/div><\/div>\n<\/div>\n<\/div><\/div>\n\n
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      \"How
      How have garden bird counts changed 2010-2020<\/figcaption><\/figure>\n\n\n\n

      <\/p>\n\n\n\n

      \"Kua
      Kua p\u0113hea te rerek\u0113 o ng\u0101 tatauranga manu o te k\u0101ri? How have bird counts changed 2010 – 2020<\/figcaption><\/figure>\n\n\n\n

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      How we calculate NZ Garden Bird Survey results<\/h2>\n\n\n\n

      The general idea behind the survey is to convert the individual bird counts people contribute into meaningful estimates of wider population changes over time. Counts from every garden surveyed are linked to their location within a neighbourhood, suburb, district and region to calculate how bird counts change over time at each of these spatial scales.<\/p>\n\n\n\n

      We expect a species whose population is increasing over time to show an increase in counts and vice versa. While this is simple in principle, because there are different numbers of gardens in different regions, and different people decide to participate in some years, it might appear as though bird count numbers have changed, when it is just the proportion or location of survey returns that have changed.<\/p>\n\n\n\n

      The type of garden surveyed (rural or urban), whether people feed birds, and the total number of gardens surveyed in a region also add complexity. Statisticians refer to this as \u2018noisy data\u2019 because there are so many variables to take into account.<\/p>\n\n\n\n

      To reduce this noise, we use cutting edge statistical techniques to account for these variables. Following bootstrap analysis and bias-correction of the modelled data, estimated trends in bird populations over the past 5- and 10-year periods are summarised nationally and regionally according to their direction (decline or increase) and size (rapid to shallow).<\/p>\n\n\n\n

      These long-term trends are called \u2018signals\u2019 and show a persistent increase or decrease in the abundance of a species. We categorise these signals in the following way:<\/p>\n\n\n\n

      \"Graphic:<\/figure>\n\n\n\n

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      When using samples to estimate wider populations, we need some way of measuring whether the sample actually reflects the wider population. We used 80% confidence intervals for the average percentage change in each species\u2019 counts to evaluate confidence in our estimates. We generally have more confidence at the regional level than district or suburb.<\/p>\n\n\n\n

      The easiest way to improve this confidence at the district or suburb level is to increase the number of bird counts done. The more people who participate, the greater the strength of our evidence for what\u2019s happening to garden birds at the local scale.<\/p>\n\n<\/div><\/div>\n<\/div><\/div>\n\n

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      How have bird counts changed?<\/h2>\n\n\n
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      Maps | Changes in species counts across regions 2020<\/h3>\n\n\n\t\t\t