2009 Garden Bird Survey - progress report
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Silvereyes ar feeder. Image - Maria Aiau
The house sparrow was the most common species in the garden bird survey again this year. The average of 12.2 per garden was higher than last year (11.4) and the year before (9.4). As in previous years, house sparrow numbers were higher in the north than in the south.
A major result from the survey is a large decrease in silvereye numbers, 6.4 per garden this year compared with 8.9 last year and 10.2 in 2007. Several observers commented on this decrease, and some suggested disease was the cause. They reported silvereyes with growths around the bill, eyes and legs last year. The growths could have been avian pox, a virus that can be transmitted by contact with infected birds, when they congregate around bird feeders, for example, or by ingestion of contaminated food or water. Little is known about this disease in New Zealand, and further investigation is warranted.
Other preliminary results from the survey are the continued increase in tui numbers, a large increase in myna numbers, and a decrease in greenfinch numbers. These changes could be annual variations rather than a continuing trend. Several more years’ data will be needed to confirm any long-term trends.
The results reported here are progress results from 1790 observers. The figures may change when all data are analysed.
| Top 10 bird species in 2009 | |
| Species | No. |
| House sparrow | 12.2 |
| Silvereye | 6.4 |
| Starling | 3.3 |
| Blackbird | 2.9 |
| Tui | 1.4 |
| Fantail | 1.0 |
| Myna | 1.0 |
| Goldfinch | 0.9 |
| Chaffinch | 0.9 |
| Song thrush | 0.9 |
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Comparison of numbers of some of the most common birds per garden in 2007, 2008, and 2009 (preliminary data)