Tuis rise, waxeyes wane in bird survey
Some native birds are visiting New Zealand gardens in bigger numbers, but introduced species are still in decline.
The State of NZ Garden Birds 2017 report by Landcare Research, released this week, showed a slight rise in the numbers of tui and keruru¯ , possibly due to improved predator control.
But it also revealed the puzzling case of the continuing decline of the silvereye, one of New Zealand’s most common native garden birds. Sightings of the bird, also known as the waxeye, have almost halved in gardens around the country since the survey began in 2007.
Nelson saw a rapid decline of 52 per cent in the silvereye population, with other species such as song thrush, goldfinch and dunnock or hedge sparrow in a moderate decline. However, tui counts were up 16 per cent.
Survey founder and Landcare Research associate Dr Eric Spurr said the silvereye had declined by 43 per cent nationally in the past decade. Rapid declines were also detected in the Southland, Otago, West Coast, Wellington and Gisborne regions.
‘‘We don’t yet fully understand what is driving these changes, but increasingly warmer winters may mean silvereyes are less likely to come into gardens in search of food.’’
Spurr said that of the introduced species, only the greenfinch had increased in counts since 2007 nationwide.
Forest and Bird chief conservation adviser Kevin Hackwell said people were doing ‘‘a great job’’ at pest control that was helping birds such as tui and kereru.
He said the decline in other species could be because of several reasons, one being that some introduced species might be in competition with native birds.
‘‘There’s an increase in tui – there could be some competition there. I’ve seen tuis take on blackbirds.
‘‘I could also be a lack of visibility instead of a drop in numbers.’’
The report was based on 31,000 bird counts collected by volunteers in their backyards as part of the New Zealand Garden Bird Survey for just over a decade.
Landcare Research ecologist Dr Catriona MacLeod said the decline in silvereye counts could be a warning sign that something was changing for the species.
‘‘Birds act as ‘backyard barometers’, telling us about the health of the environment we live in, and we should be listening.’’