Citizen scientists make a difference

Welcome swallows have only been breeding in New Zealand for 60 years

CITIZEN science is all the rage at the moment. Scientists have realised that by enlisting members of the public in their research projects everybody benefits.

More data is processed, more observations made, taxpayers can see where research funding goes and non-scientists with time and skills can help make discoveries.

One citizen science project that has been going for 10 years is the New Zealand Garden Bird Survey, run every winter since 2007 by Eric Spurr at Landcare Research. Members of the public volunteer to spend one hour counting the birds in their backyard, and last year nearly 29,000 took part all over the country.

Observers might vary in their bird knowledge, and time and weather might vary from place to place, but with thousands of participants all those differences average out and we can look at trends in numbers and kinds of birds observed from one year to the next.

Most birds in our backyards are introduced species: sparrows, blackbirds, starlings and mynas. Some native species also appear in the top 10: grey warblers, fantails and tui. In fact, tui seem to be slowly increasing in numbers around the country, especially in Canterbury where they were almost completely absent. This is probably thanks to increased predator control in cities and more native plants in gardens.

Silvereyes (whose Maori name tauhou means "stranger") self-introduced in the 19th century, so are technically a native bird, and they're the most common native species in our backyards.

But their numbers fluctuate quite a bit from year to year. Sightings have dropped by 44 per cent over the last 10 years, but rather than a decline in numbers, this probably means fewer silvereyes are overwintering in our gardens.

This species is also quite happy living in native bush and tends to forage in gardens in cold winters. With climate change, New Zealand winters are getting milder, so silvereyes aren't coming to town.

One big change has been a 55 per cent increase nationwide in sightings of swallows since 2007 (it's 87 per cent in Manawatu-Whanganui). Welcome swallows first bred in New Zealand in 1958 and quickly spread. They're now one of our commonest birds.

Swallows are perfectly happy living near humans, and they prefer to nest under eaves or bridges. They hunt insects on the wing, and they're especially common in rural areas where there's plenty of open country and bodies of water.

One worrying trend revealed by the survey has been the gradual decline of several species of introduced birds, like goldfinches, chaffinches and starlings.

Starlings are down 43 per cent in Manawatu-Whanganui over 10 years. Who would lament fewer starlings, you might ask? It's true that DoC doesn't spend much time worrying about introduced birds, and biology students prefer to do their PhDs on endangered native species.

But declines in dunnocks and thrushes indicate that something is going on. Perhaps our gardens are becoming more paved and sterile environments, perhaps it's our continued love of pet cats.

Trends like this are only revealed by a long-term survey, which is difficult to do with the shorter timeframes of today's research grants, and impossible to do across the entirety of New Zealand. The contributions of citizen scientists make it possible.

The Garden Bird Survey starts on Saturday, June 24 and runs until Sunday, July 2. If you want to take part, go to gardenbirdsurvey.landcareresearch.co.nz for tally sheets and instructions.

-Dr Mike Dickison is curator of natural history at the Whanganui Regional Museum