Urban bird-feeding makes life tough for tiny national bird

Urban bird-feeding makes life tougher for tiny national favourite

Backyard bird feeding is great for some birds but not so good for one popular tiny native, a new study from the University of Auckland has found.
Backyard bird feeding is great for some birds but not so good for one popular tiny native, a new study from the University of Auckland has found.

The research, by PhD Candidate Josie Galbraith, Senior Lecturer Margaret Stanley and Associate Professor Jacqueline Beggs of the University’s School of Biological Sciences, builds on earlier research into New Zealanders’ backyard feeding habits.

The latest study, published in the Proceedings of the National Academy of Sciences (PNAS), looked at the effects of common bird feeding practices on particular species of birds and whether supplementary feeding of bread and seeds favours some species over others.

It found two introduced species in particular benefitted most: the common sparrow (Passer domesticus) and spotted dove (Streptopelia chinensis). Sparrow abundance was 2.4 times higher at feeding sites and spotted dove 3.6 times higher.

But the native grey warbler (Gerygone igata), voted New Zealanders’ Bird of the Year in 2007, significantly decreased in abundance at feeding sites, with numbers dropping by more than half.

The findings on the diminutive grey warbler, one of the most commonly-heard songs in New Zealand’s forest, is concerning, says Ms Galbraith.

“They typically forage on insects in the tree canopy but their ability to forage efficiently may be being affected by the disruption of higher densities of other birds at feeding sites,” she says. “There is some evidence their numbers are declining anyway, so this study does add to that concern.”

The researchers monitored 23 North Shore gardens over 18 months, with feeding at 11 sites and no feeding at 12 sites. In all, 33 species, a total of 18,228 birds, were recorded. The most commonly-observed species were sparrows, spotted doves, blackbirds, silvereye and myna.

They found the abundance of spotted doves in particular increased rapidly within two months of the start of feeding, suggesting the birds were moving to feeding sites from surrounding areas.

“This work certainly suggests bird-feeding favours introduced birds such as spotted doves over native birds, which mostly eat insects, nectar and fruit,” Dr Stanley says.

The study is published in the Proceedings of the National Academy of Sciences.

ENDS

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