Dave Kelly of the University of Canterbury explains how some introduced birds can pollinate native flowers, but they don’t very often. His assistant Jenny Ladley helps study bird pollinators in native forest. Watch silvereyes on flowers and find out about the importance and limits of this pollinator. Dave explains why they focus research on bird pollinators rather than insects.
DR DAVE KELLY
Introduced birds can do some pollination, and if you have a look at the list of all the birds ever seen going to flowers of native plants, you do find some introduced birds there, particularly starlings, house sparrows, chaffinches, but what we found is that they don’t do it very often. If you actually sit and watch native plants for a while and you record the birds that come by, you almost never see introduced birds doing this.
And I think there’s two reasons for that. One is that actually most of the introduced birds that were brought in were from Europe, and Europe doesn’t have a lot of pollinating birds, and so we have finches and things that are out there looking for seeds and insects. And then secondly, when we do have a bird that does some pollination like the European starling, they’re mostly in areas that have gardens, in towns and sort of more human-modified landscapes, and they’re going to the introduced plants there more so they don’t turn up in the forest very often, they don’t go to the native plants very often. So it turns out we can’t really rely on those introduced birds to be much help.
Silvereyes – they’re a very interesting bird – they’re very small, they’re very common, you see them in towns, and it’s a species that arrived here after Europeans. We know the date they arrived – 1856. So they got here on their own so they’re native, but obviously a recently arrived native. They’re very adaptable, they’re all through the bush as well, they pollinate a lot of plants, they do a lot of fruit dispersal, they’re eating insects and so on, they’re very useful, and they’ve filled a gap that some of the rarer native birds like stitchbirds and saddlebacks and so on used to be doing, but they’ve disappeared from quite large areas now. I sometimes joke about how we should set up a silvereye appreciation society because people, you know, don’t give them enough respect.
But the one thing that silvereyes have limits on, they’re so small that they’ve got a short tongue, they can’t reach into the big flowers and they can’t swallow the bigger fruits. So they’re doing a good job but only on the smaller flowers and the smaller-fruited plants. But in that they’re really important, they’re doing about a third of all the flower visits. We did this quantitative thing on all the native plants we could find, and tūī, bellbirds and silvereyes are doing 85% of all the flower visits, and if we didn’t have those three, we’d be in trouble.
I think about two-thirds of native plants are insect pollinated. So the smaller flowers, little open things and so on – they’re often green or white – and those are usually visited by insects. We’ve been focusing on the smaller percentage of native plants that are bird pollinated because we suspected that actually the birds were in more trouble – native birds had decreased more than native insects had.
And the other thing that helps insect-pollinated plants is that we’ve brought in some of the world’s best insect pollinators, honey bees and bumble bees – they’re everywhere. And so what that means is we think that insect-pollinated native plants are probably getting a reasonable amount of visitation from native and introduced insects, so we’ve concentrated on the bird-visited species.
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Thomas Doerig, SuperBinox Productions
Brad Howlett, Plant & Food Research