Bird pollination in New Zealand
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Dave Kelly of the University of Canterbury explains abiotic pollination by wind and biotic pollination by animals. He shows the characteristics of bird-pollinated flowers and the birds that carry out their pollination, with footage of tūī and bellbird feeding. Dave also explains the meaning of the ecological term ‘mutualism’.
DR DAVE KELLY
You can divide pollination into abiotic and biotic. So biotic is where an animal’s involved. Abiotic is where there’s no animal involved, and about a third of New Zealand plants are wind pollinated including all these beech trees, southern beech all round here, that’s wind pollinated. So they just release tons and tons of pollen and it blows around whatever direction the wind’s going, and then it’s trapped somewhere else. So about a third of New Zealand plants and the grasses, for example – in fact, all the things that give people hay fever – they’re all wind pollinated.
The biotic ones don’t need to produce so much pollen because it’s delivered more or less purposefully by an animal, and about two-thirds of New Zealand plants are pollinated by animals and most of those are pollinated by insects. And then we’ve got a smaller group – about 8% or something of the New Zealand flora is bird pollinated.
The native bird-pollinated New Zealand plants are pretty much everything you can think of that’s got a decent flower, so the stuff like New Zealand flax, pōhutukawa, rata, the tree fuchsia, the native mistletoes, kaka beak, kōwhai – pretty much any native plant you can think of that has a flower that people plant in their gardens that’s big and obvious cause birds go to it.
There’s two ways to figure out the characteristics of bird-pollinated flowers. They’re large, they’re usually red or yellow, they’ll have lots of nectar in them and often the branches are robust enough to take a bird because they’re much heavier than insects.
Birds that feed a lot on nectar have a beak and a tongue that’s long enough to get inside the flowers. They also have a brush tongue, so the end of the tongue has all these tiny little sort of papillae on it like a paintbrush and so basically that sucks up the nectar. They stick the tongue in and the nectar’s sucked up into this sort of brush-like structure very quickly.
The introduced finches, sparrows and so on go around looking for seeds to eat – they don’t usually feed on nectar – whereas the bellbird, tūī, stitchbird, the native pollinating birds, they’ve got a longer beak, longer tongue and they’re able to handle the flowers appropriately.
A mutualism is an interaction between two species where they both get a benefit. So in pollination, the bird gets a feed of nectar and the plant gets its pollen moved from one flower off to another plant somewhere, so they’re both benefiting. And so you get quite different dynamics in ecological terms between mutualistic relationships where, if one species is doing well, the other does well, whereas with competition or predation, if one species is doing well, the other is sort of doing worse.
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