Wednesday, April 14, 2010

Is Sallow Britain's only Native Bird-Pollinated Plant?

It’s been a slow spring in North East England and there still aren’t many flowers around, so the blooming of sallow catkins must provide a real lifeline for newly emerged pollen-eating insects like this hoverfly. Sallow – aka goat willow, aka pussy willow – is unusual in that it exists as separate male and female trees and pollen must be transferred between the two - which may be some distance apart - for seeds to be produced. Catkins of both sexes produce nectar, which is what attracts butterfly and bee pollinators, but it’s mainly pollen that most hoverflies are looking for; visiting and cross-pollinating female trees isn’t high on their agenda.

But blue tits are attracted by the nectar too and they visit trees of both sexes. Quentin Kay at Swansea University first noted this, back in 1985 (you can read his original research paper in Bird Study here) and it may be that goat willow is our only native bird-pollinated plant. Bird pollination is common in the tropics and sub-tropics, where hummingbirds have become nectar specialists, but it’s rare in cooler climates.

For more posts on tree ID click here

11 comments:

  1. Hi Phil,
    Hummingbirds are common in North America too. In British Columbia very plentiful.

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  2. That's something I've noticed Phil, the number of Blue Tits pecking away at the catckins.

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  3. Hi Barry, I'd forgotten how widespread hummingbirds are over there in the New World...

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  4. Thanks Emma, when they're preoccupied with refuelling it's an opportunity to move in close...

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  5. Hi Keith, until I read that paper I'd always assumed that the blue tits were after insects, rather than nectar. I think there are some records of blackcaps visiting Mahonia flowers in gardens for nectar too..

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  6. Hi Phil, I posted a piece on Friday which includes a catkin picture (Birch I think). I would really like to know for certain - there were no leaves open so it was hard to id. If you have time, I would welcome you comments. (It was this post of yours which attracted me to the buzzing in the willow, then seeing the bees feeding on the willow catkins was amazing)

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  7. Hi Emma, I think the catkins are hazel that have been scorched by frost.....

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  8. Hi Phil, in the photo above is that a male or female flower? (And supplementary question, why?!)..

    I'm going to guess it's a female and I'm looking at the stigma and styles and it doesn't seem as golden as the picture in your post today (11Apr11 - Trees in Flower part 2). I'm always looking for memorable id tips!

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  9. Hi Dougie, it's a male, because of the long stamens tipped with golden anthers. If you double-click the image to enlarge it a bit you can see pollen grains on the stamen filaments and on the hoverfly. If you run your finger over a newly opened male goat willow catkin it will usually become coated with pollen...

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  10. Thanks Phil. Top tips. I shall try that out.

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