Tuesday, July 20, 2010

Avian chimera?

When I was a child, one of my most treasured possessions - second only to my collection of plastic model animals - was an encyclopaedia of vertebrate animals (OK, I was a pathetic kid). I'd spend hours studying the entries, from aardwolf to zorilla, and hungering for all the wonderful creatures that lived where I didn't.
My enthusiasm was largely restricted to fur-covered beasts, but there was one exception. One image, of a bird, kept catching my attention. It didn't look like a bird. It was a small fluffy creature clothed in soft greys, with a fuzzy crest and long tail. It was dangling underneath a tree branch and flaunting a tummy as smooth and round as a well-fed kitten's. My book said it was a mousebird (a name that seemed as strange as sphinx or griffin), and it belonged to an ancient order found only in Africa.

Haunted by this image, I was determined, when I finally made it to Africa (the Mecca of mammal-devotees), to find a mousebird and see whether the photo in my childhood 'bible' had lied.
What I found surpassed my expectations: mousebirds don't just look strange, they're delightfully weird.

Unlike other birds, a mousebird's feathers don't grow in orderly tracts (lines), they sprout out recklessly all over the body, giving the bird a furry look. This photo, of a local speckled mousebird (Colius striatus), was borrowed from here.

Even as I write this, a small flock of red-faced mousebirds is whistling from the bushes outside my window. I still feel a thrill on seeing them. Although demure in cinnamon and grey, this species sports a scarlet Zorro mask and a pencil tail. But what's really cool about mousebirds is the way they scurry through the branches. When feeding, they dangle beneath the branch with legs splayed sideways, hang upside down from grappling-hook toes or use their bill to haul themselves up to higher branches. They can do these weird, un-birdlike things because their legs are set unusually far forward and they've got two reversible toes (that is, they can swivel to point either forward or backward; not that they can be worn inside-out).

Among their other strange habits, mousebirds seduce their lovers with a bouncing courtship dance in which they bob up and down so vigorously their feet leave the perch. Photo by Martin Heigan.

But if you look closely at what these little birds are doing, as they scamper about the bushes, you're in for a shock. They're harvesting leaves! Their beaks have a sharp cutting edge (called a tomium) specially designed for cutting up veggies. Although they also like to feast on fruit, flowers and buds, at suppertime, young leaves is their dish of choice.
Not shocked?
Then tell me, how many small birds have you seen munching leaves??
There's a good reason for this (no, not poor observation skills). Leaves are dismally low in calories (ask any dieter) and folivores (leaf-eaters) must eat loads if they're to get the energy they need; a problem when it comes to getting airborne. What's worse, leaves are mighty difficult to digest. The only way to break down the cellulose is by fermentation with the help of gut-dwelling microorganisms; and these little guys work sloooowly.

Of the world's six mousebird species (all of whom call Africa home), two hang out around here. This is the red-faced mousebird (Urocolius indicus). Photo borrowed from here.

So how do vegan mousebirds cope?
Firstly, they're seriously into energy-saving. At night the flock huddles tightly in a rugby scrum, which lets each bird save 40-50% on its overnight heating bills. And on chilly nights, or when food is scarce, mousebirds don't even try to stay warm; they cold-bloodedly sink into a torpor, letting their body temperature fall by 8-10 degrees C. Once the sun rises, they hang about basking, feathers fluffed out, until they're feeling their usual hot-blooded selves (41.5 C). This helps them get by on fewer calories.

And how does a small flighty bird cope with a huge bellyful of rotting leaves? By restricting their leaf-munching to the late afternoon. In this way, they've got all night to digest their burdensome meal, freed from the need to find their wings.

Speckled mousebirds stoking up their leaf-fermentation vats (i.e. warming their tummies in the sun). Photo by Martin Heigan.


  1. Thank you for this post about mousebirds. I was so impressed by them when I visited South Africa. Especially the way they never perch upright, and often hang with their feet splayed between two branches. They are so engaging to watch.

  2. What a great post! You ought to submit this for publication in the Open Laboratory anthology!

  3. I am not a birder Lynda but had to learn about them when I started as a courier. Lovely post and info as always.

  4. How facinating! How did I ever get grey hair without learning about these delightful little birds.

    And you write so well!

  5. John,
    Yes, they're little contortionists. Maybe I should train them up, and win fame and fortune with my acrobatic Mousebird Circus.

    Thanks for the encouragement. I never really think of my posts as science blogging - too 'everyday' and casual.

    Mousebirds are undoubtedly the non-birders bird!

    Mousebirds: Africa's best kept secret!
    Do you think they'll boost tourism?

  6. Aah !! the mousebirds I love these Birds every Saturday morning I feed them a banana on a tree stump in my Garden after their breakfast they sit on a high branch sunning themselves, with a pot belly facing the Sun so cute :)

  7. Philip,
    I envy you. I'd love to be able to attract into my garden all the lovely fruit-eaters that live along the river here (e.g. purple-crested louries, green pigeons, trumpeter hornbills, thick-tailed bushbabies) but I can't figure out how to do so without also attracting the vervets and baboons.

  8. Just wanted you to know that I read your blog regularly. It's captivating. Keep up the great work. Elaine

  9. I have always found mousebirds to be very comical and enjoy watching them. We have a flock of them that frequent the wooded areas of the suburb, but they are quite shy. I have only managed to get close enough to photograph them once, while they were sunning themselves in a tree - now I know why.
    Seeing the civet was a real gem - I have only seen them in the wild a few times when I was still a child.

  10. Elaine,
    Nice to hear from you, and thanks for the encouragement.

    Sunning is a favoured activity for almost everthing (including me!) right now. I think the civet was also out soaking up some rays after a 'near-frosty' night.

  11. Wow Lynda, what a cool bird! I have never heard of this bird but having never been to Africa, I guess that's not unusual.

    I enjoy learning about creatures new to me and really enjoyed your post. You gave us some great information on this species and awesome pictures to go with it. I will have to add Africa to my itinerary and also get back to your blog to read up on the Mongoose.

  12. Larry,
    I'm glad you enjoyed the post. Get your skates on: Africa is the place to be!

  13. Hi Lynda

    This is the best blog in the whole world! I learn some thing every day! I have always loved looking at bird in the trees they are just so amazing!

  14. We have got so many brownheaded parrot and
    grey-headed bush shrike!

  15. Hi Lynda
    My own mousebird tale...

    I'm trying to 'rescue' a young bird that crashed into our glass door yesterday. I nuzzled him until he seemed to be 'back to normal' and then put him into a tree, which had his mom and pop chittering and fussing around their prodigal.

    Unfortunately, he fell out of the tree again - and I now have guardianship over a fully feathered but clearly inept youngster. I have no experience of the species, so I've been doing my homework via the www. He is on a diet of Purity baby food (pear) and I've given him an old towel to nuzzle in. The blanket seems welcome, as he's cuddled into it at present.
    He's greedily indulging in the Purity from a syringe, not too fussed by hand contact after only a day, and feasting (and pooping copiously!) on wild ink berries from the tree he lived in.
    I feel so sad to have to confine him, but the neighbourhood feline patrol will have him in no time - in fact, the Major of said patrol is my very own Russian Blue predator ;-)

    For 'Mouse's' sake, and my daughters', I am praying fervently for his survival. I fear that he may have a physical problem which hinders flight, which will mean that he must remain with us in a cage. I don't know if the laws are in favour of my keeping him, but I can't see any other way. ( I live in Cape Town)
    Loved your article!

  16. Chanti,
    Good luck with Mouse. I hope he makes a full recovery and can rejoin his family.


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