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From Mongolia to India, then straight back again

Updated Tuesday 18th October 2011

Bar-headed geese have one of the most demanding migratory patterns of all birds. Lucy Hawkes describes how they have adapted to the challenge

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Interviewer:
Now back in June on Saving Species we heard from Bangor University scientist Lucy Hawkes, who’s studying the migration physiology of bar-headed geese, which summer in Mongolia and winter in India, crossing the Himalayas twice on their journey, which is no mean feat.  The geese have proved to be superbly adapted to this extraordinary journey, with organs and tissues working at extremes they can endure altitudes and very low oxygen levels.  Well Lucy returned to Mongolia in July to retrieve heart rate monitors which had been fitted to 30 of the geese last year, and she’s with me now.

So before we talk about the geese themselves and the heart rate monitor work, let’s talk about Mongolia, what sort of landscape were you working in, Lucy?

Lucy Hawkes
Mongolia’s an incredible country of just vast never ending rolling landscapes of tundra.  It’s probably one of the most overgrazed countries in the world, having said which there are huge numbers of flocks of sheep and horses and yaks, so the terrain is basically just comprised of very short grass, which also happens to be ideal forage for bar-headed geese.

Interviewer
How did you make your way through Mongolia, do you have fixers out there to tell you where the geese are?

Lucy Hawkes
We worked with a group called the Mongolian Academy of Sciences, and they set us up with drivers and technicians, and we've been working with them for four years now.  It takes us two and half days to drive out from the capital and it’s a very bumpy ride.  It also is a very difficult terrain for surveying for animals as well, so we have to undergo enormous amounts of time in vehicles to actually manage to get anywhere near bar-headed geese.

Interviewer
Well the journey itself must be fascinating, but when you get to the places, are they vast lakes or small lakes in the tundra?

Lucy Hawkes
We specifically target one big lake called Terkhiin Tsagaan Lake in Western Mongolia, because it’s huge.  It’s one of the biggest lakes in Mongolia.  And bar-headed geese go to these lakes for one major reason.  They're in Mongolia because they are breeding but they're also taking this as an opportunity to drop and regrow their flight feathers.  Flight feathers get easily worn down over the course of a year, and so at some point they need to be replaced for nice new shiny firm ones.  And during this time these birds can't fly, so they're very vulnerable to terrestrial predators.  If you start hanging out next to a lake though, you can jump onto a lake whenever a terrestrial predator comes along and hopefully remain safe.

Interviewer
Give me a good description of a bar-headed goose, because not many of us have been lucky enough to go out to Mongolia and see them in their native habitat.

Lucy Hawkes
You may be lucky enough to see them in the UK.  They're very pretty birds, so they tend to be kept in ornamental collections, and I know that there are some in Slimbridge as well.  The bar-headed goose is a very pale grey bird.  It’s about two kilos in weight, so it’s a good armful I suppose in size.  It’s got a lovely white head with two distinct black bars behind its eyes, bright yellow beak and bright orange legs.

Interviewer
And where does it live, what’s its range in the world?

Lucy Hawkes
Its natural range extends from the southernmost tip of India all the way up to in the furthest north Russia.  You might find it as far west as Kyrgyzstan and you might find it as far east as China.

Interviewer
So these populations you're studying, they're migrating from breeding grounds in Mongolia south to India, and that means they’ve got to cross the Himalaya Mountains.

Lucy Hawkes
Indeed, which is an unbelievably challenging feat.  One thing that our tracking has revealed is that the birds actually cross the mountains at the same time of year when humans try to make their ascents of Everest.  Both humans and geese seem to be waiting for this ideal weather window when conditions become the most benign as the time that they choose to cross.

Interviewer
We've heard stories of terrific feats of bar-headed geese supposedly being the most, the highest altitude migrants out, but do these birds, as far as you know, do they go over the top or do they go through the Himalayas?

Lucy Hawkes
It didn’t seem to make an awful lot of sense to us that these birds would be flying over the peaks of say Mount Everest, when you could perhaps just go through the valleys next to them.  And we've satellite tracked 62 of them so far, and all of them have been following the valleys rather than the peaks of the mountains.  The maximum altitude we've recorded from any of these birds was 6,540 metres.  Which is still incredible, that would be plenty enough to make us feel really quite dizzy and a little bit sick.  Without sufficient acclimatisation we'd actually have trouble surviving at that altitude.

Interviewer
Well, talking of dizziness, that brings us to your work really.  You're studying bar-headed geese to find out how they make these journeys and how they use oxygen, how they conserve resources on those journeys, so can you sum up what your work has been about?

Lucy Hawkes
So our work is trying to find out what strategies maybe the birds might use to kind of play the conditions to their advantage.  The big finding that we've had so far is that the birds actually wait for a specific weather window to cross the Himalayas.  So during the day, as the sun heats the ground, the air starts to rise, because obviously heat rises, and that means that you eventually have a very strong uphill wind blowing.  And this is true if you go to the Andes or the Alps or the Himalayas or any mountain region on earth.  In the Himalayas this means an uphill wind blows really reliability every single day.  You might think bar-headed geese would use that as an opportunity to go, we actually found the opposite.

Those winds are quite strong and they're also quite turbulent, so a little bit dangerous flying in those winds, so the bar-heads actually wait for those winds to stop.  It might sound a little bit crazy, but at night it’s also an awful lot colder.  Colder air is denser, it’s got more molecules of all the various component gasses within a particular volume, that also means there’s going to be a little bit more oxygen there, and we think they go at night perhaps because they're both risk averse and also because they're trying to use conditions where more oxygen is present.

Interviewer
Yeah, so this oxygen use is absolutely critical to the way that they migrate.  What have you discovered about that?  Have you discovered that they're physiologically adapted in any particular way to undergo these strenuous journeys?

Lucy Hawkes
We've been very fortunate to work with a big team of colleagues who've made some of those findings for us.  For instance we know that bar-headed geese have a mutation in their haemoglobin that makes it a little bit more hungry for oxygen, it will take it up a little bit more readily.  They’ve also got a lot more blood circulating to their flight muscles than other birds perhaps do, and also they’ve got slightly larger wings compared with other geese as well, so these are some sort of what might appear very minor adaptations but taken together they actually make these geese into really amazing athletes.

Interviewer
So when you went back in July, you were trying to retrieve heart rate monitors that you'd put on 30 of the geese, how did you get on?

Lucy Hawkes
We managed to retrieve nine of them, and we think that’s a pretty good return.  This is the Tibetan Plateau after all, this is one of the largest land masses on earth, we’re literally looking for a needle in a haystack, so we couldn’t believe that we were able to get almost a third of those loggers back.  Catching the geese however is quite something else!

Interviewer
So how do you go about it?  I mean if they're moulting, they're flightless, are they?

Lucy Hawkes
They are, which is obviously a massive advantage for us.  In brief, we set the nets into basically sort of a funnel on the bank of a lake.  We get onto the lake in kayaks.  And the thing to do really is just be where you don’t want the geese to be.  So we basically herd them into the nets but we do it ever so gently and ever so carefully, and eventually the geese will decide they’ve had enough of being on the same lake as us and they decide to get out.  Our job is to try and make them get out into our nets, and at that point we can close a little gate, surround them on all four sides and capture them.

Interviewer
So this is gradually corralling them in kayaks and then paddling furiously to try and persuade them to go onto land and catch them in the nets.  How did you get on?

Lucy Hawkes
We managed to catch 100% of the birds.  We did five catches altogether, and every single one we caught all of the birds that we aimed to catch, which was fantastic.  We've come a long way in that regard.  We caught just over 400 birds altogether over the three week trip to Mongolia, and those included those nine birds carrying heart rate loggers.

Interviewer
Do you have any results at all from those heart rate loggers?  Can you draw any conclusions from it, or is it too early at this stage?

Lucy Hawkes
So the heart rate loggers altogether contained over 14 Gigabytes of data, so an enormous amount of analysis needs to be done.  We've made a start.  Those have shown some really interesting things.  For instance some of the geese’s heart rate actually dropped to about 40 beats per minute overnight.  That’s really, really low; you wouldn’t even expect to see that in a human.  But the really astounding thing we saw was a 25 hour long flight where the bird’s heart rate was sustained, and in addition to having heart rate we also had something called an accelerometer, and an accelerometer not surprisingly measures acceleration.  Well it measures it forwards, backwards, left, right, up and down, and that tells us a little bit about how the animal’s moving, and by looking at that data we could see that the animal was actually consistently flapping for that whole 25 hour period, so we know that bird made an entire 25 hour migration, which is just astounding.

Interviewer
Well it’s an astonishing feat, even in normal conditions, but at high altitude it must demand enormous energy resources.

Lucy Hawkes
Absolutely, and we think that at the beginning of the flight it would have started on the Tibetan Plateau, and its heart rate was quite a lot higher, probably because the oxygen is so much more scarce there, because you're at high altitude.  As the flight went along, the heart rate dropped and dropped and dropped, and towards the end we think the bird probably was just basically gliding down and was having quite an easy time of it, and its heart rate dropped down to about 240 beats per minute, which is high for us but not very high for a flying bird at all.

Interviewer
Well no.  As you followed these remarkable birds, you must have learnt a lot about their migration strategy and you must have learnt an awful lot about the habitats that they're using en route as well.  What’s the bigger picture for conserving bar-headed geese?  I mean do they need conserving, are they in danger at all or are they doing quite well?

Lucy Hawkes
For wide ranging species like the bar-headed goose, a real conservation conundrum is being able to actually measure if the population is increasing or decreasing.  That’s easy if they only occur over a small area and you can count them all, you can figure it out one year, count them again the next year and you know if they're going up or down.  Bar heads occur over such a massive area it’s really difficult to make those counts.  So our tracking is enabling us to direct our efforts to count birds in specific places and in specific times of the year when we believe that we may have captured large portions of the population.  As yet, those counts have not been made and they need to be made over several years in order to be robust, so we don’t know if bar-heads are threatened or not.

One very important thing regards bar-headed geese is that they are thought to be vectors of avian influenza.  They occur in several places where bird flu is known to be present, in for instance poultry farms, so they’ve been suggested to be suitable vectors.  We've been swabbing bar-headed geese for avian influenza as part of our work as well, and we've never yet detected one positive result.

Interviewer
If you stand in a certain place in the Himalayas and look at a particular valley, will you see large numbers of bar-headed geese travelling down there, or are they diffuse.  Do they travel down lots of different areas; do they have their favourite fly ways?

Lucy Hawkes
I think one of the problems is that they'd be flying at night, so you probably wouldn’t see them, but you probably would hear them.  Apparently bar-heads call while they're flying, and I don’t think that’s so much to do with communication as the fact that they're flapping their wings so hard it’s expanding and contracting their lungs, and it’s probably a bit like Monica Seles playing tennis, you know, just ‘huh!’ just comes out.  But I believe that there must be tens of thousands of bar-heads crossing particular valleys in the Himalayas, and that that would be most likely in March and also in October.  So anybody who’s just been to the Himalayas this month or is just about to go may well see some.

The other thing that’s really interesting about bar-heads migrating at high altitude is that they are performing a type of locomotion that requires huge amounts of oxygen but huge amounts of oxygen aren’t available, so how do these tissues manage to cope in very low oxygen conditions?  Well some of the ramifications of that have importance when we think about conditions when we as humans suffer very low oxygen conditions, such as when we’re having a stroke or perhaps a heart attack, so some of the biomedical implications of how the system manages to cope may in fact one day lead to some discoveries that may help us to recover from those kinds of events.

Interviewer
And, as far as other geese are concerned, do bar-headed geese show adaptations beyond, over and above what most other geese show, that they are definitely adapted to this particular high altitude migration?

Lucy Hawkes
We believe that to be the case, although I think there are a large number of different species that can cope very well, probably at high altitude and also in low oxygen conditions.  One of the world records for birds being found at extremely high altitude is held by the lowly mallard, a mallard duck was sucked into an aeroplane engine at about, I think it was about 1200 metres.  They I guess scraped the bits off later and confirmed that it was a mallard.  So there are probably other species of birds up there.  I'm also aware that a pilot at cruising altitude spotted a flock of swans flying in formation as well.

Interviewer
So bar-headed geese don’t necessarily hold the crown when it comes to high altitude flying?

Lucy Hawkes
I think they hold the crown for the most regular high altitude migrants, but I'm not sure that they hold the absolute Guinness world records.

Interviewer
Thank you very much Lucy.  Thank you Lucy Hawkes from the University of Bangor for sharing the information of bar-headed geese, and may your work continue.

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Image of a bar-deaded goose Creative commons image Icon Work found at Wikimedia / CC BY-SA 3.0 under Creative-Commons license Bar–headed goose
 

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