Migration madness

I’ve been back on Islay for a month now – and it’s flown by! The most exciting thing about this autumn has been the chance to catch up with our GPS tagged white-fronts from last year, hopefully combined with downloading their valuable data gathered over their summer away.

Is it bad to have favourites? Tag 21

The initial joy at finding an old friend alive, well and back on Islay with the tag still attached quickly changes to an extremely nervous wait once the downloading kit is unpacked and pressed into action. Is the tag still working? Will it send me the data? Will it painfully cut out halfway through a download? When the numbers start whirring through on the computer screen and the magic words "all data imported J" flash up (yes, it really does give you a J!) there might have been a bit of a fist pump and a little jig; anyone who’s ever seen me dance will know that’s not a pretty sight - hopefully no one was watching..

Migration data! Spring-Autumn 2014

Different birds = different colours. Tag 21 is red, 22 is dark blue

The good news is that 6 birds willingly parted with their data, giving us a remarkable insight into their migration routes, Icelandic staging areas and remote West Greenland breeding areas – this location data from the tags really is the next best thing to actually being there.

West Greenland happenings

It’s revealed some trials and tribulations associated with migration – and strategies the birds use to overcome them. The return leg from Iceland to Islay this year seems to have been particularly arduous – almost entirely due to the weather. Tag “BLO 19” (before anyone says anything I know she needs a proper name..!) left her journey really late, only leaving Iceland on the 10^th of November. She got her timings horribly wrong though, as she quickly met a series of Gale Force South Easterlies once she was out over the North Atlantic. Rather than pressing on into such a strong headwind and wasting precious energy, she ditched and sat on the sea for at least 6-8 hours. She did this twice more over the next 2 days before she made it to South Uist on the evening of the 13^th. Here she over-nighted before heading on down to Islay in the morning. To put this 4-day marathon in perspective, Tag BLO 27 completed the same journey (just less than 1500km), three weeks earlier, in 16 hours. Clearly, though, this strategy worked for BLO 19 – maybe if she’d ploughed into the headwind for 3 days she wouldn’t have made it at all – definitely  better late than never!

BLO 19 back to Islay. Circles indicate lengthy stopovers at sea

Wind map of the 12/11/2014 - middle of BLO 19's Iceland - Islay leg

Other birds tried a different tactic: just go with the flow! Two of these windsurfers were tags BLO 21 and 22. They were both blown off course on amazingly different paths back to Islay, 21 was up way north of the Faroes at one stage (look at first picture - northernmost red line), whilst 22 was well to the North West of the Irish coast (south-westernmost blue line). Other Greenland white-fronts clearly experienced similarly tricky conditions; a bird from Loch Ken in Dumfries and Galloway was seen in Norway, for instance.

In terms of ditching at sea these 3 Tundra bean geese in the North sea have life sussed though: not just taking a rest from flying, but catching a lift at the same time!

http://pelagicbirder.blogspot.co.uk/2014/11/bouncing-beans.html

Summer days

Currently on a pretty wet and windy ferry crossing back to Islay for the winter and quietly hoping i’m not going to be that guy that gets sea sick.. Which seems as good a time as any to re-start the old goose blog; once again you can get all your exciting goose related facts and anecdotes all in one place!

But for those still reading (a pretty grand assumption, i know..), you’ll no doubt be pleased to hear I’m going to start by talking about ducks. Ducks are cool. Everybody likes ducks. And over the summer I was lucky enough to work on what has to be our most enigmatic and mysterious UK breeding duck – the common scoter.

Scoters are sea ducks, spending almost all their lives in shallow seas feeding on shellfish, only fleetingly visiting a few Scottish freshwater lochs in order to breed. Because of this marine lifestyle, most people only ever see them from a coastal vantage point as a series of small black and brown dots bobbing around in the waves, which, i have to admit, has never really excited me before. But when seen close up they are actually a pretty striking bird – well, the males are at least; jet black with a splash of bright yellow on the top of the bill, the females are the classic fairly dull brown of so many duck species.

Male common scoter

Don’t let the “common” part of the name fool you – scoters are in real trouble as a British breeding bird, likely having declined by well over 50% in the last 20 years to the current population of maybe 40 pairs. We also know virtually nothing about them – which is a bit of a problem when it comes to coming up with conservation measures to stop them going extinct as a breeding bird in this country.

So it was pretty lucky that us species research folk at the Wildfowl and Wetlands Trust got some funding to investigate their breeding ecology on a couple of West Highland lochs over the summer. We started by finding some nests; easier said than done when you only have 15 females between two lochs that are both about 12 km long – serious needles in haystacks time. With a lot of effort and fair bit of luck we managed to find 9, not bad considering only 20-30 have ever been found before. We could monitor these nests using cameras and temperature loggers placed in the bottom of the nest cup to see how many hatched successfully and if they failed why, were they predated and, if so, by what? Similarly, any ducklings that hatched were followed to the point that they either disappeared, or successfully fledged. All pretty basic stuff, but never done before.

Cosy looking nest

Early impressions suggest that when nests were located within good cover (nice tall and thick vegetation, like old-growth heather) hatching success was pretty good, although some birds nested on some small grassy islands with very little cover – and these did very poorly indeed, not surprising really!

Scoter ducklings are very sweet. They leave the nest after a day or so and trundle down to the loch after mum, often a trek of a few hundred metres over rough ground and through thick, snaggly vegetation. Once on the water though, they are completely at home, diving to feed on aquatic invertebrates almost immediately, bobbing back up like fluffy corks and quickly bunching up behind an ever alert mum. Sadly though, more than half of them died within the first week – thereafter survival is fairly constant, but fewer than one in five of those that hatched survived through to fledging.

Common scoter female with week-old ducklings

Trying to reduce duckling mortality might prove tricky, but we think we can quite easily improve the nesting habitat available on these lochs – hopefully this will mean more successful nests and we get more ducklings onto the water; if mortality rates remain the same then a few more ducklings should survive to fledging. 

Bum deal?

So I realised I haven’t really gone into any detail as to how I’m spending my days and why. Cue a couple of slightly more science-y posts. You’ve been warned. For this project we’re using the full spectrum of data collection techniques; from very simple and easily repeated sampling in the field, to brand new and genuinely cutting-edge tracking devices. The telemetry is pretty cool and sexy, and is already showing us facets of the white-front’s lives that would be simply impossible to see otherwise. But, you’re going to have to wait for next time to hear about that! For now I’m going to explain how and why I’ve spent a fair bit of time ageing the birds here on Islay, and why I spend a couple of days every fortnight looking solely at goose bums. Yes. I do.

Adult Greenland white-fronts enjoying the Islay sun - it's a surprise, but you have to make the most of it!

It’s a pretty legitimate question to ask why! It might be surprising, but a goose’s bum can tell us a great deal about a goose’s recent history, current environment and its future prospects; to the extent that in some species during spring, it is even possible to predict, with reasonable accuracy, how many goslings an individual will return with the following autumn! Fat is the reason it’s possible to infer so much from a bum – like many of us, geese store fat in their bums. For any long-distance migrant, fat is their most valuable commodity; their fuel for migration. The fatter you are before migration, the likelier you are to successfully complete the journey and be in better condition for breeding. For geese, a bum is like a fuel tank. And big really is bootylicious.

We can, therefore, estimate any given individual’s body condition simply by looking at its bum and giving it a rating, or scoring, against some pre-determined scale. And we have one of those – made earlier of course. It’s called the Abdominal Profile Index (API) and is the basis of a lot of what I’m up to. The beauty of the API is that (with an experienced eye for a goose bum!) it is extremely quick and easy to score the body condition of large numbers of individuals – and from a distance.

When your diet is almost entirely vegetarian, it can take a lot of work to put on weight. Eating high quality food, and/or being able to spend long periods of time feeding mean an individual can fatten fairly easily. However, it may be that there is variation in the ability of individuals, flocks or even populations to access sufficient food resources to put on weight – and, if so, we would expect to see variation between their API’s as a result. Have a quick look at white-fronts in the photos; you should be able to see a clear difference in the size and shape of their bums!

This variation is most visible and important during the autumn and late winter/early spring, when the geese are feeding up rapidly just after and just before migration – to recoup the fat lost on the way here and to put on those extra few pounds prior to leaving. At other times of the winter, being very fat isn’t necessarily a good thing – being heavy slows you down and makes you less manoeuvrable, in turn making you more vulnerable to predation. The geese respond by regulating their body mass during the middle of winter – storing fat, but not compromising their survival.

We are looking at API variation at three scales with the Islay white-fronts. The first is between populations. The API’s on Islay as a whole can be compared with the birds that winter at Wexford in Ireland – a population that is doing much better than any other. If Islay API’s are significantly lower than Wexford, especially at migration departure point, then that would suggest the Islay birds are being restricted by their wintering site. The second scale is between the different flocks (or sub-populations) here on Islay. This will help determine if some flocks are unable to access resources as well as others; which will tie in neatly with work we’re doing characterising the habitats the white-fronts prefer (and where it’s available) and recording disturbance levels through the winter – both  potential causes of body condition variation. The third scale is at an individual level. Having a number of neck-collared birds means we can follow and individual’s body condition through the winter and relate this precisely to the areas and habitats they’ve used through the winter.

a family group in Iceland. Spot the juveniles!

Who knew a goose bum could tell you so much?! Ageing, on the other hand, does pretty much exactly what it says on the tin. It is equally easy, simply counting the number of juveniles and adults in each flock and converting to a proportion or percentage. Luckily, it is quite easy to separate an adult white-front from a juvenile, with a few characteristic differences that can be easily seen in the field. The most striking is the lack of the black belly-bars on the juveniles. Equally, the juveniles (to start with at least) are missing the white “frons”, or forehead, seen on the adults. Finally, the juveniles have a dark nail, right on the tip of their beak. This starts fading to the pale orange-white of the adult fairly quickly though..

2 juveniles with a parent. One in the background too!

Again, proportion of young is informative at different scales. At its simplest, the proportions of juveniles from all the wintering flocks get collated to calculate the productivity of the global population annually. Clearly, this is very useful for monitoring the long-term population trends of the Greenland white-fronts – which make pretty grim reading; a 40% decline in fewer than 15 years. It is also possible to compare between wintering populations. This year (so the 2013 breeding season) the Islay birds seem to have done pretty well, sitting somewhere around 16 – 17% young. I haven’t seen a global total yet, but it seems that other winter resorts have fared pretty poorly again. Last year, for instance, global productivity was about 4%. To put that in perspective, that’s essentially one successful brood per hundred adults. Not particularly clever.  Even productivity of 17% is only five or six pairs returning with goslings. They can get away with that, being a long-lived bird with high annual adult survival rates – they can’t at 4%. And they’ve had poor breeding seasons for a number of years now. We can also look at productivity between flocks on Islay. Given long-term datasets, it may be possible to link some variables – habitat quality, for instance – to variation in productivity within the island.

Losing it

Let me clear one thing up before I start. I’m not talking about mental meltdowns here; I’m doing pretty well. If you’re thinking Adam Scott chasing a major title, or Neil Cavanagh during exam season, I’m afraid you’ll be disappointed. Instead, I’m focussing on losing yourself, or a part of you. Might sound pretty deep and philosophical – it’s not.

The reason for all this lost chat is that Islay seems to be filling up with waifs and strays. Unsurprisingly, geese feature quite strongly here – but two I have particularly enjoyed. The first is a juvenile pale-bellied brent goose, who has had to resort to hanging out with the barnacle geese. Pale-bellied brent breed about as far north as you could wish to go (probably further..), right up in high Arctic Canada. They migrate south via Iceland, where I would guess this youngster got separated from his parents and ended up with the masses of barnacle geese.  Similarly, my second refugee (a juvenile pink-footed goose) probably lost its family in Iceland too and hitched a migration-route lift down to Islay with the Greenland white-fronts. Both these babies have actually not done too badly; about 80 brent geese even winter here on Islay (though some distance from this juvenile) and, whilst pink-feet tend to winter in mainland Scotland down to Norfolk, this baby pinkie will probably return with the white-fronts to their Iceland mid-migration pit stop, where, with a bit of luck, it’ll find its own kind returning to breed. The baby pinkie I see almost every day, always with the same white-fronts. I’m developing a bit of a soft spot for him!

The juvenile pink-footed goose in with some young Greenland white-fronts. Daddy white-front looking very worried in the back!

It’s not that unusual for ducks and geese to end up on a different migration flyway (what we call a major migration route) by accident. This year on Islay there have been reports of a few lesser Canada geese – B. c. hutchinsii for all you bird nerds out there. In layman’s terms that means real ones, not just the big fat ones sitting on a golf course near you – and a green-winged teal; both North American species. Previous years have seen snow geese (N. America) and red-breasted geese (breed in Siberia, winter in S.E. Europe) turn up here.

Red-breasted goose. An endangered species that breeds in Siberia. 

It just goes to show what a challenge migration can be, especially your first one. It’s a key reason why young migratory geese remain with their parents for much of their first year; learning and inheriting routes, staging sites and winter destinations. Most birds don’t use this strategy, with adults often migrating some time before the juveniles are ready to go. These youngsters really are in at the deep end, having to follow a strong instinctive drive and learn routes and safe stopovers en route.

Iceland gull showing off its pure white wing-tips over a dark and stormy Loch Indaal

The next two wanderers to pitch up here were two of the northern gull species that arrived in the New Year, almost certainly due, to some extent, to the wild and windy weather. Glaucous and Iceland gulls are both most commonly associated with Iceland, and, to be fair, I think the Icelanders picked the prettiest one to bear their name. They’re both very similar, but the Iceland gull has a slightly rounder, friendlier, forehead, whilst the glaucous has a seemingly meaner, more aggressive facial expression. The most striking feature of both is their completely primary wing feathers. This has given them the moniker “white-wingers” amongst birders and is more noticeable than you think, even amongst a number of herring gulls – which can look pretty similar again, but have distinct black wingtips.

Glaucous gull. A mean looking bird!

Finally, I saw a common crane up here last week. Quite what that was doing up here is anyone’s guess; there aren’t any others anywhere nearby. Sadly, it was just flying over, so I never got a good look or a photo, but there are rumours that it was seen a week before my sighting, so hopefully it is still tucked away somewhere up here. It certainly was doing a much better job scaring the barnacle geese than a few scarecrows and gas guns. I don’t think they’d ever seen anything that big before, and obviously reckoned it could eat a load of them all in one go if it wanted to. It frightened the living daylights out of them!

And so to the losing a part of you part of the story. A bit of a mouthful.. Yesterday I saw the young stag I photographed early in the autumn (http://chasingeese.blogspot.co.uk/2013/10/early-impressions.html) down on the Mull of Oa. Clearly he’d been in the action and had a scrap or two during the rut because his antlers had taken a fair bit of wear and tear. His right one had snapped off just above the brow tine and the left brow tine was also looking somewhat abbreviated. At least he’ll be shedding them pretty soon and growing a new pair over the summer for next autumn.  He’s certainly pretty vain and enjoys posing for photos, walking up to about 15 yards from my office (the car) and then standing beautifully silhouetted against the rising sun. If only he had a full set of antlers…

Looking pretty scruffy..