Common Ringed Plover geolocator study in Ammarnäs

This is my first contribution to this blog and thus my first visit to Ammarnäs in June. But more importantly my first real field work season in the area. Finally! Between the 10th and 27th of June I, together with a master student, had the pleasure to work with Common Ringed Plovers (Charadrius hiaticula, see below for a picture) in Björkfjället. The aim for the work in Ammarnäs is to compare migration patterns of the population breeding in the mountain range with those breeding in the milder, coastal areas on the same latitude. Our coastal study site is the island Malören, which is located in the middle of the Bothnian Bay. By comparing those sites we will be able to control for geographical latitude and distance to the nearest possible wintering grounds. The idea is to better understand how differences of the annual cycle, such as onset of breeding and length of the breeding season, affect the migration distance and timing. And vice versa. The study will be conducted over three years by deploying light level geolocators and monitor the onset of incubation at each site. Apart from this we are also interested in changes in onset of breeding in the mountain range over the past 50 years.

Nest searching around Båssajaure.

Arriving to Ammarnäs this early in the season was thrilling. Snow was still covering much of the tundra and Ammarfjället, which is situated on higher altitudes. But regardless, up there, life is already coming back and multiplying. The first day was a warm up. We joined Rob and Morrison (the Skua team) to Gelmetje for some skua catching. The day after we took our first steps up on Björkfjället to find a suitable area that hosts high enough densities of breeding ringed plovers. Finding such areas will make the upcoming seasons, when the geolocators are to be retrieved, much easier. That day we went Ruohtakvàggie (Ruohta Valley) which consists of a chain of lakes, making it a potential good area. Coming out to a new potential study site is always exciting, but there is also some anguish. Especially since the only background information we had was that plovers occur, but no further information about densities. I must say that I felt very discouraged and crestfallen after that first day. The general area was vast and suitable plover habitat was scattered all over the place. Partly because of the geophysical properties of the area, partly because of the snow cover. Also, we only saw a few ringed plovers and neither of them showed any sign of having a nest around.

Nest of common ringed plover.

The next couple of days were better. We decided to reconnaissance in an area further east, around Båssajaure (Lake Båssa). Initially we did not find many plovers. Actually, we had better luck with mammals. In a distance, out on the ice of an unnamed lake, we spotted something brown lumber around: a wolverine!!! The beast could be seen for 45 minutes as we slowly approached, carefully searching the slope facing the lake for plovers. In the end we were only 150 meters away before it decided to cross the lake to continue to search for food on the other side. As we continued forwards we found the first two plover nests and the first geolocators could be deployed.

A Wolverine!

After that we realized that we had found our spot. During three overnight trips, we were able to locate 12 nest and catch 23 plovers, which all were fitted with geolocators. On the best day we tagged no less than six birds within 8 hours! Now the long wait starts: will the birds be back next year?

Linus Hedh

A Common Ringed Plover with a freshly deployed geolocator.


Its been just over a week that Morrison and I arrived in Ammarnäs. Our expectations were high: there had been rumours about high lemming numbers over the past weeks and months. But we also had some concerns: did the lemmings survive warm periods with rain in early spring?

After arrival in the early morning of 10 June and a nap, we went up to the main Long-tailed Skua study area: Raurejaure, to explore the first part of the area. Our heart sunk when the skuas that we encountered were hardly alarming or defensive, and we were unable to locate any nests: was this going to be yet another non-breeding year? I couldn’t quite believe it! Normally, there are about four pairs in the area that we checked; now there were only two pairs present.

Norwegian Lemming (Lemmus lemmus) in Björkfjället.

Next day things were looking much, much, much brighter! Up in Gelmetje, we found several nests, including two of birds with geolocators of which we retrieved one. From then on, it just got better and better. Nests of skuas carrying geolocators were found, and we were very successful in trapping these individuals. At the time of writing, one day before we leave Ammarnäs, we retrieved 15 geolocators! Tomorrow morning we’ll do our final attempt to trap SV, the final loggerbird that we failed to catch so far…

So why didn’t we find nests on the first day? One reason is, that the first pair we encountered nested on a very unusual location: on top of a big rock. This is so unusual, that I blindly assumed the bird that was sitting there wasn’t incubating… Another pair, further into the area, had a very similar nest location. Reportedly, snow cover had been extensive into the first days of June, that is, when Long-tailed Skuas lay eggs. Apparently, these birds selected the first parts that became snow-free. Still, we haven’t even seen this in 2015, when snow melted even later.

A very unusual nest location (of AF/KR), on top of a rock!

Another remarkable phenomenon we have encountered this year more than earlier years, is change of partners and territories. For example, AF had been breeding up on a large hill since 2007, but has now much downhill to pair up with KR, the former partner of KJ. NZ changed location about 1 km to pair with KO, that used to be with KG. In each case, males kept their territories but females switched partner and therefore territory.

Regarding the results of the geolocator tracking: that has to wait. All batteries are flat, meaning we’ll need to send them to the manufacturers to download the data. If we are lucky, together they may contain 31 full annual cycles! Fingers crossed…

So, finally a breeding year for the Long-tailed Skuas in Ammarnäs!

Long-tailed Skua happily breeding.

New field season approaching

Over the next weeks, we will blog again on this site to keep you up-to-date about our fieldwork in Ammarnäs (Sweden) and Slettnes (Norway).

In Ammarnäs, the team will focus on Long-tailed Skuas, which may finally breed again after three non-breeding years. Rumors about reasonable to high rodent abundances have reached us during the past months, so fingers crossed rodents are still abundant at the time of writing, when the skuas should just have started laying… If so, we finally get the chance to retrieve the 20+ geolocators that have been deployed during the previous breeding season, in 2015. Another project in Ammarnäs, that started last year, is focusing on Dotterels and is led by Christian and Tim.

In Slettnes, Ingrid and Hans will – for the sixth year – follow the whereabouts of the Arctic Skua colony. Main focus will be on reading colour-rings to further refine our survival estimates, survey the colony to see if the 50% decline over the previous two decades is continuing, monitoring breeding effort and success, and retrieve geolocators. Let’s hope they are doing better this year than during the previous disastrous years!

Both in Ammarnäs and Slettnes, first teams arrive on 10 June. Watch this space!

New paper: migratory divide in Red-necked Phalaropes

In October 2015 at the 2nd World Seabird Conference in Cape Town, South Africa, an international collaboration was started to combine geolocator tracking data of Red-necked Phalaropes from breeding sites across the Western Palearctic. Now, a joint paper is published in Frontiers in Ecology and Evolution, showing a migratory divide between populations from Greenland, Iceland and Scotland migrating to the eastern Pacific, and populations in Fennoscandia and Russia migrating to the Arabian Sea. Especially the western route to the Pacific is amazing – a migration route not shared with any other Western Palearctic species. Phalaropes using the two routes and wintering areas differ in migration strategies and also in the amount of movements within the wintering area. Only few studies have shown such diversity in movement strategies among subpopulations within a species.

It has been a tremendous job to collect all this data, especially because Red-necked Phalaropes are far less site-faithful than, for example, Long-tailed Skuas, albatrosses or other seabirds. Out of 10 geolocators deployed, on average 3 were resighted and recaptured. Even if recaptured, things can go wrong: some loggers failed prematurely and others were lost. Considering the effort required for each and every logger, the paper is also a testament to the willingness of people to share their data and the power of international collaboration!

Hence, thanks to all collaborators, in particular Yann Kolbeinsson, Olivier Gilg, Jose Alves
Malcolm Smith, Aleksi Lehikoinen, who led the fieldwork at the other sites.

Please read the full paper here.

Unravelling the mysteries of the Dotterel

The higher ridges and plateaus rising high above our study areas in Ammarnäs are home to an elusive bird: the Dotterel. Over the years, whilst working on Long-tailed Skuas and Red-necked Phalaropes, we have often heard Dotterels displaying and passing by from one ridge to another. Yet, our knowledge about their breeding ecology, habitat use and migration ecology is rather limited. Therefore, we have started a colour ringing project by which we hope to learn about their basic ecology such as habitat use, survival and site faithfulness.

Dotterels breed in low densities which makes it difficult to find a nest; over the years we have only incidentally found one. This year we have managed to find 8 nests! We find nests by following a male, which is the breeding sex, back to the nest. This may not seem difficult, but the bird’s plumage matches perfectly with their habitat which makes it almost impossible to locate a breeding individual, especially since they are only flushed when approached very closely. The trick is to search for a foraging male, and to stick with it when found! So far, we have caught seven males on the nest, using a walk-in-trap, for colour-ringing and sampling.

The males have proven to be very committed fathers. It amazes us that some males stay on the nest until we mildly push it off to measure the eggs and estimate the stage of incubation. The males behave very calm and often continue breeding as soon as we have finished our measurements as if nothing happened.


On the other hand, female Dotterels are less committed to their brood and leave most of the breeding duties to the male. It is thought that females migrate further north after completing a clutch to do another breeding attempt. Surprising was our observation of a breeding female on the nest! Most females we encounter are in small groups of 2-6 birds. We have managed to catch some of these females using mist nets and tape lure. Let’s find out if we can get some ring recoveries in future seasons, possibly further north…

The 2018 field season is almost at an end. A few days are left to check Dotterel nests, ring chicks and explore some ridges before we migrate back south.

Morrison Pot

Another failed breeding year for the Long-tailed Skuas in Ammarnäs, despite good Lemming numbers!

In Ammarnäs the Dutch/German/Swedish crew have had their first week of fieldwork. Summer came early this year and most of the tundra snow cover has melted. The first rumours of lemming presence and territorial Long-tailed Skuas observed by others at the field station made us eager to get out in the field. We were accompanied by journalists from Radio Sveriges who were keen on learning more on the research that is done at Ammarnäs. Peter gave an excellent interview that was aired on national radio on Friday the 15th.

Peter is explaining our projects to Jonatan Martinsson from Radio Sveriges.

However, a few moments after crossing the treeline for the first time in 2018 we saw that our worst case scenario had played out on the tundra. The pair of Long-tailed Skuas that traditionally breeds at the Geppejaure area had left their territory already. Two colleagues at the station had observed them showing aggressive territorial behaviour just 3 days earlier.

After entering the Raurejaure area and exploring some good skua spots we had to draw a most disappointing conclusion: it’s going to be yet another non-breeding year, again! This is the third non-breeding year in a row… The strange thing is: up at the tundra Lemmings are present. We found quite some winter nests and corridors, which betrays their presence, and Tim and Noel even caught one alive! We also observed other raptors that may rely on Lemmings, such as Rough-legged Buzzard, several Short-eared Owls, and Hen Harrier on the tundra, and breeding Tengmalm’s Owl is present in the village. However, number of waders are low which could indicate high predation pressure. We were surprised to find one skua nest with a single egg that was already hatching. This means an extremely early start from this pair, and possibly also most other pairs that have tried but already failed. The day after we could at least see the first Long-tailed Skua chick for most of us who have only been in Ammarnäs in non-lemming years. However, on Björkfjället a large flock of 77 Long-tailed Skuas is already present, which indicates that most individuals have given up their breeding attempts and will soon be out to sea.

On the bright sight, we have more time to spend on our new Dotterel project! We have seen several individuals displaying and found our first territorial birds up at Gájsátje, the mountain that we have nicknamed ‘Miracle Mountain’. First catching attempts failed, as a territorial female escaped from our net, but looked promising! Tomorrow we will continue exploring Björkfjället and try to find nests of Dunlin and Dotterel.

Morrison Pot & Tim van der Meer

The new field season is approaching!

In less than a month, a new field season will start in Ammarnäs and Slettnes! We are all excited to get up there during what will be the last field season within my PhD project on the long-distance migration of Arctic seabirds, but hopefully/probably not the last one ever.

In Slettnes, our aim is to continue the work from previous years: retrap Arctic Skuas with geolocators and monitor their breeding activities. The geolocator tagging has revealed extreme migrations across the Atlantic and we are currently working on publishing these results. Very exciting stuff! Hence, we are hoping for a good breeding year, allowing us (Hans, Ingrid and me) to increase our sample size some more by recapturing many tagged individuals.

We have been concerned about the apparent large decline of the Arctic Skua colony over the past two decades (see this handout). Our hypothesisis is that the skuas suffer from the combined effects of an apparently bad food situation for seabirds and predation pressure by Red Foxes on the Arctic Skuas. Foxes do not only feed on skua eggs, but even manage to take adults, as was shown last year by a Red Fox photographed while holding a dead Arctic Skua (carrying a geolocator) presumably to its den. To better document the activities and prey spectrum of foxes, we will bring some camera traps that we plan to deploy at fox dens.

In Ammarnäs, Tim van der Meer, Christian Hoefs, Morrison Pot and Peter Antkowiak and others will take care of the work. They are preparing themselves for a busy year, as a lemming ‘increase-year’ is expected. This means lemming numbers are growing but not yet peaking. Lemmings were virtually absent during the last two years, causing Long-tailed Skuas to skip breeding. This year, skuas are expected to breed and the team will try to find as many nests, read colour-rings, and recapture birds with geolocators, as they can.

Otherwise, some interesting side-projects will be ran: Tim and Christian have the ambitions to start a study on Dotterel – a species so beautiful it is almost a miracle, and with an interesting migration. In addition, we are taking part in two circumpolar initiatives: one on migration of Dunlin (meaning some more geolocators should be retrieved) and the other on Arctic food web interactions (with nest predation of waders as a central theme).

The best bird of the season happened to be a mammal

This years’ field season has ended! Geert and Ingrid left Slettnes and Morrison and Rob left Ammarnäs on 2 July. Despite the poor breeding season for both skua species, some valuable data and observations have been collected. In total, 14 geolocators have been retrieved from Arctic Skuas, some with 1.5 years of data on some of them. The Long-tailed Skuas of Ammarnäs will have to wait another year before they can hand in their geolocators.

As I wrote in the previous blogpost, we have recaptured several Red-necked Phalaropes with loggers: 4 in Slettnes (1 female) and 4 in Ammarnäs (all females). One was deployed in 2014 and another in 2015 and they should have more than one year data. The high number of females is exciting (see my previous post).

Unfortunately, we have been unable to recapture any of the eight geolocators deployed last year on Dunlins, although we resighted three of them early in the season. High predation pressure, shown by both an artificial nest experiment (using quail eggs in fake nests to measure predation rate) and monitoring of Dunlin nests, is the likely explanation of this failure. Hopefully they return next year again!

On our last day in Ammarnäs, we went up to Björkfjället to finish the artificial nest experiment. We also wanted to see the Shorelarks, a species that has declined tremendously in the Swedish mountains. We were also hoping to catch a glimpse of the Wolverine that Martin saw a few days earlier. After a failed attempt to see this mysterious species, one of the large European mammalian predators, we didn’t really expect to find it. Then, at a distance of ca. 3km, I noted a Wolverine running downhill to a Reindeer carcass (with a White-tailed Eagle feeding on it)! We couldn’t believe our eyes! See the blurry video at long range below, where it is carrying a bone uphill. I couldn’t have dreamed up a better way to end the field season!

Phalarope females

In both Slettnes and Ammarnäs we have been successful in recapturing Red-necked Phalaropes carrying geolocators, including several females. Interestingly, one of these females from Ammarnäs carried a logger that Tim and I gave her in 2014. She has managed to escape our catching attempts for several years!

In previous years, we had more recaptures of males than females, which has everything to do with their breeding system: females ‘only’ lay eggs and leave the incubation and rearing of the chicks to the males. Males can thus be captured on the nest, which makes it easy to target a specific individual and allows several catching attempts, while females can only be captured by mist net. The increasing number of females in our sample allows us to have a first look at hypotheses pertaining to the earlier arrival at the breeding grounds of females compared to males, something we already hinted at in our JAB paper. Do they: 1) start spring migration earlier, 2) migrate faster or 3) winter closer to the breeding grounds than males? We haven’t analyzed the new females yet, but the tracks of our first three females (captured in previous years) confirm that females arrive – on average – five days earlier than males. They showed similar stopover and wintering areas as males, excluding option 3 (closer wintering grounds). Option 1 and 2 require more detailed analyses, but large overlap between the sexes in the timing of departure from the wintering area, suggest option 2 (faster migration) rather than 1 (early departure).

But how to (re)capture phalaropes? Ingrid compiled the video below, which Janne proudly presented at school!


Late breeding phalaropes in Ammarnäs

Normally, the Red-necked Phalaropes in Gelmetje start egg laying between 10-15 June, with some nest appearing a little later. This year, it took a long time before we found the first nest: an incomplete clutch on 21 June. Many pairs were still hanging around in pairs, apparently still in the process of finding a suitable nest location or still laying eggs. This gave us the opportunity to capture several pairs, thus with females that yet have to start laying. These females were all surprisingly heavy: mostly between 40 and 45g. Until now, we only recorded such weights at the end of their stay, around 10 July, when they are fattening for migration.

We have managed to recapture two phalaropes with geolocators: both females! Surprisingly, one of these carried a logger that Tim and I gave her back in 2014. Amazing! The battery was empty, so we will have to return the logger to the manufacturer to get the data. Can’t wait to see her tracks! I am all the more curious as we have only a small number of tracks of females. Because phalaropes have reversed sex roles (except laying eggs, females do not contribute to incubation or chick care), females leave earlier than males, but also arrive earlier. With the growing number of tracks of females, we can investigate how females accomplish this early arrival (we already discussed this briefly in our JAB paper). Do they winter closer by? Do they migrate faster, or do they depart from the winter sites earlier than males?

Another bird with a geolocator, a remarkably pale male, and the partner of the female with the 2014 geolocator, remains to be recaptured. We will try again tomorrow!

A satisfied Morrison looking at a male Red-necked Phalarope we captured last week.


Although we resighted three Dunlins with geolocators early in the season, we have failed to capture any of them. The valley where they were breeding last year is now virtually devoid of Dunlins (and Golden Plover). The last sighting of one of the geolocator-birds was in a flock of failed/non-breeders. Possibly, its nest was predated shortly after laying, when there was still a lot of snow. In Gelmetje, we did not see a single Dunlin this entire season, while the numbers in Björkfjället also appear low.

Sadly, Christian, Peter and Jesper, who have been of great help during the past two weeks, have left Ammarnäs. Only about a week to go for Morrison and me.