30 October: Robs’ public defence

Dear all,

After five PhD-years, 13 field seasons and walking several thousand kilometres across the tundras of Ammarnas and Slettnes, I am very happy to announce that on 30 October, 11 AM, I will defend my PhD thesis entitled ‘Seabirds linking Arctic and ocean’ in the aula of the Wageningen University, Generaal Foulkesweg 1, Wageningen.

This is a public event, so anyone interested in skuas and phalaropes, or seabirds in general, is warmly invited!

Thanks to all who have helped me to get here. It has been an incredible journey!

All the best, Rob


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.

Final sweep up at Slettnes

The short field season has ended at Slettnes, both practically – because we left the area after two weeks – but sadly also for the birds, because we must conclude that also the 2019 breeding season failed completely. None of the colour-ringed birds we resighted managed to prevent foxes from taking their eggs, but also unknown birds (to us) failed to do so. Because working in the field and approaching nests always carries the risk of leaving traces which might lead potential predators to nests, we also recorded nest fates of nest that we did not visit, but only observed from a distance. Also those nests disappeared within a few days after laying the first egg.


Red fox captured by a camera trap
Hans holding ‘Spotty’, the dark phase skua with the typical white spots on its wings

So what did we learn from this season? The plans of this final sweep up season for Rob’s PhD project was to try to recapture as many as possible of the loggers that we put out in 2014-2016 and still had not recaptured, read colour rings to see who returned, and to get a general impression of the success of the breeding season. Well the breeding season was (again) quite dramatic, due to low food (fish), not only near Slettnes, but also in the Varangerfjord, where the arctic terns and kittiwakes apparently left their colonies due to food shortage (as we heard from Tomas Aarvak of Birdlife Norway). Our birds laid relatively small eggs and apart from two pairs, all clutches consisted of one egg only. Either because they were not able to produce more than one egg, or their nests were already predated before they managed to lay the second one. In combination with the high fox activity, not a single chick was produced this year. With a lot of effort we managed to recapture six birds and relieve them from their loggers, and we identified 37 other individuals by their colour rings, that will contribute to estimates of annual adult survival rates. Survival in these skuas is high; a typical adult life span is about eight years. As to replace itself each bird has to produce only one son or daughter in this period that becomes a breeding adult. This means that even a few lost breeding years in a row may not be a problem for the population. However, every once in a while the birds should be successful and in such a year all things should come together: enough food, low predation rates and enough birds in the colony to enable a successful defence against predators. With the declining number of breeding pairs at Slettnes such a window of opportunity is urgently needed. Here the last truly good year is now as long ago as 2014. Indeed, this season we encountered several skuas ringed as chicks in 2014 for the first time as adults in the colony. Fingers crossed that these may breed successfully in the years to come…

ZA, ringed as a chick in 2014 and now returned to the colony

Late year at Slettnes Arctic skua colony

Late season at Slettnes

Sometimes a biologist feels like Sherlock Holmes. Every breeding year in the Arctic is different, but how come the skuas are so late this year? We are here for over a week now and only today at 19th June the majority of the skuas start to lay eggs, roughly two weeks later than on average. Did they really only start now or did they try before, but were their eggs taken by foxes or other predators and is this the second wave? It is difficult to find out, but given the high predation rates the latter may well be the case. Also the food situation does not seem to be brilliant, with low feeding concentrations of seabirds at sea indicating that there is not a lot of fish out there. It does not resemble last year at all  when masses of birds were feeding out at sea.

To discover who is taking skua eggs we placed eight camera traps at different nests. The camera responds to movement, that can be either cause by the incubating bird, a predator or a reindeer moving through the area. Somehow the camera traps seem to protect the nests as we have the impression that nests with camera traps survive longer than those without. At the only one (so far) in which the egg disappeared the picture says it all and gives a nice summary of life at Slettnes: the midnight sun, a skua taking off and a red fox stealing the egg in the middle of the night. If skuas have no nest, catching them to retrieve loggers is practically impossible. But despite high predation rates, we managed to catch back three birds, of which one has a logger that contains data since 2015! Now that more birds with loggers started breeding we have more opportunities to retrieve loggers of birds that we failed to catch last year because they lost their clutch.

caught by cameratrap: fox taking egg of Arctic skua nest in the reflection of the midnight sun. Time of the crime: 01:38


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.

PhD defence in Groningen

Dear all,

I write this post to invite you to the defence of my thesis “A golden life: Ecology of breeding waders in low Lapland” that will take place next 7th of September at 11h in the Academy building of Groningen (Broerstraat 5).

I am very happy to have arrived to this point and I would love to share it with you.

It will be a pleasure to see anyone interested on the topic there!


New paper out on primary moult in northern hemisphere skuas

A paper I wrote with Rohan Clarke, Peter Pyle and Kees Camphuysen has been accepted for publication in The Auk, the journal of the American Ornithological Society! It can be downloaded here and is titled “Timing and duration of primary molt in Northern Hemisphere skuas and jaegers”.

The paper presents estimates for primary moult timing and duration in all four northern hemisphere skuas: Great, Pomarine, Arctic and Long-tailed Skua, including multiple age-classes (for as far as they are identifiable…). Moult data is difficult to obtain for oceanic wanderers like skuas, as they perform their moult at sea where fieldwork is costly and capturing seabirds is ‘challenging’, to say the least. Recently, people realized that molt data can be obtained from (digital) photography. With a growing popularity of bird watching, bird photographing, pelagic birding trips, and the sharing of large numbers of images over the internet, a very comfortable and cheap way to collect data has emerged. Over the past years, we collected photos of nearly 2000 individual skuas, photographed at sea or near-shore by about 600 photographers. Many photos were found at online sighting portals like www.waarneming.nl and ebird.org, but we were also greatly helped by many people sharing their pictures through e-mail. From these pics, we inferred the primary moult score and subsequently estimated three moult parameters: the mean start date of moult, the standard deviation in this start date, and the mean moult duration.

What we found in this study is that, as expected, larger species took longer to moult, but this also meant that larger species had a hard timing in avoiding temporal overlap between moult and migration. In general, migratory birds avoid overlap of moult and migration, but we found that Great Skua moult throughout its autumn migration! A rare strategy, possibly facilitated by a very low migration speed through an area with good food availability. Another interesting find is that among the three smaller species, their very first moult cycle took longer than later ones. As soon as they started migrating, moult cycles would run more or less parallel to adults. We suggest that this shorter moult cycle reflects a time constraint set by migration.

This study would not have been possible without all photographers willing to share their pictures. A huge thanks to them!