12 weeks of fieldwork along the Swedish coast

This years field season started May 1 and ran until mid-July. It was the result of collaboration with BirdLife Sweden. The main goal was to attach GPS loggers to Caspian terns and lesser black-backed gulls, both adults and juveniles.
The purpose?
To find out how/when/where they forage and migrate in order not only to increase our basic knowledge about these (in Sweden) endangered seabirds but also to better inform lawmakers on how and where to protect them. Some ‘bonus’ species where supplementary data was required from past years included great black-backed gull, herring gull, common and black guillemot, and razorbills. For this season I was based mainly in Fågelsundet, Uppland, Sweden but as the terns and gulls have colonies all over the country there were many long trips along the coast from Furö, Småland in the South to Rödkallen, Norrbotten, in the North.

The beginning of the season was spent brushing up on manuals for all the different loggers that are currently on birds and will be put on birds, manufacturing and mending traps, checking base station components, purchasing tools, etc. We got a shipment of over 45 GPS/GSM loggers in mid-May, all of which needed to be tested and prepped for deployment. I got some help with this from Martin Beal who was over for 2 weeks.
This seasons assortment of loggers, some old, some very new.

Fine-tuning harness attachment…who knew bananas would come in handy?
The first animals we caught and attached loggers to in May were some of the bonus species, great black-backed gull and herring gull as they are the earliest breeders of the bunch we work with. Great black-backed gulls are the largest birds I’ve ever worked with and I’m very grateful to Lennart Söderlund, local collaborator at Fågelsundet, who took the brunt of the blows delivered by their heavy beaks.      
One of this year’s bonus species, a great black-backed gull tagged and ready for release.
In late May it was time for the Caspian tern adults. This year 11 were caught in total on Furö, Långa Hållet, Fågelsundet, and Rödkallen. It was the first time adult Caspian terns were tagged with GPS loggers in Småland and Norrbotten and it will be very exciting to see where these Caspian terns spend their time foraging and what flyway(s) they use on migration. Here's a clip of a release of an adult Caspian tern with a logger.

Caspian tern in flight with logger.
Early to mid-June it was time for the lesser black-backed gull adults to be tagged. We had great success on Rödkallen, Norrbotten where 8 individuals (4 each of Caspian tern and lesser black-backed gulls) were caught on the same trip! This was the first time we were at this colony so this goes to show that inexperienced seabirds (i.e. never been caught before) are easier to catch than those that know what we’re up to.
Lars Harnemo, one of many collaborators, with adult lesser black-backed gull tagged on Rödkallen, Luleå.
In late June it was the Caspian tern chicks’ turn to get their loggers, at any rate the earliest ones. We want to tag the juveniles because we know so little about what they do when they leave the colony, whether they migrate to the same places and along the same routes as adults and where/when they are at their most vulnerable. 31 juveniles ended up being tagged. Last year most juveniles were predated before fledging so this year it will be interesting to see if survival is higher and where they end up going. At the very least we hope to see exactly which predator exerts the most pressure (most likely white-tailed sea eagle).
A Caspian tern chick just old enough for rings.
Claes Kyrk holding a juvenile Caspian tern old enough for rings and a logger, this time tagged on Furö, Småland.
Last but not least were common guillemots and razorbills on Gunnarstenarna, Stockholm. For these we had special GPS/GSM loggers capable of recording dives. They’re the last of the bunch and were tagged in July. Here we’re interested in their foraging movements during breeding, and whether both species use the same areas or partition the resources between them.
Mikael Odenstig on Gunnarstenarna with a common guillemot with GPS/GSM dive logger
As ever, the field season is full of surprises and helping out collaborators with their study species. Highlights included a Ural owl chick-ringing trip (I now understand why they’re called ‘slaguggla’ in Swedish) and the ringing of hundreds of starling chicks.
One of the perks of the field season is helping collaborators with their study species, here ringing of an arctic skua chick.
And here, a black guillemot chick.

So, to summarize, I spent 12 weeks in the field, applied 67 loggers of various sizes, shapes, capabilities and manufacturers to 6 species of seabird. It was a busy field season to say the least, and that is how it should be! Now all that remains is to kick back and, to paraphrase Dr. Seuss, see all the places they’ll go. 


Common Ringed Plovers: meeting an old friend!

Little ringed plover trapped in Vomb. 
This year's field season in the south (Skåne and Öland) has come to an end. As usual the target has been to catch breeding common ringed plovers to retrieve and deploy various data loggers on Öland. This year’s field season has also concerned retrieval of activity loggers from little ringed plovers around Lund. More about the aim of these specific project can be read about in a previous blogpost from 2017!

It was with great excitement I visited Ottenby the first time in mid-March to see if any plovers had returned yet. Usually the plovers are early and around March 10 many can be seen along the lighthouse road. However, spring had to wait for a while. The meadows were still covered by snow and ice, and only a handful of early arrivals were fighting the cold winds. 

Snow and ice along the light house road.
Then things moved forward swiftly and at last the birds spread out over the area. Males were displaying over their territories in the characteristic “butterfly” flights and the breeding season proceeded as usual. Only a couple of days of harsh weather covered the ground with snow again. But this did not hinder the duties of the plovers. The first nests were found in middle of April and from that point it was time for catching. Several individuals with activity loggers had returned. These loggers were deployed last year instead of the regular light level geolocators.

However, common ringed plovers are long lived and even if “regular” light level geolocators are not deployed anymore, old ones may return. In order to recognize the plovers in the field, each caught bird are individually marked with color rings for easy identification in the field. One female was immediately identified as one that was breeding and equipped with a geolocator in the area in 2013. Remarkably the logger was still on her! Five years have passed! Five years back and forth from the breeding and wintering ground. Unfortunately, the battery in such device do not last for that long, but at least two autumn migration and one spring migration should have been recorded. 

A true hero: this female was logged in 2013 and only this year I was able to catch her.
Soon after the catching at Ottenby was initiated there were time for the little ringed plovers around Lund to start with their breeding choirs. Soon after the first observations we started to search for active nests, which is not easy to find. Last year 22 activity loggers were deployed. The field season was a big success! Seven activity loggers were retrieved, among them one from 2016. 

Well camouflaged little ringed plover nest

This was the end of chapter one of this year’s field season. Now waits a second spring in the north. First stop will be Kalix and a small island in the Happaranda archipelago, Malören, and second will be Abisko.

/Linus Hedh


Expedition to the High Arctic desert – Henrik Krøyer Holme July 2017

In late June a party of three: Morten Frederiksen (Aarhus University, DK), Arne Andersson (CAnMove) and Jannie Fries Linnebjerg (Former CAnMove, now Aarhus University) went to the High Arctic desert to participate in a project initiated by Aarhus University. The aim was to investigate the foraging areas of the two Arctic seabird species: Ivory gull (Pagophila eburnea) and Sabine’s gull (Xema sabini).

These two species only breed in the Arctic, so in order to find them, we had to postpone the Scandinavian summer-life and move to a small caravan in Northeast Greenland for three weeks in July. Ivory gulls and Sabine’s gulls breed in small colonies and are known to breed on the islands of Henrik Krøyer Holme, approx. 15 km off the mainland of Northeast Greenland. The area is extremely remote, which means logistic challenges, such as chartered flights from Svalbard to the Danish airbase Station Nord, and airlift with a small Twin Otter aircraft to the study site.
The team is ready for take-off from Station Nord to Henrik Krøyer Holme.
The orange caravan (the camp site), kindly lent to us by the Danish Meteorological Institute.
Henrik Krøyer Holme is located close to the North East Water polynya, or area of recurring open water in the pack ice. However, in some years the islands remain linked to the mainland by fast ice far into the summer, and this was the case in 2017. This meant that terrestrial predators such as Arctic foxes (Alopex lagopus) had access to the islands. Many birds choose not to risk breeding under these conditions, and instead wait for a better year.

This was the case for the ivory gulls, which did not breed at all on the islands this year, but fortunately, (at least for us!) the Sabine’s gulls struggled on with their breeding. This gave us the opportunity to deploy GPS loggers on eight breeding birds, and we could follow their whereabouts by remotely downloading positions from the loggers.

Several days were spent wandering about the island, trying to locate the breeding birds.
The main island is about 10 km2, so there was quite a lot of ground to cover.

Catching the birds turned out to be more difficult than expected, so a lot of time and energy went into
modifying traps and trying all sorts of different catching methods.

A Sabine’s gull equipped with a GPS data logger on a leg-loop harness.
Along with the work, there was of course also time to enjoy the harsh but exotic polar landscape and wildlife, like spotting walruses (Odobenus rosmarus) and narwhals (Monodon monoceros) close to the ice edge. And the Arctic fox, although making life difficult for birds and scientists, is very cute!
Arctic fox with an Eider egg.

Armed to the teeth. We never saw a polar bear, but did have one visiting our
camp when we were out in the field.

Polar bears are normally very curious and cautious when encountering new things.
Polar bears do not like raw oats…
Nor toilet bins…
And our rubbish was not that interesting to the polar bear either…luckily.

The photographer is busy shooting eiders and does not see the polar bear in the background...

The landscape at Henrik Krøyer Holme is proper Arctic desert, with very little vegetation.
Only six species of flowering plants have been registered on Henrik Krøyer Holme.
One of them is the Arctic poppy (Papaver radicatum
Arne trying to get a close-up picture of an angry Arctic tern.

The rough terrain was hard on our boots. After four days, Mortens sole had pretty
much come off the boot and he had to screw it back on.

Three interesting and nice weeks had come to an end. And I think we were all slightly relieved when the plane finally arrived :)

Arne & Jannie


A summary of the summer with nightjars (2:2)

The nightjar´s plumage lets the bird blend in in the habitat
Last week marked the end of a quiet successful field season with the nightjars in Småland, SE Sweden. We mainly experienced relatively calm, dry, and warm summer weather which boosted the activity of the nightjars as well as provided good trapping conditions throughout the season. As a result, we managed to retrieve eight activity loggers to add to the one mentioned in an earlier blog post.
We did also retrieve five GPS-tags containing migration data with high spatial resolution. We have in an earlier study based on light logger-derived data gained knowledge about the large-scale temporal and spatial migration pattern of our birds. The GPS-tags will allow us to go one step further and look into the birds´ decision making regarding e.g. departure decision, route choice and wind selectivity along the entire migration route.
As the nightjars are about to set out for the journey to their nonbreeding ranges we will stay behind and begin the exiting work analysing the retrieved data.

A nightjar demonstrating its huge gape



Common Ringed Plovers from south to north (2:2)

The field station with the lake Latnjajaure in the background, still covered with ice and snow.
Loading up a helicopter with three weeks worth of supply and field equipment is always exiting. Loading one that it’s heading to a place where data loggers sitting on Common Ringed Plovers is even more exiting. Except for my self three other people were preparing for getting up to Latnjajaure (jaure means lake in Sami) in Abisko, working with everything from plant phenology to gas emissions in post-permafrost sites. With the mountains in our bearing we took off from the helipad in Abisko on the 14th of June.

A newly ringed Common Ringed Plover with an activity logger visible on the back.

The reason for my stay was to catch Common Ringed Plovers. As mentioned above to retrieve geolocators, but also deploy new ones. In an earlier blog post from June 13th I mentioned that this year I use activity loggers. This gives the opportunity to in better detail describe a number of aspects of flight performance in the Common Ringed Plover, such as duration of individual flight bouts and the number of flights and consecutive stop-overs. The overall aim is to compare these aspects between populations migrating different distances and breeding/wintering in different climate zones. The population this field trip is aimed for breeds close to one of the Abisko Scientific Research Stations/Swedish Polar Research Secretariat’s field station in Latnjavaggi (vaggí means valley) approximately 15 km west of Abisko. 

A Common Ringed Plover nest beautifully placed among flowering Alpine Azela (krypljung) and Dwarf Willow (dvärgvide).
Despite the present warm weather down in Abisko there was as usually much snow left up around the lake. This year was particularly late and much of the previous breeding sites were covered with snow. During the first days I was somewhat worried that the plovers had given up the site already in the beginning of June, when they usually arrive. The only two individuals observed during the first two days were one unmarked (new) and an old friend who has had a territory close to the field station for the three subsequent years. However, this season he ended up alone.  Slowly however, more individuals showed up. One male I was very exited to see again. Also he has kept his territory since the beginning of the project in 2014. What makes him extra special is that he used the same exact nest scrape for three years in a row. This year there was a new scrape, but located only ten meters from the previous one.

Measuring the wing area, one of the many measurements taken.
The first bird was caught short after incubation had started. Following that most birds in the valley where caught except for the lonely male. Right after midsummer several waders were seen on the lakeshore. Among them the first Ruffs ever observed in Latnjajaure, a small flock of Common Ringed Plover and the first Dotterel for the season. This individual came flying on high altitude through the valley. That behaviour together with the flocking behaviour of the plovers made me draw the conclusion that these were failed breeders moving towards initial staging areas.

Not long before the first helicopter back to Abisko was going I stumbled upon a new nest. It turned out that both the male and the female was ringed and logger at a previous year. The female carried a logger that were deployed in 2015, which means that it could potentially contain data from two consecutive years! Due to these and a couple of days of bad weather, which did not give any opportunity for trapping, I missed the helicopter. 
Bad weather in the summer could mean snow in the mountains.
After a couple of trapping attempts a few days later I managed to retrieve both loggers. After making sure, to the best of my ability, that there was no more breeding pairs I hiked back to Abisko with a total of four geolocators to be analysed when coming back to Lund.

The fantastic bird life in the area is not the only thing that amazes. This is a Diapensia lapponica, a resistant pincushon plant that each year survives thick snow cover, freezing and thawing during the flowering period, and trample by reindeers. This particular clone is a real champion since it is, judged by the size, about 800 years old. Maybe it started its life during Marco Polo adventures in eastern Asia?

 Amazing morning at Torneträsk, in Abisko, after coming down from Latnjajaure.

/Linus Hedh


Visiting the Caspian Terns of Ostrobothnia

The end of May is high time for incubation amongst the Caspian Terns of the Baltic. So with this knowledge in hand I headed for Ostrobothnia, to the Kristinestad archipelago to meet up with the resident tern expert and collaborator, Patrik Byholm. This archipelago has a markedly high density of breeding Caspian terns with a colony of about 70 breeding pairs and some 25 solitary breeding pairs in the area.
The Kristinestad archipelago boasts a nice diversity of the classic Baltic seabirds such as Common Eiders, Ruddy Turnstones, and White-tailed Eagles as well as healthy contingency of the ever-charismatic Little Gull
The goal of the trip was to catch adult terns for the attachment of GPS-GSM loggers for revealing migration and habitat use movements. To begin the season we had 4 birds with working tags returning and setting up their breeding attempts, each on their respective islands. So our task was to catch the un-tagged partners of these tagged individuals to be able to then later tag the young as well to hopefully get the successful migratory movements of an entire family group. Exciting stuff, but first things first we had to catch the un-tagged partners. To our good fortune a newly formed pair of terns just so happened to be two birds that were already tagged! Two-birds-one-stone kind of luck!

Ingströmsberget; a rather typical breeding island for a solitary pair of Caspian Terns. Other inhabitants include Great Black-backed Gulls, and Barnacle Geese.
The first day out was an unequivocal success, with both the un-marked adults being captured and tagged. This was a relief as capturing the right individual on the first attempt greatly reduces the stress for all parties involved.

Patrik releases our first individual Caspian Tern of the season, complete with a new GSM backpack.
Not all days are made for sea-faring! This is especially true when the work involves landing on exposed islands in high winds. So our off days were spent in the forest checking a collection of pygmy-owl boxes that Patrik had set up back when he was still in high school. This provided a wonderful opportunity to take full advantage of my time and build a broad perspective the bird life of the region, from the eider of the outermost islands, to the red-breasted flycatcher of the innermost forest patches. A welcomed contrast!
A partial clutch of few day old pygmy owl nestlings. The large feathers are leftovers from avian prey brought back to the nest by the male. These end up becoming insulating nest-lining!)

When the sun returned, as did we to the sea. We continued surveying islands for possible Caspian Tern breeding activity and also set up a remote camera on the colony island of Gubbstenen. These cameras allow for remote re-sighting of ringed adults breeding on the colony, as well as identification of predation events by eagles, ravens and the like.

The remote camera gets settled in amongst the breeding terns of the Gubbstenen colony.
In the last few days of my time in the archipelago we had 2 loggers left to deploy so we decided to try and capture a new pair. We identified an apparently solitary breeding pair on an island that seemed to lend itself to expedient trapping. So we gave it a shot. The first day went without a hitch, with the target bird captured and the tag deployed. Thereafter the pair was given a days rest so as to avoid disturbing their incubation too much. Upon our subsequent return to the island we realized that the pair was in fact not alone on the island but that two other pairs had set up shop and laid eggs! It had become a veritable mini-colony. With the title of ‘solitary pair’ defenestrated, we decided the information would be of no less value and went ahead and captured the remaining partner of the original pair.
A GPS-GSM logger that will communicate with the cellular network to provide information on the birds whereabouts is looped around bird’s legs and loose ends are sewed up for secure fitting.

With all GPS-units deployed and many amazing birds and environments observed I hopped on the ferry back to Sweden, where other tern-inhabited archipelagos beckoned!

Baltic glory

- Martin Beal