Another non-breeding year

An ‘increase year’ was expected for the lemmings and other rodents in Ammarnäs. In such years, rodent populations slowly recover from a crash and build up towards a next peak. At such intermediate rodent densities, Long-tailed Skuas in Ammarnäs usually breed at least in the best area: Raurejaure.

Today we (Morrison Pot and I) crossed the tree line in Ammarnäs for the first time this season. After only about ten minutes the disappointment already sank in: this was going to be another non-breeding year for the Long-tailed Skuas. The second in a row, thereby repeating the pattern of 2012/2013. A pair was sitting quietly, occasionally picking some berries or insects. At this date, one of the partners should be incubating an egg…

The good news is that we resighted several colour-ringed skuas and all were still carrying their geolocators. Two birds have apparently switched partner, meaning two ‘famous’ birds are now missing: KJ, known for its extremely aggressive nest defense, and KM, a bird that we used to see on every visit to Raurejaure, as it bred at the ‘entrance’ of the area.

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NR had apparently changed it partner for an unringed bird, which was KM since 2014. Also KR apparently switched partner, as KJ was replaced by an unringed bird.

Another promising observation is that of a male Dunlin carrying a geolocator! Hopefully we will be able to recapture this bird. This bird is part of a big circumpolar effort to track the migrations of all subspecies of Dunlin – there are many!

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Dunlin with geolocator taking a nap.
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A new field season!

Today, the 2017 field season started in Slettnes. After arrival, Hans and Rinse already had a first quick look in the colony and resighted some Arctic Skuas carrying geolocators. There seems to be lots of snow up in the mountains – not only in Finnmark but also in Ammarnäs. Morrison and I will not arrive in Ammarnäs until next week, so hopefully the snow will melt quickly in the coming days…

Our main aim is to recapture Arctic and Long-tailed Skuas, Red-necked Phalaropes and also Dunlins carrying geolocators so we can map their movement since the last year. Whether we can retrap them depends on whether they return to the same spot and whether or not they breed this year. We will know soon!

New paper on ecology of Golden plover chicks

Machín et al. 2017

We are very happy to share with you the publication of our last paper: “Habitat selection, diet and food availability of European Golden Plover Pluvialis apricaria chicks in Swedish Lapland”. It has been a long way but it is finally here!! Click here!

This study shows the prey preferences of Golden plover chicks in the alpine tundra in northern Sweden, as well as their habitat use and food availability. Interestingly, a peak of bibios (Bibionidae, also known as marsh flies) at the end of the season in 2011, made the chicks change their diet to practically only feed on them, so we highlight the importance of this seasonal effects on the food availability, ergo diet, survival and growth of the chicks. We also show that plovers in Lapland do not have Tipulids (Crane Flies) as their favorite prey, as it happens to be in another population (UK), where chicks rely on them.

We are recently working on the second part of this story, analysing which factors influence the growth of the chicks. Hope to show it to you soon!

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New paper out on consistency in Long-tailed Skua movements

One of the aspects of migration that continues to fascinate people, is the ability of individuals to return to the same spot (either a wintering or breeding site), year after year. Such site-faithful individuals can be relatively easy to record, but recording site INfidelity has always been a major difficulty: if a bird doesn’t turn up where it was last year, you didn’t detect it, or it either moved or died. Tracking studies do not suffer from these problems, and now that tracking studies are producing data from individuals over multiple years, we can finally study the degree of consistency in routes and site selection over the entire annual cycle.

Recently, we published a paper reporting on this subject in Long-tailed Skuas. The paper is published in a theme section on ‘individual variation in migration and foraging in seabirds’ of the journal Marine Ecology Progress Series and can be accessed here. Don’t forget to click on the supplement, which contains a nice animation of the tracks!

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Over half of the geolocator data used for this study was obtained from the Long-tailed Skuas in Ammarnäs, with the other part coming from colleagues working in Greenland and Svalbard. Together, we mapped nearly a hundred annual migrations of 38 individual Long-tailed Skuas. Several individuals were tracked over four or five years.

The emerging pattern is remarkable. While Long-tailed Skuas are generally faithful to their route from the previous year, they occasionally choose to go somewhere completely different. The highest consistency is found in early winter, around the time when they arrive at the main wintering area. After mid-winter, individuals start to deviate from their previous route. Such deviations can be huge: one individual went to the Benguela Current in four years, but after arriving in the second and fourth year, it simply flew 5200 km across the Atlantic to spend the remainder of the winter in the Falkland Current, near Argentina! In both occasions it used virtually the same route to get there and ended up in the same area. These patterns suggest they first check out local conditions before deciding where to go subsequently: either continue on their usual route, or on some alternative.

We also showed that individuals can show both ends of the spectrum: individuals showing ‘flexibility’ (deviations from their previous route), are not necessarily always flexible, they can also follow the same route twice.

Slettnes: successfull field season despite low breeding numbers

DSC01292The season is coming to an end. At least for us staying in the area. There are still skuas with chicks, although not many. In total we recaptured 19 loggered Arctic Skuas and retreived their migration information over the last year. We gave all these birds new loggers and caught an additional 7 birds that also got loggers. Quite unexpectedly we got yet another logger back. The other day we met a British couple that were staying in the area already for a week. They were making a film on the nesting and hatching of a red-throated diver nest. They found one of our loggers with a bit of the blue ring attached. They picked it up but later put it down on a tussock, because they thought we put it there intentionally for some kind of measurements.

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our heroes: the UK couple with “the precious”

Then they ran into Barbara Ganter and Hans-Ulrich Rosner, our fellow researchers working on Dunlin in the area, who told them that we would be extremely interested in getting the logger back!When we met the couple they had just spent 2 hours searching for ‘the precious’, but could not find it back. Together we searched for another hour systematically and checked every tussock in an area the size of a quarter football field. Just at the point when we were about to give up, one of them found it back!! The couple was so relieved! And they were the heroes of our day of course! That brings our total to 20! Last year we ringed 53 birds. It is clear that a large part of those either did not return, did not breed, or whose eggs hatched before we had a chance to catch them. One of the things we will dive into in the analyses if the El Nino may have had any effect on the early breeding season for some pairs or the lack of breeding for other pairs.

Left: Four-year-old Arctic Skua with still some barred feathers. Right: The most exciting time of the day: reading out retrieved loggers!
Left: Four-year-old Arctic Skua with still some barred feathers. Right: The most exciting time of the day: reading out retrieved loggers!

We are also seeing back the first birds that were ringed as chicks in 2014. That was a very good breeding year resulting in some 100 chicks ringed of which a large proportion also colour ringed. They do not breed yet, but hang around and sometimes seem to team up with a breeding pair.

In contrast to other areas in Europe we had extremely good and warm weather. Yesterday it was even 27 degrees! The caretaker of the lighthouse told us that no one in the nearby village Gamvik could remember that such temperatures were ever recorded before! Even swimming in the Barents Sea is not an achievement anymore.

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Lighthouse in Mediterranean weather!
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Announcement of talk by Hans.

On last Sunday Hans gave a presentation at the lighthouse for locals of Gamvik and tourists. It was well visited and it was striking to notice that people do not seem to be aware that they are in a very special place, home to the largest colony of Arctic Skuas! We are leaving Slettnes now and will return next year to meet up with our world travellers once more.

 

couple of dark phase skuas both with loggers
Pair of dark phase Arctic Skuas, both with loggers.

Leaving Ammarnäs

After only three weeks of fieldwork, we are leaving Ammarnäs today already. With no breeding skuas and lower-than-usual abundance of some waders, including Red-necked Phalaropes, it was a rather short and ‘slow’ field season. Even so, we have been successful in deploying 14 new geolocators on phalaropes, and, more importantly, we managed to recapture four of them; two males and two females. I will dedicate the coming period to the analysis of these tracks in comparison with those obtained at other sites between Greenland and Tobseda (or Yamal, if Jasper has been successful!).

Catching the last five phalaropes has been a rather wet experience. For some reason, the few small flocks of phalarope females choose to occupy the least accessible ponds: those with extensive buoyant vegetation mats. Its easy to sink deep into this… We are using adjusted rubber boots to enter these ponds, with holes in it to let the water out. And we take off our pants to keep them dry… But in several cases this was not enough: we were sinking waist-deep into the mud and vegetation. The last phalarope to be captured took some extra effort. Christian eventually swam to it in order to flush it into the mistnet, successfully!

During the last few days, we ringed some chicks of Red-necked Phalaropes, Ruff, Redshank and Common Sandpiper. Another highlight for all of us was a recently hatched Common Cuckoo chick in a Meadow Pipit nest. The little monster had already showed the door to the Meadow Pipit chicks, which lay dead outside the entrance.

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One of the lakes in Gelmetje with floating vegetation and Red-necked Phalaropes.
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Ruff chicks!

Food shortage at Slettnes

vole regurgitated by by skua
vole regurgitated by skua
very tame Arctic skua
very tame Arctic skua

You wouldn’t think we are at 71°N, with today’s temperature: 22°C, warmer even than in Rome and hardly any wind. This means mosquito bonanza!

Nearly all Arctic Skuas have hatched by now, but we have seen no chicks older than 1 or 2 days and several nests with dead chicks. The feeling that the food situation is bleak this year settles in more and more. Arctic Terns are not breeding either and one skua threw up a vole. The outskirts of the colony are either vacant or birds hang around but have not produced eggs.

The only breeding pair of Great Skuas lost their chicks within a few days, another sign that even they cannot feed their chicks. The logger information shows that the breeding Arctic skuas go out to sea sometimes for more than a full day leaving their partner at the nest.

In the meantime we managed to recapture 19 individuals from last year. It was a struggle against time, since many nests hatched so early. Catching them on a nest with a chick does not seem to work at all. Apparently the chicks need less brooding than e.g. waders and if we take the chick away they won’t return to the nest to sit on the egg left. Also we found out there are at least 50 ways why the catching fails, despite the fact that the snare system works well in principle. Either the battery power is too low, the bird simply escapes, the distance is too far for the remote control, the bird won’t sit down or in the worst case, the coil of the snare is broken.

The loggered birds showed the same variation as last year, wintering in south-America, South Africa, the Caribean, West Africa and one even off the coast of Spain. Of the four couples we recaptured the partners each went their own way, so they probably meet each other only here on the breeding grounds again.

On the Red-necked Phalarope front we also had some successes: 4 recaptured birds. One loggered bird lost its logger and one lost its nest, making catching impossible. Three of them went to the Arabian Sea, one even as far south as Mozambique. Of two of the birds we had tracks from last year. The tracks in the consecutive years were nearly copies!

dead Arctic skua chick
dead Arctic skua chick found in a nest