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!
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!
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!
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.
We are back at our scenic study area in Slettnes in the far north of Norway. ‘We’ in this case consist of: Hans Schekkerman, Rinse van Vliet, Marc van Roomen, Janne Schekkerman, Geert Aarts and Ingrid Tulp. Goals for this year is to retrap as many Arctic Skuas and red-necked Phalaropes, with geolocators loaded with data of their whereabouts from the previous year(s), as possible. Last year was extremely early with first skua nests hatching already at 12 June, this year is the opposite. First nests are expected to hatch only at 28th of June. There was an exceptional load of snow in Northern Norway this year, the vegetation is two weeks behind a ‘normal’ schedule. But given that there is enough snow free area at Slettnes, this cannot be the reason for the late start of the skuas. Hopefully the loggers will reveal what kept them so long before arriving here. Up to now we only managed to recapture 4 skuas. We still miss a lot of known birds. Up to now we resighted 37 of the total of 73 birds colour-ringed in the previous years. Many of them still need to start breeding. Yesterday (13 June) we found several one egg nests that just started. All in all we have the impression that breeding numbers are considerably lower here in Slettnes in the period we are coming here (since 2014) than they were in 1998, when the last inventory was carried out. To check this idea, we are going to do a colony wide census this year, something we did not do systematically yet in the recent years.
The red-necked phalaropes are at a more normal time schedule. Groups of males and females are on the lakes, twittering and chasing each other. Hormones are swarming around along the lakes edges! The first birds already have nests. We use a new method to catch the swimming phalaropes: a mistnet held flat between two persons immerged in the water just below the water surface, wait until the birds swim over it and then quickly lift the net from the water and flapping the bird! Yesterday we caught five birds within ten minutes this way. We already managed to retrap three loggered males (of which one unfortunately lost his logger).
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.
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!
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!