Black-tailed Godwits signal drought resistant meadows in the hot summer of 2018

Ruth Howison, Jos Hooijmeijer and Theunis Piersma report:

The Netherlands is home to over 85% of the northwest European breeding population of the continental subspecies of Black-tailed Godwits Limosa limosa limosa (Fig. 1). Black-tailed Godwits are an iconic meadow bird and the national bird species of The Netherlands. The Dutch population originated in the wet grassland meadows created by many generations of Dutch dairy farmers (Beintema 1986). However, due to intensification of agricultural practices (Kentie et al. 2015, Howison et al. 2018), the population has declined by over 75% since the first population size estimates in the 1960s (Kentie et al. 2016)

Howison Fig1
Figure 1. A Black-tailed Godwit, individually marked with colour-rings, issuing alarm calls to nearby chicks from an elevated position. (Photo: R.A. Howison).

For the past 15 years, the RUG team ‘Skries’ (most years consisting of ca. 10 paid field technicians and ca. 10 students and international volunteers) has carefully monitored godwit population events (establishment, nest locations, egg and chick production and postbreeding movements) within what is now a 11,400 ha study area in southwest Friesland (municipality Súdwest Fryslân). In addition, the locations of a small number of black-tailed godwits population have been tracked with solar PTT satellite transmitters (Microwave Telemetry, Columbia, MD).

In 2018, Europe experienced one of the hottest summers on record. Extreme temperature anomalys bring with them extreme weather as heat waves, droughts, and floods, which negatively impact agricultural as well as natural systems. For southwest Friesland, air temperatures in early March dipped below average, freezing most of the countryside (Fig. 2). However, soon May and June followed with maximum daily temperatures exceeding the upper limits of the long term average calculated over the past 28 years.

Howison Fig2
Figure 2. Daily temperatures (oC) from 1 January until 24 August 2018 plotted against the long-term average ±SD (from 1990 to 2018), obtained from Stavoren, The Netherlands.

Using vegetation indices measured at 16-day intervals by satellite imagery (see Howison et al. 2018 for methods) at the level of fields, we tracked the response of the grassland habitat in the province of Friesland. We compared the situation on 10 May 2018 (Fig. 3a), the moment when grass biomass is high, i.e. just before the widescale mowing, with the situation on 14 August 2018 (Fig. 3b), i.e. when the negative impacts of the drought on the vegetation were most evident. Based on this comparison, we mapped (Fig. 3c) where the impact of drought was light or even absent, i.e. where plant growth increased (Green), where drought had a negative impact, i.e. the vegetation index had decreased (Red), and where vegetation showed little change (Yellow).

Howison Fig3
Figure 3. Tracking habitat change with vegetation indices (MODIS EVI) between (a) 10 May 2018, (b) 14 August 2018, (c) Log change ratio between the two dates, where Red indicates a decrease in greenness, Yellow indicates little or no change, and Green indicates an increase, (d) The spatial distribution of Black-tailed Godwits, overlaying the log change ratio, during the postbreeding period 2018 (after 15 June 2018).

We then compared two measures of godwit distribution with this quantitative assessment of the impact of drought on the grassy vegetation. (1) By weekly counts of all godwits in all 3014 fields in our study area, we measured the godwit distribution during territory establishment, egg-laying and early incubation (26 March to 22 April 2018). (2) On the basis of the locations of individually colour-marked birds and godwits tagged with satellite transmitters, we quantified the distribution of postbreeding godwits fuelling up for southward migration from 15 June to 15 August (Fig. 3d).

During territory establishment and early nesting, when their movements are necessarily constrained, the godwits in southwest Friesland occurred on meadows which suffered slightly, yet significantly, less from drought than unused grasslands (Fig. 4). However, during the postbreeding period, the godwits concentrated at meadows where little change in plant growth had occurred during the drought (Fig. 3d & Fig. 4). We note also that southwest Friesland suffered more from the drought than Friesland as a whole (comparison of the two right bar in Fig. 4).

Howison Fig4
Figure 4. The effect of the summer drought measured as a loss in greenness (y-axis) was less in fields in southwest (ZW) Friesland used by godwits in the establishment and early nesting period (first column) than in southwest Friesland as a whole (third column). This effect was quite a bit stronger in the distribution of postbreeding godwits (second column). Note also that the effects of drought were more severe in southwest Friesland (third column) than in Friesland as a whole (fourth column). If the capital letters above the bars are different, the categories are statistically significantly different from each other.

The preference of Black-tailed Godwits for fields in southwest Friesland that, later in summer, suffered the least from the drought of 2018, suggests that the godwits are indicating fields with healthy ‘working’ soils, where capillary processes allow the groundwater to reach the plants even when water tables are low. Godwits indicate drought-resilient grasslands.


Beintema, A. J. (1986) Man-made Polders in The Netherlands: A traditional habitat for shorebirds. Colonial Waterbirds 9, 196-202.

Howison, R. A., Piersma, T., Kentie, R., Hooijmeijer, J. C. E. W. & Olff, H. (2018) Quantifying landscape-level land-use intensity patterns through radar-based remote sensing. Journal of Applied Ecology 55, 1276-1287.

Kentie, R., Both, C., Hooijmeijer, J. C. E. W. & Piersma, T. (2015) Management of modern agricultural landscapes increases nest predation rates in Black‐tailed Godwits Limosa limosa. Ibis 157, 614-625.

Kentie, R., Senner, N. R., Hooijmeijer, J. C. E. W., Márquez-Ferrando, R., Masero, J. A., Verhoeven, M. A. & Piersma, T. (2016) Estimating the size of the Dutch breeding population of Continental Black-tailed Godwits from 2007 – 2015 using resighting data from spring staging sites. Ardea 104, 213-225.




An update on the progress of the exceptionally snow-rich breeding season in northeast Greenland

On 20 July 2018, Jeroen Reneerkens reported:

I recently wrote about the excessive amount of snow in northeast Greenland and how shorebirds are struggling to reproduce, and some risk-takers to survive, this year.  My blog received a lot of attention: it was also posted on the popular birding webpage Birdguides, Scientific American wrote an article about it and I was invited to the studio of ‘Vroege Vogels’ for a live interview on Dutch national radio.

Now that it is mid-July, which is when usually the majority of Sanderling and other shorebirds in northeast Greenland hatch, I thought that it would be appropriate to write an update of the situation, as well as answer some questions I was asked.

Was this a record late snow melt? How unusual is the situation?

The time of onset and the progress of the snow melt was not abnormal. It was the amount of snow that had fallen in late spring (April and May), when temperatures along the northeast coast of Greenland are still below 0 °C, which was unusually large. Such a large amount of snow just takes a very long time to melt, even though the temperatures in June were normal (on average ca. 5 °C) and it was sunny. Since the establishment in 1996 of the research station Zackenberg, in northeast Greenland (74°28’N 20°34’W), such amounts of snow have never been documented before.

Snow cover Zackenberg in three years
Large annual variation in snow cover in the Zackenberg valley. Photos taken from the same position on 10 June in 2010, 2013 and 2018 (source: Greenland Ecosystem Monitoring)

What is the current situation?

My colleagues from Aarhus university, who are still in Zackenberg, reported that the amount of snow in early July was still excessive (80% of surface snow covered on 10 July). Also, a third dead, apparently starved, Sanderling was found. A few more Sanderlings that were ringed in Zackenberg in previous years showed up, but the number of observed individuals observed is still much lower compared with previous years.

Also, these birds do not seem to prepare for breeding, but forage in small flocks apparently to get into condition to prepare for migrating southwards. On 8 July, Jannik Hansen reported: “There are hardly any Red Knots left in the area. Also many Sanderlings have left, and flocks of 10-20 Dunlins are flying around now.” Jannik estimated that only ca. 15% of the area usually used by Sanderlings to incubate is free of snow (in average years, many clutches would hatch around this date), and possibly 2-3 % of the area used by Dunlins.

Snow in Zackenberg summer 2018
Extensive snowpack in Zackenberg, northeast Greenland in summer 2018. Photo: Jeroen Reneerkens

Still, Jannik found a Sanderling female incubating a clutch of four eggs on a snow-free patch of ca. 7 by 15 meters. By briefly floating the eggs in water, he could estimate that it was incubated for approximately 3 days, which would indicate a hatch date of 28 July. Only 5% of 707 Sanderling families that I monitored between 2003 -2017 hatched on 28 July or later, so this is very late. In most cases in earlier years such late clutches will represent replacement clutches of pairs whose first clutch fell victim to egg predators. It remains to be seen whether the single clutch found in Zackenberg survives until hatch. We have shown before that early in the summer, when the area of tundra covered by snow is still large , clutches run a larger risk to get eaten by egg predators, probably because the snow-free area in which predators search for prey is smaller.

Northeast Greenland is very large and remote, so there is not a lot of local information. Luckily, we also collaborate with Johannes Lang and Benoît Sittler and their team who work at Karup Elv, on Traill island (72°29’N 23°59’W) ca. 240 km south of Zackenberg. As in Zackenberg, the tundra surface was ca. 95 per cent covered in snow, in late June on Traill island, but on 12 July it was estimated to be only 50 per cent. So snow in the southern part of the NE Greenland national park seems have melted faster than farther northwards.

Johannes initially also reported that the tundra was very silent with very few birds around, but on 12 July they had already found three Sanderling clutches, which are predicted to hatch around 26 July. Johannes reports that he suspects that the clutches were laid in an area that was still snow covered at the end of June. Three Sanderling nests are very few compared to other years when more than 10 nests would have been found by this date at Traill island. Johannes and Benoît still observe Sanderling pairs which they expect to give up reproduction soon. The researchers did not find more than these three Sanderling clutches this year. Their discoveries however indicate that some Sanderling pairs managed to produce a very late clutch despite the excessive snow and its slow melt.

Sanderling Zackenberg 16 June 2017_in_landscape
A Sanderling on the tundra with less snow, Zackenberg 16 June 2017. Photo: Jeroen Reneerkens

Were conditions similar this year across the entire Arctic?

The Arctic tundra used by breeding shorebirds is very large and snowfall is often a regional weather phenomenon. The entire east coast of Greenland has experienced a lot of snowfall during late spring which took a long time to melt away. We do not know in detail what the conditions were in other parts of the Sanderling breeding range (Pearry land in north Greenland, Ellesmere island in Canada), which use the East Atlantic flyway.

The conditions on the tundra near Barrow, Alaska, where Global Flyway Network collaborator Bart Kempenaers and his team studies Red Phalaropes, Semipalmated sandpipers and Pectoral Sandpipers was also exceptionally late due to a large amount of snow. Much fewer shorebirds were around, but those that waited for the snow to melt eventually bred ca. 1 month later than average.

In the Russian Far East, from Sakhalin to Chukotka, the spring was also cold and late (Evgeny Syroechkovskiy, personal communication), and so was the spring in parts of the Canadian Arctic (Paul Smith in an interview with Scientific American).

In contrast to the situation in Greenland and Alaska, on the Taimyr peninsula in Siberian Russia Global Flyway Network researchers Jan van Gils, Thomas Lameris and Mikhail Zhemchuzhnikov experience a very warm summer with on some days temperatures as high as 22 °C! So snow has melted fast there and the first Red Knot chicks hatched on 8 July. More details in their blog.

familie Kanoet
Red Knot adult and chick. Photo: Jeroen Reneerkens

Will there be no reproductive success at all for shorebirds breeding in east Greenland?

Next to the already mentioned four Sanderling nests that were found (one in Zackenberg and three on Traill island), a clutch of a Common Ringed Plover was found in Zackenberg on the same snow free patch of tundra of 7 by 15 meter on which the single Sanderling nest was discovered. The Ringed Plover nest was however already discovered and eaten by an Arctic fox –as indicated by the foot prints in the snow next to the nest location- the day after discovery. Also one of the three Sanderling clutches on Traill island fell victim to an egg predator already. I expect that few shorebirds will manage to successfully hatch and fledge chicks this year in Northeast Greenland.

Kanoet juveniel strand
Few juvenile Red Knots should be expected to appear along NW European wetlands in 2018. Photo: Jeroen Reneerkens

Is a delayed breeding season a problem?

First of all, it should be noted that it seems that the majority of shorebirds did not even attempt to breed, but instead did not arrive in their usual breeding territories but probably stayed further southwards. The few birds that risked to fly to Zackenberg had difficulties to survive the period with lack of invertebrate food, as indicated by the three casualties and the (very) low body masses of birds we caught at the end of June. The few shorebirds that managed to lay a clutch, did so with a serious delay. Because the emergence of insects depends on the timing of snow melt, both birds and their prey are similarly delayed: so what is the problem with a delayed start of breeding for shorebirds?

I expect that the arthropods will appear late and very synchronously, causing a short but very high abundance of insects. In such cases, chicks will have a very short period only to profit from this burst of insect abundance. We have shown that in years with short-lasting peaks of arthropod abundance, Sanderling chick growth was relatively poor.

What is the effect on the shorebird populations?

I suspect low reproductive success of Greenland breeding shorebirds this year, and possibly also a lower survival. I would like to document this, but I can only do so with the help of many observers. You can count the number of adult and juvenile Sanderlings at your beaches until mid November. Please download the manual here, which is also available in French, German and Spanish.

That the extensive snow cover has impacts on the Greenlandic shorebirds can already be observed. Several observers have reported unusually large numbers of Red Knots and Sanderlings in early July, which suggests that indeed many shorebirds that would usually breed in east Greenland have returned early. Jim Wilson reported on 4 July: “Knots in summer plumage have been turning up in UK in the last week and that is too early – even for returning females.” And Klaus Günther, working in the German Wadden Sea reported that “among some 5.000-6.000 Knots the % of adult birds was 25% two days ago [on 2 July] on Sylt!  Normally you will see only 1-3 % adults in summer among the grey juveniles.

It is difficult to say whether (and how) a population will deal with a year with very low reproductive success. The future will tell. I hope that I may count on your continued support with useful observations of colour-ringed Sanderlings and from counts of adults and juveniles in late summer and early autumn.

Juveniele drieteenstrandloper
Juvenile Sanderling. You can help monitor this year’s reproductive success by counting adult and juvenile Sanderlings in flocks at your local beaches. How to do that? You can here download a manual in English, French, German or Spanish. Photo: Jeroen Reneerkens

Is this phenomenon the result of climate change and may we expect this to happen more often?

It is impossible to say whether the exceptional amount of snow this year is the result of a changing climate. However, warmer average global temperature will cause a higher rate of evaporation, more water vapour in the atmosphere will result in more precipitation in Arctic regions. If this precipitation in the Arctic falls in winter or late spring, it will often be in the form of snow. Climate models, predict that global precipitation will increase but that changes in precipitation will not be evenly distributed. Some locations will get more snow.

Information used in this blog was received from Martin Bulla, Jan van Gils, Klaus Günther, Jannik Hansen, Bart Kempenaers, Thomas Lameris, Johannes Lang, Benoît Sittler, Evgeny Syroechkovskiy and Jim Wilson


News from the faraway wild Arctic. On Red Knots and the Dutch-Russian expedition to the Taimyr Peninsula

A report from the 2018 Dutch-Russian expedition in Taimyr. The team members are Mikhail Soloviev, Anastasia Popovkina, Jan van Gils, Job ten Horn, Victor Golovnyuk, Thomas Lameris, Mikhail (Misha) Zhemchuzhnikov  and Maria Sukhova:

“It is always a risky business to set up experiments in the field. And especially when the field site is located in northern Taimyr (76.1 N 98.5 E), in Russia, and when the experimental animals are nesting Red Knots.

On 29 May 2018, when Jan van Gils, Mikhail Soloviev and their team arrived in Khatanga, the last human-populated place on their way, there were still many uncertainties about their field season.

Would they be able to arrange a helicopter flight to get back from the field or will they have to hitch-hike an icebreaker and have a compulsory late-summer cruise through Franz-Joseph Land Archipelago? What will be conditions at the Taimyr field site? And, most important, will there be nesting Red Knots?

In the helicopter to the field site. Only part of the team is visible: team leaders Mikhail Soloviev (centre) and Jan van Gils (far left),  Victor Golovnyuk (2nd left), Thomas Lameris (far right)  and Maria Sukhova (2nd right). Not in the photo but surely in the heli: Anastasia Popovkina, Job ten Horn, Misha Zhemchuzhnikov.

Everything has worked out so far! The helicopter flight back is agreed upon. The weather has been good most of the time, sometimes even too good, since 22 °C is not what one should expect at this location.

And the Red Knots apparently do their best to make researchers happy. On 9 June they were singing around the field camp, and within a week the team had identified 14 nesting territories.

On 13 June, Job ten Horn found the first Red Knot nest with two eggs. The next one was found by Jan, on 18 June (even though he was nest-searching in a fog). By 24 June, eight nests had been found and 11 Red Knot males had received radio transmitters. On 1 July, the team was celebrating the deployment of the first satellite transmitter. By now, three female Red Knots are being tracked through the Argos satellite service.

We have no high quality field photos of 2018 yet due to limited internet connections, but to give an idea about what Red Knots on the tundra look like, here a male with his chick in Sterligova, Taimyr in 1994. Photo: Jan van de Kam.

Crane flies started to emerge in the first days of July, and there are plenty around. Right in time, as after several days of dog-weather with snowfall last Sunday the first Red Knot chicks hatched! The weather then has become good enough for some researchers to go for a dip in a lake. But it all changed very quick, and on Friday chicks from three clutches met this world for the first time in snow and frost.

Fingers crossed the things will roll on as luckily onwards. Hopefully the many Arctic Skuas nesting in the area and Arctic Foxes wandering around will find something else to eat.”

Part of the Russian-Dutch NIOZ team: Misha Zhemchuzhnikov, Jan van Gils & Thomas Lameris are ready for the field season.



Bohai 2018 Update 5/6

Again this 2018 migration season the GFN team worked in Bohai Bay, China, to study Red Knots and Great Knots on northward migration. Chris Hassell, Adrian Boyle and Matt Slaymaker post regular updates on the Australian Global Flyway Network website. Here is the overview of all posts of this season.

By 30 May, the team had recorded 3,776 colour-banded or flagged birds, the majority of which are from NW Australia. They have precisely 1,000 Broome/80-mile Beach colour-band observations, of 321 individual combinations dominated by 273 Red Knots. The total of 876 individually identifiable birds includes birds banded in Australia (Victoria, Queensland, South Australia), Russia (Chukotka & Kamchatka), New Zealand, Thailand, Japan, and Hong Kong, among others.

Vastleggen in volledig scherm 3-7-2018 144045.bmp

The team also reports on the state of land reclamation projects (with a port development threatening to take 54 km2 of mudflats). Another issue is cordgrass Spartina encroaching the mudflats, They say: “it has expanded rapidly along the Nanpu mudflats and is now present at all our survey sites. The good news, however, is that this year the problem has been acknowledged by the local government, and a team of workers has been busy clearing out the dead grass to allow better access to living stems”.

By the time they published the final report on 6 June, they had accumulated 4,122 flag and colour-band observations, the highest total since 2015. This includes birds from 21 banding regions and they have seen flags or bands on 14 species. Their total of 1,097 NW Australia colour-band observations is the second highest total in 9 years of visits to the site!

Vastleggen in volledig scherm 3-7-2018 144135.bmp



Excessive spring snowfall results in a non-breeding year for shorebirds in NE Greenland

Jeroen Reneerkens of the University of Groningen studies breeding Sanderlings, for the first time in 2003 and since 2007 annually. He works from the Danish Zackenberg Research Station (74°28’N 20°34’W) in NE Greenland that was established in 1996, and is the research base for various experts monitoring the biotic and abiotic environment of NE Greenland.

Jeroen reports about his remarkable 2018 field season:

I study how rising temperatures may affect the reproductive success of Sanderlings in Zackenberg, NE Greenland. Due to a disproportionate degree of climate warming in the Arctic, shorebirds that migrate to the Arctic to breed are strongly suspected to be negatively affected by ongoing climate change. Niels Martin Schmidt and his team have indeed established that the summer temperatures in Zackenberg have steadily increased during the last decades.

One of the Sanderlings that is part of the long-term study on Sanderling reproduction in Greenland. Photo: Jeroen Reneerkens

The expected consequence of the warming Arctic summers are a mismatch in timing between arthropods (think insects and spiders), and their shorebird predators. Indeed, the emergence of crawly creatures in the pitfall traps in Zackenberg has advanced in the last two decades, but I learned that Sanderlings in Zackenberg did not adjust the timing of their incubation. Puzzling.

So to further study the ecological interactions between Sanderlings and their prey (and the predators of Sanderling eggs such as Arctic foxes), this summer of 2018 I visited Zackenberg for the 13th time. It turned out to be an exceptional season…

Snow, very much snow!

Sanderlings and other Arctic shorebirds start laying eggs when the snow melts, which usually happens in the first weeks after their arrival, around late May or early June. Shorebirds are so-called income breeders, which means that females produce their eggs from locally acquired food. Their food appears only as soon as the tundra soil becomes snow-free.

Snow melts quicker with higher summer temperatures but it’s not that straight forward because climate models also predict that the amount of winter precipitation (i.e. snow fall) will increase. If that is true, more snow may counteract the effects of warming summers on the timing of emerging of arthropods.

The study area in NE Greenland: in mid-June 2018 the tundra surface was close to 100% covered in snow. Photo: Jeroen Reneerkens

Before I migrated north to follow the Sanderlings, my Danish colleagues who were in Zackenberg since early June had already reported that there was a lot of snow on the tundra and warned me that I should prepare myself for a late breeding season. On satellite images of mid-June 2018 the tundra surface was close to 100% covered in snow, and not only in Zackenberg but in the entire Northeast Greenland national park. After a delay of two days due to fog in Zackenberg in which the small chartered planes cannot land, I arrived in Zackenberg on 14 June.

In the last two weeks of June usually most Sanderling are on their nest while some late breeders, or birds whose first clutches fell victim to egg predators, can be found singing or foraging in pairs while the females gather insects to produce eggs. But not this year…

The amount of snow was so extensive, that the majority of the shorebirds in the Zackenberg valley had flocked together in the snow-free area around the field station. Very lean birds were walking between the wooden buildings in the research station and could be approached up to a few meters, probably because they were not willing to spend their last energy and the much needed time to forage on escaping from human researchers.

Zackenberg research stationas only snowfree shorebird haven
The near vicinity of the research station Zackenberg was the only snow-free area in the wide surroundings. Photo: Jeroen Reneerkens

Catching shorebirds within the research station

It was clear that no shorebirds were going to nest within the next few weeks, if at all this summer. This exceptional situation gave me the opportunity to document the effects of the large amounts of snow on the behavior of shorebirds and their condition.

Usually, food left-overs from the station’s kitchen are discarded via a hose into the nearby Zackenberg river, such that its smell will not attract Polar Bears to the station. However, the river also only started running on 20 June, which is 16 days later than the average date in 1998-2017; a new record. The researchers were forced to get rid of the grinded food remains onto the tundra close to the station. Luckily, it did not attract Polar Bears, but it did attract a flock of several tens of shorebirds, mainly Sanderlings, Turnstones and Red Knots.

Turnstones, together with a Red Knot and a Sanderling, foraging at the end of the sewage hose, close to a strategically placed trap. Photo: Jeroen Reneerkens

This gave me and my Danish colleague Jannik Hansen (Aarhus University) the possibility to catch birds and assess their body condition. We managed to catch 31 Sanderlings, 23 Turnstones and 12 Red Knots. Several birds were recaptured 1-3 times within a few days.

Jannik Hansen ringing a Knot near the sewage of the research station
Jannik Hansen ringing a Red Knot caught in the snow free area around the Zackenberg research station. Photo: Jeroen Reneerkens

All individuals were in poor condition. Sanderlings weighed on average 44 grams (range: 33.6-54.6 grams). In comparison, Sanderlings in winter in the Netherlands weigh between 50-55 grams and incubating Sanderlings weigh on average 57 grams. It is good to realize that the incubating females have already produced a four-egg clutch weighing ca. 48 grams before they start incubation!

ringing shorebirds at the station
During the social Saturday evenings in the station, we continued catching and ringing shorebirds from the terrace. Photo: Jeroen Reneerkens

The locally colour-ringed birds were resighted daily near the sewage outlet and between the station buildings near snow edges. I daily woke up and went to bed with sightings of colour-ringed birds just a few meters from my bedroom window. The food waste close to the station was probably a unique opportunity for shorebirds, as there is only one village and a handful of stations in entire NE Greenland. The body masses of recaptured Sanderlings showed that they could maintain or even increase their body mass. But not all of them.

I found two dead Sanderlings near the station who seemed to have starved to death. One of them weighed 34 grams at first capture and only 32.6 grams when recaptured a few days later. It was found without head, weighing 26 grams. The other, un-ringed but intact, Sanderling weighed 31.8 grams which indicates that many of the Sanderlings were in very poor condition, indeed.

decapitated starved Sanderling
A Sanderling was found starved (and decapitated), weighing 26 grams. Its mass upon capture a few days earlier was 34 grams. Photo: Jeroen Reneerkens

I was delighted with the recapture of a Sanderling which I ringed in Zackenberg as a 7–day old chick on 14 July 2012 and was now almost 6 years old. Luckily, with a weight of 54 grams, she was among the few birds in a good condition.

The sewage near the station did not only attract hungry shorebirds, but also served as a feeding tray for the local Gyrfalcons. Jannik and I almost daily observed one of these large white falcons hunting shorebirds, often flying only a few meters over our heads! Although we did not witness a successful attack, prey remains and plucked feathers in the vicinity of the station indicated that either the Gyrfalcon or possibly Arctic foxes were preying on the starving shorebirds.

A non-breeding year?

During the two-week period that I was in Zackenberg, I did not hear a single singing Sanderling and only a few times I heard a singing Red Knot or Dunlin. I observed two Sanderling pairs, which however seemed to have broken up, or at least could not be found again, during the following days.

Also surprisingly few Sanderlings that were locally colour-ringed were observed. Because Sanderlings are very site faithful to their breeding territories, and given that the snow conditions were similar in the whole range of northeast Greenland, I think that the majority of Sanderlings never arrived in Zackenberg but stayed in more southerly regions with better feeding possibilities.

In recent years, Sanderling hatch dates in Zackenberg ranged between 27 June and 30 July (average 12 July). With an incubation duration of 22 days and four days to lay the clutch of four eggs, this implies that Sanderlings usually start laying around 16 June and at the very latest at 4 July. Given that on 27 June all of the Sanderling habitat in the Zackenberg valley was still covered under at least a meter of snow, it is very unlikely that Sanderlings and other shorebirds will breed this year in Zackenberg, or even entire Northeast Greenland.

On 27 June 2018, the Zackenberg valley was still completely covered with ca. 1 meter deep snow. The vicinity of the research station visible in the middle of the photo was the only area freed of snow. Photo: Jeroen Reneerkens

Request to report the proportion of juvenile Sanderlings within flocks

What are the consequences of a non-breeding season for the Sanderling population? This will depend on the scale at which the snow cover has affected Sanderling reproduction. The Sanderling breeding area is larger than northeast Greenland only, and it is possible that outside the area affected by snow, Sanderling reproduction will be good this year.

I ask for your help to document the effect of snow conditions on Sanderling reproduction and to score the number of juvenile Sanderlings within flocks at your local beaches. I prefer you to repeatedly observe and score the percentage of juvenile birds in the same area between August and November, following a standardised protocol. You can find more information in the manual which can be downloaded below. Download the Sanderling Ageing Manual here.


Klaassen, M., Lindström, Å., Meltofte, H. & Piersma, T. (2001) Arctic waders are not capital breeders. Nature, 413, 794.

Reneerkens, J., Schmidt, N.M., Gilg, O., Hansen, J., Hansen, L.H., Moreau, J. & Piersma, T. (2016) Effects of food abundance and early clutch predation on reproductive timing in a high Arctic shorebird exposed to advancements in arthropod abundance. Ecology and Evolution, 6, 7375–7386.

Reneerkens, J., van Veelen, P., van der Velde, M., Luttikhuizen, P. & Piersma, T. (2014) Within-population variation in mating system and parental care patterns in the sanderling (Calidris alba) in northeast Greenland. The Auk: Ornithological Advances, 131, 235–247.

Schmidt, N.M., Mosbacher, J.B., Nielsen, P.S., Rasmussen, C., Høye, T.T. & Roslin, T. (2016) An ecological function in crisis? The temporal overlap between plant flowering and pollinator function shrinks as the Arctic warms. Ecography, 39, 1250–1252.



Satellite-tagging on the edge – 1st report 2018: Connecting NW Australian Red Knots to their staging sites

Eva Kok (Royal NIOZ and PhD student at the University of Groningen) reports about satellite-tagging Red Knots in two major wintering areas of the East Asian–Australasian Flyway in NW Australia: Roebuck Bay and Eighty Mile Beach. In February 2018, she worked there together with team leader Chris Hassell (GNF Australia) and PhD student Drew Bingrun Zhu, and was supported by the AWSG, Ying Chi Chan and Lee Tibbitts.

“It has been more than two months since the NWA expedition 2018. More than ever it was an expedition full of challenges, mainly due the arrival of cyclone Kelvin. After a lot of rain, and waiting, we were eventually successful in catching and equipping 2 gram satellite PTTs on Red Knots using the full body harness. In the past two months we have been excitedly following the movements of these birds.

Drew Bingrun451
A Red Knot with colour-rings and a 2 gram satellite PTT, held by Eva Kok. Photo: Drew Bingrun

We caught the Red Knots well in advance of the expected migration to the breeding grounds to give them time to adjust to wearing the tiny tracker and gain sufficient amounts of energy stores to take on the long-distance flight north. According to expectation, the first few weeks were characterized by short-distance movements on the mudflats between foraging grounds and high tide roosts.

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Red Knots on Eighty Mile Beach, just released after being equipped with a 2 gram satellite PTT Photo: Drew Bingrun

The first movements happened in the first week of April when two birds, who were caught on Eighty Mile Beach (80MB) before the cyclone hit us, moved up to Broome and mingled with the tagged birds that we caught later in Broome. This is a regular movement, and the birds settled on the mudflats of Broome where Chris and Kerry saw the knots growing fat (see picture below).

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Satellite-tagged Red Knots “hanging out” and getting fat on the beach of Roebuck Bay. Photo: Kerry Hadley

On 25 April our wait was finally rewarded when the first bird, caught at Roebuck Bay on 18 March, finally decided to cross the Timor Sea to fly to Borneo. For a moment we thought this was the signal for migration to start, but in the meantime the other birds did not show any sign of migratory movement, and the days passed by.

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On 25 April 2018, the first Red Knot crossed the Timor Sea to fly towards Borneo

Eventually the real wave of departure started almost three weeks later! Then six other Red Knots exchanged the mudflats of Broome for the mudflats in Indonesia and the Philippines. On 22 May 2018 already two Red Knots had reached China and we can’t wait for them to show us where they will go next to breed.”

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Tracks on 22 May 2018. Two Red Knots in Bohai: one still in Nanpu and one north in Yingkou. Three birds at S China coast: near Wenzhou, Zheijang , near Fuzhou, Fujian, and near Macau/Hong Kong. Also note the birds still in Borneo and Vietnam.

Video by Drew Bingrun: Eva Kok and Chris Hassell releasing satellite-tagged Red Knots.



The field work in NW Australia in February 2018 that made it possible for us to successfully deploy Red Knots with solar-panelled satellite-transmitters was funded by the MAVA foundation. We want to thank the members of the expedition of the Australasian Wader Studies Group (AWSG) for their help and support in the field.

Bohai 2018 Update 4: 22 May

The GFN team is in Bohai Bay, China, to study Red Knots and Great Knots on northward migration. Chris Hassell, Adrian Boyle and Matt Slaymaker post regular updates on the Australian Global Flyway Network website. Here is the fourth of this season.

This week the team reports a lot of exciting information about bird numbers. We will not give it all away here. Besides the shorebird work, the birding this week has been fantastic. On top of the good numbers of regular migrants, they found a few unusual and/or out of range species. Read for yourself in the PDF at GFN website.

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One the study sites at Nanpu, the Hangu wind farm. Note the potential moving hazard for shorebirds and the introduced Spartina grass becoming established on the mudflats. Photo: GFN Team Bohai Bay

Bohai 2018 Update 3: 13 May

The GFN team is in Bohai Bay, China, to study Red Knots and Great Knots on northward migration. Chris Hassell, Adrian Boyle and Matt Slaymaker post regular updates on the Australian Global Flyway Network website. Here is the third of this season.

In short, the team reports that it has been a busy week  in Bohai with early mornings, lots of people and loads of birds. They did a shorebird count of the whole study site coastline and nearby salt ponds, and of course spent long hours re-sighting. This time they also report on an invasion of human visitors to the coast:

Drew, Leiming, Tong and Hebo, together with a large team of volunteers, joined to work on their various projects, and of course Theunis was there!

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Left: Mud sampling by Red Knots and shorebird researchers. Right: Researchers catch up with Theunis at Nanpu. Photos: Chris Hassell and team, taken from Bohai Update 3

Also Katherine Leung from Hong Kong joined for a week’s scanning. Scott Weidensaul from the USA spent a few days with the team and Terry Townshend dropped by for a weekend.

Hank and Wendy Paulson spent a morning birding on the sea wall and surrounding area. The Paulson Institute has been influential in helping to attain Nature Reserve status for Nanpu mudflats and the birds behaved impeccably for their visit!

And there is a competition! With a prize for the 1st mail to Chris Hassell with the correct subspecies of a Mai Po – Hong Kong re-sighting (photo in report).

For an overview of this season’s reports go here.

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Great Knot 7YRYB was seen again

A report from David Chan (volunteer for Coastal China Survey) on 12/5/2018:

It was a sunny day after a few days of rain and disappointment. Not many Great Knots were seen on the mudflats at Lianyungang for the past few days. Hebo brought us to this last site hoping to find more knots there, especially a Great Knot carrying a solar-paneled satellite transmitter (also called a PTT – Platform Terminal Transmitter -, or simply “sat-tag”). From its location data we knew it was there. Fortunately, we counted a few thousand Great Knots foraging near shellfish farms. So besides continuing the foraging study of Great Knots by filming them, the next task, obviously, was to find our sat-tagged friend, the bird carrying the satellite transmitter, who led us all the way to this site.

Throughout the whole day, we scanned different flocks of Great Knots hoping to find it. The light turned softer at the golden hour and sunset was near but we did not want to give up on scanning. In a flock of resting knots, two Great Knots with colour-rings caught our attention. Looking closely, we saw an antenna attached on one of them. Immediately we knew that this was the bird!

This sat-tagged Great Knot at Lianyungang was coded 7YRYB. 7YRYB was banded with a yellow flag (Roebuck Bay, Australia) and four colour-rings (Yellow-Red-Yellow-Blue, so YRYB). 7YRYB was a she (identified by DNA techniques) banded 29/09/2016 at Richards Point in Roebuck Bay and fitted with a satellite tag. Yet, her migration journey was not ordinary. After banding, she flew two thousand km to Papua New Guinea and stayed there for the whole breeding season of 2017 (see Chris Hassell’s blog on 19/04/2018).

Her northward migration this year started on April 10 with a four thousand km direct flight to Taiwan. Surprisingly, one local birder Mr Lin Jer An was able to photograph her on April 16th and took a video the next day (see Chris Hassell’s blog). It is always delightful to see photos of birds carrying a PTT tag doing fine. She left Taiwan around April 20th and arrived at Jiangsu Province on the next day.  After a few days, she flew north to Lianyungang and we saw it on May 8th.

It was a joyful moment watching the seemingly fattening 7YRYB feeding at Lianyungang. Direct observation and foraging videos help us understand the birds’ condition and behaviour (you can watch the video above). Unfortunately, the building of a big port nearby might affect this section of mudflat and the thousands of shorebirds that stop here during their migration. An all too familiar issue in coastal China but some good news is also out now (more information in Wader Study, also in Mandarin, and on

Her migration journey was amazing, from Australia to Papua New Guinea, and from Papua New Guinea to China. She revealed some interesting movements and brought people caring and studying shorebirds along the flyways together, from Australia, Alaska, Taiwan and China. Migratory birds like 7YRYB connect scientists, conservationists and bird-lovers. We hope the stories of 7YRYB may raise awareness about their survival and the threats they are facing.

We wish her all the best on the coming journey and breeding season. Godspeed.

David Chan

12/05/2018 (World Migratory Bird Day 2018)

[David works with Ginny (Ying Chi Chan) from Royal NIOZ Netherlands Institute for Sea Research and University of Groningen, The Netherlands].

Please note this article is derived from raw data and has had no checking or statistical analysis applied to the PTT data.

H35 is on her way to the breeding grounds again

News from Bingrun Zhu (Drew) – College of Life Sciences, Beijing Normal University (BNU) and University of Groningen (RuG).

Drew studies the melanuroides population of Black-tailed Godwits. He does field work in Bohai Bay and Inner Mongolia in China, but also in Thailand and Australia (read more here). Currently he is in Bohai Bay. He reports:

I’m very happy to share this exciting news: one of the female Black-tailed Godwits (H35) that I caught in the spring of 2017 in Hangu, Tianjin (Bohai Bay, China) is now heading north again!

H35 in 2017 in Hangu, Tianjin ( China) where she was issued a solar-panelled satellite tag. Photo: Bingrun Zhu

After a cozy winter time in Samut Sakhon of Thailand, she left her wintering grounds on 11 April 2018. Then she flew directly north-east to near Poyang Lake, Nanchang Province of China, and disappeared for quite some days. She showed up again on 26 April at Dongying, Shandong Province (instead of meeting me at the North shore of Bohai Bay). She started the trip northward again on 7 May, and now 5 days later she has already reached Russian soil. She is outside a city named Borzya, Zabaykalsky Krai Province, only 700km east of Lake Baikal.

I hope she’ll have a successful breeding season out there, and will stay away from hunters…

The track of H35 in 2018: from her wintering grounds Samut Sakhon in Thailand, to Borzya in Russia