Arctic geese like the Barnacle goose that breed on the Russian tundra and winter in the Netherlands need to increase the speed of their return trips, as the tundra spring starts weeks earlier – possibly skipping their fuelling stops on Baltic islands and along the White Sea, a model study shows.

The Barnacle goose is one of about ten Arctic goose species (including species from Greenland, Svalbard and Siberia) that can be found wintering on coastal wetlands and river banks in the Netherlands and surrounding countries, like Denmark and Belgium, often depending on the seasonal weather fluctuations. The Barnacle goose winters in large groups and breeds in northern Russia on the tundra shores of the Barents Sea (Kolokolkova Bay). Feeding stops are typically made on islands in the Baltic Sea, like Gotland and Saaremaa, and along coasts of the White Sea. In response to early-onset tundra spring geese may have to skip these stops in order to return more quickly to their nesting grounds.

A mismatch with a caterpillar is easy to imagine, grass is just there isn’t it?

We know insectivorous migratory birds can experience a temporal mismatch, as these birds need to time nesting and hatching just before a seasonal peak in insect availability. But what about herbivorous migratory birds, we asked ourselves…

Well, even grass consumption depends on careful timing – an Arctic goose would tell you. When you’re looking for a spring protein boost, the first growth is what you’re after.

In part 42 of our special series about the ecological consequences of climate change we take a closer look at the Barnacle goose and other tundra species that winter in the Netherlands, based on a geese behaviour model study that was published in Global Change Biology in April 2017 by a team of 6 researchers led by ecologist Thomas Lameris of the Netherlands Institute of Ecology (NIOO-KNAW).

Many migratory birds suffer ‘temporal trophic mismatches’ because their northern breeding grounds warm (much) faster than their southern wintering areas

Several migratory birds get into climate trouble because their breeding grounds are warming faster than their wintering grounds – leading to a timing mismatch with species they depend on.

This temporal mismatch is observed for many European-African migratory bird species (due to strongly skewed warming at this longitude and especially rapid spring warming in western Europe) – and is possibly even stronger for species that nest on the Arctic tundra, like the red knot, due to what climatologists refer to as ‘Arctic Amplification’ – the fact that the speed of climate change in the Arctic is about 4 times as high as the global average, and still twice as fast as in temperate Europe.

Birds that consequently suffer temporal mismatches with other species they depend on are often insectivores though, that may need to time their arrival, nesting and hatching very carefully with a peak in spring or summer food availability. Missing that peak by just a week may mean the difference between successful nesting and a failed attempt at producing a next generation. For several of such long-distance migratory insectivores population declines are already attributed to climate change.

Now we would be inclined to think there’s less stress when you can simply eat grass – and it’s true, the Dutch researchers write, that lengthening of the Arctic growing season offers some compensation space, but also for grass-eating birds there is an ideal window that depends on a peak in availability of the most nutritious grass.

“Geese can only breed successfully when they start breeding within a short period after the onset of spring (the “breeding window”). As weather conditions vary between years, the start of this breeding window is also variable. The geese cannot predict this moment exactly, but can make an estimation based on the general climatic conditions along their flyway.”

Currently populations of most Arctic goose species are doing very well still, mostly because of the guaranteed high-caloric food availability during their winter stay in the North Sea area, that lasts until some time in April, when they sense it’s time to start their return trip.

This usually includes a week-long grazing stop on Baltic islands followed by another week-long grazing stop on the shores of the White Sea, that is also snow-free around that time – showing fresh stores of spring grass. Then finally in early May the Barnacle geese reach Kolokolkova Bay along the Barents Sea where they start nesting within days.

If the birds stick to that exact routine the model predicts they will face serious population declines by the second half of the century due to an increasing trophic mismatch:

“According to our simulations for geese that did not anticipate, reproductive success can be reduced by 50%–90% under temperature rise of 1–3°C in the temperate and 2–6°C in Arctic regions, which are conditions predicted by the IPCC for the period of 2046–2065.”

Can ‘behavioural plasticity’ prevent a temporal mismatch?

Evolution in geese phenology is interesting, as young geese can directly learn from the choices they see their parents make. This has helped geese to adapt to past environmental changes and may also help them cope with the consequences of future climate change.

The computer model of the Dutch researchers shows the answer lies in properly fuelling up in the Netherlands (where caloric density is high), and then attempting a direct flight back to the tundra, skipping several stops for early spring grass snacks along both the Baltic Sea and the White Sea.

Such a change in behaviour could save the birds up to two weeks time and compensate for the effects of low to medium warming – but not of high warming scenarios, when even optimised behaviour changes cannot prevent a time lag of 10 to 12 days, the model shows:

“Before reaching the breeding grounds, almost all geese in our model flew nonstop from the Wadden Sea to the Kanin site, skipping the Baltic Sea and White Sea sites, and the departure from the Wadden Sea was thus synchronous with arrival at the Kanin stopover site. Geese arrived at the Kanin stopover site as soon as potential intake rates in Kanin exceeded those in the Wadden Sea in all temperature scenarios, except for the most extreme warming and amplification scenarios (+5°C & 2.0–2.5× amplification), when they departed 10–12 days later.”

Please take a moment to enjoy this video by We Love Earth – showing Barnacle geese and other Arctic species as they winter in the Netherlands.

The bigger climate story is on biome level: possible disappearance of all European tundra

We think if you’re a tundra grass-eater you may be able to cope with such direct effects of warming that you may experience as an individual species. But let’s not lose sight of the bigger picture when assessing climate impacts. What should probably be a far larger concern, both spatial and ecological, is a story that’s quite comparable to the Arctic marine ecosystem: the possible disappearance of the European-Russian tundra biome altogether, due to taiga creep.

Geese may be clever and compared to other birds they may have relatively large behavioural plasticity. But you can’t expect them to switch to a diet of pine tree shoots or birch leaves when it’s spring grass they need.

Or if you want to stick to the wording ecologists would use: that would classify as a spatial climate mismatch – and if we would have to guess we would say that’s probably a larger concern globally, and also the bigger climate story these beautiful Arctic birds are facing.

© Rolf Schuttenhelm | www.bitsofscience.org