Migrating geese are losing the race north - and their chicks are paying the price

For many animals — not just the rats — life can be a race. For migrating animals, like the barnacle goose, it's often a race to get to their breeding grounds at just the right time.

Climate change, however, is causing the barnacle goose — a smaller European cousin of the Canada goose — to race north far faster than normal. The birds arrive exhausted and depleted, and their chicks are suffering as a result.  

A rush to the breeding grounds

Dr. Bart Nolet, an animal ecologist at the Netherlands Institute of Ecology, has been tracking the movements of the geese, which winter around the shore of the North Sea and spend their summers in the Russian Arctic.

They've historically made their 3000-kilometre long spring migration by "surfing the green wave," which is a way of enjoying a prolonged spring along their route northwards, where the season's arrival is always one step ahead of them. Normally, the geese interrupt their flight with regular pit-stops to refuel and build body mass—fats and proteins that help them to breed at their destination.

But now that polar regions are warming much faster than other areas as a result of climate change, barnacle geese are discovering that the "green wave" is racing north ahead of them. They're getting cues from the vegetation and temperature along their flight that indicate spring is moving north at a much faster rate — and therefore they must, too. In response, they speed up their journey in order to arrive on time and compete for a good spot in the colony. This, however, means skipping the stops they used to make to rest and feed, and the costs of that seem dire.

Faster, but not stronger

Because of their ever-faster race northwards, Dr. Nolet has found that when the barnacle geese get to their breeding grounds, their energy stores are depleted. They need to spend time foraging before laying and incubating their eggs, which, under normal circumstances, they'd do soon after arrival.

By testing the isotope ratios in the eggs, the researchers found that the nutrients that made their way into the eggs were only foraged at the breeding grounds rather than at the refueling areas, proving that they'd made few stops along their journey. After the draining journey, the geese had to forage for seven to 10 days before laying their eggs.

So while geese now arrive earlier, the delay in breeding means the goslings aren't being hatched any sooner than before. And of those goslings that do hatch, far fewer are surviving than those whose parents enjoyed nutrient-filled stops along the way.

Though barnacle geese are moving faster than ever, they're still losing the race.

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