Migratory birds pay the bill for Arctic warming: Deakin research

A warming globe has been directly linked to higher mortality among one of the world’s most iconic Arctic-breeding, migratory shorebirds.

Scientists from Deakin University’s Centre for Integrative Ecology within the School of Life and Environmental Sciences were among an international research team which found that rapid warming of the red knot's (Calidris canutus) high-Arctic breeding grounds produced smaller offspring which later led to higher rates of death than normal.

The research, “Body shrinkage due to Arctic warming reduces red knot fitness in tropical wintering range”, is published in today’s edition of Science, and included researchers from the Netherlands, Poland and Russia. 

Senior author and Centre for Integrative Ecology Director Professor Marcel Klaassen said that at their tropical wintering grounds, smaller red knots with shorter bills had more difficulty reaching high-quality food, and hence experienced lower rates of survival.

“We now fear that this climate-induced body shrinkage and associated survival effects may well extend to other Arctic migrants,” Professor Klaassen said.

He said red knots with small bills had a high chance of dying after flying 9,000 kilometres from the Siberian Arctic to tropical shores in Africa, where they escaped the Arctic winter, because their beaks were unable to reach the best shellfish food buried in the coastal sediments.

While the birds studied for the research migrated to Africa for the Arctic winter, the species has populations that fly throughout the world, including to Australia. Many species within the shorebirds group are increasingly listed as critically endangered in Australia, among other parts of the globe.

“During their non-breeding period these shorebirds have to increasingly share coastal habitats with humans,” Professor Klaassen said.

“It is a no-brainer that is leading to major conflicts and not making life particularly easy for these birds. But climate warming, which is particularly noticeable in the Arctic, is having an additional negative effect on these birds and that came as a very unpleasant surprise to us.”

The research team analysed the timing of snowmelt within the red knot’s breeding grounds during the past 33 years and found snow began to melt approximately half a day earlier than the previous year each season.

“Over the same period, 1990 juvenile red knots on their way to West Africa were caught and their body sizes measured in Gdańsk Bay, Poland, with results showing they were smaller after Arctic summers in which the snow melted earlier,” Professor Klaassen said.

“We then followed them as they arrived at the Banc d’Arguin, Mauritania, in West Africa, and found that offspring with small bills were eating other food than the ones with longer bills.”

Between 2002 and 2013, 2,381 red knots were also tagged and monitored during the annual expeditions to Banc d’Arguin, showing that birds with shorter bills had lower survival rates.

Professor Klaassen said the discovery of rapid body shrinkage and its downstream effects on population size could extend to other Arctic migrants, which could help explain why many shorebird species were decreasing in numbers.

This will be the focus of future research by Professor Klaassen in collaboration with the Australasian Wader Studies Group.

“But the study also highlights that we need to compensate for the difficult times the red knot and possibly other shorebird species are currently experiencing and protect remaining habitat and not make their life unnecessarily more challenging than it is already,” Professor Klaassen said.

Click here to view and use images. Credit must be given to photographer Jan van de Kam.