On Alaska’s North Slope, scientists tread carefully across clumps of tussock grasses toward a fast-flowing stream draining the imposing Brooks Range of ice and snow. Near Galbraith Creek, they string out a mist net for white-crowned sparrows. The birds have recently arrived from southerly latitudes, intent on feasting on the insects that will soon descend on the tundra like storm clouds.
The Arctic summer is short-lived, and sparrows have only a few weeks to establish territories, find mates, lay eggs and raise their chicks on a steady diet of bugs. From every ensnared bird, the scientists collect blood, feather and faecal samples to see what they are eating and how that changes over the summer.
