Living sentinels for climate change effects

Migrating birds affected by climate change in the Arctic may have lower survival chances in their tropical habitats Humans have long used animals as sentinels for threats to their own well-being. Canaries in coal mines are a classic example. On a global scale, studies of birds were key to detecting environmental problems caused by the excessive use of pesticides (1, 2). The recent loss of up to 98% of some vulture populations highlights the widespread dangerous effects of diclofenac use in cattle (3). Bee populations, sentinels for global insect losses, are also declining owing to the combined stress from pesticides and other environmental changes caused by humans, resulting in a widespread loss of pollination services (4). On page 819 of this issue, van Gils et al. (5) highlight another global ecological warning sign, this time linked to Arctic warming. They show that long-term changes in the body architecture of Arctic wading birds can affect their survival in their tropical wintering range.