Science 331, 1019 (2011)

The world's approximately 10,000 bird species are key “mobile links” in most major ecosystems, from tropical rainforests to the depths of the Antarctic Ocean. Birds provide crucial ecosystem services, including seed dispersal, pollination, predation, scavenging, nutrient deposition, and ecosystem engineering. Countless plant species depend on mutualistic relationships with birds for their survival. However, threats such as habitat loss, introduced species, and exploitation, exacerbated by the growing impact of climate change, are causing large population declines and extinctions among birds (see the photo). As a result, hundreds of species now contribute negligibly to ecosystem function and are “functionally extinct”. Researchers have speculated that these losses could lead to declines in dependent plants, but experimental proof has been scarce. On page 1068 of this issue, however, Anderson et al. show that the functional extinction of three kinds of pollinating birds on an island in New Zealand has reduced pollination, seed production, and plant density in a dependent shrub.