By David W Inouye. A male broad-tailed hummingbird (Selasphorus platycercus), visits a scarlet gilia (Ipomopsis aggregata) flower at the Rocky Mountain biological laboratory (RMBL), in Colorado. These migratory hummingbirds fly from Mexico to Colorado each summer to reproduce, and are the primary pollinators of scarlet gilia flowers. Long-term studies of the phenology of the hummingbirds and the flowers they visit have been conducted since 1973 at RMBL, and show that the timing of both of these partners in the ecosystem service of pollination are changing, but not at the same rates

Photograph: David W. Inouye/BMC Ecology Image Competition