This painting highlights the importance of different habitats for the survival of migratory birds. This flower is specialized for hummingbird pollination, and is a critical food source during their migration. Most North American hummingbirds migrate to warmer tropical climates in the fall. The Rufous hummingbird (Selasphorus rufus), shown here, can travel 3,000 miles (4,320 km) from Alaska to Mexico for the winter. Desert flowers like this Echeveria subsessillis play a critical role in providing hummingbirds with enough energy to complete their long journey. Hummingbirds, in return, serve as pollen couriers between plant populations - transferring flower pollen between plants often located miles apart. This makes hummingbirds a “mobile keystone species” because of their extensive movement over large geographic areas. Banding studies show that once a hummingbird learns its migration route, it often retraces that route every year, revisiting the exact same flowering plants as long as it lives. Preserving ecosystems around the world is critical for the survival of all migratory species.