the precision of flowering time is set in the genes. ocotillo blooms at the time hummingbirds migrate north through the chihuahuan desert. while flowering time of many desert plants is brought forth by rains, ocotillo blooms by the calendar to coincide with the presence of hummingbirds. the high, colorful clusters of ocotillo flowers, visible from long distances, attract hummingbirds to the abundant nectar. as the birds probe the flowers they are dusted with pollen on the bill or fore-crown feathers. The timing of blooming and migration is critical. unless the flowers are open when birds pass through on their annual migration, they will not be pollinated and the birds will have no food - a guide to northern chihuahuan plants.