Pollination
Hummingbirds are the most familiar nectar-feeding birds for North Americans, there are analogous species in other parts of the world. Flowers attractive to hummingbirds, which hover in front of the flower, tend to be large red or orange tubes with a lot of dilute nectar produced during the day. Since birds do not have a strong response to scent, they tend to be odourless. Perching birds need a substantial landing platform, so sunbirds, honeyeaters, and the like are less associated with tubular flowers.