Causes and symptoms. Fatigue may be the result of one or more environmental causes such as inadequate rest, improper diet, work and home stressors, or poor physical conditioning, or one symptom of a chronic medical condition or disease process in the body.
1 A hummingbird will use its tongue to lap up nectar from flowers and feeders. 2  A hummingbird's tongue is grooved like the shape of a W. 3  Hummingbirds have tiny hairs on the tip of the tongue to help lap up nectar.
Hummingbirds have no sense of smell but have very keen eyesight. Hummingbirds do not suck nectar through their long bills, they lick it with fringed, forked tongues. Capillary action along the fringe of their tongue helps draw nectar up into their throats so they can swallow. A hummingbird can lick 10-15 times per second while feeding.