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.
But hummingbirds are an enigma. They are among the most studied families of birds, yet every time we think we know all there is to know about their habits, they do something that flies in the face of that knowledge. What they eat is a case in point. Seeing hummingbirds flit from flower to flower, early naturalists presumed the birds were getting liquid nourishment in the form of nectar from the blooms, just as bees do. This, they thought, was all the birds ate. This reasoning, however, had its detractors.