The two most popular outdoor activities in America are gardening and bird watching. Hummingbirds are a source of equal admiration and devotion among both groups. This is probably because these tiny birds never cease to amaze and fascinate those of us who truly enjoy them.
Hummingbirds are often known as living jewels. This is because the feathers of the hummingbird are the most specialized of any bird feathers. On the throat of a hummingbird, it is only the outer third of each feather that is iridescent, due to the fact that it is this part of the feather that contains platelets which are filled with air bubbles. The platelets partially reflect back light, thus causing the brilliant colors that are seen on hummingbirds.
When the early European explorers wrote home about hummingbirds, they were dismissed as being liars or totally crazy and not in their right mind. This is because no one believed that it was actually possible for a bird the size of an insect to exist.
Even when they are at rest, hummingbirds use enormous amounts of energy. The small body size of the hummingbird helps prevent them from overheating, because it dissipates the excess heat. If a human being were to burn calories at the same rate as the hummingbird does, the human would literally cook from the inside!
At night, hummingbirds must lower their body temperature to ensure they will survive the night. They do so at night by entering into a state known as torpor, which is a state similar to hibernation. Hummingbirds must enter this state to ensure that the birds won’t actually starve to death before down. Torpor is a type of deep sleep where an animal lowers its hart and metabolic rate. In a state of torpor the hummingbird lowers its metabolic rate by as much as 95%. A torpid hummingbird consumes up to 50 times less energy than when awake. The lowered metabolic rate also causes a cooled body temperature. A hummingbird’s night time body temperature is maintained at a level which is barely sufficient to maintain life. This level is known as their set point and it is far below the normal daytime body temperature of 104°F or 40°C known for other birds of similar size.
The sleep of torpid hummingbirds is a sleep that is as deep as death. According to the book, American Ornithology, written by Alexander Wilson in 1832, torpor is described as follows: "No motion of the lungs could be perceived … the eyes were shut, and, when touched by the finger, [the bird] gave no signs of life or motion."
It takes approximately 20 minutes for a hummingbird to awaken from a state of torpor. When awakening, the hummingbird’s heart and breathing rates increase and they vibrate their wing muscles. The bird’s blood supply will be warmed by heat being generated by their vibrating muscles or from shivering. Shivering helps to warm the hummingbird’s body temperature by several degrees each minute and the bird awakens with enough energy reserves to see him through to his first feeding of the morning. Hummingbirds reliably awaken from torpor one or two hours before dawn without any known cues from the environment. It appears that the bird’s internal circadian clock is responsible for signaling when it is time to awaken from the state of torpor.
It takes a lot to ensure that these jewels of the aviary world even make it through the night. They are truly one of natures most beautiful an amazing creatures. Let’s make sure that we never take their beauty or their efforts to fight for their own survival each day for granted. Without these tiny creatures, the world would be a far less beautiful place.