Appreciating hummingbirds

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Pontiac Perspective Peter J. Gauthier


Pontiac Perspective Peter J. Gauthier

Summer is here and the birds are in their abundance for our delight and investigation. Certainly, one of the most spectacular and unique of the bird species is the hummingbird. There are more than 300 species of hummingbirds – all of them in the New World (North and South America). Here in the Pontiac region, the Ruby-throated Hummingbird is the most common species. (Note: only the male has the red or ruby throat.) But all hummingbirds display some unusual and interesting features.
First are their aerial capabilities. Hummingbirds can hover and fly forward and backward like a helicopter. However, they can also operate similar to a jet. They can reach speeds of 80 kilometres per hour and travel long distances during migration. They flap their wings at rates of 12 to 80 times per minute. This flapping creates the “humming” sound of hummingbirds.
Hummingbirds drink nectar from flowers and have beaks specially adapted to this task. To get additional nutrients, they also prey on insects and spiders. Iridescence on their feathers makes them sparkle in the sunlight. Prism-like cells under the top layer of the feathers split the light into different wavelengths. The result is that a shift in position will result in a shift in colour. Without sunlight, hummingbirds appear black.
Hummingbirds also illustrate a mathematical principle: the ratio of surface to volume of a body. Increases in volume are faster than increases in surface area. This relationship between surface area and volume has biological consequences. Small creatures, such as insects, can breathe directly through their skin. But as animals become larger, their volume is too large to accommodate breathing through the skin. Such animals need lungs or gills to get enough air required for their biochemical processes. What is interesting is that hummingbirds are just at the limit where lungs become necessary. In fact, the largest insect (breathing directly through the skin), the Goliath Beetle, is slightly larger than the smallest hummingbird.
One more biological consequence of size is metabolic rate. Small animals lose heat at a higher rate than larger animals. Combine this with the energy needed for rapid wing flapping and the result is that hummingbirds have the fastest heart beat of all animals outside of insects. It can be as much as 1,200 beats per minute. To conserve energy, these birds are capable of slowing down their metabolism at night. They enter a state of torpor during which breathing and heart beat are reduced to a minimum, thus conserving energy during periods of low activity.
Hummingbirds are truly amazing. Their antics are unparalleled in the avian world and they embody some fundamental mathematical principles that govern the world we live in.