Since there are an incredible number of birds (about 8,700 species) and the differences between them are countless, the bird enthusiast needs a method to organize this exciting array of diversity. Ornithology has devised a system of systematics or taxonomy to classify the birds based on their similarities and differences. In 1735, Karl von Linne (Linnaeus), a Swedish botanist, proposed the basic system upon which taxonomy is built today. In the scheme of things, hummingbirds belong to the Kingdom Animales (animals), the Phylum Chordata (animals with a hollow dorsal nerve cord), the Class Ayes (birds), the Order Trochiliformes (hummingbirds), and the Family Trochilidae (hummingbirds). The Family Trochilidae is further divided into more specific groups of related hummingbirds, known as Genera (genus is the singular). Each Genus is composed of one or more individual species.
Trochilidae, the hummingbird family, has at least 319 and as many as 339 species in 123 genera. They range in size from the giant Purple Martin-sized 8-1/2 inch long Patagona gigas of the South American Andes to the tiny Cuban Bee hummingbird, Melasuga helenae, whose length of 2-1/2 inches is 50% tail and bill. The Bee weighs about 2 grams, the giant about 20. Due to the large number of species, the incredible variation in the plumage of the males, and many adaptive forms of the shapes and lengths of bills, the taxonomy of the Hummingbird Family is complex.
Hummingbirds are found only in the Western Hemisphere, living in North, Central and South America and the Caribbean Islands. More than half of the species is found in the equatorial belt in Ecuador and Columbia. The farther you go from the equator, the fewer species of hummingbirds you find. 21 species are found in the United States, but only 8 penetrate far above the Mexican border. Twelve species breed in the western U.S., thanks to the continuity of our mountain chains with those of Mexico. The Ruby-throated is the only common hummer found in the eastern U.S. The Rufous includes Alaska in its range and is the most northerly hummingbird migrant. In all, 13 species nest in the U.S., but only 4 do so in Canada.
Not content to live on the mainland or adjacent islands, hummingbirds have colonized far-flung islands. Nineteen species are found in the West Indies and the Bahamas. Four hundred miles out in the Pacific from Chile there is a tiny group of islands called the Juan Fernandez group. Two species of hummers inhabit them. One is the Chilean Firecrown hummingbird that is also found on the mainland between Argentina and Chile. The other, called the Juan Fernandez hummingbird, is native and restricted to the archipelago. It has been there for quite a long time — long enough to differentiate itself into two distinct races on islands that are 100 miles apart.
Often hummingbirds are associated with tropical rainforest, but actually they live in all climates and altitudes. Most hummers in North America migrate to escape the cold of winter. They live in temperate forest, tropical jungles, deserts, and in eastern North America they are found on the seacoast. One of the easiest ways to find hummers is to put up a feeder or plant some flowers. Before too long, a bright, tiny, glittering hummingbird will become a frequent visitor as it feeds on sweet nectar, often pollinating flowers at the same time.
Hummingbirds were not known in Europe until the voyages of Columbus. But their tiny size and iridescent colors made them desirable as ornaments for women’s hats. Early in the nineteenth century they were important products in the trade between Europe and the Americas. In one year, one dealer in London imported more than 400,000 skins from the West Indies! The slaughter of countless millions of hummingbirds may have been responsible for the extinction of some species that are now identified only from old trade skins and are unknown to be living anywhere in the wild.
The metallic colors of hummer feathers are not due to different pigments. The feathers have only two pigments that produce black or rufous coloration. It is the refraction of light by specialized feathers that provide the flashing colors that range across the entire visible spectrum, from ruby red to intense violet. This is interference coloration, like that seen in a soap bubble. You may have noticed that the color of a hummer’s gorget can change if he changes position. That is because the precise angle that the sun strikes the feathers alters the color. The feathers can change from a brilliant red to black with only a small change in relation to the position of the light source. The barbules of hummingbird feathers are flattened and twisted so that the microscopic feather surface faces the observer. The melanin granules responsible for the refraction of light are arranged in lines of oval platelets that contain many small air bubbles. The specific color reflected depends on the thickness of the platelets and the sizes of the air bubbles.
Hummingbirds hover in mid-air while drinking nectar or collecting insects. To do this, they have some unusual physical adaptations. Their bills are exceedingly thin and pointed, and come in a range of sizes and shapes. Most of our North American hummers have bills that are decurved to some extent. Their extremely long tongues are extensible because of a bony hyoid apparatus that curves backward and upward around the eye sockets. The tongue is split, but not hollow. It does not suck fluid up through a straw, but the tip of the tongue probably can absorb fluids rapidly by capillary action. A hummer does not leave its tongue in nectar to feed like a moth, but instead quickly inserts and removes it. Insects are not sucked up directly, but they may get caught in the sticky substance on the fringed edges of the tongue. Even though a few hummers have serrated edges on their bills, they are not able to manipulate insects or hold them in their bills for more than a few seconds.
The wings of hummingbirds are long and narrow and swept back like a high-speed plane. Up to one third of their total body weight is in specialized flight muscles that sustain wing beats up to 80 beats per second. Their flight is swift and daring, with many abrupt starts and stops. They can hover, and fly forward and backward, up and down, upside-down and sideways. They rotate the shoulder joint and turn the wings completely over on the backstroke as well as on the forestroke. This allows the fore part of the wing to cut the air in a “figure eight” on both backstroke and forestroke which allows the bird to hover like a helicopter. Broad stiff tails are used as a rudder during swift changes in direction. The legs and feet, used for perching, are very small, almost nonexistent.
If hummers lack anything, it is an ability to vocalize. Only a few species, including Anna’s and Costa’s, produce anything more than simple, high-pitched twitters.