General Information about Hummingbirds


Hummingbirds - Who Are They?

Hummingbirds are called so for the sound that they produce during a flight. These are one of the most amazing birds on earth and are famous for their variety of colorations and speed of wings. It is believed that the species originated from insect-eating swift-like birds that inhabited the northern Andes Mountains of South America.

Hummingbirds - Distribution

Nowadays, Hummingbirds are found in North, Central, and South America. The density is greater in areas that are closer to the equator. The Hummingbird inhabits almost all zones including tropical forests and deserts. Earlier, they were extensively hunted because of their feathers. Yet, people soon realized that there is a danger of extinction for this species. Nowadays, Hummingbirds are becoming well adapted to living near humans. However, about 9 species remain critically endangered.
The species is so fast that it can escape such predators as snakes, falcons, cats, etc., unless taken by surprise. The Hummingbird is very brave and will attack other birds that attempt to invade its territory. An amazing ability to maneuver helps Hummingbirds to feel safe in the wild. Thus, habitat loss remains one of the most acute threats for the species. The human population is ever expanding forcing the Hummingbird from its natural habitats and the process is hard to control. It is possible, though, to attract Hummingbirds to gardens and preserve necessary habitats by maintaining flower sites.

There are more than 300 kinds of the Hummingbird; the bee Hummingbird (Mellisuga helenae) is the smallest and the giant Hummingbird (Patagona gigas) is the largest. They all have different feathering and their long slim bills are of different shapes. All the species are called "nectivores," as they feed on nectar that is gathered with their long bills.
The Bold and The Beautiful
While the majority of the 328 species of hummingbird inhabit the tropics, hummingbirds can be found from Argentina to Alaska, from sea level to 15,000 feet, and from humid jungles to deserts, temperate forests, grasslands, coastlines, and urban areas. In some species, individuals cover very little territory in their daily activities, often staying close to a single flowering plant all day. In others, the birds range farther, yet sometimes travel a similar route each day.

Hummingbirds from across the spectrum of species are known for their aggressive personalities. They will defend their breeding and feeding turf by dive-bombing competitors and occasionally stabbing them with their needle-like bills. Then, when chicks are fledged or flowering is over, they may abandon their fiercely protected territory and move on.

Scientists and bird-watchers have spent lifetimes trying to unlock the mysteries of the hummingbird family, called the Trochilidae. Early observers were convinced that no bird could fly backward. George Campbell, Duke of Argylle, declared that hummingbirds just “fell backward” out of a flower when they were finished feeding. Charles Darwin was among the first credible scientists who tried to figure out how hummingbirds fly. He concluded that hummingbirds expand and contract their tail feathers to stay aloft in a vertical position. However, the real answer lies in their wings rather than their tails. Unlike those of other birds, hummingbirds' elbows and wrist bones are fused and virtually immobile. Yet the range of motion at the shoulder is a full 180 degrees. Most birds are capable of creating lift only on the wing's downstroke. For a hummingbird, every wing motion is a power stroke, as lift is created on both the downstroke and the upstroke.

HUMMINGBIRD BEHAVIOR

FLIGHT

Hummingbirds can fly right, left, up, down, backwards, even upside down. While other birds get their flight power from the downstroke only, hummingbirds have strength on the up-stroke, as well.  

A hummingbird's wing is flexible at the shoulder, but inflexible at the wrist.
When hovering, hummingbirds hold their bodies upright and flap their wings horizontally in a shallow figure-8. As the wings swing back they tilt flat for a moment before the wings are drawn

Most hummingbirds flap their wings about 50 or so times a second. This means all we can see is a blur. The Magnificent Hummingbird is an exception; sometimes it flaps it wings slow enough for individual wing beats to be perceived.

The tiny feet of hummingbirds are almost useless except for perching; if hummers want to travel two inches, they must fly. Hummingbirds lift from perches without pushing off; they rise entirely on their own power, flapping their wings at almost full speed before lifting off. Though they fly very fast, they can suddenly stop and make a soft landing. They are so light they do not build up much momentum.





FEEDING

Hummers have a fast breathing rate, a fast heartbeat, and a high body temperature. They must feed every 10 minutes or so all day, and they may consume 2/3 of their body weight in a single day.A major part of a hummingbird's diet is sugar. They get it from flower nectar and tree sap. Hummers also need protein in order to build muscles, so they eat insects and pollen. The tongue of a hummingbird has grooves on the side, which are used to catch insects in the air--also from leaves and spider webs.  

Hummingbird bills are long and tapered, perfectly suited for probing into the center of tubular flowers for the nectar, which they take up at the rate of about 13 licks a second. Often one can see long translucent tongues spilling out of their long beaks, licking the air, as they approach bright colored flowers.   
Hummers have good memory; they can remember food sources from previous years. As they feed hummers accidentally collect pollen as they feed and move from flower to flower, they help the flowers to reproduce. Many flowers, like penstemons, seem to be specifically designed to accommodate hummingbirds.

DISPLAY

Hummingbirds communicate with one another by making visual displays. Males sometimes raise the feathers bordering the gorget and toss their heads from side to side, while uttering shrill sounds. Females and young are more likely to do perched displays in which they spread their tail feathers to show the white tips.
Sometimes both males and females do shuttle-flights, which are rapid back and forth movements in front of another bird. During the shuttle flight, the tail and gorget may be displayed.

Dive display are only done by the males. At key points in the dive, buzzing, whistling, or popping sounds might be made with the wing feathers or the vocal cords. The trajectory of the dive is U-shaped. At the top of the arc, the bird may be quite high in the air


COURTSHIP

Hummingbirds communicate with one another by making visual displays. Males sometimes raise the feathers bordering the gorget and toss their heads from side to side, while uttering shrill sounds. Females and young are more likely to do perched displays in which they spread their tail feathers to show the white tips.
Sometimes both males and females do shuttle-flights, which are rapid back and forth movements in front of another bird. During the shuttle flight, the tail and gorget may be displayed.

Dive display are only done by the males. At key points in the dive, buzzing, whistling, or popping sounds might be made with the wing feathers or the vocal cords. The trajectory of the dive is U-shaped. At the top of the arc, the bird may be quite high in the air.

The narrowly-focused shuttle dance of the male is usually part of a courtship ritual. After finding a ready female, he flies in front of her in short, rapid arcs.

The dance field may be about ten inches wide.

We once saw a black-chinned hummingbird shuttle like this in front of a female that was perched in a mesquite. Looking intimidated, she moved her head back and forth to watched his awesome arial movements, which were only inches from her face; then she hung upside-down by her toes as he mounted her.

In some hummingbirds--mostly species that are south of the border--the males gather in communities, which are called leks. Then they all sing together to try to entice females to come into the neighborhood for mating

Hummingbird Migration

Although hummingbird migration is not well documented by large numbers of banding records, we do know a few facts, and we can draw logical inferences about some of the unknown areas. ("Banding" means trapping a bird and wrapping a tiny numbered strip of aluminum around one leg. This is currently the only way to identify individual hummingbirds. Species are studied by gathering data on large numbers of individuals.)

Each hummingbird species has its own migration strategy, and it's incorrect to think of "hummingbirds" as a single type of animal, all alike. This article will discuss Ruby-throated migration, because it's likely that more people see that species than all the others in North America combined, and its dynamics are similar to other species, although the dates and locations vary. An exception is Anna's Hummingbird, which typically does not migrate but may wander up- and downslope following seasonal food resources.

Banding studies suggest that individual birds may follow a set route year after year, often arriving at the same feeder on the same day. We do not know if any individual bird follows the same route in both directions, and there are some indications that they do not.

Why migrate?
As with most of our migratory birds, hummingbirds apparently evolved to their present forms during the last ice age. They were (and largely still are) tropical birds, but as the great ice sheets retreated from North America, they gradually expanded their ranges to exploit rich temperate food resources and nesting space, filling unoccupied niches in the U.S and southern Canada while evading intense competition in the tropics. Some songbird species have adapted completely to our variable North American climates, in part by becoming vegetarians in winter, and don't migrate. But hummingbirds are carnivores (nectar is just the fuel to power their flycatching activity), and depend on insects that are not abundant in subfreezing weather, so most of them must retreat back "home" to Central America in the winter or risk starvation. A few Ruby-throated remain along the Gulf coast each winter instead of continuing to Central America, perhaps because they are too old or sick to make another trans-Gulf flight or too young (from very late nests) to have had time to grow fat and strong enough to migrate; their survival chances depend on the severity of each particular winter, and many perish in unusually cold years. Another small population winters in the Outer Banks of North Carolina.

Northward Migration
Most Ruby-throated Hummingbirds winter between southern Mexico and northern Panama. Since hummingbirds lead solitary lives and neither live nor migrate in flocks, an individual bird may spend the winter anywhere in this range where the habitat is favorable, but probably returns to the same location each winter. Ruby-throats begin moving north as early as January, and by the end of February they are at the northern coast of Yucatan, gorging on insects and spiders to add a thick layer of fat in preparation for flying to the U.S. Some will skirt the Gulf of Mexico and follow the Texas coast north, while most apparently cross the Gulf, typically leaving at dusk for a nonstop flight of up to 500 miles, which takes 18-22 hours depending on the weather. Although hummingbirds may fly over water in company of mixed flocks of other bird species, they do not "hitchhike" on other birds. Some hummingbirds land on offshore oil rigs or fishing boats to rest. Individual birds may make landfall anywhere between southern Texas and central Florida. Before departing, each bird will have nearly doubled its weight, from about 3.25 grams to over 6 grams; when it reaches the U.S. Gulf coast, it may weigh only 2.5 grams. It's also possible that a few Ruby-throats island-hop across the Caribbean and enter the U.S. through the Florida Keys.

Males depart Yucatan first, followed about 10 days later by the first females. But the migration is spread over a three-month period, which prevents a catastrophic weather event from wiping out the entire species. This means that a few birds will arrive at any location very early (the dots on the migration map), but the bulk of the population will follow later, so you may not see your first hummingbird for several more weeks. Each individual has its own internal map and schedule, and "your" birds may arrive early, late, or anywhere within a two-month span.

Once in North America, migration proceeds at an average rate of about 20 miles per day, generally following the earliest blooming of flowers hummingbirds prefer. The northern limit of this species coincides with that of the Yellow-bellied Sapsucker; if the earliest males arrive in Canada before sufficient flowers are blooming, they raid sapsucker wells for sugar, as well as eat insects caught in the sap. The northward migration is complete by late May. Banding studies show that each bird tends to return every year to the same place it hatched, even visiting the same feeders. See the Ruby-throated migration map for the species' range and earliest arrival dates.

Southward Migration
Unlike the Rufous and other hummingbirds of the western mountains, where freezing nights are common even in summer, Ruby-throats aren't well adapted to cold temperatures; they have a tough time below the mid-20s (F), and don't enter torpor as regularly as their western cousins to conserve energy. To avoid the cold, and the scarcity of food when flowers stop blooming and insects stop flying, they go south. Some adult males start migrating south as early as mid-July, but the peak of southward migration for this species is late August and early September. By mid-September, essentially all of the Ruby-throated at feeders are migrating through from farther north, and not the same individuals seen in the summer. This is difficult to see, since they all look alike, but has been proven by banding studies. The number of birds migrating south may be twice that of the northward trip, since it includes all immature birds that hatched during the summer, as well as surviving adults.

For a hummer that just hatched, there's no memory of past migrations, only an urge to put on a lot of weight (see above) and fly in a particular direction for a certain amount of time, then look for a good place to spend the winter. Once it learns such a route, a bird may retrace it every year as long as it lives. The initial urge is triggered by the shortening length of sunlight as autumn approaches, and has nothing to do with temperature or the availability of food; in fact, hummingbirds migrate south at the time of greatest food abundance. When the bird is fat enough, it migrates. It's not necessary to take down feeders to force hummingbirds to leave, and in the fall all the birds at your feeder are already migrating anyway. If you remove your feeder, birds will just feed elsewhere, but may not bother to return to your yard the next year. I recommend continuing to maintain feeders until freezing becomes a problem.

Many people notice that adult males migrate earlier than females, because in the last month or so there may be no birds with red throats at feeders. However, remember that immature Ruby-throats of both sexes look much like their mothers. Young males often have a "5 o'clock shadow" of dark throat feathers in broken streaks, and many develop one or more red gorget feathers by the time they migrate. Immature females may have much lighter streaks in their throats, but no red.

There is evidence that fewer Ruby-throats cross the Gulf in fall than in spring, most instead following the Texas coast back into Mexico. Perhaps the hurricane season is a factor, and the genes of many birds with a tendency to fly over water were lost at sea during storms.

We still have many more questions than answers about hummingbird migration. Until technology provides radio transmitters small enough for a 3-gram hummingbird to carry safely, banding is the best tool to collect data on individual birds. But since only a few dozen people in North America - almost all of them amateurs like me - are licensed to handle hummingbirds, progress is slow and the odds of recapturing a banded bird are very low.

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