Hummingbirds : helicopter & fighter aircraft combined

Amethyst woodstar hummingbird (male) (Attribution - Dario Sanches from SÃO PAULO, BRASIL & CC BY-SA 2.0)

Amethyst woodstar hummingbird (male) (Attribution – Dario Sanches from SÃO PAULO, BRASIL & CC BY-SA 2.0)

Hummingbirds (family Trochilidae) are nature’s engineering marvel in true sense. Inhabiting Americas they are exceptionally remarkable in many respects. Perhaps, they are the only birds that can hover in mid-air like a helicopter, move forward and even backward, right or left, up or down and even turn upside down while feeding on nectar from flowers. Another astonishing fact is that they can stop abruptly while in flight and within no time, again accelerate to reach their maximum speed of some 45 km per hour in forward level flight. They also have the highest rate of wingbeats in the avian world.

Fastest wingbeats

They are known for the fastest wingbeats in the bird world. In flight their wings appear as a blur to human eyes. To measure the speed of wingbeats highly sophisticated equipments are needed. At 7.5 cm (3 in) and under 3 grams in weight, Amethyst woodstar (Calliphlox amethystine) is not only one of the smallest birds in existence, it has the highest rate of wingbeats. A few species in this large family have so far been measured and among them amethyst woodstar rates as high as 90 beats per second.

These birds are found in most of central and eastern South America proper, in Argentina, Brazil, Colombia, Bolivia, Ecuador, Paraguay, French Guiana, Guyana, Suriname-(the Gujanas), Venezuela and Peru. It’s range surrounds the Amazon countries into the Andes foothills and higher elevations of upstream river systems, but is not along the Amazon River proper in the central Amazon Basin, or the central upper Basin; it is in Brazil at the river’s outlet, and upstream for about 500 km.

Ruby-throated hummingbird (Archilochus colubris) beats its wings at the rate of 200 per second during the courtship flights, but this incredible speed is restricted to the narrow tips of the primaries only, rather than the entire wings.

Ruby-throat hummer

Ruby-throat hummer

One of the smallest species in the family it weighs only 3 gm (0.11 oz), but is one of the most surprising long-distance flier attaining speed of up to 80 km per hour. During migration some birds embark on a 20 hours nonstop journey of 845 km (525 mi) across the Gulf of Mexico. They go further up to another 1,600 km (1,000 mi) into Central America. This feat is impressive, as a non-stop flight over water would seemingly require a caloric energy that far exceeds an adult hummingbird’s body weight. However, researchers have discovered the tiny bird can double its fat mass by approximately one gram in preparation for their Gulf crossing, and then expend the entire calorie reserve from fat during the non-stop crossing when food and water are unavailable. Yet this is just one stage in its routine autumn migration of up to 3,200 km. from the eastern USA to wintering grounds in Central America.

Hummingbirds, in general, possess more feathers per body area than any other bird in the world, but in absolute terms it is the whistling swans that have the highest number of feathers. Now when it comes to lowest number of feathers in absolute terms it is again hummingbird – ruby-throated – with 940.

Classified under 115 genera with approximately 330 species, hummingbirds are restricted to West Indies and north, central and South America. Many of them are migratory. They are small birds of usually green, black and brown colors with brightly colored iridescent plumage on the throat, crown, head and back. With long and narrow wings, they have slender and pointed, short to long bills, which are straight to decurved. Hummingbirds are arboreal having rounded, square, or forked tails. In some species tail feathers are modified or elongated. Inhabiting forests they have short legs with small feet. Nesting in trees they feed on nectar and insects. They are known for their rapid flight.

Anna's_hummingbird (CC BY 2.0)

Anna’s_hummingbird (CC BY 2.0)

Engineering of Flight control

To help them achieve flight control, nature has made special modifications in their bodies. They have many skeletal and flight muscle adaptations which allow great agility in flight.  Muscles make up 25–30% of their body weight – the largest relative to body size of any known bird. They have long, blade-like wings that, unlike the wings of other birds, connect to the body only from the shoulder joint.  This adaptation allows the wing to rotate almost 180°, enabling the bird to fly not only forward but backward, and to hover in mid-air, flight capabilities that are similar to insects and unique among birds.  Hummingbird hovering has been estimated to be 20% more efficient than performed by a helicopter drone.

Analysis of the main wing bone, the humerus, shows that it is specifically adapted for hovering flight. The bone is relatively short with proportionally massive deltoid-pectoral muscles which permit pronounced wing supination during upstroke while hovering.

The bird’s ability to hover is due to its small mass, high wingbeat frequency and relatively large margin of mass-specific power available for flight. Several anatomical features contribute further, including proportionally massive major flight muscles (pectoralis major and supracoracoideus) and wing anatomy that enables the bird to leave its wings extended yet turned over (supine) during the upstroke. This generates lift that supports body weight and maneuvering

Hummingbirds achieve ability to support their weight and hover from wing beats creating lift on the downstroke of a wing flap and also on the upstroke in a ratio of 75%:25%, respectively, similarly to an insect. Like insects, these birds too gain lift during hovering partially through inversion of their cambered wings during an upstroke. During hovering, hummingbird wings beat up to 80 times per second.

Hovering flight is made possible by a figure-of-eight movement of the wings. While the bird is on station in the mid-air it moves its wings rapidly forwards and backwards, instead of up and down, the tips tracing a figure of 8 (eight). With every change of wingbeat the wings are turned through 180 degrees. While both the strokes produce lift, they also cancel each other out, leaving it hovering in the air. Its broad tail helps in achieving the precise manoeuvres. It is capable of hovering for four hours non-stop, if necessary, which means that it, can beat its wings more than 10 lakh (one million) times without any pause.

Comparison with aircraft

If compared with flying machine, hummingbirds use more fuel in relation to their size than a jet fighter aircraft. To achieve this they also have highly efficient system for obtaining oxygen and a digestive system capable of quickly processing large amounts of food.

Comparison with other warm-blooded animals

In view of the above facts, it is very natural that hummingbirds, in which some of the species weighing less than a large moth, must have very high-energy demand. Each bird consumes about half of its body weight every day in sugar (nectar) and to supplement its diet with necessary proteins it also eats insects and spiders. All this constitutes not more than 15 grams of food in quantity terms, while large eagles can eat up to one kilogram of meat in a day, which is only a quarter of the body weight. In other words these birds have the highest energy output, per body weight, of any warm-blooded animal.

Hummingbird nest with two chicks in Santa Monica

Hummingbird nest with two chicks in Santa Monica

Comparison with humans

While comparing hummingbirds work rate with humans it has been claimed that if a man uses his energy at the rate of a hovering hummingbird, he would soon run out of cooling sweat, his body would then heat up to 750 degrees F (399 degrees C), beyond the melting point of lead, and would burst into flames.

At night, these birds do not sleep in the manner other birds do. Due to their exceptionally high metabolism and inability to store food, during cold nights when temperature drops significantly they enter into hypothermic torpor to conserve energy. They go into the state of suspended animation – a dormant state that reduces their energy output to one-twentieth of that of normal sleeping. In this way they are never more than a few hours from death by starvation. They have daytime body temperature of about 40 degrees C. In the night they allow it to fall to near ambient, sometimes a decrease of over 28 degrees.

Hummingbirds have one of the highest metabolic rates of any animal, with normal heartbeat rate of about 1100 beats per minute (bpm) increasing up to 1260 (bpm) in extreme cases and lungs with a breathing rate of about 255 times a minute even at rest. Their oxygen consumption is about 4 ml oxygen/g/hour at rest. During flight, the consumption of oxygen per gram of muscle tissue rises to approximately 10 times higher than that seen for elite human athletes. Whereas in a normal resting adult human heart rate ranges from 60–100 beats per minute (bpm) and the typical respiratory rate for a healthy adult at rest is 12–20 breaths per minute.

Being a nectar-feeder ‘hummers’ (named after the noise of their wings) have a special-purpose tongue, which is very long, extendible and grooved, becoming tubular towards the tip, with a ‘brush-like ‘ modification. While feeding, they remain stationary over a flower and insert their long pointed bill, inside it. As the tongue touches the nectar it is ‘pumped’ along the tongue with the aid of capillary action.

More than what they suck from flowers in the form of nectar, they make good by spreading pollen to other flowers to fertilize them and thereby enlarge their numbers. For each sip of sugary solution, birds get a fresh dusting of pollen, which they carry, inadvertently though, to another flower and help many plants to get pollinated. No wonder, this way these birds have earned the reputation of being one of the most important pollinators among the birds.

All fliers have special affinity to one color or the other. Bees are attracted to ultraviolet rays; but hummingbirds like red light, therefore, some plants, such as bananas, advertise their nectar-stores to these birds, with their red and orange petals.

Large scale persecution

These wonderful birds have always faced persecution at the hands of man. In 19th century large number of them were killed and stuffed to decorate ladies hats. The scale of killing can be understood by the fact that in a single year as many as 400,000 skins were imported by one dealer alone in London. At present, habitat destruction is a major threat to numerous species. To name a few, fewer than 250 Sapphire-bellied Hummingbirds (Lepidopyga lilliae) are left in coastal mangrove forests destroyed since 1970; Nine-and-a-half centimeter long Mangrove Hummingbird (Amazilia boucardi) that feeds on mangrove flowers is endangered by coastal development and pollution; a few hundred Chestnut-bellied Hummingbirds (Amazilia castaneiventris) are surviving in mountains. This 8.5cm bird is threatened by urban sprawl and plantations; eleven-centimeter long Blue-capped Hummingbird (Eupherusa cyanophrys) is an inhabitant of tropical mountain forests, most of which has been occupied by fruit growers and the remaining were destroyed by 1997 hurricane.

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