Buondì a tutti,
stamani vedremo insieme uno dei più piccoli esemplari del mondo alato...nella prima parte grazie a wikipedia conosceremo le sue caratteristiche e le sue abitudini, nonchè le meravigliose immagini. Riporto solo stralci dai ricchi documenti di wikipedia perciò per approfondimenti consiglio la visione ai link originali.
Mentre nella seconda parte scopriremo alcune curiosità ma soprattutto il simbolismo totemico che, in parte, ho già anticipato nel titolo.
FONTE IMMAGINE: http://it.wikipedia.org/wiki/File:Stripe-tailed_Hummingbird.jpg
I Trochilidi (Trochilidae Vigors, 1825) sono una famiglia di uccelli dell'ordine Apodiformes, comunemente noti come colibrì.
Sono uccelli di piccole dimensioni, dal peso che varia da 5 a 20 grammi: il più grande è il colibrì gigante (Patagona gigas) che pesa, in media, circa 20 g ed è lungo fino a 21,5 cm.
Le penne hanno un colore particolarmente brillante. La colorazione non è dovuta alla pigmentazione delle penne. Queste sono ricoperte da piccolissime lamelle cornee trasparenti che contengono microscopiche bolle d'aria, che funzionano da prismi ottici. Il raggio di luce viene così scomposto nei suoi colori originari dando una colorazione cangiante diversa a seconda dell'angolo di osservazione.
Distribuzione e habitat
La maggior parte delle specie è concentrata nelle foreste tropicali dell'America centrale e meridionale
Hanno eccezionali capacità di volo, grazie alla più grande apertura alare, in rapporto alle dimensioni del corpo, di tutti gli uccelli. Sono gli unici uccelli ad avere la capacità di volare all'indietro. La frequenza del battito alare è la più elevata di tutti gli uccelli. Per il colibrì gigante è di 8-12 battiti al secondo, per colibrì di medie dimensioni di 20-25 battiti al secondo. Il battito alare delle specie più piccole può raggiungere anche 100 battiti al secondo durante le evoluzioni del corteggiamento. Il loro battito cardiaco, la cui frequenza media è circa 10 volte quella di un essere umano, può raggiungere picchi di 1260 battiti al minuto.
La femmina costruisce da sola il nido, mentre il maschio, dopo l'accoppiamento, esegue voli acrobatici per attirare altre femmine.
I nidi sono costruiti intrecciando muschi, licheni e fili d'erba, peli di animale e piume. Il tutto viene legato da fili di ragnatela, che il colibrì raccoglie nella foresta. I nidi vengono fissati alle foglie o ai filamenti vegetali con nettare rigurgitato, usato come colla.
La femmina di solito depone 2 uova bianche che cova per 100-130 giorni a seconda della specie. I piccoli vengono nutriti dalla madre che rigurgita nelle loro gole il nettare e gli insetti predigeriti. Dopo circa 70 giorni i piccoli escono dal nido e vengono nutriti per oltre 2 settimane prima di divenire autonomi. La femmina del colibrì, per entrare in una nuova zona ricca di nettare, si concede al maschio dominante del gruppo in cui essa vuole entrare.
La famiglia comprende circa 355 specie, raggruppate in 2 sottofamiglie
FONTE IMMAGINE: http://it.wikipedia.org/wiki/File:Male_Ruby-Throated_Hummingbird_1.jpg
FONTE IMMAGINE: http://it.wikipedia.org/wiki/File:Sword-billed_Hummingbird_%28Ensifera_ensifera%29.jpgFONTE:
From Wikipedia, the free encyclopedia
Hummingbirds are birds that comprise the family Trochilidae. They are among the smallest of birds, most species measuring in the 7.5–13 cm (3–5 in) range. Indeed, the smallest extant bird species is a hummingbird, the 5-cm Bee Hummingbird. They can hover in mid-air by rapidly flapping their wings 12–90 times per second (depending on the species). They can also fly backwards, and are the only group of birds able to do so. Their English name derives from the characteristic hum made by their rapid wing beats. They can fly at speeds exceeding 15 m/s (54 km/h, 34 mi/h).
FONTE IMMAGINE: http://en.wikipedia.org/wiki/File:Archilochus-alexandri-002-edit.jpg
FONTE IMMAGINE: http://en.wikipedia.org/wiki/File:Colibri-thalassinus-001-edit.jpg
Hummingbirds drink nectar, a sweet liquid inside certain flowers. Like bees, they are able to assess the amount of sugar in the nectar they eat; they reject flower types that produce nectar that is less than 10% sugar and prefer those whose sugar content is stronger. Nectar is a poor source of nutrients, so hummingbirds meet their needs for protein, amino acids, vitamins, minerals, etc. by preying on insects and spiders.
Most hummingbirds have bills that are long and straight or nearly so, but in some species the bill shape is adapted for specialized feeding. Thornbills have short, sharp bills adapted for feeding from flowers with short corollas and piercing the bases of longer ones. The Sicklebills' extremely decurved bills are adapted to extracting nectar from the curved corollas of flowers in the family Gesneriaceae. The bill of the Fiery-tailed Awlbill has an upturned tip, as in the Avocets. The male Tooth-billed Hummingbird has barracuda-like spikes at the tip of its long, straight bill.
The two halves of a hummingbird's bill have a pronounced overlap, with the lower half (mandible) fitting tightly inside the upper half (maxilla). When hummingbirds feed on nectar, the bill is usually only opened slightly, allowing the tongue to dart out and into the interior of flowers.
Like the similar nectar-feeding sunbirds and unlike other birds, hummingbirds drink by using protrusible grooved or trough-like tongues. Hummingbirds do not spend all day flying, as the energy cost would be prohibitive; the majority of their activity consists simply of sitting or perching. Hummingbirds feed in many small meals, consuming many small invertebrates and up to twelve times their own body weight in nectar each day. They spend an average of 10–15% of their time feeding and 75–80% sitting and digesting.
Co-evolution with ornithophilous flowers
FONTE IMMAGINE: http://en.wikipedia.org/wiki/File:Purple-throated_carib_hummingbird_feeding.jpg
Hummingbirds are specialized nectarivores and are tied to the ornithophilous flowers they feed upon. Some species, especially those with unusual bill shapes such as the Sword-billed Hummingbird and the sicklebills, are co-evolved with a small number of flower species.
Many plants pollinated by hummingbirds produce flowers in shades of red, orange, and bright pink, though the birds will take nectar from flowers of many colors. Hummingbirds can see wavelengths into the near-ultraviolet, but their flowers do not reflect these wavelengths as many insect-pollinated flowers do. This narrow color spectrum may render hummingbird-pollinated flowers relatively inconspicuous to most insects, thereby reducing nectar robbing. Hummingbird-pollinated flowers also produce relatively weak nectar (averaging 25% sugars w/w) containing high concentrations of sucrose, whereas insect-pollinated flowers typically produce more concentrated nectars dominated by fructose and glucose.
Aerodynamics of flight
FONTE IMMAGINE: http://en.wikipedia.org/wiki/File:Hummingbird_Aerodynamics_of_flight.jpg
Hummingbird flight has been studied intensively from an aerodynamic perspective using wind tunnels and high-speed video cameras.
Writing in Nature, the biomechanist Douglas Warrick and coworkers studied the Rufous Hummingbird, Selasphorus rufus, in a wind tunnel using particle image velocimetry techniques and investigated the lift generated on the bird's upstroke and downstroke. They concluded that their subjects produced 75% of their weight support during the downstroke and 25% during the upstroke. Many earlier studies had assumed (implicitly or explicitly) that lift was generated equally during the two phases of the wingbeat cycle, as is the case of insects of a similar size. This finding shows that hummingbirds' hovering is similar to, but distinct from, that of hovering insects such as the hawk moths.
The Giant Hummingbird's wings beat at 8–10 beats per second, the wings of medium-sized hummingbirds beat about 20–25 beats per second and the smallest can reach 100 beats per second during courtship displays.
A trail of wake vortices generated by a hummingbird's flight. Discovered after training a bird to fly through a cloud of neutrally buoyant helium-filled soap bubbles and recording airflows in the wake with stereo photography.
FONTE IMMAGINE: http://en.wikipedia.org/wiki/File:Hummingbird_wake_Pengo.svg
With the exception of insects, hummingbirds while in flight have the highest metabolism of all animals, a necessity in order to support the rapid beating of their wings. Their heart rate can reach as high as 1,260 beats per minute, a rate once measured in a Blue-throated Hummingbird. They also consume more than their own weight in nectar each day, and to do so they must visit hundreds of flowers daily. Hummingbirds are continuously hours away from starving to death, and are able to store just enough energy to survive overnight.
Hummingbirds are capable of slowing down their metabolism at night, or any other time food is not readily available. They enter a hibernation-like state known as torpor. During torpor, the heart rate and rate of breathing are both slowed dramatically (the heart rate to roughly 50–180 beats per minute), reducing the need for food.
The dynamic range of metabolic rates in hummingbirds requires a corresponding dynamic range in kidney function. The glomerulus is a cluster of capillaries in the nephrons of the kidney that removes certain substances from the blood, like a filtration mechanism. The rate at which blood is processed is called the glomerular filtration rate (GFR). Most often these fluids are reabsorbed by the kidneys. During torpor, to prevent dehydration, the GFR slows, preserving necessities for the body such as glucose, water and salts. GFR also slows when a bird is undergoing water deprivation. The interruption of GFR is a survival and physiological mechanism unique to hummingbirds.
Studies of hummingbirds' metabolisms are highly relevant to the question of how a migrating Ruby-throated Hummingbird can cross 800 km (500 mi) of the Gulf of Mexico on a nonstop flight. This hummingbird, like other birds preparing to migrate, stores up fat to serve as fuel, thereby augmenting its weight by as much as 100 percent and hence increasing the bird's potential flying time.
Hummingbirds have long lifespans for organisms with such rapid metabolisms. Though many die during their first year of life, especially in the vulnerable period between hatching and leaving the nest (fledging), those that survive may live a decade or more. Among the better-known North American species, the average lifespan is 3 to 5 years. By comparison, the smaller shrews, among the smallest of all mammals, seldom live more than 2 years. The longest recorded lifespan in the wild is that of a female Broad-tailed Hummingbird that was banded (ringed) as an adult at least one year old then recaptured 11 years later, making her at least 12 years old. Other longevity records for banded hummingbirds include an estimated minimum age of 10 years 1 month for a female Black-chinned similar in size to Broad-tailed, and at least 11 years 2 months for a much larger Buff-bellied Hummingbird.
Hummingbirds are restricted to the Americas from southern Alaska to Tierra del Fuego, including the Caribbean. The majority of species occur in tropical and subtropical Central and South America, but several species also breed in temperate climates and some hillstars even occur in alpine Andean highlands at altitudes of up to 5,200 metres (17,100 ft). The greatest species richness is in humid tropical and subtropical forests of the northern Andes and adjacent foothills, but the number of species found in the Atlantic Forest, Central America or southern Mexico also far exceeds the number found in southern South America, the Caribbean islands, the United States and Canada. While less than 25 different species of hummingbirds have been recorded from the United States and less than 10 from Canada and Chile each, Colombia alone has more than 160 and the comparably small Ecuador has about 130 species.
Only the migratory Ruby-throated Hummingbird breeds in continental North America east of the Mississippi River and Great Lakes. The Black-chinned Hummingbird, its close relative and another migrant, is the most widespread and common species in the western United States, while the Rufous Hummingbird is the most widespread species in western Canada.
Most hummingbirds of the U.S. and Canada migrate south in fall to spend the winter in northern Mexico or Central America. A few southern South American species also move to the tropics in the southern winter. A few species are year-round residents in the warmer coastal and interior desert regions. Among these is Anna's Hummingbird, a common resident from southern California inland to southern Arizona and north to southwestern British Columbia.
The Rufous Hummingbird is one of several species that breed in western North America and are wintering in increasing numbers in the southeastern United States, rather than in tropical Mexico. Thanks in part to artificial feeders and winter-blooming gardens, hummingbirds formerly considered doomed by faulty navigational instincts are surviving northern winters and even returning to the same gardens year after year. Individuals that survive winters in the north, however, may have altered internal navigation instincts that could be passed on to their offspring. The Rufous Hummingbird nests farther north than any other species and must tolerate temperatures below freezing on its breeding grounds. This cold hardiness enables it to survive temperatures well below freezing, provided that adequate shelter and feeders are available.
Systematics and evolution
In traditional taxonomy, hummingbirds are placed in the order Apodiformes, which also contains the swifts. However, some taxonomists have separated them into their own order, Trochiliformes. Hummingbirds' wing bones are hollow and fragile, making fossilization difficult and leaving their evolutionary history poorly documented. Though scientists theorize that hummingbirds originated in South America, where there is the greatest species diversity, possible ancestors of extant hummingbirds may have lived in parts of Europe to what is southern Russia today.
There are between 325 and 340 species of hummingbird, depending on taxonomic viewpoint, divided into two subfamilies, the hermits (subfamily Phaethornithinae, 34 species in six genera), and the typical hummingbirds (subfamily Trochilinae, all the others). However, recent phylogenetic analyses suggest that this division is slightly inaccurate, and that there are nine major clades of hummingbirds: the topazes and jacobins, the hermits, the mangoes, the coquettes, the brilliants, the Giant Hummingbird (Patagona gigas), the mountain-gems, the bees, and the emeralds. The topazes and jacobins combined have the oldest split with the rest of the hummingbirds. The hummingbirds are the second most specious bird family on earth (after the tyrant flycatchers).
Fossil hummingbirds are known from the Pleistocene of Brazil and the Bahamas; however, neither has yet been scientifically described, and there are fossils and subfossils of a few extant species known. Until recently, older fossils had not been securely identifiable as those of hummingbirds.
In 2004, Dr. Gerald Mayr of the Senckenberg Museum in Frankfurt am Main identified two 30-million-year-old hummingbird fossils and published his results in Science. The fossils of this primitive hummingbird species, named Eurotrochilus inexpectatus ("unexpected European hummingbird"), had been sitting in a museum drawer in Stuttgart; they had been unearthed in a clay pit at Wiesloch–Frauenweiler, south of Heidelberg, Germany and, because it was assumed that hummingbirds never occurred outside the Americas, were not recognized to be hummingbirds until Mayr took a closer look at them.
Fossils of birds not clearly assignable to either hummingbirds or a related, extinct family, the Jungornithidae, have been found at the Messel pit and in the Caucasus, dating from 40–35 mya; this indicates that the split between these two lineages indeed occurred at that date. The areas where these early fossils have been found had a climate quite similar to the northern Caribbean or southernmost China during that time. The biggest remaining mystery at the present time is what happened to hummingbirds in the roughly 25 million years between the primitive Eurotrochilus and the modern fossils. The astounding morphological adaptations, the decrease in size, and the dispersal to the Americas and extinction in Eurasia all occurred during this timespan. DNA-DNA hybridization results  suggest that the main radiation of South American hummingbirds at least partly took place in the Miocene, some 12–13 mya, during the uplifting of the northern Andes.
Wing Structure and Colours
Many of the Hummingbird species have bright plumage with exotic colouration. In many species, the coloring does not come from pigmentation in the feather structure, but instead from prism-like cells within the top layers of the feathers. When light hits these cells, it is split into wavelengths that reflect to the observer in varying degrees of intensity. The Hummingbird wing structure acts as a diffraction grating. The result is that, merely by shifting position, a muted-looking bird will suddenly become fiery red or vivid green. However, not all hummingbird colors are due to the prism feather structure. The rusty browns of Allen's and Rufous Hummingbirds come from pigmentation. Iridescent hummingbird colors actually result from a combination of refraction and pigmentation, since the diffraction structures themselves are made of melanin, a pigment.
In myth and culture
Aztecs wore hummingbird talismans, the talismans being representations as well as actual hummingbird fetishes formed from parts of real hummingbirds: emblematic for their vigor, energy, and propensity to do work along with their sharp beaks that mimic instruments of weaponry, bloodletting, penetration, and intimacy. Hummingbird talismans were prized as drawing sexual potency, energy, vigor, and skill at arms and warfare to the wearer.
* The Aztec god Huitzilopochtli is often depicted as a hummingbird. The Nahuatl word huitzil (hummingbird) is an onomatopoeic word derived from the sounds of the hummingbird's wing-beats and zooming flight.
* One of the Nazca Lines depicts a hummingbird.
* The Ohlone tells the story of how Hummingbird brought fire to the world.
* Trinidad and Tobago is known as "The land of the hummingbird," and a hummingbird can be seen on that nation's coat of arms and 1-cent coin as well as its national airline, Caribbean Airlines.
* Auto enthusiasts named Chrysler's reduction gear Starter motor, used from the early 60s to the late 90s, the Highland Park Hummingbird.
FONTE IMMAGINE: http://en.wikipedia.org/wiki/File:Selasphorus_rufus_on_Saltspring_Island.jpg
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