hummingbirds

Hummingbirds are small birds in the family Trochilidae. They are known for their ability to hover in mid-air by rapidly flapping their wings, 15 to 80 times per second (depending on the species). Capable of sustained hovering, the hummingbird has the ability to fly deliberately backwards or vertically, and to maintain position while drinking from flower blossoms. They are named for the characteristic hum made by their wings.

Hummingbirds are attracted to many flowering plants—shrimp plants, Heliconia, bromeliads, verbenas, fuchsias, many penstemons—especially those with red flowers. They feed on the nectar of these plants and are important pollinators, especially of deep-throated flowers. Most species of hummingbird also take insects, especially when feeding young.

The Bee Hummingbird (Mellisuga helenae) is the smallest bird in the world, weighing 1.8 grams. A more typical hummingbird, such as the Rufous Hummingbird (Selasphorus rufus), weighs approximately 3 g and has a length of 10-12 cm (3.5-4 inches). The largest hummingbird is the Giant Hummingbird (Patagona gigas), with some individuals weighing as much as 24 grams.

Most male hummingbirds take no part in nesting. Most species make a neatly woven cup in a tree branch. Two white eggs are laid, which despite being the smallest of all bird eggs, are in fact large relative to the hummingbird's adult size. Incubation is typically 14-19 days.

Appearance

Hummingbirds bear the most glittering plumage and some of the most elegant adornments in the bird world. Male hummingbirds are usually brightly coloured. The females of most species are duller.

The names that admiring naturalists have given to hummingbirds suggest exquisite, fairylike grace and gemlike brilliance. Fiery-tailed Awlbill, Ruby-topaz Hummingbird, Glittering-bellied Emerald, Brazilian Ruby, Green-crowned Brilliant, Festive Coquette, Shining Sunbeam, and Amethyst-throated Sunangel are some of the names applied to birds in this group.

Aerodynamics of hummingbird flight

Hummingbird flight has been studied intensively from an aerodynamic perspective: Hovering hummingbirds may be filmed using high-speed video cameras.

Writing in Nature, biophysicist 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. This finding shows that hummingbirds' hovering is similar to, but distinct from, that of hovering insects such as the hawk moths. The differences result from an inherently dissimilar avian body plan (Warrick et al., 2005).

Metabolism

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 heartbeat can reach as high as 1260 beats per minute, a rate once measured in a Blue-throated hummingbird [1]. They also typically consume more than their own weight in food each day, and to do that they have to visit hundreds of flowers daily. At any given moment, they are only hours away from starving. However, they 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 heartrate and rate of breathing are both slowed dramatically (the heartrate to roughly 50-180 beats per minute), reducing their need for food.

Studies of hummingbirds' metabolism are highly relevant to the question of whether a migrating Ruby-throated Hummingbird can cross 800 km (500 miles) of the Gulf of Mexico on a nonstop flight, as field observations suggest it does. This hummingbird, like other birds preparing to migrate, stores up fat to serve as fuel, thereby augmenting its weight by as much as 40 to 50 percent and hence increasing the bird's potential flying time. (Skutch, 1973)

Range

Hummingbirds are found only in the Americas, from southern Alaska and Canada to Tierra del Fuego, including the West Indies. The majority of species occur in tropical Central and South America, but several species also breed in temperate areas. Excluding vagrants, sometimes from Cuba or the Bahamas, only the migratory Ruby-throated Hummingbird breeds in eastern North America. The Black-chinned Hummingbird, its close relative and another migrant, is the most widespread and common species in the western United States and Canada.

Most hummingbirds of the U.S. and Canada and southern migrate to warmer climates in the northern winter, though some remain in the warmest coastal regions. Some southern South American forms also move to the tropics.

The Rufous Hummingbird shows an increasing trend to migrate east to winter in the eastern United States, rather than south to Central America, as a result of increasing survival prospects provided by artificial feeders in gardens. In the past, individuals that migrated east would usually die, but now many survive, and their changed migration direction is inherited by their offspring. Provided sufficient food and shelter is available, they are surprisingly hardy, able to tolerate temperatures down to at least -20°C.

Systematics and evolution

Traditionally, hummingbirds were placed in the order Apodiformes, which also contains the swifts. In the Sibley-Ahlquist taxonomy, hummingbirds are separated as a new order, Trochiliformes, but this is not well supported by additional evidence.

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). This arrangement has been extensively verified (see review in Gerwin & Zink, 1998).

The modern diversity of hummingbirds is thought by evolutionary biologists to have evolved in South America, as the great majority of the species are found there. All of the most common North American species are thought to be of relatively recent origin, and are therefore (following the usual procedure of lists starting with more 'ancestral' species and ending with the most recent) listed close to the end of the list. However, as seen below, the actual origin of the hummingbird lineage now seems to have been parts of Europe to what is southern Russia today.

Genetic analysis has indicated that the hummingbird lineage diverged from their closest relatives some 35 million years ago, in the Late Eocene, but fossil evidence has proved quite elusive. Fossil hummingbirds are known from the Pleistocene of Brazil and the Bahamas - neither of which has been scientifically described -, and there are fossils and subfossils of a few extant species known, but until recently, older fossils had not been securely identifiable as hummingbirds.

Then, 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 Nature^{citation needed]}. 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 never believed 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, proving 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 in this timespan. DNA-DNA hybridization results (Bleiweiss et al, 1994) suggest that the main radiation of South American hummingbirds at least partly took place in the Miocene, some 12-13 mya, durng the uplifting of the northern Andes.

Lists of species and genera

• Alphabetical list
• List of hummingbirds in taxonomic order

Hummingbirds and humans

Hummingbirds sometimes fly into garages and become trapped. It is widely believed that this is because they mistake the hanging (usually red-color) door-release handle for a flower, although hummingbirds can also get trapped in enclosures that do not contain anything red. Once inside, they may be unable to escape because their natural instinct when threatened or trapped is to fly upward. This is a life-threatening situation for hummingbirds, as they can become exhausted and die in a relatively short period of time, possibly as little as an hour. If a trapped hummingbird is within reach, it can often be caught gently and released outdoors. It will lie quietly in the space between cupped hands until released.

Hummingbird feeders and nectar

The diet of hummingbirds requires an energy source (typically nectar) and a protein source (typically small insects). For nectar, hummingbirds will happily take artificial nectar from man-made feeders. Such feeders allow people to observe and enjoy hummingbirds up-close while providing the hummingbirds with a reliable supply of nectar, especially when flower blossoms are less abundant.The feeders can be placed as high as 60 meters maximum. Homemade nectar can be made from 1 part white, granulated table sugar to 4 parts water, boiled to make it easier to dissolve the sugar and to purify the solution so that it will stay fresh longer. The cooled nectar is then poured into the feeder. Honey should not be used because it spoils quickly and is prone to culture a bacterium that is dangerous to hummingbirds.^[1] Diet sweeteners should also be avoided because, though the hummingbirds will drink it, they will be starved of the calories they need to sustain their metabolism.

Some commercial hummingbird foods contain red dyes and preservatives which are unnecessary and have not been studied for long-term effects on hummingbirds. While it is true that bright colors (especially red) attract hummingbirds, it is better to use a feeder that has some red on it, rather than coloring the water. There are suggestions that red dye is harmful to hummingbirds ^[2] . Yellow dyes also cannot be used, as it has been known to attract bees and wasps. Commercial nectar mixes may contain small amounts of mineral nutrients which are useful to hummingbirds, but hummingbirds get all the nutrients they need from the insects they eat, not from nectar, so the added nutrients are also unnecessary. Authorities on hummingbirds recommend just plain sugar and water (Shackelford et al., 2005).

A hummingbird feeder, should be easy to refill and clean. Prepared nectar can be refrigerated for 1 to 2 weeks before being used, but once placed outdoors it will only remain fresh for 2-4 days in hot weather or 4-6 days in moderate weather before turning cloudy or developing mold. Hummingbirds can be seriously harmed if they sip from a feeder with nectar that has gone bad. When changing the nectar, the feeder should be rinsed thoroughly with warm tap water, flushing the reservoir and ports to remove any contamination or sugar build-up. If dish soap is used, it needs extra rinsing so that no residue is left behind. The feeder can be soaked in dilute chlorine bleach if black specks of mold appear.

Other animals are also attracted to hummingbird feeders. It is a good idea to get a feeder that has very narrow ports, or ports with mesh-like "wasp guards", to prevent bees and wasps from getting inside where they get trapped. Orioles are known to drink from hummingbird feeders, sometimes tipping them and draining the liquid. If this becomes a problem, it is possible to buy feeders which are specifically designed to support their extra weight and which hummingbirds will use too. If ants find your hummingbird feeder, one solution is to install an "ant moat", which is available at specialty garden stores and online.

Hummingbirds in myth and culture

• The Aztec god Huitzilopochtli is often depicted as a hummingbird.
• One of the Nazca Lines depicts a hummingbird.
• The Ohlone tells the story of how a Hummingbird brought fire to the world. See an article at the National Parks Conservation Association's website for a recounting.
• Trinidad and Tobago is known as "The land of the hummingbird," and a hummingbird can be seen on that nation's 1 cent coin.
• Many popular songs have been written under the title "Hummingbird", including separate works by B.B. King, Wilco, Leon Russell, John Mayer, Frankie Laine, Cat Stevens, Seals and Crofts, Merzbow and Yuki.

See also

• Hummingbird Hawk-moth
• Hemaris, another genus of sphinx moths confused with hummingbirds
• Hummingbird feeder

References

• Bleiweiss, Robert; Kirsch, John A. W. & Matheus, Juan Carlos (1999): DNA-DNA hybridization evidence for subfamily structure among hummingbirds. Auk 111(1): 8-19. PDF fulltext

• del Hoyo, J.; Elliott, A. & Sargatal, J. (editors) (1999): Handbook of Birds of the World, Volume 5: Barn-owls to Hummingbirds. Lynx Edicions, Barcelona. ISBN 84-87334-25-3

• Gerwin, John A. & Zink, Robert M. (1998): Phylogenetic patterns in the Trochilidae. Auk 115(1): 105-118. PDF fulltext

• Meyer de Schauensee, Rodolphe (1970): A Guide to Birds of South America. Livingston, Wynnewood, PA.

• Shackelford, Clifford Eugene; Lindsay, Madge M. & Klym, C. Mark (2005): Hummingbirds of Texas with their New Mexico and Arizona ranges. Texas A&M University Press, College Station. ISBN 1-58544-433-2

• Skutch, Alexander F. & Singer, Arthur B. (1973): The Life of the Hummingbird. Crown Publishers, New York. ISBN 0-517-50572X

• Warrick, D. R.; Tobalske, B.W. & Powers, D.R. (2005): Aerodynamics of the hovering hummingbird. Nature 435: 1094-1097 DOI:10.1038/nature03647 (HTML abstract)

Footnotes

1. ^ http://faq.gardenweb.com/faq/lists/hummingbird/2003021845028716.html
2. ^ http://www.hummingbirds.net/dye.html

External links

• The Hummingbird Society
• Hummingbird Society's Photo Gallery
• "Operation Ruby Throat: The Hummingbird Project"
• Hummingbirds.net
• Hummingbirds of the World
• Hummingbirds
• How to Photograph Hummingbirds
• Hummingbird videos on the Internet Bird Collection
• Video (.wmv) (.mp4 - iPod) Hummingbird hovers and feeds. Licensed under Creative Commons Attribution-ShareAlike. Stored at blip.tv
• Video (.wmv) Hummingbird shaping a nest. Licensed under Creative Commons Attribution-ShareAlike. Stored at blip.tv
• Video (.wmv) Hummingbird adding spider's web to nest. Licensed under Creative Commons Attribution-ShareAlike. Stored at blip.tv
• Video (.wmv) Hummingbird adding downy seed to nest. Licensed under Creative Commons Attribution-ShareAlike. Stored at blip.tv