Bird Island

Bird Island (Namibia)

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Bird Island as seen from the Namibian coast

Bird Island is a man-made platform off the coast of Namibia between Walvis Bay and Swakopmund. It serves as a breeding ground for birds (primarily Cape Cormorants) and yields a large amount of guano which is collected and sold.^[1][2]

[edit] History

Bird Island was conceived and constructed by Adolf Winter, a German who emigrated to South West Africa (now known as Namibia) in 1912. Winter took a train from Swakopmund to nearby Walvis Bay and saw a natural offshore formation called Bird Rock, covered in guano from many birds. On the return trip he noticed the guano had been washed away by the sea, and saw a business opportunity.
Bird Island began as a wooden platform measuring four meters square, three meters above the sea. Winter finished this initial construction in March 1930. One year later he had enlarged the platform to 16 meters square, and by August 1931 had extended it to 1600 square meters. By this point a considerable amount of guano was collected and sold annually, and expansion of the platform continued at a slower pace until 1937, when a large shipment of timber allowed building the platform out to its current size of 17,000 square meters.

[edit] Economics

Arrangements for transporting guano to shore

The guano collected from Bird Island is considered high quality for its high nitrogen content relative to other guano collection facilities in the region. It is cleaned in Swakopmund to remove feathers and other debris, ground to a powder, and exported to Belgium for US$285 per ton.^[3] The platform yields approximately 650 tons of guano annually.

[edit] References

1. ^ http://web.uct.ac.za/depts/stats/adu/walvisbayguanoplatform.htm
2. ^ http://www.namibweb.com/guano.htm
3. ^ Plaque at the National Marine Aquarium of Namibia, Swakopmund

Coordinates: 22°52′43″S 14°32′09″E / 22.8786°S 14.5357°E / -22.8786; 14.5357

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Bird Island

Algoa Bay

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Algoa Bay with Port Elizabeth in the foreground

Algoa Bay is a wide inlet along the South African east coast, some 425 miles (683 kilometres) east of the Cape of Good Hope. It is bounded in the west by Cape Recife and in the east by Cape Padrone. The bay is up to 436 m deep. The harbour city of Port Elizabeth is situated adjacent to the bay, as is the new Coega deep water port facility.

Contents [hide] 1 Port Elizabeth 2 Portuguese discovery 3 Islands 3.1 The St Croix group 3.2 The Bird Island group 3.3 Bird and wildlife 3.4 Conservation issues 4 Hazards 5 See also 6 References 7 External links

[edit] Port Elizabeth

The metropolitan municipality of Nelson Mandela Bay, which includes Port Elizabeth, is located on the western shore of Algoa Bay.

[edit] Portuguese discovery

The Portuguese explorer Bartolomeu Dias was the first European to reach Algoa Bay in 1488, where he planted a wooden cross on a small island now called St Croix or Santa Cruz island.^[1] He gave the bay a name meaning "Bay of the Rock", which was changed in Portugal to Bahia de Lagoa or Bay of the Lagoon, and which eventually became Algoa Bay.
Joshua Slocum talks about Algoa Bay in his book 'Sailing Alone Around the World':

“

The early Portuguese navigators, endowed with patience, were more than sixty-nine years struggling to round this cape before they got as far as Algoa Bay, and there the crew mutinied. They landed on a small island, now called Santa Cruz, where they devoutly set up the cross, and swore they would cut the captain's throat if he attempted to sail farther. Beyond this they thought was the edge of the world, which they too believed was flat; and fearing that their ship would sail over the brink of it, they compelled Captain Diaz, their commander, to retrace his course, all being only too glad to get home. A year later, we are told, Vasco da Gama sailed successfully round the "Cape of Storms," as the Cape of Good Hope was then called, and discovered Natal on Christmas or Natal day; hence the name. From this point the way to India was easy.

”

[edit] Islands

The bay contains six named islands in two groups of three that according to BirdLife International “are of considerable importance as they are the only islands along a 1,777 km stretch of coastline between Cape Agulhas and Inhaca Island in Mozambique." The combined surface area of these islands is said to be 40 hectares.
Close inshore, near the new Ngquru harbour development at Coega, on the north-eastern outskirts of Port Elizabeth, is the St Croix group, consisting of a main island of that name and two lesser islets, Jahleel Island just off the Ngquru breakwater and Brenton Island on the seaward side. The second group consists of Bird, Seal and Stag Islands. All six islands and their adjacent waters are declared nature reserves and form part of the Addo Elephant National Park. The islands are closed to the public.
Also worthy of mention, if only as an obstacle to navigation, is Despatch Rock, 2.4 km due east of the Port Elizabeth suburb of Summerstrand. The rock, which is submerged at high tide, is marked with a light. Further south, about a kilometre southwest of Cape Recife, the western starting point of the bay is Thunderbolt Reef. Though not in the bay, this hazard to navigation has claimed many ships carelessly entering or leaving. Thunderbolt Reef is submerged save for spring low tides and the surf crashing on it can be observed from the mainland.

[edit] The St Croix group

St Croix Island seen from the nearest landfall at Hougham Park, just east of the Coega harbour development. From here the island is about 4 km to sea. Two disused stone bungalows, used by guano collectors and then by the local university for research purposes are visible.

St Croix Island at 33°47′58″S 25°46′11″E / 33.79944°S 25.76972°E / -33.79944; 25.76972 (St Croix) is 3.9 km from the nearest land and rises to 59 m.^[2] The BirdLife fact sheet states the 12 hectare island is only 58 m above sea level. It adds that the island is rocky and “supports minimal vegetation”. The island runs 700 m along a northwest, southeast axis and is about 300 m wide at its broadest – along the west coast. Its highest point is halfway along the north coast.
Brenton Island (33°49′3″S 25°45′54″E / 33.8175°S 25.765°E / -33.8175; 25.765 (Brenton Island)) is equally sparsely vegetated and is less than 20 metres in elevation, and is roughly 250 m by 200 m in size with a northwest-southeast orientation. It is 5.75 km to sea from the nearest point on the mainland and 1.75 km south of St Croix. Jahleel, at less than 10 metres in height, is just over a kilometre from the closest beach and less than that from Ngquru’s 2.6 km long eastern breakwater. Jahleel is about the same size as Brenton and has a north-south axis. It is 5.75 km west of St Croix.

[edit] The Bird Island group

For other places with the same name, see Bird Island (disambiguation).

Brenton Island seen from the same location as the previous image. The island is just less than 6km offshore.

In 1755, the East Indiaman Doddington was wrecked here while underway from Dover to India. Most of the passengers and crew perished, but a few managed to make it to the islands where they were marooned for seven months until one of their number, a carpenter, was able to make a boat for them. The survivors subsisted primarily on fish, birds and eggs until they were able to reach land. The ship was carrying a significant quantity of gold and silver, some of which was illegally salvaged in more recent times.^[3] Bird Island was named by the survivors as they left the island in their boat.^[4]
Bird Island (33°50′26″S 26°17′10″E / 33.84056°S 26.28611°E / -33.84056; 26.28611 (Bird Island)), Seal Island and Stag Island lie in close proximity some 40 km east of the St Croix group or 53 km due east of Port Elizabeth and 7 km from the nearest landfall at Woody Cape – part of the Addo Elephant National Park. Bird Island has a lighthouse, erected in 1898 after a series of wrecks in the vicinity of the island. Doddington Rock, West rock and East Reef lie just South-West of the group of islands.
At 19 hectares, Bird Island is the largest of the Algoa Bay islands – according to BirdLife. It is relatively flat and rises to 9 m. Seal Island is 0.6ha in size and lies 360 m north of Bird Island. Stag Island is even smaller at 0.1ha and is 320 m north-west of Bird Island. "Much of the island group is covered by sparse growth of mixed vegetation dominated by the fleshy herb Mesembryanthemum (fig marigold/icicle plants). Tetragonia (Duneweed) and Chenopodium (Goosefoot) form localised thickets that provide cover for some seabirds," the fact sheet says.

[edit] Bird and wildlife

The BirdLife fact sheet adds that 14 species of seabirds, several species of shorebirds and 33 species of terrestrial birds have been recorded on the islands. Eight seabird species were known to breed on the islands in 2007. “These are the only islands off southern mainland Africa where Sterna dougallii (Roseate Tern) breeds regularly.”
The islands are also home to 43% of the global population of the African Penguin (Spheniscus demersus), the majority of which are on St Croix. St Croix also holds a locally significant breeding population of Cape Cormorant (Phalacrocorax capensis).
Bird Island is one of only six breeding sites in the world for the Cape Gannet (Morus capensis). “Larus dominicanus (the Kelp Gull) and Haematopus moquini (the African Oystercatcher) are found throughout the Algoa Bay complex. The island group is also known to hold large numbers of Sterna vittata (Antarctic Tern), which in winter roost on the island in their thousands (regularly holding between 10% and 20% of the estimated total Afrotropical non-breeding population).” The island is also home to a Cape Fur Seals (Arctocephalus pusillus).

[edit] Conservation issues

The St Croix group and a 300 m maritime zone around each island became South Africa’s island marine reserve in 1981 and were administered as part of the then-Woody Cape Nature Reserve. Up to then, the islands had fallen under the control of the Guano Islands section of the Division of Sea Fisheries. The Eastern Cape Nature Conservation service, which subsequently became the Directorate of Nature Conservation of the Eastern Cape Province, managed the islands after April 1992 according to BirdLife. The Woody Cape reserve was subsequently incorporated into the Addo National Elephant Park, which then boasted that it was home to Africa’s “big six” – the elephant, lion, leopard, rhinoceros, buffalo and the Great White Shark that inhabits the bay.
Conservationists are wary of the Ngquru development which in time, in addition to a deep water port will include a heavy-industry complex. Mooted occupants include an aluminium smelter and an oil refinery. They see the development as posing, according to BirdLife:

“

a huge threat to the seabirds of the St Croix group. The development would result in increased pollution and shipping activity, which would affect all breeding seabirds negatively.

”

The NGO notes that the population of the African Penguin in the bay has been increasing steadily during the last century. “There are only a few growing colonies in the world, and it is thought that these birds may be relocating here from colonies that are in decline in the Western Cape or farther afield. Certain factors are known to affect seabirds throughout their ranges. Competition with commercial fisheries, especially purse-seining for surface-shoaling fish such as anchovy (Engraulis capensis) and pilchard (Sardinops sagax), has been implicated as one of the most significant factors causing seabird population declines." The organisation has recommended that marine reserves with a radius of 25 km be created around important breeding islands, and that commercial fishing be banned or restricted in these zones.
The fact sheet continues: “An unpredictable threat, which is difficult to control, is chronic pollution by crude oil or other pollutants which spill into the ocean when tankers break open, wash their tanks, dump cargo or pump bilge. The African Penguin (Spheniscus demersus) is particularly susceptible to these events, and a single oil disaster has the ability to severely affect populations. It is believed that the breeding sites in Algoa Bay, at the eastern extremity of the species' range, are at highest risk as they are closest to the major oil-shipping routes.”

[edit] Hazards

Nautical charts of the bay^[5] caution mariners that "projectiles and badly corroded mustard gas containers have been found in the area between Cape St Francis and Bird Island out to depths of 400 metres. Trawlers should exercise the greatest caution."
The chemical weapons were dumped in the bay in the aftermath of World War II. During that conflict, Port Elizabeth was used as a research, manufacturing and storage site for Allied poison gas. An official at the SA Navy's Hydrographic Office recalls that at least one trawler once snagged a projectile or canister in its nets and that the crew were badly burned.^{[citation needed]} The condition of the canisters and projectiles are not currently known. There is no record of any recent incidents.

Bird food

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This article's tone or style may not be appropriate for Wikipedia. Specific concerns may be found on the talk page. See Wikipedia's guide to writing better articles for suggestions. (January 2010)

A mixture of seeds in a bird feeder

Bird food is food (often varieties of seeds) eaten by birds. Humans generally make or buy bird food to feed to pet birds or use in birdfeeders. Birdfood can be natural or commercial. The choice of what to use as birdfood depends on the species of bird being fed.

Contents [hide] 1 Natural bird food 1.1 Seed 1.2 Non-seed 2 Commercial bird food 2.1 Nonfarm 2.2 Farm 3 External links 4 References

[edit] Natural bird food

Bushtits eating suet from a bird feeder

[edit] Seed

Black sunflower seeds are highly recommended for use in bird feeders because they attract a wide variety of birds, have a high ratio of meat to shell, and are high in fat content.^[1][2] Other common birdseeds include niger, or thistle seed, a favorite of goldfinches, millet for sparrows and juncos, and safflower for cardinals, among others.^[1][2].

[edit] Non-seed

Not all birds eat seeds. Suet (beef or mutton fat) is recommended for insect-eating birds like nuthatches and woodpeckers.^[1] Nectar (essentially sugar water) attracts hummingbirds.^[1] Bread and kitchen scraps are often fed to ducks and gulls. Chickens are commonly fed corn, wheat, barley, sorghum and milling by-products.
These seeds and non-seed supplies are commonly obtained as by-products on farms, but can also be bought from independent retailers.

[edit] Commercial bird food

[edit] Nonfarm

A wide variety of commercial bird food is available to bird owners, combining a variety of seeds in a single mix. Individual types of bird tend to pick out their favorite seeds and leave the rest uneaten, to be picked up by other birds.^[2][3]

[edit] Farm

Farmed birds fed commercial bird food typically are given very specific scientifically designed preblended feed. Examples of commercial bird food for chickens include chick starter medicated crumbles, chick grower crumbles, egg layer mash, egg layer pellet, egg layer crumbles, egg producer pellet, and broiler maker med crumbles. Pellet crumbles are often prepared for tiny chicks. Mash is more finely ground.

Bird feeding

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A bird table, with a Wood Pigeon on the roof, in an English garden. The table provides water, peanuts, sunflower seeds, and a seed mix.

Bird feeding is the activity of feeding wild birds, often by means of a bird feeder.

Contents [hide] 1 History 2 Activity 3 Types 4 Impact 5 Economy 6 See also 7 References 8 External links

[edit] History

James Fisher has written that the first person recorded as feeding wild birds was the sixth century monk Saint Serf of Fife who tamed a robin by feeding it. In the harsh winter of 1890-91 in Britain national newspapers asked people to put out food for birds. In 1910 in the United Kingdom, Punch magazine declared that feeding birds was a "national pastime."^[1] Bird feeding has grown into the United States' second most popular hobby behind gardening.^[2] To celebrate the bird feeding hobby, February was named National Bird-Feeding Month by congressional decree in 1994.^[3]

[edit] Activity

See also: Bird food

Bird feeding is typically thought of as an activity of bird enthusiasts. People who feed wild birds often attempt to attract birds to suburban and domestic locations. This requires setting up a feeding station and supplying bird food. The food might include seeds, peanuts, bought food mixes, fat, kitchen scraps and suet. Additionally, a bird bath and grit (sand), that birds store in their crops to help grind food as an aid to digestion, can be provided.
Feeding bread to waterfowl at parks, lakes and rivers is also a popular activity.

[edit] Types

Certain foods tend to attract certain birds.^[4] Finches and siskin will be attracted by niger^[5] and Jays love corn. Hummingbirds love nectar. Mixed seed attracts many birds. Black oil sunflower seed is favored by many seed-eating species. Different feeders can be purchased specialized for different species.
Garden birds can be fed using peanuts, seed, coconut or fat using a variety of feeders.^[6]
After the station is established, it can take some weeks for birds to discover and start using it. This is particularly true if the feeding station is the first one in an area or (in cold-winter areas) if the station is being established in spring when natural sources of food are plentiful. Therefore, beginners should not completely fill a feeder at first. The food will get old and spoil if it is left uneaten for too long. This is particularly true of unshelled foods, such as thistle seed and suet. Once the birds begin taking food, the feeder should be kept full. Additionally, people feeding birds should be sure that there is a source of water nearby. A bird bath can attract as many birds as a feeding station.^{[citation needed]}

[edit] Impact

A study conducted in the city of Sheffield, UK, found that the abundance of garden birds increased with levels of bird feeding. This effect was only apparent in those species that regularly take supplementary food, raising the possibility that bird feeding was having a direct effect on bird abundance. In contrast, the density of feeding stations had no effect on the number of different bird species present in a neighbourhood.^[7]
The use of bird feeders has been claimed to cause environmental problems;^[specify] some of these were highlighted in a front-page article in The Wall Street Journal. ^[8]
Prior to the publication of the Wall Street Journal article, Canadian ornithologist Jason Rogers also wrote about the environmental problems associated with the use of bird feeders in the journal Alberta Naturalist.^[9] In this article, Rogers explains how the practice of feeding wild birds is inherently fraught with negative impacts and risks such as fostering dependency, altering natural distribution, density, and migration patterns, interfering with ecological processes, causing malnutrition, facilitating the spread of disease, and increasing the risk of death from cats, pesticides, hitting windows, and other causes.
In a paper in the journal Oecologia, it was reported that feeding of blue tits and great tits with peanut cake over a long time period significantly reduced brood size. This was driven by smaller clutch sizes in both species and lower hatching success rates for blue tits.^[10] Studies by the University of Freiburg and Environment Canada found that blackcaps migrating to Great Britain from Germany had become adapted to eating food supplied by humans. In contrast blackcaps migrating to Spain had bills adapted to feeding on fruit such as olives.^[11]

[edit] Economy

Large sums of money are spent by ardent bird feeders, who indulge their wild birds with a variety of bird foods and bird feeders. Over 55 million Americans over the age of 16 feed wild birds and spend more than $3 billion a year on bird food, and $800 million a year on bird feeders, bird baths, bird houses, and other bird feeding accessories.^[12] The activity has spawned an industry that sells supplies and equipment for the bird feeding hobby.
In some cities or parts of cities (e.g. Trafalgar Square in London) feeding pigeons is forbidden, either because they compete with vulnerable native species, or because they abound and cause pollution and/or noise.^{[citation needed]}

[edit] Adaptations for flight

1 Axillaries; 2 Margin (Marginal underwing coverts); 3 Lesser underwing coverts; 4 Median underwing coverts (Secondary coverts); 5 Greater underwing coverts (Secondary coverts); 6 Carpal joint; 7 Lesser underwing primary coverts; 8 Greater undering primary coverts; 9 Secondaries; 10 Primaries

The most obvious adaptation to flight is the wing, but because flight is so energetically demanding birds have evolved several other adaptations to improve efficiency when flying. Birds' bodies are streamlined to help overcome air-resistance. Also, the bird skeleton is hollow to reduce weight, and many unnecessary bones have been lost (such as the bony tail of the early bird Archaeopteryx), along with the toothed jaw of early birds, which has been replaced with a lightweight beak. The skeleton's breastbone has also adapted into a large keel, suitable for the attachment of large, powerful flight muscles. The vanes of the feathers have hooklets called barbules that zip them together, giving the feathers the strength needed to hold the airfoil (these are often lost in flightless birds).
The large amounts of energy required for flight have led to the evolution of a unidirectional pulmonary system to provide the large quantities of oxygen required for their high respiratory rates. This high metabolic rate produces large quantities of radicals in the cells that can damage DNA and lead to tumours. Birds, however, do not suffer from an otherwise expected shortened lifespan as their cells have evolved a more efficient antioxidant system than those found in other animals.^{[citation needed]}

[edit] Evolution of bird flight

Main article: Origin of avian flight

Marine birds fly at Cape Hay in the High Arctic

Most paleontologists agree that birds evolved from small theropod dinosaurs, but the origin of bird flight is one of the oldest and most hotly contested debates in paleontology.^[3] The four main hypotheses are: "from the trees down", that birds' ancestors first glided down from trees and then acquired other modifications that enabled true powered flight; "from the ground up", that birds' ancestors were small, fast predatory dinosaurs in which feathers developed for other reasons and then evolved further to provide first lift and then true powered flight; and "wing-assisted incline running" (WAIR), a version of "from the ground up" in which birds' wings originated from forelimb modifications that provided downforce, enabling the proto-birds to run up extremely steep slopes such as the trunks of trees; and "Pouncing Proavis", which posits that flight evolved by modification from arboreal ambush tactics.
There has also been debate about whether the earliest known bird, Archaeopteryx, could fly. It appears that Archaeopteryx had the brain structures and inner-ear balance sensors that birds use to control their flight.^[4] Archaeopteryx also had a wing feather arrangement like that of modern birds and similarly asymmetrical flight feathers on its wings and tail. But Archaeopteryx lacked the shoulder mechanism by which modern birds' wings produce swift, powerful upstrokes; this may mean that it and other early birds were incapable of flapping flight and could only glide.^[5] The presence of most fossils in marine sediments in habitats devoid of vegetation has led to the hypothesis that they may have used their wings as aids to run across the water surface in the manner of the basilisk lizards.^[6]

[edit] From the trees down

This was the earliest hypothesis, encouraged by the examples of gliding vertebrates such as flying squirrels. It suggests that proto-birds like Archaeopteryx used their claws to clamber up trees and glided off from the tops.^[7]
Some recent research undermines the "trees down" hypothesis by suggesting that the earliest birds and their immediate ancestors did not climb trees. Modern birds that forage in trees have much more curved toe-claws than those that forage on the ground. The toe-claws of Mesozoic birds and of closely-related non-avian theropod dinosaurs are like those of modern ground-foraging birds.^[8]

[edit] From the ground up

Feathers are very common in coelurosaurid dinosaurs (including the early tyrannosauroid Dilong).^[9] Modern birds are classified as coelurosaurs by nearly all palaeontologists,^[10] though not by a few ornithologists.^[7][11] The original functions of feathers may have included thermal insulation and competitive displays. The most common version of the "from the ground up" hypothesis argues that bird's ancestors were small ground-running predators (rather like roadrunners) that used their forelimbs for balance while pursuing prey and that the forelimbs and feathers later evolved in ways that provided gliding and then powered flight.^[12] Another "ground upwards" theory argues the evolution of flight was initially driven by competitive displays and fighting: displays required longer feathers and longer, stronger forelimbs; many modern birds use their wings as weapons, and downward blows have a similar action to that of flapping flight.^[13] Many of the Archaeopteryx fossils come from marine sediments and it has been suggested that wings may have helped the birds run over water in the manner of the Jesus Christ Lizard (Common basilisk).^[14]
Most recent attacks on the "from the ground up" hypothesis attempt to refute its assumption that birds are modified coelurosaurid dinosaurs. The strongest attacks are based on embryological analyses, which conclude that birds' wings are formed from digits 2, 3 and 4 (corresponding to the index, middle and ring fingers in humans; the first of a bird's 3 digits forms the alula, which they use to avoid stalling on low-speed flight, for example when landing); but the hands of coelurosaurs are formed by digits 1, 2 and 3 (thumb and first 2 fingers in humans).^[15] However these embryological analyses were immediately challenged on the embryological grounds that the "hand" often develops differently in clades that have lost some digits in the course of their evolution, and therefore bird's hands do develop from digits 1, 2 and 3.^[16][17][18]

[edit] Wing-assisted incline running

The WAIR hypothesis was prompted by observation of young chukar chicks, and proposes that wings developed their aerodynamic functions as a result of the need to run quickly up very steep slopes such as tree trunks, for example to escape from predators. Note that in this scenario birds need downforce to give their feet increased grip.^[19][20] But early birds, including Archaeopteryx, lacked the shoulder mechanism by which modern birds' wings produce swift, powerful upstrokes; since the downforce on which WAIR depends is generated by upstrokes, it seems that early birds were incapable of WAIR.^[5]

[edit] Pouncing Proavis model

This theory was first proposed by Garner, Taylor, and Thomas in 1999:

We propose that birds evolved from predators that specialized in ambush from elevated sites, using their raptorial hindlimbs in a leaping attack. Drag–based, and later lift-based, mechanisms evolved under selection for improved control of body position and locomotion during the aerial part of the attack. Selection for enhanced lift-based control led to improved lift coefficients, incidentally turning a pounce into a swoop as lift production increased. Selection for greater swooping range would finally lead to the origin of true flight.

The authors believed that this theory had four main virtues:

• It predicts the observed sequence of character acquisition in avian evolution.
• It predicts an Archaeopteryx-like animal, with a skeleton more or less identical to terrestrial theropods, with few adaptations to flapping, but very advanced aerodynamic asymmetrical feathers.
• It explains that primitive pouncers (perhaps like Microraptor) could coexist with more advanced fliers (like Confuciusornis or Sapeornis) since they did not compete for flying niches.
• It explains that the evolution of elongated rachis-bearing feathers began with simple forms that produced a benefit by increasing drag. Later, more refined feather shapes could begin to also provide lift.

[edit] Uses and loss of flight in modern birds

Birds use flight to obtain prey on the wing, for foraging, to commute to feeding grounds, and to migrate between the seasons. It is also used by some species to display during the breeding season and to reach safe isolated places for nesting.
Flight is more energetically expensive in larger birds, and many of the largest species fly by soaring and gliding (without flapping their wings) as much as possible. Many physiological adaptations have evolved that make flight more efficient.
Birds that settle on isolated oceanic islands that lack ground-based predators often lose the ability to fly. This illustrates both flight's importance in avoiding predators and its extreme demand for energy.