Category: Birds
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With around 10,000 living species, the birds are the largest class of tetrapod vertebrates. They are an extremely diverse and successful group, including species as different as the tiny bee hummingbird and the enormous African ostrich, and inhabit virtually every ecosystem on the planet. Often referred to as "glorified reptiles", birds have evolved from theropod-like feathered dinosaurs, which are themselves convergent in as much as "birds" evolved at least two other times in the form of Microraptor and Rahonavis. Modern birds are characterised by a combination of features, the most prominent of which is, of course, powered flight (that has independently been invented by bats and insects as well as the extinct pterosaurs). Flightlessness, however, has evolved repeatedly in birds as well.
Birds present many insights into evolutionary convergence and show some fascinating parallels with mammals, particularly in the evolution of key innovations such as endothermy ("warm-bloodedness"), which has been linked to the evolution of parental care. Parental care, being a particular hallmark of birds and mammals (despite having evolved independently in other groups as well), might have promoted complex social structures as well as vocalisations. Birds are famous for their singing, but the song of birds has evolved at least three times independently and also shows important convergences with other animals, including humans. Some birds rival mammals in intelligence and cognitive abilities, particularly the New Caledonian crows, which are famous for their tool use.
Within the mammals we find classic convergences relating to placental and marsupial ecomorphs, and a remarkably similar parallelism is also found in the birds. Examples include a whole series of fascinating analogues between the two major Neoaves lineages, the coronavians and the metavians, as well as the striking similarities between the Old World vultures and New World vultures. Both groups of vultures are divided into ecological categories that reflect distinct feeding strategies, such as general scavenging of the carcass, preference for soft innards and offal and discarded scraps. Similarly we see ecomorphological convergence in the raptors, with six identifiable ecomorph categories: those that hunt fish, reptiles and amphibians, other birds and mammals, as well as those that are scavengers or generalists. Moving beyond the general documentation of ecomorphs, birds also provide examples of convergence at the community level, such as amongst those inhabiting Mediterranean-type habitats (of additional interest because of the evidence for convergent evolution in Mediterranean-type floras), tidal marshes and peatlands.
Other notable instances of convergence involving birds include cases relating to specific genetics, biochemistry, enzymes and sensory systems. Convergences in plumage colouration are connected to molecular pathways for protein or pigment synthesis and the production of repellent chemicals that serve various functions such as defence against predators and ectoparasites (e.g. lice) has independently evolved in several bird groups. One famous example are the pitohuis from New Guinea. The hoatzin is a curious bird from South America, well known for its climbing abilities and its consumption of leaves. To assist gut fermentation of the vegetation, hoatzins have independently evolved the ability to synthesise lysozyme, showing a striking convergence with the digestive system found in ruminant mammals and some monkeys. In terms of sensory perception, a rather remarkable convergence is the evolution of echolocation, famously in the South American oilbirds and also the Asian swiftlets. Most other birds evidently rely on vision, which in itself is of interest because of the convergent evolution in such features as ultraviolet vision (e.g. in blue tits and kestrels).
| Topic title | Teaser text | Availability |
|---|---|---|
| Migration in birds and insects | n/a | Unavailable |
| Convergence in ovenbirds and woodcreepers | n/a | Unavailable |
| Convergence in ducks and their relatives | n/a | Unavailable |
| Convergence in hawks | n/a | Unavailable |
| Flightlessness in birds | n/a | Unavailable |
| Foregut fermentation in birds | A foregut-fermenting bird was long considered a paradox. But what about the hoatzin, a curious South American bird known locally as the "stinking pheasant" thanks to its smell of fresh cow manure? | Available |
| Co-operative breeding | n/a | Unavailable |
| Daily torpor in birds and mammals | n/a | Unavailable |
| Nest-building in birds | n/a | Unavailable |
| Endothermy ("warm-bloodedness") | n/a | Unavailable |
| Owls and frogmouths | n/a | Unavailable |
| Brood parasitism in cuckoos and other birds | Obligate brood parasitism has evolved several times independently in birds. Apart from the cuckoos, it can be found in four other, only distantly related families. | Available |
| Teaching in humans, meerkats, birds and ants | n/a | Unavailable |
| Honeycreepers | n/a | Unavailable |
| Kiwi and kokako: mammal-like birds of New Zealand | n/a | Unavailable |
| Ultraviolet (UV) vision in insects and vertebrates | n/a | Unavailable |
| Vibrational communication in animals | What on earth could an elephant or treehoppers have in common with a seismometer? | Available |
| Pressure sensitivity and the tactile sense (excluding the lateral line) | The star-nosed mole is famous for, well, its nose, but do you have any idea what these peculiar 'tentacles' are for? The answer is rather touching and, of course, convergent... | Available |
| Trabeculae (skeletons) | n/a | Unavailable |
| Echolocation in birds: oilbirds and swiftlets | The best known example of echolocating birds are the South American oilbirds (Steatornis caripensis), so called because their flesh yields abundant oil. | Available |
| Evolution of birds from feathered reptiles | Birds, in the sense of flying descendants of feathered reptiles (a more expansive group than the "true" birds in today's skies), evolved at least twice, and possibly as many as four times, from within the theropods. | Available |
| Feathers and similar integumentary structures | n/a | Unavailable |
| Hummingbirds, sunbirds and honeyeaters | One of the most well known examples of convergence among birds is between hummingbirds, sunbirds and honeyeaters, all of which are small, dominantly nectar-feeding birds. | Available |
| Beak structures in reptiles and birds | Among reptile taxa with beak structures, we find several cases of convergent evolution, for example between turtles, Uromastyx lizards, a number of herbivorous dinosaurs and the tuatara (Sphenodon) of New Zealand. | Available |
| Independent eye movement in fish, chameleons and frogmouths | One of the most surprising convergences amongst animals is that seen between a small fish that lives in coral sands, known as the sandlance, and the lizards known as chameleons. | Available |
| Gliding in feathered reptiles | A number of reptile species have been discovered in the Mesozoic fossil record, bearing feathers that were apparently used to support gliding locomotion, rather than true, powered flight as we see in present day birds. | Available |
| Wire plants, moas and elephant birds | Madagascar and New Zealand were once home to giant herbivorous birds. And the plants have not forgotten... | Available |
| Telephoto eyes in animals | Pursued by the paparazzi? Watch out for those animals equipped with telephoto lenses... | Available |
| Lysozyme | Lysozymes are common antibacterial enzymes that protect our eyes and nose from infection, but some animals have recruited them for a rather different purpose... | Available |
| Birds as ecomorphs | n/a | Unavailable |
| Bird song | n/a | Unavailable |
| Intelligence and cognition in birds | House sparrows are known to gain access to shopping malls by flying in front of sensors that operate sliding doors, whilst herons have been shown to be adept fishers using baits and lures. | Available |
| Filter feeding in whales, birds and reptiles | Filter feeding is most familiar in the baleen whales , but closely analogous arrangements have appeared at least twice in the birds, first the flamingos and second the sub-antarctic broad-billed prions. | Unavailable |
| Birds: insights into convergence | Intriguing ecological and morphological parallels can be found among the Neoaves. Many of these forms were initially believed to be each other's closest relatives, but are now widely recognised as classic examples of convergence. Think how similar swifts and swallows are, but they are only distantly related. | Available |
| Structural colouration in birds | In the great majority of birds both the colour of the feathers (plumage) and the skin is a result of so-called structural colouration which arises from the interaction of the light with ordered biological tissue | Unavailable |
| Gut fermentation in herbivorous animals | Ever tried eating a newspaper? Don't. Plant cell walls contain cellulose, which is notoriously difficult to digest. Considering that all vertebrates lack the enzymes to attack this polysaccharide, how do so many of them manage to survive on a plant diet? | Available |
| Pigmentation in birds | The striking plumage of the turaco owes its colour to turacoverdin. Interestingly, this is a copper based pigment and is also convergent in the jacanas, a group of wading birds. | Unavailable |
| Tool use in birds | What animals can drop stones into a water-filled tube to bring floating food within reach, bend wire to form a hook and use a short stick to retrieve a longer one that allows them to fish for food? Obviously chimpanzees? No, New Caledonian crows have evolved sophisticated tool use independently. | Available |
| Sleep in animals | Suffering from insomnia? Fruit flies do as well... | Available |
| Woodpeckers and woodpecker-like birds and mammals | You think woodpeckers are unique? Consider the ovenbirds. Or even the curious aye-aye. | Available |
| Plumage in birds | Exampes of convergece in bird plumage are the well-known tendency for different groups of tropical sea-birds to have dark plumage, and what may represent Müllerian mimicry in the pitohuis, which are famous for their convergent use of toxic alkaloids. | Unavailable |
| Insecticide production: from plants to primates | Application of insecticides, such as against mosquitoes, has been documented in several primates and birds. | Unavailable |
| Hummingbirds and hummingbirdoid moths | Like other birds hummingbirds are warm-blooded, but so independently are the hawk-moths, which like a number of insects have evolved thermoregulation. | Available |
| Vultures: insights into convergence | Vultures are not only charistmatic birds in the popular imagination, but are strikingly convergent, as the Old World and New World vultures are not closely related. | Unavailable |
| Parental care in vertebrates, echinoids, molluscs and brachiopods | The independent evolution of parental care is far more widespread than birds and mammals, extending as far as molluscs and echinoderms! | Unavailable |
| Play in birds, mammals and octopus | Social play is the hall-mark of the most intelligent of this planet’s species, and there is a particularly striking convergence between birds and mammals. | Unavailable |
| Penis form in mammals, turtles, birds and octopus | The specific case of a penis with a hydrostatic structure, as well as an array of collagen fibres that allows both expansion and guards against aneurysms, has evolved in a strikingly convergent fashion in mammals and turtles. | Available |
| Simple tool use in owls and cephalopods | Burrowing owls place pieces of collected dung. These attract insects such as beetles that are then eaten by the owls. | Available |
| Personality in vertebrates and cephalopods | Personality in the vertebrates might, therefore, be deeply embedded in their phylogeny, although this does not rule out the convergent appearance of more complex personality traits in more advanced vertebrates, notably birds and mammals. | Unavailable |
| Lekking in birds, fish, mammals and cephalopods | Complex interactions between males and females prior to mating have evolved independently many times. Amongst the most familiar examples are leks. | Unavailable |
| Asymmetric eye use in octopus, dolphins and birds | In a number of cases one eye is used in preference to another. This convergent phenomenon is found in octopus (cephalopods), dolphins, birds, and other animals. | Unavailable |
