The bee-eaters are a group of near-passerine birds in the family Meropidae. Most species are found in Africa and Asia, with a few in southern Europe, Australia, and New Guinea. They are characterised by richly coloured plumage, slender bodies, and usually elongated central tail feathers. All have long down-turned bills and pointed wings, which give them a swallow-like appearance from a distance.
As the name suggests, bee-eaters predominantly eat flying insects, especially bees and wasps, which are caught in the air by sallies from an open perch. The stinger is removed by repeatedly hitting and rubbing the insect on a hard surface. During this process, pressure is applied to the insect thereby extracting most of the venom.
Most bee-eaters are gregarious. They form colonies, nesting in burrows tunnelled into the side of sandy banks, such as on the sides of rivers. As they mostly live in colonies, large numbers of nest holes may be seen together. The bee-eaters lay 2–9 white eggs per clutch, depending on species. Most species are monogamous, and both parents care for the young, sometimes with assistance from other birds in the colony.
Bee-eaters may be killed by raptors, their nests are raided by rodents and snakes, and they can can carry parasites. Some species are adversely affected by human activity or habitat loss, but none meet the International Union for Conservation of Nature's vulnerability criteria, and all are therefore evaluated as "least concern. Their conspicuous nature means that they have been mentioned by ancient writers and incorporated into mythology.
The bee-eaters have often been considered to be related to other families, such as the rollers, hoopoe and kingfishers, but birds apparently of these families were distinct at least forty million ago, so the relationship is not close, and opinions as to the nearest relatives differ, although the kingfishers seem most likely.
The bee-eaters are generally similar in appearance, although they are normally divided into three genera. Nyctyornis comprises two large species with long throat feathers, the blue-bearded bee-eater and the red-bearded bee-eater, both of which have round wings, a ridged culmen, feathered nostrils and a relatively sluggish lifestyle. The purple-bearded bee-eater is the sole member of Meropogon, which is intermediate between Nyctyornis and the typical bee-eaters, having rounded wings and a "beard", but a smooth culmen and no nostril feathers. All the remaining species are normally kept in the single genus Merops. There are close relationships within this genus, for example the red-throated bee-eater and the white-fronted bee-eater form a superspecies, but suggested new genera have not been generally accepted.
Species in taxonomic order
|Phylogeny based on a 2007 study.|
The bee-eater family contains the following species.
- Genus: Nyctyornis
- Genus: Meropogon
- Purple-bearded bee-eater, Meropogon forsteni
- Genus: Merops
- Little bee-eater, Merops pusillus
- Blue-cheeked bee-eater, Merops persicus
- Green bee-eater, Merops orientalis
- White-throated bee-eater, Merops albicollis
- Swallow-tailed bee-eater, Merops hirundinaeus
- Blue-tailed bee-eater, Merops philippinus
- Black bee-eater, Merops gularis
- Blue-headed bee-eater, Merops muelleri
- Blue-moustached bee-eater, Merops mentalis
- Red-throated bee-eater, Merops bulocki
- White-fronted bee-eater, Merops bullockoides
- Blue-breasted bee-eater, Merops variegatus
- Cinnamon-chested bee-eater, Merops oreobates
- Black-headed bee-eater, Merops breweri
- Somali bee-eater, Merops revoilii
- Böhm's bee-eater, Merops boehmi
- Blue-throated bee-eater, Merops viridis
- Olive bee-eater, Merops superciliosus
- Rainbow bee-eater, Merops ornatus
- European bee-eater, Merops apiaster
- Chestnut-headed bee-eater, Merops leschenaulti
- Rosy bee-eater, Merops malimbicus
- Northern carmine bee-eater, Merops nubicus
- Southern carmine bee-eater, Merops nubicoides
Some authorities split the green bee-eater into three species, the Asian green bee-eater Merops orientalis, the Arabian green bee-eater, M. cyanophrys and the African green bee-eater, M. viridissimus.
The bee-eaters are morphologically a fairly uniform group. They share many features with related Coraciiformes such as the kingfishers and rollers, being large-headed (although not as large-headed as their relatives), short-necked, brightly plumaged and short-legged. Their wings may be rounded or pointed, with the wing shape closely correlated with foraging habitat and migratory tendencies. Shorter, rounder wings are found on species that are sedentary and make shorter foraging flights in denser forests and reedbeds. Those with more elongated wings are more migratory. All the bee-eaters are highly aerial; they take off strongly from perches, fly directly without undulating, and are able to change directions quickly, although they rarely hover.
The bills of bee-eaters are curved, long and end in a sharp point. The bill can bite strongly, particularly at the tip, and is used as a pair of forceps with which to snatch insects from the air and crush smaller prey. The short legs have weak feet, and when moving on the ground a bee-eater's gait is barely more than a shuffle. The feet have sharp claws used for perching on vertical surfaces and also during nest excavation.
The plumage of the family is generally very bright and in most species dominated or at least partly green. The two carmine bee-eaters are mostly rose-coloured. Most of the Merops bee-eaters have a line through the eye and many have differently coloured throats and faces. The extent of the green in these species varies from almost complete in the green bee-eater to barely any in the white-throated bee-eater. Three species, from equatorial Africa, have no green at all in their plumage, the black bee-eater, the blue-headed bee-eater and the rosy bee-eater. Several species have long streamers in the tail, and in a few species these are ended with expanded spatulae.
There is little visible difference between the sexes in most of the family. In several species the iris is red in the males and brown-red in the females, and in species with tail-streamers these may be slightly longer in males. Both the European and red-bearded bee-eaters have differences in the colour of their plumage, and the rainbow bee-eaters have differently shaped tail-streamers. There are however probably undocumented instances where bee-eaters are sexually dichromatic at the ultraviolet end of the colour spectrum, which humans cannot see. A study of blue-tailed bee-eater found that males were more colourful than females in UV light. Overall colour was also affected by body condition, suggesting that there was a signalling component to plumage colour. Juveniles are generally similar to adults, except for the two Nyctyornis species, in which the young have mainly green plumage.
Bee-eaters have calls that are characteristic for each species. Most sound simple to the human ear, but show significant variability when studied in detail.
Distribution and habitat
The bee-eaters have an Old World distribution, occurring from Europe to Australia. The centre of diversity of the family is Africa, although a number of species also occur in Asia. Single species occurs in each of Europe, (the European bee-eater), Australia (the rainbow bee-eater) and Madagascar (the olive bee-eater, also found on mainland Africa). Of the three genera, Merops, which has the majority of the species in the family, occurs across the entirely of the family's distribution. Nyctyornis is restricted to Asia, ranging from India and southern China to the Indonesian islands of Sumatra and Borneo. The genus Meropogon has a single species restricted to Sulawesi in Indonesia.
Bee-eaters are fairly catholic in their habitat. Their requirements are simply an elevated perch from which to watch for prey and a ground substrate in which to dig their breeding burrow. Because their prey is entirely caught on the wing they are not dependent on any vegetation type. A single species is found inside closed rainforest, the blue-headed bee-eater, where it forages close to the ground in poor light in the gaps between large trees under the canopy. Six other species are also closely associated with rainforest, but occur in edge habitat such as along rivers, in tree-fall gaps, off trees overhanging ravines or on emergent tree crowns above the main canopy.
Species that breed in subtropical or temperate areas of Europe, Asia and Australia are all migrants. The European bee-eaters that breed in southern Europe and Asia migrate to West and southern Africa. Another population of the same species breeds in South Africa and Namibia; these birds move northwards after breeding. In Australia the rainbow bee-eater is migratory in the southern areas of its range, migrating to Indonesia and New Guinea, but occurs year round in northern Australia. Several species of bee-eater, such as the white-throated bee-eater, are intra-African migrants. The most unusual migration is that of the southern carmine bee-eater, which has a three-stage migration; after breeding in a band between Angola and Mozambique it moves south to Botswana, Namibia and South Africa before moving north to its main wintering grounds in northern Angola, Congo and Tanzania.
The bee-eaters are diurnal (active by day), although a few species may migrate during the night if the terrain on route is unsuitable for stopping or if they are crossing the sea. They are highly social, and pairs sitting together are often so close together that they touch (an individual distance of zero). Groups may roost in the same fashion as well. Some species are highly gregarious in the non-breeding season, and many species are colonial in the breeding season as well.
The social structures of the red-throated bee-eater and the white-fronted bee-eaters have been described as "the most complex of any bird species anywhere in the world".:298 The birds exist in stable colonies located on nesting cliffs, and have a stable structure year round. These colonies are composed of clans of two or three pairs, their helpers, and offspring. Within the colony the males alternate between guarding their mate and attempting to make forced copulations with other females. The females in turn attempt to lay eggs in their neighbour's nests. Some individuals also specialise in kleptoparasitism, stealing prey collected by other colony members. The colony's daily routine is to emerge from the nesting holes or roosting branches soon after dawn, preen and sun themselves for an hour, then disperse to feed. Feeding territories are broken down by clan, with the clan defending the territories from all others of the same species, including clans of the same colony. The clans return to the colony before dusk, and engage in more social behaviour before retiring for the night. Colonies are situated several hundred metres apart and have little to do with each other, although young individuals may disperse between colonies. As such these species can be thought to have four tiers of social kinship, the individual pair, the family unit, the clan and the colony as a whole.
Bee-eaters spend around 10% of their day on what are known as comfort activities. These include sunning themselves, dust bathing and water bathing. Sunning behaviour helps warm birds in the morning, reducing the need to use energy to raise their temperature. It also has a social aspect, as multiple birds adopt the same posture. Finally, it may help stimulate parasites in the feathers, making them easier to find and remove. Due to their hole-nesting bee-eaters accumulate a number of external parasites such as mites and flies. Together with sunning, bouts of dust bathing (or water bathing where available), as well as rigorous preening, keep the feathers and skin in good health. Bathing with water involves making shallow dives into a water body and then returning to a perch to preen.
Diet and feeding
The bee-eaters are almost exclusively aerial hunters of insect prey. Prey is caught either while in continuous flight or more commonly from an exposed perch from which the bee-eater watches for prey. Smaller, rounder-winged bee-eaters typically hunt from branches and twigs closer to the ground, whereas the larger species hunt from tree tops or telegraph wires. One unusual technique often used by carmine bee-eaters is to ride the back of bustards.
Prey can be spotted from a distance; European bee-eaters are able to spot a bee 60 metres (200 ft) away, and blue-cheeked bee-eaters have been observed flying out 100 metres (330 ft) to catch large wasps. Prey is approached directly or from behind. Prey that lands on the ground or on plants is usually not pursued. Small prey may be eaten on the wing, but larger prey are returned to the perch to be beaten against the perch to kill them and break up the body. Insects with poisonous stings are first smacked on the branch, then, with the bird's eyes closed, rubbed to discharge the venom. This behaviour is innate, as demonstrated by a juvenile bird in captivity, which performed the task when first presented with wild bees. This bird was stung on the first five tries, but by ten bees, it was as adept at handling bees as adult birds.
Bee-eaters consume a wide range of insects; beyond a few distasteful butterflies they consume almost any insect from tiny Drosophila flies to large beetles and dragonflies. At some point bee-eaters have been recorded eating beetles, mayflies, stoneflies, cicadas, termites, crickets and grasshoppers, mantises, true flies and moths. For many species the dominant prey item are stinging members of the order Hymenoptera, namely wasps and bees. In a survey of 20 studies the proportion of the diet made up by bees and wasps varied from 20% to 96%, with the average being 70%. Of these honeybees can comprise a large part of the diet, as much as 89% of the overall intake. The giant honeybee is a particularly commonly eaten species. These bees attempt to congregate in a mass defence against the bee-eaters.
Bee-eaters are seasonally monogamous, and some species are monogamous over multiple seasons, although migratory species form new pair bonds each breeding season. The courtship displays of the bee-eaters are rather unspectacular, with some calling and raisng of throat and wing feathers. The exception is the "butterfly display", of the white-throated bee-eater, in which the wings of both sexes are held out the birds are calling. Most members of the family engage in courtship feeding, where the male presents prey items to the female, and such feeding can account for much, if not all, of the energy females require for egg creation.
Like almost all Coraciiformes the bee-eaters are cavity nesters. In the case of the bee-eaters the nests are burrows dug into the ground, either into the sides of earth cliffs or directly into level soil. Both types of nesting site are vulnerable, those on level ground are vulnerable to trampling and small predators, whereas those in cliffs, which are often the banks of rivers, are vulnerable to flash floods, which can wipe out dozens or hundreds of nests. Many species will nest either on cliffs or on level ground but prefer cliffs, although Böhm's bee-eater always nests on level ground. The burrows are dug by both birds in the pair, sometimes assisted by helpers. The soil or sand is loosened with jabs of the sharp bill, then the feet are used to kick out the loose soil. It has been suggested that riverine loess deposits that do not crumble when excavated may be favoured by the larger bee-eaters. There may be several false starts where nests are dug partway before being abandoned; in solitary species this can give the impression of colonial living even when that is not the case. The process of nest building can take as long as twenty days to complete, during which time the bill can be both blunted and shortened. Nests are generally used only for a single season and are rarely used twice by the bee-eaters, but abandoned nests may be used by other birds, snakes and bats as shelter and breeding sites.
Bee-eaters may nest as single pairs, loose colonies or dense colonies. Smaller species tend to nest solitarily, while medium-sized species have small colonies, and larger and migratory species nest in large colonies that can number in the thousands. In some instances colonies may contain more than one species of bee-eater.In species that nest gregariously, breeding pairs may be assisted by up to five helpers, which in at least the red-throated and white-fronted bee-eaters are known to be male offspring from a previous year. They may alternate between breeding themselves and helping in successive years.
Predators and parasites
The little bee-eater and red-throated bee-eaters are hosts of the greater honeyguide and the lesser honeyguide, both brood parasites. The young honeyguides kill the bee-eater's chicks and destroy any eggs. The begging call of the honeyguide sounds like two bee-eater chicks, ensuring a good supply of food from the adult bee-eaters.
Bee-eaters may be infested by several blood-feeding flies of the genus Carnus, and the biting fly Ornithophila metallica. Other parasites include chewing lice of the genera Meromenopon, Brueeliaa and Meropoecus, some of which are specialist parasites of bee-eaters, and the stickfast flea Echidnophaga gallinacea. The hole-nesting lifestyle of bee-eaters means that they tend to carry a higher burden of external parasites than non-hole-nesting bird species. Bee-eaters may be also be infected by protozoan blood parasites of the genus Haemoproteus including Haemoproteus meropis.
The International Union for Conservation of Nature (IUCN) assesses species vulnerability in terms of total population and the rate of any population decline. None of the bee-eaters meet the IUCN vulnerability criteria, and all are therefore evaluated as "Least-concern species".
Open country species, which comprise the majority of bee-eaters, have mostly expanded in range as more land is converted to agriculture, but some tropical forest species have suffered declines through loss of habitat, although no species or subspecies gives serious cause for concern. There is some human persecution of bee-eaters, with nest holes being blocked, adults shot or limed, or young taken for food. More generally problematic is the unintended destruction of nests. This can occur through cattle trampling, as with the blue-headed bee-eater in Kenya, or loss of forests, with massive conversion of native forest to oil palm plantations in Malaysia being particularly concerning.
A study of the carmine bee-eater in Zimbabwe showed that it was affected by deliberate interference and persecution and loss of woodlands, and that nesting sites are lost though poor water management leading to river bank damage, dam construction and panning for gold. Colonies are increasing concentrated into the national parks and the Zambezi Valley. The well-studied European bee-eater is trapped and shot on migration in countries bordering the Mediterranean, an estimated 4,000-6,000 annually being shot in Cyprus alone, but with a global population of between 170,000 and 550,000 pairs even losses on that scale make little overall impact.
As conspicuous birds, bee-eaters were mentioned by ancient writers such as Aristotle and Virgil, who both advised bee-keepers to kill them. Aristotle knew that bee-eaters nest at the end of tunnels up to 2 metres (6.6 ft) long and the size of the clutch. He said that nesting adults were fed by their own young, based on the observed actual help at the nest by related birds. In Greek mythology, the Theban Botres was fatally struck by his father when he desecrated a ritual sacrifice of a ram to the god Apollo by tasting the victim's brains. The god took pity on him, turning him into a bee-eater.
The Ancient Egyptians believed that bee-eaters had medical properties, prescribing the application of bee-eater fat to deter biting flies, and fumigating the eyes with bee-eater legs to cure an unspecified female complaint.
In Hinduism, the shape of the bird in flight was thought to resemble a bow, with the long bill as an arrow. This led to a Sanskrit name meaning "Vishnu's bow" and an association with archer gods. Scandalmongers were though to be reincarnated as bee-eaters, because of the metaphorical poison they bore their mouths.
Depictions in classical art are rare for such striking birds. The only known Ancient Egyptian example is a relief, probably of a little green bee-eater, on a wall of Queen Hatshepsut’s mortuary temple, and an early Roman mural depicting blue-cheeked bee-eaters was found in the villa of Agrippina. Bee-eaters have been depicted on the postage stamps of at least 38 countries, the European and Carmine bee-eaters being the most common subjects, with 18 and 11 countries respectively.
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