The order Coraciiformes includes kingfishers and their allies: rollers, hornbills, ground hornbills, cuckoo rollers, bee-eaters, motmots, wood hoopoes, todies, and the hoopoe. This diverse assortment of birds is unusually colorful and mostly of Old World origin.
Kingfishers are small, colorful birds that are found on all continents except for Antarctica. There are 14 genera and 86 species that occupy a diversity of habitats from dry woodlands to tropical forests. Kingfishers are robust little birds with large heads, small feet, and a stout build; bill shape varies with prey type. The toes of kingfishers have syndactyl configuration, with the second and third toes partially fused. All kingfishers have particularly keen eyesight but limited mobility of the eyes within the sockets; they compensate for this with fast, flexible movements of the head.
Despite the name ‘kingfisher’, these birds consume a wide variety of prey including insects, aquatic invertebrates, fish, reptiles, amphibians, earthworms, and even other birds. Forest-dwelling species are ‘sit-and-wait’ predators, and patiently wait for prey to come along before they strike. Animals inhabiting riparian areas (areas near water) are true fishers. Piscivorous (fish-eating) kingfishers have a special nictitating membrane that covers their eyes when they dive for prey; this protective membrane impedes their vision and they have to rely on tactile sensations to catch their prey once they enter the water. Fishers use different methods of catching their prey, for example, the pied kingfisher fishes from hovering flight while the sacred kingfisher dives from a perch.
Kingfishers are monogamous and will typically have 2-3 clutches in a given breeding season. Nests are usually excavated in holes in the ground, but tree cavities and termitaries are also used. Both members in a breeding pair participate in defending a territory and raising the young. Some species, like laughing kookaburrahs in Australia, have complex social systems in which ‘helpers’ assist in rearing the young. Kingfishers are solitary nesters with the exception of the pied kingfisher of Africa, which nests in loose social colonies.
Hornbills reside in tropical and sub-tropical habitats in Africa and Asia. All hornbills have a robust, down-curved bill. The family name Bucerotidae comes from the Greek ‘buceros’ which means cow horn. They are the only bird to have fused neck vertbrae (the atlas and axis), most likely to support their stout bill. There are 55 extant species of hornbills, all of Old World origin. Hornbills are sexually dimorphic, with males being larger than females. Many hornbills are frugivores (fruit-eaters) and are important seed dispersers. While some species are strictly herbivores, and a couple species carnivorous, most hornbills are omnivores.
The majority of hornbills have a casque ornamenting their beak- a ridge that protrudes atop the mandible. This morphological adornment is most-likely used to advertise the species, age, and sex of an individual, but can also function in differing capacities. For instance, the black-casqued hornbill’s casque opens to the mouth cavity and serves to amplify the sound of vocalizations. Other hornbills use their casques to fight, knock fruit from trees, dig, and defend themselves.
Perhaps the most interesting feature of hornbill natural history is their unique reproductive behavior. Courtship entails the male and female prospecting nest sites together, mutual preening, and courtship feeding. Once a breeding pair has mated, the female will enter the nest cavity and seal herself inside for the entire duration of incubation! After preparing the exterior of the cavity, she will enter the hole and seal herself inside it, creating an organic wall made of her own feces mixed with food particles and other materials that the male will bring her; her only connection to the outside world is a narrow vertical slit which allows ventilation. The female will lay her eggs in the nest and remain sealed inside for the entire nesting cycle. While she is in her self-made incubator, the male will feed her and protect the nest site. She maintains a hygienic nest cavity by eliminating feces and food debris through the slit. While sealed inside, she will molt her feathers and re-grow them before her departure from the nest. Once the chicks are old and strong enough to leave the nest, she will bust through the wall of the nest chamber allowing her and her fledglings to fly free.
Ground hornbills are more primitive than true hornbills and they do not have the same number of cervical (neck) vertebrae. Females do not seal their nest chambers in the same manner as true hornbills nor do they practice any form of nest sanitation. An interesting anatomical feature of the ground hornbills that is shared with some Oriental species of hornbills is a preen gland covered in an unusually dense tuft of feathers. This tuft serves in aiding the application of the oils produced by the gland, which the hornbills apply to their bills, casque, and plumage with pigment. Ground hornbills are almost entirely carnivorous and use their large, robust beaks to capture prey as large as squirrels and hares.
Note: Sometimes hornbills are placed in their own order, the Bucerotiformes.
Motmots, distant relatives of kingfishers, are colorful, medium-sized insectivores that inhabit the New World tropics. Their tails are unusually unique in their racquet-like appearance, with their two longest tail feathers absent of barbs on the distal (farthest) portion and a small tuft of barbs on the very distal tip. When perched, they swing their tails in a pendulum-like fashion in order to attract attention from their conspecifics. Motmots have strong, powerful bills and excavate their own earthen cavities in which to raise their young. They consume a variety of insects and will also take lizards, snakes, frogs, and berries. Some animals in the tropics have been observed eating poison dart frogs!
Todies are tiny Ciconiiforms indigenous to the Caribbean Islands, each being endemic to a specific island. They are common in lowland areas and have an unusually high tolerance for human presence. Like miniature versions of their motmot cousins, insectivorous todies share many of the same behavioral traits. While specific color variations vary, all todies are mostly iridescent bright green with a conspicuous red throat patch that inflates when the birds are vocalizing. Todies are extremely attentive parents, with both the male and female attending to the chicks. They have been observed to feed their young up to 140 times in a single day, the highest juvenile feeding rate of any bird in the world!
Bee-eaters are remarkably-colored, vocal birds occupying savanna, steppe, and tropical habitats in Africa, Asia, Europe and Australia. Twenty-three species comprising 3 genera, they have long tails, large beaks relative to their body size, a down-curved bill, and short legs. Bee-eaters are highly social, and nesting colonies of these birds are one of the most amazing spectacles in the bird world. Like their relatives the kingfishers, bee-eaters excavate earthen tunnels in which to make their nest; these are typically constructed in banks or cliffs by the hundreds and thousands in the more social species. These colonial nesters have some of the most complex social interactions of any birds in the world. Bee-eaters are the bane of bee-keepers and many thousands of them are killed each year as they are considered major pests and cause economic loss to keepers.
They consume volant (flying) insects and have a particular penchant for honeybees. On average, an adult bee-eater and her young require 225 bee-sized insects a day to survive! Similar to some species of kingfishers, bee-eaters are a sit-and-wait predator, remaining perched until they have an opportunity to strike. The majority of bees available outside the hive are venomous worker bees, and when bee-eaters seize them, they return to their perch and rub the insects on the perch to discharge them of their stinger and poison sacs before consuming them. While an abundance of insects ensure that bee-eaters have a reliable source of food, they are opportunists and will take advantage of easily-provided prey; for instance, some bee-eaters follow migrating swarms of locusts, others travel to bush fires to eat insects fleeing the flames, and others follow grazing ungulates to pursue the insects they flush as they graze - some even perch on the backs of such grazers for a free ride as they hunt!
Rollers consist of 17 species grouped into 5 genera in 3 families. They are colorful, conspicuous birds similar in body size and form to corvids (crow-like birds). Rollers are so named because of their tumbling courtship flight. They spend most of the day defending their territories and eating sparsely until dusk when they voraciously pursue winged termites. These agile fliers can consume up to half their body weight in a single feeding! Rollers are highly migratory and can form flocks of tens of thousands of birds. They can be found in savannas and forested and woodland areas of Africa, Eurasia, and Australia.
The cuckoo roller, an endemic of Madagascar, is a closely-related cousin of the true rollers. It resembles a cuckoo more closely than a true roller and its toes have zygodactyl orientation (2 toes facing forward and 2 toes facing backward), similar to cuckoos. Cuckoo rollers are remarkably tame for a wild bird. They live in pairs and hunt from perches in the forest canopy. They are particularly fond of hairy caterpillars and animals examined by researchers have revealed stomachs lined with caterpillar hair. Not much is known about their breeding biology, as only 2 nesting attempts have been observed by scientists.
The hoopoe is a bright, conspicuous bird inhabiting most of Africa and Eurasia. The sole member of the family Upupidae, this common bird is usually solitary and feeds on insects and small vertebrates which it stalks from the ground. Hoopoes have rounded wings and fly with butterfly-like wing beats, often pausing to perch and fan their crest feathers. They regularly sunbathe and adopt a defense-like posture with spread wings and the head thrown back and feathers fluffed while soaking up the sun. Their call is a distinctive ‘hoo-hoo-hoop’ and during the breeding season they will park atop a prominent perch and sing with great enthusiasm.
Hoopoes are not particularly afraid of humans and often nest in areas with high human activity. Young are specially equipped to defend themselves by spraying intruders to the nest with excreta and producing a liquid secretion with a horribly offensive odor to deter predators (as the young reach adulthood, the scent-producing gland is reduced in size and eventually ceases from excreting the foul liquid).
Wood hoopoes are native to Africa and are divided into 2 genera based on the shape of their bills- straight and scimitar-like, and although they are closely related, they separated from each other 10 million years ago. The scimitar-billed wood hoopoes tend to be more solitary while the straight-billed wood hoopoes are gregarious and are often found in small groups.
Wood hoopoes are lively birds and quite remarkable acrobats, often clinging to trees crosswise and hanging from their feet in search of bark-bound insects. They are affectionately called ‘cacklers’ as they are highly vocal and loud. This vociferous behavior strengthens social ties between family members. Wood hoopoes are quite altruistic and some helpers may forgo breeding opportunities to assist with the communal raising of young.
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