Common kingfisher

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Common kingfisher
Common Kingfisher (Alcedo atthis) Photograph By Shantanu Kuveskar, Mangaon, Maharashtra, India.jpg
Male A. a. bengalensis
from Maharashtra, India.
Common kingfisher (Alcedo atthis ispida) female.jpg
Female A. a. ispida
Kecskemét, Hungary
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Coraciiformes
Family: Alcedinidae
Subfamily: Alcedininae
Genus: Alcedo
Species:
A. atthis
Binomial name
Alcedo atthis
Alcedo atthis -range map-2-cp.png
  Breeding range
  Resident all year round
  Non-breeding range
Synonyms

Gracula atthisLinnaeus, 1758

The common kingfisher fishing in Italy's Po River Alcedo atthis - Riserve naturali e aree contigue della fascia fluviale del Po.jpg
The common kingfisher fishing in Italy's Po River

The common kingfisher (Alcedo atthis), also known as the Eurasian kingfisher and river kingfisher, is a small kingfisher with seven subspecies recognized within its wide distribution across Eurasia and North Africa. It is resident in much of its range, but migrates from areas where rivers freeze in winter.

Contents

This sparrow-sized bird has the typical short-tailed, large-headed kingfisher profile; it has blue upperparts, orange underparts and a long bill. It feeds mainly on fish, caught by diving, and has special visual adaptations to enable it to see prey under water. The glossy white eggs are laid in a nest at the end of a burrow in a riverbank.

Taxonomy

The common kingfisher was first described by Carl Linnaeus in the 10th edition of his Systema Naturae in 1758 as Gracula atthis. [2] [3] [4] The modern binomial name derives from the Latin alcedo , 'kingfisher' (from Greek ἀλκυών , halcyon), and Atthis, a beautiful young woman of Lesbos, and favourite of Sappho. [5]

The genus Alcedo comprises seven small kingfishers that all eat fish as part of their diet. The common kingfisher's closest relative is the cerulean kingfisher that has white underparts and is found in parts of Indonesia. [6] [7]

Description

This species has the typical short-tailed, dumpy-bodied, large-headed, and long-billed kingfisher shape. The adult male of the western European subspecies, A. a. ispida has green-blue upperparts with pale azure-blue back and rump, a rufous patch by the bill base, and a rufous ear-patch. It has a green-blue neck stripe, white neck blaze and throat, rufous underparts, and a black bill with some red at the base. The legs and feet are bright red. [7] It is about 16 cm (6+1⁄2 in) long with a wingspan of 25 cm (10 in), [7] and weighs 34–46 g (1+3⁄16–1+5⁄8 oz). [8] The female is identical in appearance to the male except that her lower mandible is orange-red with a black tip. The juvenile is similar to the adult, but with duller and greener upperparts and paler underparts. Its bill is black, and the legs are also initially black. [7] Feathers are moulted gradually between July and November with the main flight feathers taking 90–100 days to moult and regrow. Some that moult late may suspend their moult during cold winter weather.[ citation needed ]

The flight of the kingfisher is fast, direct and usually low over water. The short, rounded wings whirr rapidly, and a bird flying away shows an electric-blue "flash" down its back. [8]

In North Africa, Europe and Asia north of the Himalayas, this is the only small blue kingfisher. In south and southeast Asia, it can be confused with six other small blue-and-rufous kingfishers, but the rufous ear patches distinguish it from all but juvenile blue-eared kingfishers; details of the head pattern may be necessary to differentiate the two species where both occur. [7]

The common kingfisher has no song. The flight call is a short, sharp whistle chee repeated two or three times. Anxious birds emit a harsh, shrit-it-it and nestlings call for food with a churring noise. [7]

Geographical variation

There are seven subspecies differing in the hue of the upperparts and the intensity of the rufous colour of the underparts; size varies across the subspecies by up to 10%. The races resident south of the Wallace Line have the bluest upperparts and partly blue ear-patches. [7] [9]

Habitat and distribution

The common kingfisher is widely distributed over Europe, Asia, and North Africa, mainly south of 60°N. It is a common breeding species over much of its vast Eurasian range, but in North Africa it is mainly a winter visitor, although it is a scarce breeding resident in coastal Morocco and Tunisia. In temperate regions, this kingfisher inhabits clear, slow-flowing streams and rivers, and lakes with well-vegetated banks. It frequents scrubs and bushes with overhanging branches close to shallow open water in which it hunts. In winter it is more coastal, often feeding in estuaries or harbours and along rocky seashores. Tropical populations are found by slow-flowing rivers, in mangrove creeks and in swamps. [7]

Common kingfishers are important members of ecosystems and good indicators of freshwater community health. The highest densities of breeding birds are found in habitats with clear water, which permits optimal prey visibility, and trees or shrubs on the banks. These habitats have also the highest quality of water, so the presence of this bird confirms the standard of the water. [11] Measures to improve water flow can disrupt this habitat, and in particular, the replacement of natural banks by artificial confinement greatly reduces the populations of fish, amphibians and aquatic reptiles, and waterside birds are lost. [12] It can tolerate a certain degree of urbanisation, provided the water remains clean.[ citation needed ]

This species is resident in areas where the climate is mild year-round, but must migrate after breeding from regions with prolonged freezing conditions in winter. Most birds winter within the southern parts of the breeding range, but smaller numbers cross the Mediterranean into Africa or travel over the mountains of Malaysia into Southeast Asia. Kingfishers migrate mainly at night, and some Siberian breeders must travel at least 3,000 km (1,900 mi) between the breeding sites and the wintering areas. [7]

Behaviour

Breeding

Volunteers create a vertical bank in which common kingfishers have subsequently nested annually BR ijsvogelwand.jpg
Volunteers create a vertical bank in which common kingfishers have subsequently nested annually
Eggs of Alcedo atthis, MHNT Alcedo atthis MHNT ZOO 2010 11 160 Arcy-sur-Cure.jpg
Eggs of Alcedo atthis, MHNT

Like all kingfishers, the common kingfisher is highly territorial; since it must eat around 60% of its body weight each day, it is essential to have control of a suitable stretch of river. It is solitary for most of the year, roosting alone in heavy cover. If another kingfisher enters its territory, both birds display from perches, and fights may occur, in which a bird will grab the other's beak and try to hold it underwater. Pairs form in the autumn but each bird retains a separate territory, generally at least 1 km (1⁄2 mi) long, but up to 3.5 km (2+1⁄4 mi) and territories are not merged until the spring. [7]

The courtship is initiated by the male chasing the female while calling continually, and later by ritual feeding, with copulation usually following. [8]

The nest is in a burrow excavated by both birds of the pair in a low vertical riverbank, or sometimes a quarry or other cutting. The straight, gently inclining burrow is normally 60–90 cm (25–35 in) long and ends in an enlarged chamber. [8] The nest cavity is unlined but soon accumulates a litter of fish remains and cast pellets. [13]

The common kingfisher typically lays two to ten glossy white eggs, which average 1.9 cm (3⁄4 in) in breadth, 2.2 cm (7⁄8 in) in length, and weigh about 4.3 g (5⁄32 oz), of which 5% is shell. [5] Both sexes incubate by day, but only the female incubates at night. An incubating bird sits trance-like, facing the tunnel; it invariably casts a pellet, breaking it up with the bill. The eggs hatch in 19–20 days, one or two eggs in most clutches fail to do so because the parent cannot cover them prior. The altricial young are in the nest for a further 24–25 days, often more. [7] Once large enough, young birds will come to the burrow entrance to be fed. [13] Two broods, sometimes three, may be reared in a season. [8]

Survival

The early days for fledged juveniles are more hazardous; during its first dives into the water, about four days after leaving the nest, a fledgling may become waterlogged and drown. [7] Many young will not have learned to fish by the time they are driven out of their parents' territory, and only about half survive more than a week or two. Most kingfishers die of cold or lack of food, and a severe winter can kill a high percentage of the birds. Summer floods can destroy nests or make fishing difficult, resulting in starvation of the brood. Only a quarter of the young survive to breed the following year, but this is enough to maintain the population. Likewise, only a quarter of adult birds survive from one breeding season to the next. Very few birds live longer than one breeding season. [14] The oldest bird on record was 21 years. [15]

Other causes of death are cats, rats, collisions with vehicles and windows, and human disturbance of nesting birds, including riverbank works with heavy machinery. Since kingfishers are high up in the food chain, they are vulnerable to build-up of chemicals, and river pollution by industrial and agricultural products excludes the birds from many stretches of otherwise suitable rivers that would be habitats. [14]

This species was killed in Victorian times for stuffing and display in glass cases and use in hat making. English naturalist William Yarrell also reported the country practice of killing a kingfisher and hanging it from a thread in the belief that it would swing to predict the direction in which the wind would blow. [16] Persecution by anglers and to provide feathers for fishing flies were common in earlier decades, [13] but are now largely a thing of the past. [14]

Feeding

Male passing fish to female in spring courtship ritual Common kingfishers (Alcedo atthis ispida) male passing fish to female.jpg
Male passing fish to female in spring courtship ritual
Pellet of a common kingfisher Kingfisher pellet - 2020-02-02 - Andy Mabbett - 02 (cropped).jpg
Pellet of a common kingfisher

The common kingfisher hunts from a perch 1–2 m (3–7 ft) above the water, on a branch, post or riverbank, bill pointing down as it searches for prey. It bobs its head when food is detected to gauge the distance and plunges steeply down to seize its prey usually no deeper than 25 cm (10 in) below the surface. The wings are opened underwater and the open eyes are protected by the transparent third eyelid. The bird rises beak-first from the surface and flies back to its perch. At the perch the fish is adjusted until it is held near its tail and beaten against the perch several times. Once dead, the fish is positioned lengthways and swallowed head-first. A few times each day, a small greyish pellet of fish bones and other indigestible remains is regurgitated. [7]

The food is mainly fish up to 12.5 cm (5 in) long, but the average size is 2.3 cm (7⁄8 in). [7] In Central Europe, 97% of the diet was found to be composed of fish ranging in size from 2 to 10 cm with an average of 6.5 cm (body mass range from <0.1 g to >10 g, average 3 g). [17] [18] Minnows, sticklebacks, small roach and trout are typical prey. About 60% of food items are fish, but this kingfisher also catches aquatic insects such as dragonfly larvae and water beetles, and, in winter, crustaceans including freshwater shrimps. [7] Amphibians such as the smooth newt (Lissotriton vulgaris) may also constitute part of the diet of this species. [19] In Central Europe, however, fish represented 99.9% of the diet (data from rivers, streams, and reservoirs from years 1999 to 2013). [17] Common kingfishers have also been observed to catch lamprey. [20] One study found that food provisioning rate increased with brood size, from 1498 g (505 fishes for four nestlings) to 2968 g (894 fishes for eight nestlings). During the fledging period each chick consumed on average 334 g of fish, which resulted in an estimated daily food intake of 37% of the chick's body mass (average over the entire nestling period). The average daily energy intake was 73.5 kJ per chick (i.e., 1837 kJ per 25 days of the fledging period). [21]

A challenge for any diving bird is the change in refraction between air and water. The eyes of many birds have two foveae (the fovea is the area of the retina with the greatest density of light receptors), [22] and a kingfisher can switch from the main central fovea to the auxiliary fovea when it enters water; a retinal streak of high receptor density which connects the two foveae allows the image to swing temporally as the bird drops onto the prey. [23] The egg-shaped lens of the eye points towards the auxiliary fovea, enabling the bird to maintain visual acuity underwater. [22] Because of the positions of the foveae, the kingfisher has monocular vision in air, and binocular vision in water. The underwater vision is not as a sharp as in air, but the ability to judge the distance of moving prey is more important than the sharpness of the image. [23]

Each cone cell of a bird's retina contains an oil droplet that may contain carotenoid pigments. These droplets enhance color vision and reduce glare. Aquatic kingfishers have high numbers of red pigments in their oil droplets; the reason red droplets predominate is not understood, but the droplets may help with the glare or the dispersion of light from particulate matter in the water. [23]

Status

This species has a large range, with an estimated global extent of occurrence of 10,000,000 km2 (3,900,000 sq mi). It has a large population, including an estimated 160,000–320,000 individuals in Europe alone. Global population trends have not been quantified, but populations appear to be stable so the species is not believed to approach the thresholds for the population decline criterion of the IUCN Red List (i.e., declining more than 30% in ten years or three generations). For these reasons, the species is evaluated as "least concern". [24] [5]

Related Research Articles

<span class="mw-page-title-main">Kingfisher</span> Family of birds

Kingfishers are a family, the Alcedinidae, of small to medium-sized, brightly coloured birds in the order Coraciiformes. They have a cosmopolitan distribution, with most species living in the tropical regions of Africa, Asia, and Oceania, but also can be seen in Europe. They can be found in deep forests near calm ponds and small rivers. The family contains 116 species and is divided into three subfamilies and 19 genera. All kingfishers have large heads, long, sharp, pointed bills, short legs, and stubby tails. Most species have bright plumage with only small differences between the sexes. Most species are tropical in distribution, and a slight majority are found only in forests.

<span class="mw-page-title-main">Black-throated loon</span> A migratory aquatic bird found in the northern hemisphere

The black-throated loon, also known as the Arctic loon and the black-throated diver, is a migratory aquatic bird found in the northern hemisphere, primarily breeding in freshwater lakes in northern Europe and Asia. It winters along sheltered, ice-free coasts of the north-east Atlantic Ocean and the eastern and western Pacific Ocean. This loon was first described by Carl Linnaeus in 1758 and has two subspecies. It was previously considered to be the same species as the Pacific loon, of which it is traditionally considered to be a sister species, although this is debated. In a study that used mitochondrial and nuclear intron DNA, the black-throated loon was found to be sister to a clade consisting of the Pacific loon and two sister species, the common loon and the yellow-billed loon.

<span class="mw-page-title-main">River kingfisher</span> Subfamily of birds

The river kingfishers or pygmy kingfishers, subfamily Alcedininae, are one of the three subfamilies of kingfishers. The river kingfishers are widespread through Africa and east and south Asia as far as Australia, with one species, the common kingfisher also appearing in Europe and northern Asia. This group includes many kingfishers that actually dive for fish. The origin of the subfamily is thought to have been in Asia.

<span class="mw-page-title-main">Blue-winged kookaburra</span> Species of bird

The blue-winged kookaburra is a large species of kingfisher native to northern Australia and southern New Guinea.

<span class="mw-page-title-main">Sharp-shinned hawk</span> Species of bird

The sharp-shinned hawk or northern sharp-shinned hawk, commonly known as a sharpie, is a small hawk, with males being the smallest hawks in the United States and Canada, but with the species averaging larger than some Neotropical species, such as the tiny hawk. The taxonomy is far from resolved, with some authorities considering the southern taxa to represent three separate species: white-breasted hawk, plain-breasted hawk, and rufous-thighed hawk. The American Ornithological Society and some other checklists keeps all four variations conspecific.

<span class="mw-page-title-main">Malachite kingfisher</span> Species of bird

The malachite kingfisher is a river kingfisher which is widely distributed in Africa south of the Sahara. It is largely resident except for seasonal climate-related movements.

<span class="mw-page-title-main">Half-collared kingfisher</span> Species of bird

The half-collared kingfisher is a kingfisher in the subfamily Alcedininae that is found in southern and eastern Africa. It feeds almost exclusively on fish and frequents streams, rivers and larger bodies of water with dense shoreline vegetation.

<span class="mw-page-title-main">American pygmy kingfisher</span> Species of bird

The American pygmy kingfisher is a species of "water kingfisher" in subfamily Cerylinae of family Alcedinidae. It is found in the American tropics from southern Mexico south through Central America into every mainland South American country except Chile and Uruguay. It also occurs on Trinidad.

<span class="mw-page-title-main">European perch</span> Species of fish

The European perch, also known as the common perch, redfin perch, big-scaled redfin, English perch, Euro perch, Eurasian perch, Eurasian river perch, Hatch, poor man's rockfish or in Anglophone parts of Europe, simply the perch, is a predatory freshwater fish native to Europe and North Asia. It is the type species of the genus Perca.

<span class="mw-page-title-main">Blue-eared kingfisher</span> Species of bird

The blue-eared kingfisher is found in Asia, ranging across the Indian subcontinent and Southeast Asia. It is found mainly in dense shaded forests where it hunts in small streams. It is darker crowned, with darker rufous underparts and lacking the rufous ear stripe of the common kingfisher which is found in more open habitats. A number of subspecies have been described that differ in measurement and colour shade. Adult males have an all dark bill while females have a reddish lower mandible.

<span class="mw-page-title-main">Blyth's kingfisher</span> Species of bird

Blyth's kingfisher is the largest kingfisher in the genus Alcedo. Named for Edward Blyth, the species has also been known as Alcedo grandis and as the great blue kingfisher. Between 22 and 23 cm long, the kingfisher has deep rufous underparts with a blackish blue breast patch, and brilliant cobalt blue or azure upperparts, tinged with purple. The wings are a dark blackish green, with blue speckles and tips to some of the feathers. The bill of the male is entirely black, while the female has a dark red lower mandible. The species is distinguished from the similar blue-eared kingfisher and common kingfisher by its greater size, heavy black bill, and dark lores.

<span class="mw-page-title-main">Cerulean kingfisher</span> Species of bird

The cerulean kingfisher is a kingfisher in the subfamily Alcedininae which is native to parts of Indonesia. With an overall metallic blue impression, it is very similar to the common kingfisher, but it is white underneath instead of orange. Males average bluer than females, which have a greenish cast.

<span class="mw-page-title-main">Banded kingfisher</span> Species of bird

The banded kingfisher is a tree kingfisher found in lowland tropical forests of southeast Asia. It is the only member of the genus Lacedo. Male and female adults are very different in plumage. The male has a bright blue crown with black and blue banding on the back. The female has rufous and black banding on the head and upperparts.

<span class="mw-page-title-main">Green-and-rufous kingfisher</span> Species of bird

The green-and-rufous kingfisher is a species of "water kingfisher" in subfamily Cerylinae of family Alcedinidae. It is found in the American tropics from Nicaragua to Panama and in every mainland South American country except Argentina, Chile, and Uruguay.

<i>Alcedo</i> Genus of birds

Alcedo is a genus of birds in the kingfisher subfamily Alcedininae. The genus was introduced by Carl Linnaeus in 1758 in the 10th edition of his Systema Naturae. The type species is the common kingfisher. Alcedo is the Latin for "kingfisher".

<span class="mw-page-title-main">Black-backed dwarf kingfisher</span> Species of bird

The black-backed dwarf kingfisher, also known as the three-toed kingfisher, is a pocket-sized bird in the family Alcedinidae. It was formerly considered as conspecific with the rufous-backed dwarf kingfisher and together the species complex was known by the English name "oriental dwarf kingfisher".

<span class="mw-page-title-main">Brown-hooded kingfisher</span> Species of bird

The brown-hooded kingfisher is a species of bird in the subfamily Halcyoninae, the tree kingfishers. It has a brown head and blackish and turquoise wings. It is found in Sub-Saharan Africa, living in woodland, scrubland, forest edges, and also suburban areas. The International Union for Conservation of Nature (IUCN) has assessed it as being of least concern.

<span class="mw-page-title-main">Winchell's kingfisher</span> Species of bird

Winchell's kingfisher or the rufous-lored kingfisher, is a species of bird in the family Alcedinidae, the kingfishers. It is endemic to the Philippines, its natural habitat being lowland forests. It is threatened by deforestation, and the International Union for Conservation of Nature (IUCN) has assessed it as a vulnerable species.

<i>Gobio gobio</i> Species of fish

Gobio gobio, or the gudgeon, is a species of fish in the family Cyprinidae. This small fish is widely distributed in fresh-water streams and lakes across central and temperate Eurasia.

<span class="mw-page-title-main">Malaysian blue-banded kingfisher</span> Species of bird

The Malaysianblue-banded kingfisher is a species of kingfisher in the subfamily, Alcedininae. Its natural habitats are subtropical or tropical moist lowland forests, subtropical or tropical mangrove forests, and rivers. It is found in Myanmar, the Malay Peninsula, Sumatra, and Borneo.

References

  1. ↑ BirdLife International (2016). "Alcedo atthis". IUCN Red List of Threatened Species . 2016: e.T22683027A89575948. doi: 10.2305/IUCN.UK.2016-3.RLTS.T22683027A89575948.en . Retrieved 19 November 2021.
  2. ↑ Linnaeus, C (1758). Systema naturae per regna tria naturae, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis. Tomus I. Editio decima, reformata (in Latin). Vol. 1. Holmiae. (Laurentii Salvii). p. 109.
  3. ↑ Note: What is now the subspecies A. a. ispida is described on p. 115 as Alcedo ispida.
  4. ↑ Peters, James Lee, ed. (1945). Check-list of Birds of the World. Vol. 5. Cambridge, Massachusetts: Harvard University Press. p. 171.
  5. 1 2 3 "Kingfisher Alcedo atthis (Linnaeus, 1758)". Bird facts. British Trust for Ornithology . Retrieved 21 August 2008.
  6. ↑ Moyle, R.G.; Fuchs, J.; Pasquet, E.; Marks, B.D. (2007). "Feeding behavior, toe count, and the phylogenetic relationships among alcedinine kingfishers (Alcedininae)". Journal of Avian Biology. 38 (3): 317–326. doi:10.1111/J.2007.0908-8857.03921.x.
  7. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Fry, C. Hilary; Fry, Kathie; Harris, Alan (1999). Kingfishers, Bee-eaters and Rollers. London: Christopher Helm. pp. 219–221. ISBN   978-0-7136-5206-2.
  8. 1 2 3 4 5 Snow, David; Perrins, Christopher M., eds. (1998). The Birds of the Western Palearctic (concise ed.). Oxford: Oxford University Press. ISBN   978-0-19-854099-1.
  9. ↑ Gill, Frank; Donsker, David, eds. (2017). "Rollers, ground rollers & kingfishers". World Bird List Version 7.2. International Ornithologists' Union. Retrieved 17 May 2017.
  10. ↑ Arnold, Paula: Birds of Israel, (1962), Shalit Publishers Ltd., Haifa, Israel. p. 12
  11. ↑ Peris, S. J.; Rodriguez, R. (1996). "Some factors related to distribution by breeding Kingfisher (Alcedo atthis L.)". Ekologia Polska. 54 (1–2): 31–38.
  12. ↑ Lin, Wen-Loung; Tsai, Hsien-Hsiu; Wu, Hsuan-Ju (2007). "Effect of ditch living thing by process of original structure replacement by RC irrigation ditch" (PDF). Journal of Chinese Soil and Water Conservation (in Chinese). 38 (1): 31–42.
  13. 1 2 3 Coward, Thomas Alfred (1930). The Birds of the British Isles and Their Eggs (two volumes). Vol. 1 (Third ed.). Frederick Warne.
  14. 1 2 3 "Survival and threats". Kingfisher. Royal Society for the Protection of Birds . Retrieved 23 August 2008.
  15. ↑ "Longevity list of birds ringed in Europe". Kingfisher. EURING. Retrieved 23 August 2008.
  16. ↑ Cocker, Mark; Mabey, Richard (2005). Birds Britannica. London: Chatto & Windus. p. 300. ISBN   978-0-7011-6907-7.
  17. 1 2 Čech, M. & Čech, P. (2015). "Non-fish prey in the diet of an exclusive fish-eater: the common kingfisher Alcedo atthis". Bird Study. 62 (4): 457–465. doi: 10.1080/00063657.2015.1073679 . S2CID   85632259.
  18. ↑ Čech, M. & Čech, P. (2013). "The role of floods in the lives of fish-eating birds: predator loss or benefit?". Hydrobiologia. 717: 203–211. doi:10.1007/s10750-013-1625-3. S2CID   16257345.
  19. ↑ Davies, Nigel; Allain, Steven J. R. (2023). "Smooth newts Lissotriton vulgaris as more than just occasional items in the diet of the Eurasian kingfisher Alcedo atthis". Herpetological Bulletin. 164: 43. doi: 10.33256/hb164.43 .
  20. ↑ Čech, Martin (2017). "Lamprey (Lampetra sp.) in the diet of common kingfisher (Alcedo atthis)". Bulletin Lampetra. 8: 44–47.
  21. ↑ Čech, M. & Čech, P. (2017). "Effect of brood size on food provisioning rate in Common Kingfisher Alcedo atthis". Ardea. 105 (1): 5–17. doi:10.5253/arde.v105i1.a3. S2CID   90362897.
  22. 1 2 Sinclair, Sandra (1985). How Animals See: Other Visions of Our World. Beckenham, Kent: Croom Helm. ISBN   978-0-7099-3336-6.
  23. 1 2 3 Schwab, I. R.; Hart N. S. (May 2004). "Halcyon days". British Journal of Ophthalmology . 88 (5): 613. doi:10.1136/bjo.2004.045492. PMC   1772125 . PMID   15129670.
  24. ↑ BirdLife International (2016). "Alcedo atthis". IUCN Red List of Threatened Species . 2016: e.T22683027A89575948. doi: 10.2305/IUCN.UK.2016-3.RLTS.T22683027A89575948.en .

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