Gray token

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Gray token
Gray toko (Tockus nasutus), female Gray toko ( Tockus nasutus ), female
Systematics
Class : Birds (aves)
Order : Hornbills and hops (Bucerotiformes)
Family : Hornbills (Bucerotidae)
Genre : Tokos ( Tockus )
Type : Gray token
Scientific name
Tockus nasutus
( Linnaeus , 1766)
Subspecies
  • T. nasutus epirhinus , (Sundevall, 1850)

The Gray Hornbill ( Tockus nasutus ), also Weißschopftoko called a is Vogel art that the Rhino birds belongs (Bucerotidae) and much of sub-Saharan Africa occurs. Several subspecies are distinguished. Like all Tokos, the Gray Toko is also a cave breeder. During the breeding season, the female walls herself up in a tree cavity and hatches the eggs there while the male brings food to them. Several subspecies are distinguished in the large African distribution area.

The stock situation of the gray coconut was classified in the IUCN Red List of Threatened Species in 2016 as “ Least Concern (LC) ” = “not endangered”.

features

Gray tokos reach a body length of up to 45 centimeters and thus belong to one of the smaller toko species. The beak has a length of 8.9 to 12 centimeters in the males and 6.9 to 9.7 centimeters in the females. The males reach a weight of 220 to 258 grams, the females weigh between 163 and 215 grams.

Features of the nominate form

Gray Toko ( Tockus nasutus ), male

The males are dark gray on the head and neck. A broad, light stripe runs from above the eye to the neck. The back is pale blue with a white line drawing in the middle. The tail is black-brown, all control feathers except the middle one have a white tip. The underside of the body is whitish with a pale brown overlay, which is particularly evident on the front chest. The flight feathers are soot-brown with isabel-colored tips and hems on the outer flags. The elytra are dark brown with isabel-colored hems. The bill is black with a white spot near the base of the upper bill and a white longitudinal mark over the base of the lower bill. The horn is not particularly large and ends roughly in the middle of the beak. The feathered orbital ring and the bare throat skin are dark brown. The eyes are red-brown, the legs and feet are soot-brown.

Females correspond to males in body plumage, but are slightly smaller. The beak is smaller with a smaller horn. The beak is dark red, the small horn and the rear half of the beak are pale yellow. Like the male, the female also has a cross-mark on the lower half of the beak. Her bare throat skin is pale green. The young birds resemble the adult females, but have a smaller beak and are more uniformly dark in their plumage.

Characteristics of the individual subspecies

In addition to the nominate form, a distinction is made between three other subspecies, which are distinguished by the following features:

Gray Toko, male
  • Tockus nasatus ephirinus (Sundevall, 1850): Occurs in the south of the distribution area. Slightly smaller than the nominate shape, narrow pale hems on the wings and tail feathers. In the male, the horn is a little stronger.
  • Tockus nasatus forskalii (Hemprich and Ehrenberg, 1833): occurs on the Arabian Peninsula and differs from the nominate form in that it is darker on the top and slightly larger in size.
  • Tockus nasatus dorsalis (Gentle, 1954): Distribution area in arid Southwest Africa. Characterized by a paler upper side of the body.

To what extent a differentiation into a total of four different subspecies is justified has not yet been decided. A division in which is discussed forskalii n T., is displayed in the nominate and with the subspecies T. n. Dorsalis as part of the subspecies T. n. Ephirinus is perceived.

voice

The gray token emits high, elongated arrows. The call indicating the territory is circumscribed onomatically as pi pi pi pi pipipieu pipipieu pipipieu .

Possible confusion

Gray Toko, young bird

In parts of the distribution area of ​​the gray tooko there are three other toko species with which the gray tooko can be confused.

The Pale Beaked Toko is very similar in appearance to the Gray Toko and has a similar flight pattern. However, the distribution area of ​​the two species only overlaps in a small part of Central Africa and the Pale Beaked Toko has a horn-colored to cream-white beak. It also lacks the white lines on the back.

The Crown Toko has dark soot-brown body plumage, yellow eyes and a striking red-orange beak. The over-eye stripe is also not so clearly developed in the Crown Toko. The rock toko differs from the gray toko in its orange-red beak.

distribution and habitat

Distribution area of ​​the gray coconut

The gray Toko is widespread south of the Sahara . The area extends from Senegal in the west to Eritrea and Ethiopia in the east and also includes the south of the Arabian Peninsula along the coast. In eastern Africa it is distributed across Uganda , Kenya , southern Somalia , Tanzania , Zambia , Malawi , western Mozambique and Zimbabwe to northern South Africa and extends over Botswana and northeastern Namibia to southern Angola .

The habitat is a series of forest habitats. These range from semi-deserts with a sparse population of trees and isolated thorn bushes to open forest landscapes with individual tall trees. He avoids evergreen rainforests. It is a common bird throughout its range.

Seasonal migration movements occur again and again within its area of ​​distribution. Outside the breeding season, loose groups of up to 100 individuals can then roam around in the range in search of suitable feeding grounds. Regular north-south movements can be observed in the south of the Sahara. In Ghana and Nigeria, they migrate north from May to June when the breeding season is over. A southward movement can be seen there in the months of October to November, with groups of up to 50 individuals forming. In southern Africa they can also be found in grasslands, especially in drought years. In the Zambezi Valley and South Africa, there are seasonal migrations between high and low-lying areas.

Way of life

Food and foraging

Gray Toko, female, Serengeti

The gray coco is omnivorous, its food spectrum includes insects , small reptiles , eggs and nestlings as well as mammals, fruits and seeds.

The gray Toko typically looks for food in the treetops, only about 20 to 30 percent of its food needs are found on the ground. However, this ratio can vary regionally: In Kenya, 80 percent of its food is found on the ground, and in Ethiopia, where large insects play a major role in food, it can be seen more frequently on the ground. Basically, gray tokos are agile fliers who also catch some of their food in flight. This is the case, for example, when termites are flying. Large bees are also caught in flight and freed from their venomous sting. Gray tokos are also able to pick up rodents and roller spiders from the ground in flight. Gray tokos also follow monkeys such as baboons and zebras, as well as large birds, to catch the insects that they scare off. Gray tokos also occasionally rob the nests of weaver birds . That is why gray tokens are occasionally bullied by smaller songbirds .

Small vertebrates such as chameleons , tree frogs and lizards play a major role in meeting food needs. Fruits are often eaten, especially at the beginning of the dry season. The fruits eaten include figs and the fruits of Commiphora species. They eat the seeds of acacias, but also imported plants such as peanuts.

Reproduction

Gray tokos are monogamous birds and defend a territory during the breeding season. The size of the area depends on the density of trees. The period in which the breeding season falls varies greatly with the respective distribution area. In South Africa, for example, it falls between September and December. Usually the start of the breeding season coincides with the onset of the rainy season.

At the beginning of the breeding season, the pairs call more often, holding their beak straight up. The pair then increasingly inspects nesting holes and courtship feeding takes place, in which the male offers the female individual pieces of food in its beak. The female then begins to seal the nest cavity from the outside. The rearing of the young birds takes 72 to 86 days, with 24 to 26 days for the incubation of the eggs and 43 to 49 days for the nestling time of the young birds. The egg-laying is preceded by between 5 and 11 days, during which the female is already sitting in the nest cavity.

Nesting holes

Grautoko, female, Pilanesberg National Park , South Africa

Either a tree cave is used as a nesting hole, in arid parts of the distribution area, gray tokos also use crevices in the rock. Occasionally, gray tokos also use the nesting holes of the flamehead bearded bird , which places them in termite mounds and earthen walls.

Suitable tree hollows can be found in the marula tree and other trees of the genus Sclerocarya , acacias , trees from the genus of long filaments , the genus Deguelia , Lannea , ebony trees and mopane . The nest cavity is on average four meters above the ground. The nest holes are usually used for several years.

The female seals the entrance to the nest cavity with her faeces and leftover food. The nest cavity is padded with pieces of bark and dry leaves, which the male brings up, especially at the beginning of incubation. However, nesting material is brought in by the male during the entire breeding period.

Egg laying

As a rule, the female walled herself up in the nest cavity five to eleven days before the start of egg-laying. The clutch comprised between two and five eggs. In the Transvaal, an average of 4.3 eggs were found in the breeding caves examined, compared with 3.9 eggs in Namibia.

The laying interval between the individual eggs is between one and seven days, but typically they are laid every other day. The nestlings hatch asynchronously with a hatching distance corresponding to the laying distance.

Development of the nestlings

Gray Toko in flight

The nestlings are naked, blind and have pink skin when they hatch. At that point you weigh between 12 and 14 grams. The daily weight gain is between 7 and 10 grams during the first forty days of life.

The eyes open from the fifth day of life, on the 15th day of life the quills have already broken through. Feathers show up first on the head, neck, and underside of the body. The plumage is already very developed by the 30th day of life and is already complete by the time they leave the brood cavity. However, the wings and the control springs still grow when the nestlings are already fledged.

The female leaves the brood cavity when the oldest nestling is between 19 and 34 days old. The youngest nestling is sometimes only 13 days old. The nestlings then close the brood cavity themselves, except for a narrow gap. After they have left the nest, the female takes part in the feeding of the nestlings. After leaving the breeding cave, the young birds initially tree near the breeding cave and later join the parent birds in their search for food. Younger nestlings sometimes remain in the brood cavity, even if older nesting siblings have already left the nest. They also automatically close the entrance to the nest cavity.

Causes of mortality

According to studies in the Transvaal, 91 percent of all breeding attempts are also successful, and young birds fledge from 56 percent of the eggs. Loss of the clutch can occur if the bark growth of the nesting tree closes the nest cavity before the nest cavity is vacated.

Lanner falcons occasionally strike gray tokens. They are also successful from the spot eagles ( Hieraaetus ayresii ) and from Wahlberg eagle hunted.

attitude

Gray tokos are occasionally shown in zoological gardens. They have already reached an age of up to 20 years there.

literature

Web links

Commons : Tockus nasutus  - collection of images, videos and audio files

Single receipts

  1. ↑ Lophoceros nasutus in the endangered Red List species the IUCN 2016 Posted by: BirdLife International, 2016. Retrieved on 3 October 2017th
  2. ↑ a b Kemp: The Hornbills - Bucerotiformes . P. 124.
  3. ↑ Gray-billed Toko on Avibase , accessed October 2, 2016
  4. ↑ Calls of the gray coconut on Xeno-Canto , accessed on October 2, 2016
  5. ↑ a b c Kemp: The Hornbills - Bucerotiformes . P. 125.
  6. ↑ a b c d e f g h Kemp: The Hornbills - Bucerotiformes . P. 126.
  7. ↑ a b c Kemp: The Hornbills - Bucerotiformes . P. 127.
  8. ↑ Grummt, H. Strehlow (Ed.): Zoo animal keeping birds . P. 548.