Thumbnail sparrow
| Thumbnail sparrow | ||||||||||
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Däumlingssperber ( youth dress of the rust-colored morph) |
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| Systematics | ||||||||||
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| Scientific name | ||||||||||
| Accipiter superciliosus | ||||||||||
| ( Linnaeus , 1766) |
The Tom Thumb ( Accipiter superciliosus ) is a bird of prey from the hawk-like family (Accipitridae). The miniature sparrow is one of the smallest species of the genus Accipiter , males are about the size of a song thrush . Females are considerably larger and almost twice as heavy as the males. The species inhabits loosened tropical forests and forest edges in large parts of Central and South America. It is considered safe.
description
Thumbnail sparrows are typical representatives of the predominantly forest-dwelling genus Accipiter . Compared to other species of the genus, the short wings are relatively sharply pointed and the tail is relatively very short. Legs and toes show clear adaptations to the hunt for small and fast songbirds. They are comparatively long and thin.
With a body length of 20 to 26 cm and a wingspan of 38 to 48 cm, the species is one of the smallest of the genus. The sex dimorphism in terms of height and weight is extreme in this species. The difference is so great that there is no area of overlap between the sexes when it comes to body measurements. Adult males of the nominate form A. s. superciliosus have a wing length of 134–147 mm; Females measure 155–170 mm. Weight information on the nominate form is not yet available, males of the subspecies A. s. fontanieri weigh 62–75 g; Females 115-134 g. On average, males reach around 62% of the body weight of females.
Thumbnail sparrows show a low gender dimorphism in terms of coloration. Colored ( adult ) males are black-brown on top, with the top of the head and neck being the darkest; The back and upper wings are grayer. The rudder feathers and the wings show a brownish-gray cross-band on the upper side and a blackish cross-band on the underside on a whitish background, the rudder springs have an end band of the same color. The underside is cross-banded in white and fine gray (“ spattered ”), only the throat is monochrome white and the cheeks are spotted gray.
Females are more gray-brown on the upper side, the underside is banded more brown-gray on a creamy white background. In both sexes, the wax skin and legs are yellow, the claws are black. The iris is red.
Like some other species of the genus, juveniles show a brown and a rarer rust-colored morph . The upper side of the brown morph is brown, the skull and neck are blackish. The tail shows narrow, gray-brown transverse bands and a narrow white tip on a brown background. The underside is banded more pale brown or reddish brown on a creamy white background. The throat is a single cream color, the cheeks are correspondingly mottled pale brown or reddish brown.
In the rust-colored Morphe, the feathers of the back and the upper wing have a wide rust-colored border and only darker brown or brown banded in the center, so that the upper side appears rust-colored as a whole. However, as with the brown morph, the skull and neck are blackish. The control springs are sharply set off on a rust-colored background, but are narrowly banded in black with interruptions. The underside is banded with dark rust-brown on a pale rust-colored background. The iris is orange pale yellow in young birds of both morphs; the wax skin is yellow, the legs are pale yellow.
Vocalizations
The calls are hardly described, so far only a shrill, lined up "krii-rii-rii-rii" is known.
distribution and habitat
The range of the Thumbnail sparrow covers large parts of Central and South America. It extends in the north from eastern Nicaragua and Costa Rica to the south to the northeast of Argentina and in a west-east direction from the Pacific coast of Ecuador to the eastern tip of Brazil , including most of the Amazonia . The species inhabits loosened tropical forests and forest edges, clearings, neighboring plantations and older secondary forests; the closed and dense forest is evidently avoided. The species occurs predominantly up to an altitude of 800 m, locally up to a maximum of 1800 m.
Systematics
According to a molecular genetic investigation, the results of which were personally communicated to Storrs Olson by MJ Braun, the thumb sparrow is not closely related to the species of the genus Accipiter , as confirmed by skeletal morphological investigations by Olson. Olson therefore proposed in 2006 the separation of the species as a separate genus Hieraspiza with the name Hieraspiza superciliosa . Another molecular genetic study by Anett Kocum in 2006 confirmed this special position of A. superciliosus .
Two subspecies are currently recognized:
- A. s. superciliosus : nominate form ; South America east of the Andes.
- A. s. fontanieri : Nicaragua to western Ecuador west of the Andes; somewhat smaller, more short-tailed and darker than the nominate form, with more contrasting and darker bands on the underside.
hikes
No hikes are known.
Hunting style and diet
Thumbnail sparrows apparently hunt mainly from the raised hide in a short, fast pursuit flight. The species mainly feeds on small birds, but rodent remains have also been found in an individual's stomach. At least some individuals seem to feed predominantly on hummingbirds that are caught in a surprise attack at their regular seats or when switching between them.
Reproduction
Many aspects of reproduction have so far hardly been studied. The birds can be observed circling over the territories, flying games are not yet known. The two nests previously described, made of twigs, were high in trees, one of them in an old nest of a black-necked buzzard ( Busarellus nigricollis ). In Panama and Colombia the breeding season probably falls in the period February to June, in the south probably in the period from October to January; in northern central Brazil, large nestlings were encountered once in August. The clutch comprises one to three eggs; Information on the incubation period, the number of nestlings and the nestling time is not yet available.
Existence and endangerment
The species is mostly under-recorded because of its habitat, its relatively secret way of life and because it is confused with other species. There is no reliable information on the size of the world population, Ferguson-Lees & Christie assume a total population of less than 100,000 birds. The IUCN classifies the species as safe for 2008 ( "least concern" ).
swell
Individual evidence
- ^ J. Ferguson-Lees, DA Christie: Raptors of the World. Christopher Helm, London 2001, ISBN 0-7136-8026-1 : p. 559.
- ↑ Storrs L. Olson, Reflections on the systematics of Accipiter and the genus for Falco superciliosus Linnaeus. In: Bulletin of the British Ornithologist's Club 126 (1), 2006: 69-70. PDF
- ↑ A. Kocum: Phylogeny of the Accipitriformes (birds of prey) based on various nuclear and mitochondrial DNA sequences. Dissertation at the Ernst-Moritz-Arndt-Universität Greifswald, 2006: p. 154 ff.
- ^ J. Ferguson-Lees, DA Christie: Raptors of the World. Christopher Helm, London 2001, ISBN 0-7136-8026-1 : p. 558
literature
- J. Ferguson-Lees, DA Christie: Raptors of the World. Christopher Helm, London 2001: pp. 180-181 and 557-559, ISBN 0-7136-8026-1 .
Web links
- Accipiter superciliosus in the endangered Red List species the IUCN 2008. Posted by: BirdLife International, 2008. Accessed on 15 November, 2008.