Pointed tail hammer
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Pointed-tailed hammer ( Ammodramus caudacutus ) |
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| Ammodramus caudacutus | ||||||||||||
| ( Gmelin , 1788) |
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The pointed- tailed bunting ( Ammodramus caudacutus ) is one of the more inconspicuous colored New World chambers of North America ("Sparrows") and occurs only in the salt marshes of the Atlantic coast. It was previously regarded as conspecific with the Nelson Hammer ( Ammodramus nelsoni ). Even if hybrids between the two species occur in southern Maine and northern Massachusetts , molecular genetic studies establish the species status and a close relationship of the four species Nelsonammer, Pointed-tailed Hammer, Strandammer ( Ammodramus maritimus ) andLeconteammer ( Ammodramus leconteii ) - possibly as super species - close.
description
With a length of 11.5 to 13.0 cm, the pointed tail hammer is about the same size as a goldfinch and weighs around 15 to 23 g. The species is one of the smaller North American species of ammunition ("Sparrows") and bears its name because of the thorn-like, pointed tail feathers . The beak is dark horn-colored on top, lighter downwards. The iris is brown. Legs and feet are flesh-colored. There is no sexual dimorphism .
Adult birds have a narrow, often barely recognizable gray crown and dark brown lateral stripes. The over-eye stripe is yellowish-beige to yellow-orange, as is the beard stripe , which extends further over the sides of the neck and back up to the end of the eye stripe and thus includes the gray area of reins, cheek stripes and ear covers. The eye and chin stripes are blackish. The former begins behind the eye and extends behind the ear covers. The neck is gray like the cheeks. The chin and throat, like the underside, are white, but tinted beige and dark dashed on the chest, the flanks and the underside of the tail. The upper back is greyish and interspersed with white dashes, which, however, hardly come into their own in the worn plumage. The lower back, rump and tail-coverts are brown with beige hems. The wing plumage is largely brownish with blackish feather centers. The small arm covers are tinted olive-gray, the middle arm covers are brown with beige tips, the large arm covers and umbrella feathers are beige to whitish and increasingly lined with reddish brown towards the base. The wings are lined with narrow reddish brown to beige. The control springs are beige-brown.
The youth dress is similar to the adult dress, but is more yellowish beige in color with more extensive, albeit fine dotted lines on the underside.
voice
The inconspicuous singing (audio sample) is similar to that of the Nelsonammers, but is a little softer. It is a quiet series of pressed, hissing and slightly more accentuated sounds and can be described as ts-ts-ssssss-tsik or si-lik tssss-ssss . Calls are a very high- pitched , sharp chic or a repeated series of zig , chack or chipp sounds.
Geographic variation
Two subspecies are recognized, of which the nominate form is more common in the north, the southern subspecies A. c. diversus is small-billed and slightly darker on top.
- A. c. caudacutus ( JF Gmelin , 1788) - southern Maine to New Jersey
- A. c. diversus Bishop , 1901 - from New Jersey to the Delmarva Peninsula
distribution
The distribution of the pointed-tailed bunting is limited to the North American Atlantic coast in the area of the warm temperate and subtropical zones. It ranges from southern Maine to the Delmarva Peninsula.
Since earlier pointed-tailed and Nelson bammers were regarded as one species (English "Sharp-tailed Sparrow") and no distinction was made between "Saltmarsh Sharp-tailed Sparrow" and "Nelson's Sharp-tailed Sparrow" in the literature, the exact limit is the northern distribution is currently unclear.
hikes
The pointed-tailed bunting is a migratory bird whose wintering quarters border the breeding areas to the south and extend to Florida. The autumn migration takes place between September and the end of November and reaches its peak in October, the spring migration takes place between the end of April and the beginning of May. The species remains in the area of the Atlantic coast, but has also been found sporadically inland. Occasionally it winters in the breeding areas.
habitat
The pointed-tailed bunting colonizes salt and wet meadows with dense stands of silt grass (especially Spartina alterniflora , but also Spartina patens ), lagoon rushes or trident . Sometimes it also occurs at the edges of ditches or pond banks. It is found predominantly in the littoral of the Atlantic coast and only extremely rarely further inland.
nutrition
Little information is available about the food spectrum of the species. Presumably it feeds on small invertebrates and seeds. Food is sought on the ground or in the lowest layer of vegetation.
Reproduction
The pointed-tailed bunting is promiscuous and not territorial. Apparently there is no real pair bond. It may form colonies with poor cohesion. The breeding season is between mid-May and August. There are two main stages in oviposition. One takes place between late May and early June, the other between mid and late June. Possibly there are two annual broods.
The nest is made soon after arrival in the breeding grounds. It is a loose, extensive bowl made of grass and other plant parts, which is lined with finer material. It stands directly on the ground or, if it is waterlogged, hanging 10 cm above the water surface. It is mostly found in locations where a roof or tunnel has formed from dry grass or sedges from the previous year.
The clutch usually consists of three to five, more rarely two or up to six eggs, which are speckled reddish-brown on a greenish or bluish background and are incubated by the female for about 12 days. First shifts often fall victim to spring tides, whereupon additional shifts are made. The rearing of the young is incumbent on the female. The nestling period lasts between eight and eleven days.
Duration
Due to its limited distribution, the pointed-tailed bunting is regarded by the IUCN as endangered (“vulnerable”) and enjoys the highest protection priority in the USA. Although the species is abundant in suitable habitats, the population is declining due to habitat degradation and increasing fragmentation. On 20,000 km² of coast in the area of the distribution area there are probably only 2000 km² with suitable habitats. While the population was still estimated at 250,000 birds at the beginning of the millennium, more recent surveys suggest more likely 50,000 to 100,000, with a population of 100,000 probably being overly optimistic. In addition to the increasing use and destruction of habitats, environmental pollution, the increasing spread of the reed ( Phragmites australis ) introduced in North America and the rising sea level due to global warming represent further threats.
literature
- James Rising: Saltmarsh Sparrow (Ammodramus caudacutus) (2011), in: J. del Hoyo, A. Elliott, J. Sargatal, AD Christie, E. de Juana (eds.): Handbook of the Birds of the World Alive. Lynx Edicions, Barcelona 2014
Web links
- Ammospiza caudacuta in the endangered Red List species the IUCN 2012. Posted by: BirdLife International, 2012. Accessed February 24, 2015.
- Audio sample of the singing of the pointed tail hammer
Individual evidence
- ↑ Tayler Brooks: XC59191 Pointed-tailed Hammer Ammodramus caudacutus . xeno-canto.org. June 11, 2010. Retrieved November 3, 2019.