Texan woodpecker
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Texan woodpecker ( Dryobates scalaris ) (♂) |
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| Dryobates scalaris | ||||||||||||
| ( Wagler , 1829) |
The Texas woodpecker (Dryobates scalaris, Syn .: Picoides scalaris ) is a small great spotted woodpecker from the subfamily of the real woodpeckers, native to southwest North America . (Picinae). It is very closely related to the Nuttall woodpecker , with which it occurs sympatricly in some regions and occasionally hybridizes there. The native small woodpecker ( Dendrocopos minor ) is also a close relative of this Nearctic woodpecker. Of a total of 14 described subspecies, 8 are currently generally recognized. Because of its occurrence in arid areas, this woodpecker is often called the cactus woodpecker .
Appearance
The Texas woodpecker is extremely similar to the Nuttall woodpecker; the northern subspecies are also similar in size but are around 25 percent lighter than this. Northern and northeastern Texas woodpeckers have an average body length of 17-18 centimeters, representatives of more southern populations are somewhat smaller and darker. The subspecies Picoides scalaris leucoptilurus, which breeds in Belize, is the smallest with a maximum total length of 15 centimeters.
The Texas woodpecker is a typical great spotted woodpecker with black and white contrasting plumage. The males wear a red crown and cap. The back plumage of both sexes is clearly ladder-shaped white banded on a black background, the underside is almost pure white except for the mostly light cream-yellow, clearly black dripped flank areas. The upper tail is black, the outer control feathers have a wide white banding, the underside of all control feathers is broadly banded in white. The bill and iris are dark, feet and toes are slate gray. A wide black mask covers the middle cheek area; the underlying black stripe of beard is clearly set off from it by a white field. Face masks and beard stripes are connected in the subspecies distributed in the north, but only hinted at or not at all in the subspecies in the south of the range. Both have no connection to the black neck plumage.
The plumage of the females is a little less contrasting, the cream tint of the flank plumage is more extensive and clearer. The most conspicuous sex determination feature, however, is the completely black coloration of the vertex and neck plumage of the females.
The plumage of juvenile Texas woodpeckers is very similar to that of female plumage, but both sexes wear red apex markings, which in female juveniles often only consist of a few red feathers. Determining the sex of juvenile Texan woodpeckers is problematic in field ornithological terms.
Possible confusion
The Texan woodpecker is very easy to confuse with the Nuttal woodpecker. Overall, the Nuttall woodpecker is darker and more massive, the ladder drawing on the back is more washed out, the white segments are usually narrower and interspersed with gray. In the field of vision, white predominates in the Texan woodpecker, but in the Nuttall woodpecker black, the beard stripe in the Texan woodpecker has no connection to the dark nape of the neck. The small downy woodpecker , which is also found sympathetically in some regions , differs significantly in the unstriped black outer back and shoulder area, as well as in the almost pure white underside without any marks. In the male downy woodpecker, the red head mark is reduced to a small occipital cap.
hikes
The Texas woodpecker is largely local; Young birds seem to resettle in close proximity to their place of birth, but there are no more detailed studies on youth dismigration . Breeding birds of very high altitude areas migrate vertically in small areas in winter.
Life expectancy
There are very few re-finds of ringed Texan woodpeckers. The oldest bird found so far was 4 years and six months old.
Systematics
The Texan woodpecker belongs to a small group of small Nearctic woodpeckers, from which the Palearctic small woodpecker ( Dendrocopos minor ) probably descends. Hybridization is occupied with the downy woodpecker and with the Nuttallspecht. Usually the Texan woodpecker is assigned to the genus Picoides , previously it was classified in the genus Dryobates , a genus name that is still discussed again today and is occasionally used for the small woodpecker ( Dryobates minor ). Currently (2016) the Texan woodpecker is placed in the genus Dryobates together with five other small great spotted woodpeckers .
Up to 14 subspecies of the Texan woodpecker have been described. At least 8 are currently widely recognized. The greatest splitting into different subspecies is in the southern breeding areas of Mexico and in the Central American states. In the USA the subspecies D. s. cactophilus common; apart from its size, it is particularly conspicuous through the wide, white ladder rungs markings in the back plumage, which gave the species the English name Ladder-backed Woodpecker .
The following presentation follows Hans Winkler et al.
- Dryobates scalaris cactophilus Oberholser , 1911 : Largest part of the distribution area; southern USA to southern Mexico. - described above.
- D. s. eremicus Oberholser , 1911 : Northern Baja California. Larger than cactophilus ; longer beak and tail. Overall, it looks darker due to wider dark bands.
- D. s. lucasanus ( Xantus , 1860) : Southern Baja California. Smaller and lighter than eremicus .
- D. s. graysoni ( Baird, SF , 1874) : Tres Marias Islands ; very similar to lucasanus , but slightly smaller. Underside slightly brownish leather, chest only slightly dark dashed.
- D. s. sinaloensis Ridgway , 1887 : Southern Sonora to Guerrero , southwestern Puebla and central Oaxaca . Similar to but smaller than cactophilus ; Beard streak interrupted several times. Underside dotted rather than spotted.
- D. s. scalaris ( Wagler , 1829) : Chiapas and Veracruz . Similar to cactophilus . The forehead is yellowish-brown, the chest narrowly dashed.
- D. s. parvus ( Cabot , 1845) : Yucatán . Smaller than the nominate form. Black forehead, barely broken beard. Broad black banding on the back, flanks also clearly banded.
- D. s. leucoptilurus Oberholser , 1911 : Belize , Guatemala to northeastern Nicaragua . The smallest subspecies. Relatively dark on the top and very light, almost white on the underside. Almost unmarked flanks.
distribution and habitat
The Texas woodpecker is represented as a breeding bird in arid and semi-arid areas of the southwestern USA, in almost all of Mexico including almost all of Baja California, as well as in some other Central American states, especially in Guatemala and Honduras .
In its US distribution areas, it colonizes semi-deserts overgrown with Joshua trees , various opuntia and mesquite bushes, in higher-lying areas and where there is no competitive pressure from other woodpeckers, it also occurs in mixed pine-oak forests; regionally the species also breeds in juniper and acacia stands . Woods accompanying the river are usually only populated when the Nuttall woodpecker does not occur; Occasionally, however, these two woodpeckers become sympathetic in such habitats and in higher-lying oak-pine forests.
A clear preference for a certain altitude level has not yet been established. The Texas woodpeckers' breeding grounds are at sea level as well as at altitudes above 2000 meters. The highest nesting occurrences are likely to be in the highlands of Mexico at an altitude of over 2,600 meters.
Food and subsistence
Texas woodpeckers feed mainly insectivore on beetles and their wood-dwelling larvae, ants, caterpillars, flies and lice. Vegetarian food in the form of berries, fruit, conifer seeds or nuts is consumed if there is an appropriate supply, but overall it only plays a subordinate role. Texas woodpeckers find their prey by diligent, skilful searching of the trunk and branch surfaces, by drilling and poking, and more rarely by hammering into larval ducts lying on the surface. Significant differences in the preference for different food plants were found between the sexes: between October and June, males prefer to look for opuntia, mainly Opuntia fulgida , and stay in mesquite bushes and Joshua trees outside of this time , while females stay in mesquite bushes all year round to prefer. The females look for food more often on small, weak branches at a greater height, while males prefer to search for food in the middle of the trunk and lower crown area.
Breeding biology
Texan woodpeckers become sexually mature in their first year of life. They are likely to have a predominantly monogamous breeding season marriage, but details are not known. The courtship begins in late autumn and early winter with long series of calls, drum sequences and cave building. With the exception of the very high breeding areas, pair formation in most breeding areas seems to be completed by the end of February or mid-March.
The nest box is usually set up anew every year in different, mostly rotten trees, or in those with very soft wood. Willows and poplars predominate as cave trees, but nesting holes are also created in oaks, pines and acacias, not infrequently also in cacti, primarily in saguaros ( Carnegiea gigantea ), as well as in various yucca species. The males seem to be more involved than the females in building the nest. The nest cavity is usually over two meters high, the entrance hole is often a bit oval with a diameter of about 4 centimeters, the interior depth is about 30 centimeters. The shiny white or slightly creamy white eggs are longitudinally oval and have an average size of 21 × 16 millimeters; a full clutch consists of 4–5 (2–7) eggs; Texas woodpeckers only breed once a year, and new eggs are only laid if the clutch is lost early.
The first full clutches are found in the southern breeding areas at the end of March, further to the north and in high-altitude regions not until mid to late April. The laying period lasts until May, June clutches are mostly additional clutches. No reliable data is available on the breeding period and rearing of the nestlings; the breeding period for related species is around 12 and the nestling period 15-20 days.
Inventory and inventory trends
The population of the Texas woodpecker is currently considered safe. The total population is estimated at over 2 million individuals. Cross-state population assessments do not exist, but quite significant population declines have been found for Texas, the cause of which is unknown.
literature
- Factsheet Birdlife International engl.
- Peter E. Lowther: Ladder-backed Woodpecker (Picoides nuttallii) . In The Birds of North America, No. 555 (A. Poole and F. Gill, eds.). The Birds of North America, Inc., Philadelphia, PA. Issue 555 - (no pagecount).
- Roger T. Peterson: Western Birds . Houghton Mifflin Co. Boston 1990: pp. 224-229.
- Amy C. Weibel, William S. Moore: Molecular Phylogeny of a Cosmopolitan Group of Woodpeckers (Genus Picoides) Based on COI and cyt b Mitochondrial Gene Sequences. In: Molecular Phylogenetics and Evolution 22 (1), 2002, pp. 65-75. ( PDF 112kb , accessed November 30, 2013)
- Hans Winkler , David A. Christie, David Nurney: Woodpeckers. A Guide to the Woodpeckers, Piculets, and Wrynecks of the World. Pica Press, Robertsbridge 1995, ISBN 0-395-72043-5 .
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Sources cited
- ^ Lowther (2001) Systematics
- ^ Lowther (2001) Systematics
- ^ Lowther (2001) Systematics
- ↑ Winkler et al (1995) p. 284
- ^ Lowther (2001) Food Habits
- ↑ factsheet birdlife (2007) - census 2003
- ^ Lowther (2001) Population Status
Web links
- Videos, photos and sound recordings about Picoides scalaris in the Internet Bird Collection
- Dryobates scalaris inthe IUCN 2013 Red List of Endangered Species . Listed by: BirdLife International, 2012. Retrieved September 17, 2013.