Bald Woodpecker
| Bald Woodpecker | ||||||||||||
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Bald Woodpecker ( Leuconotopicus albolarvatus ), male |
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| Systematics | ||||||||||||
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| Scientific name | ||||||||||||
| Leuconotopicus albolarvatus | ||||||||||||
| ( Cassin , 1850) |
The white-headed woodpecker ( Leuconotopicus albolarvatus , syn .: Picoides albolarvatus ), also called nun woodpecker , is a member of the genus Leuconotopicus within the subfamily of the real woodpeckers (Picinae). The approximately buntspecht large woodpecker is found in pine-dominated mountain forests of the western United States and southwestern Canada into two subspecies. Few scientific papers are available on the biology of the species.
Appearance
With an average length of 23 centimeters and a weight of around 65 grams, the white-headed woodpecker is slightly smaller and lighter than the native great spotted woodpecker . It is the only woodpecker with a largely white head with mostly black plumage.
The head, vertex, throat and upper chest area are white without a mark in both sexes. The area around the base of the beak can be covered in yellow. The rear part is colored red in the male, this area is also white in the female. The beak is dark gray, the eyes are reddish brown. The entire body is black without drawing except for the wings. Shinier on the top and chest than the rest of the body. Depending on the incidence of light, bluish or purple color nuances can arise. The second third of the hand wings are white, at the top they are black again. This white drawing is striking in both the seated and the flying bird. The legs and toes are gray, the first toe pointing backwards is greatly shortened.
Males are slightly larger and heavier than females; Except for the red occipital spot, the sexes do not differ in color. The juvenile plumage also differs only slightly from that of colored birds. The black is less shiny, sometimes white feather tips appear in the belly area. The occipital spot is present in both sexes, but mostly smaller and not purple-red as in adult males, but paler, orange-reddish. The white markings on the wings of the hand are also less distinctive, they often appear washed out and are dirty white in color.
Vocalizations
The vocalizations of this kind are not very noticeable; many of them have a typical colored woodpecker effect . The most frequently heard call, which is used both as a contact call and as an undifferentiated presence call, is a two, often three-syllable Pii-di (nk) or Pii-di-dink . The call that can be heard throughout the year is short, hasty, very bright, almost glassy . More emotionally motivated is a high, very quickly ranked Piik..piik..piik ... In addition, other, often croaking and harsh calls can be heard.
In the pre-breeding season and early breeding season, both males and females drum intensely. Often the pii-di-dink call is interrupted by drum rolls . The vortices last about 20 single beats on average and last about a second.
Possible confusion
The white-headed woodpecker is almost unmistakable under normal observation conditions; only the pine jay ( Nucifraga columbiana ) could be a mistake in poor visibility conditions. It differs from all woodpecker species sympatric with it by the largely black rump plumage and the pure white color of the head and throat.
distribution
The distribution area of this species is in western North America, especially in the montane areas of the states of Washington , Oregon and California . The northernmost occurrences are in the vicinity of Lake Okanagan in British Columbia , the southernmost near the border with Mexico in the mountainous regions of San Diego County . From Baja California , there are currently no breeding records. To the east, the breeding occurrences extend to the states of Idaho and Nevada , where the bald woodpecker breeds in the region around Lake Tahoe .
In its entire range, the occurrences are very fragmented. The western slopes of the mountains are more densely populated than the eastern ones.
habitat
The white-headed woodpecker lives in old, tall, montane pine forests that are dominated by yellow pines ( Pinus ponderosa ). Habitats that have other types of pine such as the sugar pine ( Pinus lambertiana ) or the coastal pine ( Pinus contorta ) are preferred . Other important accompanying trees of a good white-headed woodpecker habitat are the Colorado fir ( Abies concolor ), the magnificent fir ( Abies magnifica ) and regional cypress species such as incense cedar ( Calocedrus sp.). In addition to the pine species as food trees, a sufficient supply of dead and weathered trees is essential for creating nesting holes.
The white-headed woodpecker is found exclusively in submontane, montane and subalpine forests. In British Columbia it breeds primarily at altitudes between 700 and 1000 meters, in Washington and Oregon between 850 and 1600 meters. The highest known breeding sites are on the eastern slopes of the Sierra Nevada at over 3000 meters.
Little data is available on the species’s territoriality and space requirements. During the breeding season, the pair maintain a core area near the nest hole. Neighboring districts seem to be able to overlap over a large area without causing territorial disputes. The size of the territory fluctuates considerably; in Oregon , territorial sizes of around 100 hectares were found in closed old coniferous forest stands, while in fragmented forests the space requirement of the species is significantly greater, and is over 300 hectares per breeding pair.
hikes
The white-headed woodpecker is largely a resident bird. Small-scale horizontal and vertical movements take place outside the breeding season; they are mainly triggered by a shortage of food and the effects of the weather. Few sightings outside the actual breeding area concern the states of Montana and Wyoming as well as regions on the California Pacific coast. Investigations into the loyalty to the location showed a very high mobility. Couples often only breed in an area for a season or two and then leave without knowing their migratory movements.
Food and subsistence
The diet of the bald woodpecker consists of roughly equal parts of vegetable and animal components. The distribution is, however, subject to large fluctuations regionally, seasonally and also individually. In general, animal food predominates in late spring and summer, while vegetable food is increasingly consumed in autumn and winter.
Ants and termites and their stages of development play the greatest role among prey. In addition, various types of beetles and their larvae , as well as cicadas , are often captured. In mass occurrence can scale insects are the main source of food. The vegetable diet consists mainly of conifer seeds, especially those of the yellow pine and the sugar pine. From the southern subspecies L. a. gravirostris , the large cones of the Coulter pine are also exploited. Tree saps are an important supplementary food, especially in spring.
Animal food is obtained by reading from the trunk or branch surface, by drilling and poking, probing with the tongue and by prying away pieces of bark. On the surface, feeding tunnels are also hacked, but deep hacking has only rarely been observed. The food animals are mainly preyed on living conifers, whereby all trunk and branch sections are used for foraging. When foraging for food, the bald woodpecker often flies to the lower trunk region and works its way up from there. The conifer seeds are either loosened directly from the cone, with the woodpecker occasionally hanging upside down on the cone, or the cones are torn off as a whole and taken to a forge . Storage has not yet been observed.
Breeding biology
Bald woodpeckers become sexually mature in their first year of life. They have a monogamous seasonal marriage; the pair bond does not completely disappear outside the breeding season, so that re-pairings are frequent. Courtship activities, which mainly consist of shouting and drumming, sightseeing, cave demonstrations and the cave construction itself, are observed in the southern distribution areas from around mid-March, in the areas of occurrence of the nominate form around a month later. There is only one annual brood; Additional clutches have not yet been observed. The laying period begins at the end of May and ends at the end of June.
Cave construction and cave location
The cave construction usually begins in early May. Both partners participate in the cave construction. Usually a new nest box is made every year. Nesting holes are dug into different species of conifers without any particular species being clearly preferred. Most of them are completely dead trees or taller tree stumps with a diameter of over 50 centimeters. There are also nesting holes in dead wood that are only inclined or almost lying. The nest holes are relatively deep, on average about 3 meters high. The entry hole is on average 46 millimeters wide and almost round; the depth of the cave is usually more than 20 centimeters, the width of the interior is 10 centimeters.
Clutch and brood
Every day, 4–5 (3–9) pure white eggs about 24 × 18 millimeters in size are laid. In clutches with an egg count of over 6 eggs, intraspecific brood parasitism could be present. The eggs are incubated by both partners for about 14 days. During the daytime the brood is separated approximately every hour, at night, as with almost all woodpeckers, only the male breeds. The nestlings are hoed and fed by both parents. In the first two weeks, the parents hatch into the cave for feeding, after which the feeding and the removal of the faeces at the cave entrance take place. The cubs leave the nest box after 26 days at the earliest, but their parents will look after them for a long time. Family groups can still be found in autumn, occasionally even in winter. No meaningful data are available on the reproduction rate; The type and extent of the young dispersals have not yet been adequately researched either.
Systematics
The white-headed woodpecker was first described by John Cassin in 1850 and placed in the genus Leuconerpes . A little later it formed the only species in the genus Xenopicus established by Baird . In the middle of the 20th century, all but the three-toed great spotted woodpecker were combined in the genus Dendrocopos , from which the nearctic species were finally separated and placed together with the two species of the three- toed woodpecker in the genus Picoides .
The relationship of the white-headed woodpecker within the Picoides remained uncertain. Genetic investigations have shown a close relationship to the Strickland woodpecker ( Picoides stricklandi ) and the hairpecker ( Picoides villosus ), as well as the cockade woodpecker ( Picoides borealis ). The species was finally transferred in 2015 by Jerôme Fuchs together with these species into the genus Leuconotopicus established by Alfred Malherbe in 1845 .
Two, only weakly differentiated subspecies are described: L. a differs from the nominate form that occurs in most of the distribution area . gravirostris by a slightly longer beak and a longer tail. The beak length is interpreted as an adaptation to one of the main foods of this subspecies, the seeds of the Coulter pine, whose cones are much larger than those of the pine species, which the nominate form prefers. Gravirostris occurs from the mountainous regions of Los Angeles Counties south to near the Mexican border.
Stock situation
According to Birdlife International, the total population is estimated at 72,000 individuals and viewed as stable. The species even seems to be increasing in its core areas. Regionally, however, especially from Northern California and Oregon, there are indications of partially significant population declines. Overall, the status of this species has not yet been adequately researched, so that no statements can be made about the causes and developments that limit the population.
Individual evidence
- ↑ Garrett et al. (1996) Sounds
- ↑ Garrett et al. (1996) Distribution
- ↑ Garret et al. (1996) Distribution
- ↑ Garret et al. (1996) Spacing
- ↑ Garret et al. (1996) Range
- ↑ Garrett et al. (1996) Migration
- ↑ Gebauer (2004) p. 3
- ↑ Gebauer (2004) p. 3
- ↑ Garrett et al. (1996) Feeding
- ↑ Garret et al. (1996) Breeding
- ↑ Garret et al. (1996) Breeding
- ↑ Garret et al. (1996) Demography and Populations
- ↑ Garret et al. (1996) Breeding
- ↑ Garret et al. (1996) Introduction / Systematics
- ↑ Weibel et al. (2002) p. 71
- ↑ Jérôme Fuchs and Jean-Marc Pons: A new classification of the Pied Woodpeckers assemblage (Dendropicini, Picidae) based on a comprehensive multi-locus phylogeny . In: Molecular Phylogenetics and Evolution 88 (2015) 28-37
- ↑ Alexander et al. (2006) Abstract
- ↑ Garret et al. (1996) Systematics
- ↑ data sheet (2004)
- ↑ Garret et al. (1996) Demography and Population
literature
- Matthew P. Alexander and Kevin J. Burns: Intraspecific Phylogeography and Adaptive Divergence in the White-headed Woodpecker. Condor 108 (3): 489-508. (2006).
- Datasheet Birdlife international engl.
- Martin Gebauer: White-headed Woodpecker ( Picoides albolarvatus ) In: Accounts and Measures for Managing Identified Wildlife - Accounts V. 2004 (British Columbia). [1] (pdf text; English)
- Kimball L. Garrett, Martin G. Raphael and Rita D. Dixon: White-headed Woodpecker (Picoides albolarvatus) . In: The Birds of North America Online (A. Poole, Ed.). Ithaca: Cornell Lab of Ornithology species / 252 (1996)
- 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 , Vol. 22, No. 1, January, pp. 65–75, 2002. Article pdf engl.
- Hans Winkler , David Christie, David Nurney: Woodpeckers. A Guide to Woodpeckers, Piculets, and Wrynecks of the World. Pica Press, Robertsbridge 1995, ISBN 0-395-72043-5 .
Web links
- Humboldt University, Berlin
- Avibase - The world bird database
- Good summary and voice example
- Leuconotopicus albolarvatus in the Red List of Threatened Species of IUCN 2013.1. Listed by: BirdLife International, 2012. Retrieved September 7, 2013.