Downy woodpecker

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Downy woodpecker
Downy Woodpecker (Picoides p. Pubescens)

Downy Woodpecker ( Picoides p. Pubescens )

Systematics
Class : Birds (aves)
Order : Woodpecker birds (Piciformes)
Family : Woodpeckers (Picidae)
Subfamily : Real woodpeckers (Picinae)
Genre : Dryobates
Type : Downy woodpecker
Scientific name
Dryobates pubescens
( Linnaeus , 1766)

The downy woodpecker ( Dryobates pubescens, syn .: Picoides pubescens ) from the subfamily of the real woodpeckers (Picinae) is the smallest North American woodpecker . The species widespread in North America is very closely related to the Texas woodpecker ( Dryobates scalaris ) and to the Nuttall woodpecker ( Dryobates nuttallii ). Linné's first description was based on drawings and descriptions by Mark Catesby , who gave this species its English name, Downy Woodpecker . The fluffy, white plumage area on the middle back was probably responsible for this name. Downy woodpeckers occur in a wide variety of habitats from the arctic tree tundra to evergreen, subtropical marshland on the Gulf Coast and woody trees that accompany rivers in semi-arid areas of southwestern California and Arizona . They usually nest in self-made caves and feed primarily on insects. According to the IUCN , the species is not endangered.

description

Downy Woodpecker, male
Downy woodpecker, female

The downy woodpecker is a very small, strongly contrasting black and white drawn woodpecker with a body mass of up to 27 grams and a maximum size of 17 centimeters in terms of weight and size with the Palearctic small woodpecker. The wingspan is 30 centimeters. The pure white, fluffy plumage area that runs centrally from the upper to the lower back is characteristic.

In terms of coloration, the sexes only differ in the male's small red patch on the neck, which is missing in the female. Females are usually a little heavier and a little more long-winged. Young birds molt into adult plumage in the first autumn . In the first immatural dress they already resemble strongly colored individuals, but usually wear a red forehead and crown markings in both sexes, often interspersed with clear black shaft stripes. Overall, the black-and-white contrast is less pronounced in young birds; brown tones can appear in the black areas of the plumage, and cream-colored or gray in the white. It is usually not possible to determine the sex of immature downy woodpeckers in the field ornithologically .

Appearance ( nominate form )

The upper side is characterized by a relatively wide, pure white plumage zone that runs over the entire central back. The lower back is clearly banded in white on a black background. The central, elongated control feathers are black on the upper side, the outer ones are white, usually with a few black bands or teardrop drawings on their edges. The shoulders are largely undrawn black, the arm covers are drawn in teardrop-shaped white on a black background. These white drawings can flow into one another and form large white fields. The arm and hand wings are usually triple white banded.

The entire underside is pure white, sometimes also slightly grayish, only in the rump region fine black dots can be seen.

The head is clearly drawn in contrasting black and white. The red markings typical of the variegated woodpecker are reduced to a small red patch on the neck of the male. Forehead and skull are black; A white stripe runs from the upper edge of the eye to the black neck band, which is bounded by a wide black area that extends over the eyes and ear covers and also encloses the neck. This is followed by another section of white plumage, which begins at the top of the beak and widens towards the neck and upper back. The marked streak is black, the throat white again. The bristles above the base of the beak are very pronounced. The beak is gray-black, short and pointed. The iris is black, the four-toed legs are light gray.

Downy woodpeckers fly in a typical arched flight of woodpeckers with a propulsion phase of 5 - 6 deeply drawn wing beats, which is followed by a fall phase with flung wings.

Vocalizations

Like most species of this genus, the downy woodpecker is acoustically quite conspicuous during the autumn courtship and in early spring, but is largely silent during the breeding season. All calls are rather high, pointed and not particularly loud. The most frequent call is a kwit or spade uttered by both sexes , which can be stretched in arousal situations or strung together to form sequences of sounds, so that the individual elements can hardly be distinguished. A high, falling series of sounds, called a rattle call in English, serves as a distance call . Both sexes drum, like all drumming woodpeckers, the males louder and more intense. The drum rolls are short and repeated 10-15 times a minute.

Similar species

Hairy woodpecker female. This species is very similar to the downy woodpecker, but somewhat larger, more long-billed and significantly heavier

In appearance the downy woodpecker is very similar to the hairy woodpecker , with which it occurs sympatricly in large parts of its range . In addition to the significantly smaller size of the downy woodpecker and its short beak, the outer control feathers can often provide a good identification aid: These are pure white in the hairy woodpecker, while in the downy woodpecker they usually have several black teardrop drawings. The vocalizations of these species as well as their feeding niches also differ significantly from one another.

Confusion with the closely related species Nuttallspecht and Texasspecht in the southern and southwestern parts of the distribution area can be avoided due to the ladder-like black and white drawn back of these species.

distribution

Distribution of the downy woodpecker. In the lighter colored regions the species occurs irregularly or only rarely.

The large distribution area is limited to the USA and Canada. Occasionally, it appears to breed in northern Baja California as well. The downy woodpecker should be naturalized in the Hawaiian Islands towards the end of the 19th. It is unclear whether these attempts at naturalization actually started or were unsuccessful.

The northernmost distribution areas in Alaska and Canada are in the transition zone from the taiga to the tree tundra. From the central Yukon in Alaska, the northern limit of distribution runs in an east-southeast direction to Newfoundland . However, north of 57 ° north in the west and 50 ° north in the east, the species occurs only very sparsely or only in particularly favorable years. The southern limit of distribution lies in the west in southern California and runs through central Arizona , northern New Mexico and central Texas to the coast of the Gulf of Mexico. The species occurs from sea level to altitudes of over 2700 meters.

habitat

Downy woodpeckers can colonize very different habitats, provided that there are light areas with a low canopy , with deciduous trees, especially willows , birches or poplars . The downy woodpecker is one of those woodpecker species that largely avoid old, deadwood-rich stands and prefer to colonize young trees. Occasionally, however, the species also breeds in fire-damaged coniferous forest areas, especially when fresh undergrowth is developing there. The species occurs in woody trees that accompany rivers, in parks and large gardens, in cemeteries and in other loosely tree-lined areas, also in cultivated land. In the southwest of its distribution area it inhabits citrus plantations. The species avoids closed, dense coniferous forests, but can breed in light spruce forests if individual birches or aspens are interspersed. In arid areas the species can only penetrate along rivers.

The space requirements of downy woodpeckers have been little researched. The few data suggest that areas outside the breeding season range between 2 and 12 hectares. The size of the breeding territories fluctuates around 5 hectares.

hikes

Downy woodpeckers are predominantly resident birds , but can roam undirected outside the breeding season. The northernmost populations probably largely leave their breeding grounds and move south. However, the train distances hardly exceed 1000 kilometers. Downy woodpeckers occasionally appear in northern Mexico during the winter months. Breeding birds from higher areas migrate to valleys.

Food and subsistence

When the goldenrod gall mosquito occurs in large numbers, downy woodpeckers can temporarily feed almost exclusively on their larvae

About 75 percent of the diet consists of insects and other invertebrates , the rest of fruits, berries and tree sap. Beetles and their wood-dwelling larvae, as well as ants, predominate among the insects. Together they make up about half of insect food. In addition there are weevils , Hymenoptera , caterpillars, aphids and spiders and snails consumed.

The vegetable diet consists of berries and fruits, various seeds, cereals, acorns, tree bark and tree sap. The fruits of climbing poison oak and poison ivy are very important winter foods . For a long time, the downy woodpecker was considered a pest, especially by fruit growers in the northeastern United States, as it was suspected of damaging the fruit trees through its ringing. This view has been refuted today, as downy woodpeckers primarily exploit the sap holes of sap lickers. Their own sap holes are very small, not very deep, and do not damage the trees. Downy woodpeckers often visit feeding grounds in winter.

Foraging female downy woodpecker

Downy woodpeckers obtain their insect food mainly by poking, drilling and reading off leaf, stem or branch surfaces. To a lesser extent, feeding tunnels near the surface are hammered out by wood-dwelling larvae, and galls from various insect species are opened. Downy woodpeckers pick fruits and seeds directly from the plants in question, with the woodpeckers often hanging upside down from the branches.

The food is mainly sought in living trees. Low and small diameter woodpeckers are apparently preferred, but downy woodpeckers occasionally look for dead wood either standing or lying down. Due to their small size and light weight, downy woodpeckers can exploit food sources on thin branches, in reeds or other thin stalks.

Whether the sexes generally have different food niches and use different acquisition strategies, or whether the identified differences only occur temporarily and regionally, is controversial. According to Winkler et al. Males seek their food at greater heights and on narrower branches, females more in the middle and lower trunk sections. Males are said to get their food by hammering more often than females.

behavior

Like all woodpeckers, the downy woodpecker is diurnal. Its activity phase roughly corresponds to the length of the day. The daily rest times are mainly around noon and are usually spent dozing on branches in good cover, while the nights are spent in sleeping caves, several of which are built during the year. These are usually shallower than the actual breeding caves. Downy woodpeckers take dust baths, but also bathe in water and occasionally in snow.

Agonistic behavior

Downy woodpeckers defend their breeding territory intensely against conspecifics and cave competitors. The breeding caves, the sleeping caves and some abundant food sources are defended particularly vigorously. The intra-species aggression of the couple partners is primarily directed against the same sex and is usually more violent between females than between males; Occasionally observed aggressive behavior between males and females could also be part of the courtship behavior. The rituals of aggression consist of slow butterfly flights, spiral trunk climbing and mock battles. The opponents sit opposite each other with bristling plumage, upright head feathers and a fanned tail. The opponents turn and turn their heads and spread their wings. Most of the time, these threatening rituals are sufficient so that contact fights are rare. The loser is usually followed for a while with loud shouts.

Downy woodpeckers behave extremely aggressively towards cave competitors such as wrens , tits , nuthatches , other woodpeckers and the naturalized house sparrow and attack them directly. The European star is also attacked, although it cannot use downy woodpecker holes due to its size. While downy woodpeckers usually have the upper hand in small, cave-breeding songbirds, they are subject to larger woodpeckers, which then take over and expand their burrows and occasionally eat eggs or nestlings.

Social behavior

After the family groups break up in autumn, downy woodpeckers live individually or in loose pairs. Group formations with conspecifics are random and short-lived. The species often forms small groups with tits, especially those from the genus Baeolophus .

Breeding biology

Downy woodpeckers become sexually mature at the end of their first year of life, and most breed for the first time at this age. As far as is known, they have a monogamous season partnership. Often, however, this does not seem to go out completely even after the breeding period, or to be renewed in early winter, so that long-term partnerships can also exist. Such multi-year partnerships are favored by a high supply of food, so that neither partner is forced to migrate.

Courtship and cave construction

Almost full-fledged downy woodpecker in breeding cave

The courtship begins with series of calls and drums in February in the southern and in March in the northern breeding areas. At its peak, the main elements are mutual chases and expressive flights. The female usually seems to determine the cave location. The caves are located in a dead or severely damaged, mostly rotten trunk, often below a side branch at a height of (1.5) 3.5−9 (18) meters. Downy woodpeckers prefer trunks or branches with a relatively small diameter of about 10 centimeters. The tree species is variable. Soft hardwoods are preferred, but caves are also found in conifers or hardwoods. Occasionally, downy woodpeckers build caves in telegraph poles or other wooden structures. The cave is built by both partners, but mostly by the male, in 13-20 days.

Clutch and brood

In the south, oviposition begins in April; their beginning shifts with higher degrees of latitude until July. Apparently downy woodpeckers breed only once a year; Replacement clutches are likely if the clutch is lost. The clutch consists of 4–5, on average 19 × 15 millimeters in size, pure white, shiny eggs. To the north, the clutch size increases significantly, reaching around 7 eggs in British Columbia . The eggs are incubated by both partners, but always by the male at night. The young hatch after about 12 days, usually within 12 hours. The youngest chicks often do not survive if the hatching intervals are greater. Both parents farm and feed the young. The disposal of the faeces is mainly done by the male. Brood aid by unmated females was observed in some cases. The nestling period lasts 20-23 days. After leaving the family, the boys remain with the family for about three weeks before they migrate . No data are available on the type and extent of dismigration migrations.

Systematics

The systematic position of the species is currently still being discussed. Most authors put the downy woodpecker together with other great spotted woodpeckers in the genus Picoides , in which small to medium-sized woodpeckers with predominantly black and white plumage are grouped together. Its eleven representatives are in North America. Occasionally, small woodpeckers and three- toed woodpeckers are also placed in this genus. Until a few years ago, Picoides was united with the closely related, mainly Eurasian species of the genus Dendrocopos . Some authors, like Winkler et al., Still summarize all Holarctic great spotted woodpeckers under the generic name Picoides .

Recent DNA studies have shown that the downy woodpecker is closely related to the Eurasian small woodpecker ( Dryobates minor ) and two small Nearctic species, Dryobates nuttallii (Nuttall woodpecker ) and Dryobates scalaris (Texas woodpecker ), as well as a relatively large genetic distance to other members of the genera Picoides and Dendrocopos . The downy woodpecker occasionally hybridizes with the Nuttall woodpecker and the Texas woodpecker in the southwestern part of its range and produces fertile offspring. Consequently, these four species would have to be separated from Picoides or Dendrocopos and placed in their own genus, for which the name Dryobates was proposed, a genus name that was used earlier for the three nearctic species and is now used in German taxonomy for the small woodpecker finds.

6–8 subspecies are described. This representation follows the AOU , which recognizes 7 subspecies.

  • Dryobates pubescens glacialis Grinnell , 1910 : Coastal Areas of Alaska. Very similar to P. p. leucurus , but the underside is yellowish white, the outer tail feathers are clearly marked.
  • D. p. leucurus ( Hartlaub , 1852) : Rocky Mountains from southeast Alaska south to Northern California, Arizona and New Mexico. The largest subspecies, pure white on the underside. The proportion of white on the middle back and the arm covers is greatly reduced.
  • D. p. gairdnerii ( Audubon , 1839) : Pacific coast from British Columbia to northwestern California. Relatively dark on the underside; Arm covers almost unsigned, outer control feathers clearly banded in black.
  • D. p. turati ( Malherbe , 1860) : Western inland. From Washington south to Northern California. Similar to P. p. gairdnerii , but paler on the underside and slightly smaller.
  • D. p. medianus ( Swainson , 1832) : Eastern Canada to Newfoundland, northeast USA east of the Rocky Mountains. Coloring like the nominate form, but slightly larger.
  • D. p. pubescens ( Linnaeus , 1766) : Central and southern USA east of the Rocky Mountains. This subspecies is described above.
  • D. pubescens fumidus Maynard , 1889 : Pacific coast in British Columbia southwards to northwestern Washington.

Causes of risk and life expectancy

Downy woodpeckers have a number of natural enemies, including birds of prey, such as the corner- tailed or round-tailed curb , owls, martens and, in settlements, domestic cats. Eggs and nestlings, and occasionally dormant woodpeckers, are captured by raccoons, a number of tree-climbing snakes, mainly from the genus Pantherophis, and also by rats in settlements. In addition, many woodpeckers have accidents when they collide with vehicles or fly themselves to their deaths on window panes. Direct persecution by humans, which in the past contributed not insignificantly to the thinning of the stand, especially in the fruit-growing areas of the northeastern USA, no longer plays a role today.

Little information is available on life expectancy and mortality. As with many wild animals, the mortality rate is greatest in the first few weeks of life. The oldest ringed downy woodpecker found was at least 11 years and 5 months old.

Stock situation

According to the IUCN, none of the seven subspecies is currently endangered. The downy woodpecker is the most common species of woodpecker in North America and appears to be the only one that is increasing its population slightly. In addition to winter feeding, which is widespread in the USA and Canada, forestry measures are also responsible for thinning out dense stands and thus creating more suitable breeding opportunities for the species.

literature

  • Jerome A. Jackson, Henri R. Ouellet: Downy woodpecker. In: The Birds of North America. No. 613, Philadelphia 2002.
  • David Sibley: Field Guide to the Birds of Eastern America . Christopher Helm, London 2003, ISBN 0-7136-6657-9 .
  • 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 .

Individual evidence

  1. ↑ 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 2002, pp. 65-75.
  2. ↑ Jackson et al. Introduction
  3. ↑ data sheet BirdLife international pdf engl.
  4. ^ David Sibley: Field Guide to the Birds of Eastern America . Christopher Helm, London 2003, ISBN 0-7136-6657-9 , p. 248.
  5. ↑ Jackson et al. (2001) Distribution
  6. ↑ 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 2002, pp. 65-75.
  7. ^ AJ Helbig: Notes on the systematics and taxonomy of the species list of birds in Germany. In: Limicola. 19 (2005), pp. 112-128.
  8. ↑ American Ornithologists Union: Check-list of North American birds. 5th ed. American Ornithol. Union, Baltimore (MD) 1957.
  • Jerome A. Jackson, Henri R. Ouellet: Downy woodpecker. In: The Birds of North America. No. 613, Philadelphia 2002.
  1. ^ Distribution
  2. ↑ Spacing
  3. ↑ a b c d Diet
  4. ↑ Pair Bond
  5. ↑ Population Regulation
  6. ^ First Brood Per Season
  7. ↑ Eggs
  8. ^ Cooperative Breeding
  9. ^ Distinguishing Characteristics
  10. ^ Life Span And Survivorship
  11. ^ Effects Of Human Activity
  • 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 .
  1. ↑ a b p. 285.
  2. ↑ a b c p. 286

Web links

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