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Overview
Distribution
Geographic Range
The Acorn Woodpecker is found from northwestern Oregon, California, the American Southwest, and western Mexico through the Central American highlands and into the northern Andes of Colombia.
Biogeographic Regions: nearctic (Native ); neotropical (Native )
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Global Range: RESIDENT: northwestern Oregon south through western California to southern Baja California; from northern Arizona, northern New Mexico, western Texas, south through Mexico to extreme western Panama; in South America in northern Andes of Colombia.
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National Distribution
United States
Origin: Native
Regularity: Regularly occurring
Currently: Present
Confidence: Confident
Type of Residency: Year-round
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Physical Description
Morphology
Physical Description
The Acorn Woodpecker is a medium-sized, black and white clown-faced bird with a red crown, glossy black and white head, white eyes, and white rump and wing patches. There is usually at least one red or yellow tipped feather on the throat. In Colombian populations, the male has a solid red crown while the female has a black band separating the red crown from the white forehead. The wing span of the woodpecker ranges between 13-15 centimeters.
Average mass: 73 g.
Average basal metabolic rate: 0.737 W.
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Size
Ecology
Habitat
Habitat and Ecology
- Terrestrial
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Habitat
The Acorn Woodpecker prefers pine-oak woodlands where oak trees are plentiful. They are also found in riparian corridors, and in Douglas firs, redwood and tropical hardwood forests as long as oaks are available nearby. Urban parks and suburban areas that possess numerous oak trees are often also home to the species.
Terrestrial Biomes: forest ; rainforest
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Comments: Oaks, either in unmixed open woodland or mixed with conifers (Subtropical to Temperate, locally also in Tropical zones) (AOU 1983); also semiopen habitats such as farmlands and pasturelands with scattered trees and patches of forest in Colombia (Kattan 1988). Digs and nests in cavity in live or dead trees (usually well decayed tree in Costa Rica; Stiles and Skutch 1989), 3-21 m above ground. Often roosts communally in tree cavities throughout the year (Du Plessis, 1994, Condor 96:631-637).
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Migration
Non-Migrant: Yes. At least some populations of this species do not make significant seasonal migrations. Juvenile dispersal is not considered a migration.
Locally Migrant: No. No populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).
Locally Migrant: No. No populations of this species make annual migrations of over 200 km.
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Trophic Strategy
Food Habits
The main diet of the Acorn Woodpecker consists of insects, sap, oak catkins, fruit, and flower nectar. Acorns are critical for winter survival. Occassionally, it eats grass seeds, lizards and bird eggs. The bird prefers, however, flying ants and other Hymenoptera and Coleoptera. When foraging, the woodpecker often sits at the tops of trees while flycatching. Most foraging, however, is performed in or near the canopy. The woodpecker rarely goes to the ground except to pick up grit and fallen acorns. Usually, acorns are removed singly from trees, but the bird may also break off a twig holding up to three acorns. Sapsucking is a communal affair and group members congregate at a set of holes that are used repeatedly for several years.
The Acorn Woodpecker stores insects in cracks or crevices and nuts in indiviually-drilled holes in graneries. A granary tree may hold as many 50,000 holes. Holes are usually drilled in dead limbs and in thick bark during the winter. Any dead or living tree with deep dry bark can used as granary. Studies have shown that these granaries are so important that they are one of the main reasons why acorn woodpeckers live in such large families, at least in California. Only a large group can collect so many acorns and also defend them against other groups.
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Comments: Feeds on insects in summer (e.g., grasshoppers, ants, beetles, flies); sallies from snag or fence post for flying insects; also eats tree sap and some fruit, rarely small lizards, bird eggs and nestlings. During winter eats acorns & other nuts. Stores acorns in holes drilled in trees, in crevice, or among epiphytes. In Colombia, does not store or rely heavily on acorns; feeds on insects, sap, and fruit year-round (Kattan 1988). Populations in Middle America not dependent on acorns.
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General Ecology
Social; lives in permanently territorial family groups of 2-15 individuals.
May compete with Lewis' woodpecker for food.
Winter food supply (acorns) is a major limiting factor (Hannon et al. 1987).
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Life History and Behavior
Life Expectancy
Lifespan/Longevity
Average lifespan
Status: wild: 114 months.
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Lifespan, longevity, and ageing
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Reproduction
Reproduction
Mating systems of Acorn Woodpeckers range from monogamy in some populations to cooperative polygyny. Generally, Acorn Woodpecker groups contain 1-7 male breeders that compete for matings with 1-3 egg-laying females. In groups that contain more than one female breeder, the female cobreeders lay their eggs in the same nest cavity. There is often extreme reproductive competition between joint-nesting females, who regularly destroy eggs laid by their cobreeders. After females have established a normal laying sequence, egg destruction stops. Reproduction competition between males is displayed by attempts by a male to disrupt copulation between another pair. Courtship and pair-bonding displays are absent.
Nest cavities are drilled into large dead or living limbs in trees or snags, which may contain granaries. The inside of the nest cavity is lined with fresh wood chips, and nest holes may be used repeatedly for several seasons. Average clutch size for a group with more than one female is five white, elliptical eggs. The average clutch size for a singleton female is four eggs. Eggs are laid at approximately 24 hour intervals. The incubation period is 11 days and both male and female breeders incubate. Once the chicks have hatched, all group members participate in providing food. Nestlings leave the nest after 30-32 days.
Average time to hatching: 14 days.
Average eggs per season: 4.
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May produce 2-3 broods annually. Clutch size usually is 4-5. Incubation probably lasts about 14 days. Nests cooperatively in parts of range; this behavior influenced by mast crop. Groups typically contain 1-4 breeding males, 1-2 breeding females, and 0-10 nonbreeding group offspring of past reproductive seasons. May nest as late as September or October.
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Molecular Biology and Genetics
Molecular Biology
Barcode data: Melanerpes formicivorus
There are 9 barcode sequences available from BOLD and GenBank. Below is a sequence of the barcode region Cytochrome oxidase subunit 1 (COI or COX1) from a member of the species. See the BOLD taxonomy browser for more complete information about this specimen and other sequences.
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Download FASTA File
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Statistics of barcoding coverage: Melanerpes formicivorus
Public Records: 9
Species: 23
Species With Barcodes: 1
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Conservation
Conservation Status
IUCN Red List Assessment
Red List Category
Red List Criteria
Version
Year Assessed
Assessor/s
Reviewer/s
Contributor/s
Justification
History
- 2008Least Concern
- 2004Least Concern
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Conservation Status
Although the species holds no special status, there are several threats facing the woodpecker. Many of these threats stem from habitat loss and degradation. Overgrazing, poor regeneration of oaks in California, and destruction of oak and pine forests for firewood or development are among the biggest threats facing the species.
IUCN Red List of Threatened Species: least concern
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National NatureServe Conservation Status
United States
Rounded National Status Rank: N5 - Secure
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NatureServe Conservation Status
Rounded Global Status Rank: G5 - Secure
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Relevance to Humans and Ecosystems
Benefits
Economic Importance for Humans: Negative
The Acorn Woodpecker is often considered a pest by nut and fruit farmers when the bird feeds on their crops.
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Economic Importance for Humans: Positive
Native Americans in California used Acorn Woodpeckers for food and collected their feathers for ornamentation on garments.
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Wikipedia
Acorn Woodpecker
 | This article includes a list of references, but its sources remain unclear because it has insufficient inline citations. Please help to improve this article by introducing more precise citations. (September 2010) |
The Acorn woodpecker (Melanerpes formicivorus) is a medium-sized woodpecker, 21 cm long with an average weight of 85 g.
Contents |
Description
The adult Acorn Woodpecker has a brownish-black head, back, wings and tail, white forehead, throat, belly and rump. The eyes are white.There is a small part on the small of their backs were there are some green feathers. The adult male has a red cap starting at the forehead, whereas females have a black area between the forehead and the cap. The white neck, throat and forehead patches are distinctive identifiers.When flying,they take a few flaps of their wings and drop a foot or so.You can see white circles on the wings while flying. Acorn woodpeckers have a call that is almost like they are laughing.
Breeding communities
The breeding habitat is forested areas with oaks in the hills of coastal areas and foothills of California and the southwestern United States south to Colombia. This species may occur at low elevations in the north of its range, but rarely below 1000m in Central America, and it breeds up to the timberline. The breeding pair excavate a nest in a large cavity in a dead tree or a dead part of a tree. A group of adults may participate in nesting activities: Field studies have shown that breeding groups range from monogamous pairs to breeding collectives of seven males and three females, plus up to 10 nonbreeding helpers. Young from a single brood have been found with multiple paternity.[1]
Food and homes
Acorn woodpeckers, as their name implies, depend heavily on acorns for food. In some parts of their range (e.g., California), the woodpeckers create granaries or "acorn trees" by drilling holes in dead trees, dead branches, telephone poles and wooden buildings. The woodpeckers then collect acorns and find a hole that is just the right size for the acorn. As acorns dry out, they are moved to smaller holes and granary maintenance requires a significant amount of the bird's time. They also feed on insects, sap, and fruit.
Defense and storing
The acorns are visible, and the group defends the tree against potential cache robbers like Steller's Jays and Western Scrub Jays. Acorns are such an important resource to the California populations that Acorn Woodpeckers may nest in the fall to take advantage of the fall acorn crop, a rare behavior in birds.[2] Acorn Woodpeckers can also be seen sallying from tree limbs to catch insects, eating fruit and seeds, and drilling holes to drink sap. The Acorn Woodpecker will use any human-made structures to store acorns, drilling holes into fence posts, utility poles, buildings, and even automobile radiators. Occasionally the woodpecker will put acorns into places where it cannot get them out. Woodpeckers put 220 kg (485 lb) of acorns into a wooden water tank in Arizona. In parts of its range the Acorn Woodpecker does not construct a granary tree, but instead stores acorns in natural holes and cracks in bark. If the stores are eaten, the woodpecker will move to another area, even going from Arizona to Mexico to spend the winter.
Breeding behavior
In California, Acorn Woodpeckers breed from May – July. An Acorn Woodpecker group may consist of 1-7 male breeders that compete to mate with 1-3 females. The nest is excavated in a large tree, which may also be a granary tree. Tree cavities are created in both dead and living trees and snags and nest holes are reused for many years. Females typically lay 5 eggs that are incubated for 11–14 days. Male and females incubate and tend to their young. Non-breeding helpers (young from previous years) often help with incubation and other parental duties. The young leave the nest and take their first flight at approximately 30–32 days after hatching and return to the nest to be fed for several weeks.
Breeding female
In groups with more than one breeding female, the females put their eggs into a single nest cavity. A female usually destroys any eggs in the nest before she starts to lay, and more than one third of all eggs laid in joint nests are destroyed. Once all the females start to lay, they stop removing eggs.
This bird is a permanent resident throughout its range. They may relocate to another area if acorns are not readily available. It is sedentary and very sociable.
Threats and degradation
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Acorn Woodpeckers like many other species are threatened by habitat loss and degradation. Competition for nest cavities by non-native species is an ongoing threat in urbanized areas. Conservation of this species is dependent on the maintenance of functional ecosystems that provide the full range of resources upon which the species depends. These include mature forests with oaks capable of producing large mast crops and places for the woodpeckers to nest, roost, and store mast. Residents are encouraged to preserve mature oak and pine-oak stands of trees and to provide dead limbs and snags for nesting, roosting and granary sites to help preserve the Acorn Woodpeckers population.
Popular culture
Walter Lantz is believed to have patterned the call of his cartoon character Woody Woodpecker on that of the acorn woodpecker, while patterning his appearance on that of the Pileated Woodpecker which has a prominent crest.[3]
Notes
- ^ Joste, N., Ligon, D., and Stacey, P. (1985) Behavioral Ecology and Sociobiology; Behavioral Ecology and Sociobiology 17(1):39-41
- ^ Koenig, W.D., and Stahl, J.T. (2007) Condor; 109(2):334-350
- ^ "Woody The Acorn (Not Pileated) Woodpecker". NPR. http://www.npr.org/templates/story/story.php?storyId=101665227. Retrieved 2011-09-14.
References
- BirdLife International (2004). Melanerpes formicivorus. 2006. IUCN Red List of Threatened Species. IUCN 2006. www.iucnredlist.org. Retrieved on 10 May 2006.
- Haydock J., Koenig W. D., & Stanback, M. T. (2001). Shared parentage and incest avoidance in the cooperatively breeding acorn woodpecker. Molecular Ecology, 10, 1515-1525.
- Stiles, F Gary; Skutch, Alexander Frank (1989), A guide to the birds of Costa Rica, Ithaca, New York: Comstock, ISBN 0-8014-2287-6
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Names and Taxonomy
Taxonomy
Comments: Benitez-Diaz (1993) examined variation in morphometric and plumage coloration characters and identified seven geographic units within the species (two in the U.S.), each of which is diagnosable based on combinations of discrete and continuous character states.
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