# Acorn Woodpecker (*Melanerpes formicivorus*)

The Acorn Woodpecker is a colorful bird that loves to eat acorns! They are known for their funny, loud calls and their unique habit of storing acorns in holes in trees.

- **Category:** [Birds](https://www.snappit.app/explore/categories/bird)
- **Rarity:** Common
- **Danger:** 1/5 · Very low
- **Snaps:** 40
- **Habitat:** Forests

![Acorn Woodpecker](https://commons.wikimedia.org/w/index.php?title=Special:Redirect/file/Carpintero_bellotero_-_panoramio.jpg&width=800)

Photo: panza-rayada, CC BY-SA 3.0 · [Wikimedia Commons](https://commons.wikimedia.org/wiki/File:Carpintero_bellotero_-_panoramio.jpg)

## Appearance

The Acorn Woodpecker has a distinctive black back and white belly, with a white forehead, a yellowish-white throat and white eyes set in a black stripe. Its crown is boldly red in males, while females have a black band between the red patch and the white forehead. These birds are further distinguished by a white rump visible in flight.

## Taxonomy

- **Kingdom:** Animalia
- **Phylum:** Chordata
- **Class:** Aves
- **Order:** Piciformes
- **Family:** Picidae
- **Genus:** Melanerpes

## Acorn woodpecker, up close

The acorn woodpecker (Melanerpes formicivorus) is a medium-sized woodpecker of oak woodlands from Oregon and California through Mexico and Central America to Colombia. Family groups drill trees full of small holes, called granaries, and store one acorn in each. It is one of the few birds in which several males and several females breed together in one group, helped by their grown-up young.

A clown face, a tree full of acorns and a family that works as a team. Spin it, tap it, then test yourself.

### Special abilities

- **Granary Builder** (50,000 holes in the biggest granaries): Acorn woodpecker families drill a tree full of small holes, then push one acorn into each hole to eat later. [4][3][2]
  - Each hole is about 1.3 cm wide and 3.8 cm deep, just right for a single acorn.
  - Drilling never really stops. Most of it happens in winter, and every member of the group helps.
  - As stored acorns dry and shrink, the birds move them to smaller holes so they stay snug.
  - In one study in the southwestern US, groups with more than 3,000 holes had a 58% chance that their acorns lasted the winter. With fewer than 1,000 holes the chance was 9%.
  - Chance the acorn store lasts the winter: Granary over 3,000 holes 58%; Granary under 1,000 holes 9%
- **Team Nest** (17 eggs recorded in one shared nest): Acorn woodpeckers raise their young as a team. Several breeding males and females can share one nest hole, and grown-up offspring help. [10][3][1][2][11][12][4]
  - A group can have up to 8 breeding males and 4 breeding females, plus up to 10 helpers. Most are much smaller.
  - The females in a group lay in one shared nest hole. A typical clutch is 3–7 eggs, but up to 17 have been recorded.
  - Before she starts laying, a female may remove eggs that another female has already laid. Once all the females are laying, this stops and the group cares for every egg.
  - After about a week, everyone in the group takes turns keeping the eggs warm and, later, feeding the chicks.
- **Sky Sally** (Apr–May when flycatching is its main way to feed): Most woodpeckers chisel grubs out of wood. This one waits on a high perch, then sallies out to catch insects in mid-air. [4][2][3]
  - At Hastings Reservation in California, flycatching is the main way it finds food in the nesting months of April and May.
  - It hunts from stumps, treetops or branches just above the grass.
  - Flying ants and their relatives, and beetles, are favourites.
  - Insects are the main food for the chicks. Spare ones can be tucked under loose bark for later.
- **Sap Sipper** (>50% of its diet is acorns in California): Acorns are its main food, but it also sips tree sap and eats insects, oak flowers, fruit and nectar. [4][2][3][1][13]
  - In California, acorns make up more than half of what it eats. In Arizona and New Mexico they make up 25–50%.
  - It drinks sap from small wells it drills in bark, or from holes made by sapsuckers. Sap holes are used again year after year.
  - In California it sips sap from February to early March, and again from June to August.
  - In the Andes of Colombia it seldom eats oak acorns, but it may often drink oak sap.
- **Wake-up Call** (ja-cob how field guides spell its loud call): Acorn woodpeckers are noisy birds, and their calls carry information: they know their family members by voice. [3][14][15]
  - Audubon’s field guide spells the loud call “ja-cob, ja-cob” or “wake-up, wake-up”.
  - In playback tests, birds reacted faster to the calls of strangers than to the calls of their own group.
  - They still knew the voices of old group mates that had moved to nearby groups.
  - They even noticed when two outsiders from different groups seemed to call together, which suggests they keep track of who belongs with whom next door.
- **Clown Face** (1 band of black on the crown marks a female): Its bold black, white and red face is easy to learn, and the crown tells you whether you are looking at a male or a female. [1][2][3]
  - Look for a white forehead, a yellowish to white throat, black around the bill and a black stripe around the white eyes.
  - Male: the red cap touches the white forehead.
  - Female: a black band separates the red cap from the white forehead.
  - In flight, look for a white rump and small white wing patches.
- **Woodpecker Wars** (30+ birds at the biggest battles): When the breeders of a top territory die, rival teams of brothers or sisters from nearby groups battle to take it over, and other woodpeckers come to watch. [7][16][17][18]
  - A dozen or more teams of three or four birds can fight at once. Radio tags showed some birds come back day after day and fight for up to 10 hours at a time.
  - The biggest battles drew more than 30 birds, about a third of the woodpeckers in the area. Some travelled more than 3 km just to watch.
  - Spectators spent up to an hour a day watching. Scientists think they are collecting news about their neighbours, but nobody knows for sure.
  - These power struggles can last days or even weeks, and the largest team usually wins.
- **Tail Prop** (Stiff tail feathers with thickened shafts): Like other woodpeckers, it leans back on its stiff tail to brace itself against the trunk while it drills or stores acorns. [8][3]
  - The thickened shafts of the tail feathers work like a kickstand on an upright trunk.
  - The feet grip the bark while the tail keeps the bird steady.
  - Scientists study woodpecker tail muscles to learn how the birds hold still while clinging.
  - The acorn woodpecker’s tail is wedge-shaped with pointed tips.

### Body parts

- **Red cap** [1][2]
  - Males have a red cap that runs all the way forward to the white forehead.
  - Females have a black band between the red cap and the white forehead.
  - That one band is the easiest way to tell a male from a female.
- **Clown face** [1][3][2]
  - The head has a bold “clown” pattern: a white forehead, a yellowish to white throat and black around the bill.
  - A black stripe runs around each eye and joins the black of the neck and back.
  - Field guides describe it as a clown-faced woodpecker.
- **Eyes** (White eyes in a black mask) [3][2][4]
  - Adults have white eyes set in black, which makes their stare stand out.
  - From high perches they watch for flying insects, then swoop out to catch them.
- **Bill** (1.3 cm wide storage holes) [4][5][3]
  - The bill drills storage holes about 1.3 cm wide and 3.8 cm deep, each made for one acorn.
  - In a 1979 high-speed film of a drilling woodpecker, the bill hit the wood at about 6–7 m/s.
  - Unlike most woodpeckers, the acorn woodpecker rarely chisels into wood to hunt insects.
- **Tongue** [1][6][3][4]
  - Like other woodpeckers, it has a long tongue that can reach out thanks to a special set of bones and elastic tissue.
  - In a woodpecker scanned with X-rays, these tongue bones (the hyoid apparatus) had four sections joined by three joints.
  - The acorn woodpecker mostly catches insects in the air or sips sap, so how much it uses its tongue reach has not been studied much.
- **Wings** [3][2]
  - In flight it shows a white rump and a small white patch on each wing.
  - Its wings are broad and rounded, and its flight dips up and down.
  - It uses them for swooping, acrobatic flights to catch insects in mid-air.
- **Back** (73 g average weight) [3][2][7]
  - It is black above and across the chest, with a white belly.
  - An adult weighs about 73 g on average, about the size of a robin.
  - Scientists track some birds with tiny radio tags worn on the back like a climbing harness with a bum bag, so they can follow them minute by minute.
- **Tail** [8][3]
  - Woodpecker tail feathers have thickened shafts. They act as a prop that keeps the bird steady on an upright trunk.
  - Its tail is wedge-shaped with pointed tips.
- **Feet** [8][2]
  - Woodpecker feet are built for gripping upright tree trunks.
  - It rarely goes down to the ground, except to pick up grit and fallen acorns.
- **Granary** (50,000 holes in the biggest granaries) [3][2][4][9]
  - A granary is a tree or post drilled with storage holes, one acorn per hole. The biggest have up to 50,000 holes.
  - The same granaries are used year after year, and new holes are added all the time.
  - Granaries can be in oaks, pines, redwoods, palms, utility poles, fence posts, pine cones and even the wooden trim of buildings.
  - A DNA study found the valley oak acorns in a granary came from only about 4–8 trees on average.

### Stats

| Stat | Value | Notes |
|---|---|---|
| Weight | 73 g | average adult, about the size of a robin [2][3] |
| Granary holes | Up to 50,000 | in the biggest granaries, one acorn per hole [3][2][1] |
| Storage hole | 1.3 × 3.8 cm | typical width × depth [4] |
| Breeders in a group | Up to 8 ♂ + 4 ♀ | plus up to 10 helpers; most groups are smaller [10] |
| Eggs | 3–7 | per clutch; up to 17 in a shared nest [3][1] |
| Incubation | 11–14 days | the whole group takes turns [3][4] |
| First flight | 30–32 days | after hatching [3][4] |
| Battle shifts | Up to 10 h | of fighting a day in a territory war [7] |
| Spectator trips | >3 km | travelled by some birds just to watch a battle [7] |
| Population | ≈7.5 million | estimated number of acorn woodpeckers [3] |

### Photos

- [At a granary tree in Chico, California](https://commons.wikimedia.org/wiki/File:Acorn_woodpecker_on_granary_tree-7270.jpg) (photo: Frank Schulenburg, CC BY-SA 4.0)
- [A male in cloud forest in Panama](https://commons.wikimedia.org/wiki/File:Acorn_woodpecker_(Melanerpes_formicivorus_striatipectus)_male.jpg) (photo: Charles J. Sharp, CC BY-SA 4.0)
- [A female in Chocó, Colombia, near the southern end of the range](https://commons.wikimedia.org/wiki/File:Acorn_woodpecker_(Melanerpes_formicivorus_flavigula)_female_Las_Tangaras.jpg) (photo: Charles J. Sharp, CC BY-SA 4.0)
- [Storing acorns at a wildlife refuge in Oregon](https://commons.wikimedia.org/wiki/File:Acorn_woodpecker_at_refuge_(53331979106).jpg) (photo: Megan Nagel / USFWS, Public domain)
- [A granary packed with acorns](https://commons.wikimedia.org/wiki/File:Acorn_woodpecker_with_%22granary_tree%22_full_of_acorns.jpg) (photo: Raresvent, CC BY-SA 4.0)
- [A male at his granary in Solano County, California](https://commons.wikimedia.org/wiki/File:Acorn_Woodpecker_(m)_in_granary_tree_(38978598750).jpg) (photo: Becky Matsubara, CC BY 2.0)
- [Resting on a park bench at Atascadero Lake, California](https://commons.wikimedia.org/wiki/File:Acorn_Woodpecker%2C_Atascadero_Lake%2C_San_Louis_Obispo_Co%2C_California.jpg) (photo: Kevin Cole, CC BY 2.0)
- [A female stopping for a bath](https://commons.wikimedia.org/wiki/File:Acorn_Woodpecker_(Melanerpes_formicivorus).jpg) (photo: Kevin Cole, CC BY 2.0)
- [Busy at the granary](https://commons.wikimedia.org/wiki/File:Feeling_a_bit_peckerish_-_Flickr_-_Gunn_Shots.jpg) (photo: Mark Gunn, CC BY 2.0)
- [Eating an insect in Sonoma, California](https://commons.wikimedia.org/wiki/File:Melanerpes_formicivorus_eating_-_Sarah_Stierch_04.jpg) (photo: Sarah Stierch, CC BY 4.0)

### Questions

- **Why do acorn woodpeckers put acorns in holes?** To save food for later. Each autumn the whole group stores acorns, one per hole, in a granary tree. The store feeds them through winter, and groups whose acorns last into spring nest earlier and raise more young. [4][3]
- **How many acorns can a granary tree hold?** The biggest granaries have up to 50,000 holes, each holding one acorn. Groups keep adding new holes, so a granary grows year after year. [3][2][4]
- **Do acorn woodpeckers damage houses?** Sometimes. They can drill storage holes in utility poles, fence posts and the wooden trim of buildings. They are protected by law in the US, so if they are a problem, an adult should ask a local wildlife agency for advice. Watch them from a distance and never handle one. [4][29]
- **Why do acorn woodpeckers live in groups?** Granaries are hard to build and worth defending, so families stay together. Groups can include several breeding males and females plus grown-up young that help raise the chicks. [2][10][18]
- **What sound does an acorn woodpecker make?** A loud, laughing call that Audubon’s field guide writes as “ja-cob, ja-cob” or “wake-up, wake-up”. The birds can recognise family members by their calls. [3][14]
- **Do acorn woodpeckers really fight wars?** Yes, in a way. When the breeders of a good territory die, teams of brothers or sisters from nearby groups fight for it, sometimes for 10 hours a day over several days. More than 30 birds can gather, including spectators. [7][16]
- **What do acorn woodpeckers eat?** Mostly acorns, plus flying insects such as ants, tree sap, oak flowers, fruit and nectar. In California acorns are more than half of the diet. [4][2][3]
- **Where do acorn woodpeckers live?** In oak and pine-oak woodlands from Oregon and California through the southwestern US, Mexico and Central America to the Andes of Colombia. Most stay in the same territory all year. [2][4][13]

### Acorn woodpecker myths and facts

Tap Myth or Fact for each claim, then check the answer.

- "Acorn woodpeckers eat their acorns as soon as they find them." **Myth!** In autumn the whole group gathers acorns for 4–6 weeks and stores them in granaries, to eat in winter and later. [4][3]
- "Drilling a granary kills the tree." **Myth!** The birds rarely cut into the living layer under the bark, so granary trees are usually not harmed. They are lost in the end to fire, rot or falling. [4]
- "Like most woodpeckers, it drills into wood to find insects." **Myth!** It rarely or never chisels for insects. It catches them in the air or picks them off the surface of trees. [3][4]
- "Several females can lay their eggs in the same nest." **Fact!** Joint-nesting females lay in one shared nest hole. That is how nests with up to 17 eggs happen. [2][3]
- "Woodpeckers travel kilometres just to watch a territory battle." **Fact!** Radio tags showed some spectators travelled more than 3 km and watched for up to an hour a day. [7][16]
- "A bigger group always means more chicks for each bird." **Myth!** At Hastings, monogamous pairs fledged about 2.7 young per female, against about 1.3 for each female in groups with two laying females. [4]
- "A granary can be a utility pole or a house." **Fact!** Granaries have been found in utility poles, fence posts, pine cones, the wooden trim of buildings and under roof tiles. [4]
- "The size of a male’s red cap shows how important he is." **Not proven!** We found no study showing this. What is clear is that the crown shows the sex: males have no black band between the red cap and the white forehead. [1][2]

### Acorn woodpecker records

Superlatives from decades of field studies, each checked against its source.

- Biggest acorn store: Granary trees, 50,000 holes (one acorn per hole, in granaries used for generations) [3][2]
- Most eggs in one nest: Joint-nesting females, 17 eggs (laid by more than one female in a single shared nest) [3][1]
- Biggest breeding teams: Hastings Reservation groups, 8 males or 4 females (the largest breeding coalitions seen; most are 1–3 birds) [10]
- Biggest battle crowds: Territory wars, 30+ birds (about a third of all the woodpeckers in the study area) [7][16]
- Longest daily battles: Fighting coalitions, Up to 10 hours (and some birds came back day after day) [7]
- Farthest trip to watch: Spectators, >3 km (travelled just to watch a power struggle) [7]

### A year in the life of an acorn woodpecker

From sap season to the big acorn harvest, for a family group in central California.

- **Feb–Mar**: Sap season. Birds sip sap from small wells drilled in oak bark. [4]
- **Spring**: One shared nest. Females lay about one egg a day in a single nest hole lined with wood chips. The group uses just one nest at a time. [2][20][4]
- **11–14 days**: Team incubation. At first one male and one female sit on the eggs. After about a week the whole group takes turns. [4][3]
- **Apr–May**: Flycatching time. Insects caught in the air are the main food for the chicks. [4]
- **30–32 days**: First flight. The young leave the nest and are still fed by parents and helpers. Many stay on as helpers for years. [3][10][18]
- **Jun–Aug**: Summer sap. Sap season returns. Some groups raise a second brood. [4][1]
- **Sep–Dec**: The big harvest. For 4–6 weeks the whole group gathers acorns and stores them in 1 or 2 granaries. [4]
- **Winter**: Living on savings. They eat stored acorns, drill new holes and move shrinking acorns to smaller ones. The size of the autumn acorn crop matters more than anything for next spring’s nest. [4][2][21]

### Acorn woodpecker vs red-headed woodpecker vs great spotted woodpecker

The red-headed woodpecker is a close cousin in the same genus. The great spotted woodpecker is the familiar woodpecker of British gardens.

| | Acorn woodpecker | Red-headed woodpecker | Great spotted woodpecker |
|---|---|---|---|
| Scientific name [22][23][24] | Melanerpes formicivorus | Melanerpes erythrocephalus | Dendrocopos major |
| Lives in [2][25][26][27] | Oak woods from Oregon to Colombia | Eastern North America, from the Rockies to the Atlantic | Woods, parks and gardens across Britain and Europe |
| Average weight [2][25][27] | 73 g | About 70 g | 78.7 g |
| Main foods [4][25][26][27] | Acorns, flying insects, sap | Insects, nuts, seeds and fruit | Insects under bark, seeds and nuts |
| Breeding [10][25][26] | Groups with several breeders and helpers | Pairs, thought to be monogamous | Nests from April to June |
| Nest [20][25][26] | One shared hole for the whole group | A hole both parents drill, mostly the male | A newly drilled tree hole |
| Eggs [3][28][27] | 3–7 (up to 17 in a shared nest) | 4–5 (3–7) | 4–6 |
| Sounds [3][28][26] | “ja-cob, ja-cob” or “wake-up, wake-up” | “churr-churr” and “yarrow-yarrow” | Loud call and spring drumming |
| Population [3][28][27] | ≈7.5 million | ≈1.8 million | ≈130,000 pairs in the UK |
| IUCN status [22][23][24] | Least Concern | Least Concern | Least Concern |

Only the acorn woodpecker builds big shared granaries. The red-headed woodpecker hides food one item at a time in cracks it finds.

### Are acorn woodpeckers endangered?

No. Acorn woodpeckers are common, but they depend on oaks and on big old trees for their granaries.

- **IUCN Red List:** Least Concern (LC). About 7.5 million birds from Oregon to Colombia. Counts rose slightly across the western US from 1968 to 1991, but fell in the Sierra Nevada. [22][3][4]
- IUCN Red List (BirdLife International)
- **Threat: Losing oak woodlands**: Oak woodlands in Washington, Oregon and California are shrinking because of building, farming, logging, firewood cutting and conifers spreading where fires are kept out. [4]
- **Threat: Sudden oak death** (≈50%): A tree disease caused by a water mould, Phytophthora ramorum, kills several oak species. One study estimated it could halve acorn woodpecker numbers in coastal California. [4]
- **Threat: Wildfire and smoke** (≈14%): Between 2016 and 2020, about 14% of the acorn woodpeckers in the US lived where fires burned. On smoky days, birds stayed home and visited neighbours less. [19]
- **Threat: Lost granaries**: If a granary tree burns, rots or falls, or the acorn crop fails, a group may have to leave its territory. [4]
- **Helping: Protected by law**: In the US, the acorn woodpecker is on the official list of birds protected by the Migratory Bird Treaty Act. [29]
- **Helping: Keep old oaks and dead trees**: Acorn-producing trees, tree holes and standing dead trees are what it needs most. Leaving big oaks and snags standing helps. [4]
- **Helping: Room for young oaks**: Thinning crowded oak stands can grow future granary trees, and controlled burns can help young oaks. [4]
- **Helping: Decades of watching**: Scientists have followed colour-banded acorn woodpeckers at Hastings Reservation, California, since 1968, and count acorns on 250 marked trees each year. [18][21]
- **Red-headed woodpecker** (LC): A cousin from eastern North America, with about 1.8 million birds. [23][28]
- **Great spotted woodpecker** (LC): A European woodpecker. In the UK its numbers grew by 373% from 1967 to 2024. [24][27]

### Acorn woodpecker signals

- Loud calling and birds chasing around a big granary: A power struggle: rival teams are fighting over a territory. [17][7]
- Birds sitting still in nearby trees during a fight: Spectators watching the battle, perhaps to learn who wins. [7]
- A bird chasing others away from a granary or sap tree: Guarding the family food. Granaries are the most defended thing a group owns. [2][4]
- Birds swapping places on the eggs many times an hour: Normal teamwork: group members take short turns keeping the eggs warm. [3]
- Answering a strange voice quickly: An outsider is nearby. Family voices get a slower, calmer response. [14]
- Staying at home on smoky days: Wildfire smoke: birds visit other territories less and keep close to home. [19]

### Looks

- **Male**: Black back and chest, white belly and rump, white forehead and white eyes. The red cap reaches right to the white forehead. (The crown is the only easy way to tell the sexes apart) [1][2][3]
- **Female**: The same clown face, but a black band separates the red cap from the white forehead. (Females in one group lay their eggs in a shared nest) [1][2]
- **Juvenile**: A young bird that has just left the nest, at about 30–32 days old. Parents and helpers keep feeding it. (Many young stay at home for years as helpers) [3][4][10]
- **Family group**: Several birds at the granary: breeding males, breeding females and helpers that share one nest and one acorn store. (Groups at Hastings, California, average about 4–5 adults) [10][4]

### Acorn woodpecker quiz

1. How many acorns go into each granary hole? **One.** Each hole is drilled for a single acorn. [2][3]
2. Up to how many holes can the biggest granaries have? **50,000.** The biggest granaries can have up to 50,000 holes. [3]
3. Why do acorn woodpeckers move acorns to smaller holes? **The acorns shrink as they dry.** As stored acorns dry and shrink, the birds move them to snugger holes. [4]
4. How can you tell a female acorn woodpecker? **A black band between the red cap and the white forehead.** Males’ red caps touch the white forehead; females have a black band in between. [1][2]
5. How does it catch most of its insects? **By catching them in mid-air.** It rarely drills for insects and catches them in swooping flights instead. [3][4]
6. What is the most eggs recorded in one shared nest? **17.** Up to 17 eggs, laid by more than one female. [3][1]
7. Who keeps the eggs warm after the first week? **The whole group, taking turns.** After about a week, all group members take turns. [4]
8. How far did some spectators travel to watch a territory battle? **More than 3 km.** Radio tags showed some travelled more than 3 km. [7]
9. How does Audubon’s field guide spell the call? **“ja-cob, ja-cob”.** It is written “ja-cob, ja-cob” or “wake-up, wake-up”. [3]
10. What can acorn woodpeckers tell apart by voice? **Group members and strangers.** In playback tests they reacted faster to strangers than to their own group. [14]
11. What do they drink from small wells in tree bark? **Sap.** They drill sap wells or use holes made by sapsuckers. [3][4]
12. Which tree disease threatens their oak woodlands? **Sudden oak death.** One study estimated sudden oak death could halve their numbers in coastal California. [4]

### Sources (checked 2026-10-16)

1. [Seattle Audubon Society. Acorn Woodpecker. BirdWeb.](http://www.birdweb.org/birdweb/bird/acorn_woodpecker)
2. [Harris MS. Melanerpes formicivorus (acorn woodpecker). Animal Diversity Web, University of Michigan.](https://animaldiversity.org/accounts/Melanerpes_formicivorus/)
3. [National Audubon Society. Acorn Woodpecker. Guide to North American Birds (text adapted from Kaufman 1996).](https://www.audubon.org/field-guide/bird/acorn-woodpecker)
4. [Ulev E (2007). Melanerpes formicivorus. Fire Effects Information System (FEIS). US Department of Agriculture, Forest Service, Rocky Mountain Research Station.](https://www.fs.usda.gov/database/feis/animals/bird/mefo/all.html)
5. [May PR, Fuster JM, Haber J, Hirschman A (1979). Woodpecker drilling behavior: an endorsement of the rotational theory of impact brain injury. Archives of Neurology 36:370–373.](https://doi.org/10.1001/archneur.1979.00500420080011)
6. [Jung JY, Naleway SE, Yaraghi NA, Herrera S, Sherman VR, Bushong EA, et al. (2016). Structural analysis of the tongue and hyoid apparatus in a woodpecker. Acta Biomaterialia 37:1–13.](https://doi.org/10.1016/j.actbio.2016.03.030)
7. [Cell Press (2020). Acorn woodpeckers wage days-long battles over vacant territories, radio tag data show. Phys.org, 7 September 2020.](https://phys.org/news/2020-09-acorn-woodpeckers-wage-days-long-vacant.html)
8. [Spainhower K, Meyers RA (2024). Anatomy and immunohistochemistry of woodpecker tail muscles. Journal of Morphology 285:e70003.](https://doi.org/10.1002/jmor.70003)
9. [Scofield DG, Alfaro VR, Sork VL, Grivet D, Martinez E, Papp J, et al. (2011). Foraging patterns of acorn woodpeckers (Melanerpes formicivorus) on valley oak (Quercus lobata Née) in two California oak savanna-woodlands. Oecologia 166:187–196.](https://doi.org/10.1007/s00442-010-1828-5)
10. [Koenig WD, Barve S, Haydock J, Dugdale HL, Oli MK, Walters EL (2023). Lifetime inclusive fitness effects of cooperative polygamy in the acorn woodpecker. PNAS 120:e2219345120.](https://doi.org/10.1073/pnas.2219345120)
11. [Mumme RL, Koenig WD, Pitelka FA (1983). Reproductive competition in the communal acorn woodpecker: sisters destroy each other's eggs. Nature 306:583–584.](https://doi.org/10.1038/306583a0)
12. [Haydock J, Koenig WD (2002). Reproductive skew in the polygynandrous acorn woodpecker. PNAS 99:7178–7183.](https://doi.org/10.1073/pnas.102624199)
13. [Freeman BG, Mason NA (2015). The geographic distribution of a tropical montane bird is limited by a tree: acorn woodpeckers (Melanerpes formicivorus) and Colombian oaks (Quercus humboldtii) in the Northern Andes. PLoS ONE 10:e0128675.](https://doi.org/10.1371/journal.pone.0128675)
14. [Pardo MA, Hayes CE, Walters EL, Koenig WD (2020). Acorn woodpeckers vocally discriminate current and former group members from nongroup members. Behavioral Ecology 31:1120–1128.](https://doi.org/10.1093/beheco/araa059)
15. [Pardo MA, Sparks EA, Kuray TS, Hagemeyer ND, Walters EL, Koenig WD (2018). Wild acorn woodpeckers recognize associations between individuals in other groups. Proceedings of the Royal Society B 285:20181017.](https://doi.org/10.1098/rspb.2018.1017)
16. [Barve S, Lahey AS, Brunner RM, Koenig WD, Walters EL (2020). Tracking the warriors and spectators of acorn woodpecker wars. Current Biology 30:R982–R983.](https://doi.org/10.1016/j.cub.2020.07.073)
17. [Hagemeyer N, Koenig W, Walters E (2024). Active facilitation of helper dispersal by parents and siblings in the cooperatively breeding acorn woodpecker. Research Square (preprint).](https://doi.org/10.21203/rs.3.rs-3873292/v1)
18. [Barve S, Riehl C, Walters EL, Haydock J, Dugdale HL, Koenig WD (2021). Lifetime reproductive benefits of cooperative polygamy vary for males and females in the acorn woodpecker (Melanerpes formicivorus). Proceedings of the Royal Society B 288:20210579.](https://doi.org/10.1098/rspb.2021.0579)
19. [Johnson AE, Barve S, Dreiss L, Shizuka D, Walters EL (2023). Acorn woodpecker movements and social networks change with wildfire smoke. Current Biology 33:R996–R997.](https://doi.org/10.1016/j.cub.2023.08.096)
20. [Riehl C, LaPergola JB (2023). Inclusive fitness explains behavioral diversity in a social bird. PNAS 120:e2305610120.](https://doi.org/10.1073/pnas.2305610120)
21. [Koenig WD, Walters EL, Haydock J (2009). Helpers and egg investment in the cooperatively breeding acorn woodpecker: testing the concealed helper effects hypothesis. Behavioral Ecology and Sociobiology 63:1659–1665.](https://doi.org/10.1007/s00265-009-0773-y)
22. [Wikidata: Acorn woodpecker (Q368657), IUCN status Least Concern (P141)](https://www.wikidata.org/wiki/Q368657)
23. [Wikidata: Red-headed woodpecker (Q578174), IUCN status Least Concern (P141)](https://www.wikidata.org/wiki/Q578174)
24. [Wikidata: Great spotted woodpecker (Q26209), IUCN status Least Concern (P141)](https://www.wikidata.org/wiki/Q26209)
25. [Animal Diversity Web. Melanerpes erythrocephalus (red-headed woodpecker). University of Michigan.](https://animaldiversity.org/accounts/Melanerpes_erythrocephalus/)
26. [RSPB. Great Spotted Woodpecker. Birds and wildlife.](https://www.rspb.org.uk/birds-and-wildlife/great-spotted-woodpecker)
27. [British Trust for Ornithology. Great Spotted Woodpecker. BirdFacts.](https://www.bto.org/understanding-birds/birdfacts/great-spotted-woodpecker)
28. [National Audubon Society. Red-headed Woodpecker. Guide to North American Birds.](https://www.audubon.org/field-guide/bird/red-headed-woodpecker)
29. [US Code of Federal Regulations, 50 CFR 10.13: List of Migratory Birds (2023 edition).](https://www.govinfo.gov/content/pkg/CFR-2023-title50-vol1/xml/CFR-2023-title50-vol1-sec10-13.xml)

## Measurements & details

- **Length:** 21-23 cm
- **Wingspan:** 42-45 cm
- **Weight:** 0.065-0.085 kg
- **Lifespan:** 5-16 years
- **Clutch Size:** 3-7
- **Incubation:** 11-14 days

## Diet & Feeding

These clever birds eat mostly acorns and other nuts, but also enjoy insects, fruits, and tree sap.

- **Primary Foods:** acorns, insects, tree sap, fruits, nuts, seeds
- **Foraging Method:** Foraging

## Ecological connections

- **Eaten by:** [Cooper's Hawk](https://www.snappit.app/explore/cooper-s-hawk) (*Accipiter cooperii*) — A hawk that preys on adult woodpeckers.
- **Eaten by:** [Red-tailed Hawk](https://www.snappit.app/explore/red-tailed-hawk) (*Buteo jamaicensis*) — One of several hawks that can prey on adult woodpeckers.
- **Eaten by:** [Gopher Snake](https://www.snappit.app/explore/gopher-snake) (*Pituophis catenifer*) — Preys on eggs and young nestlings in cavities.

## Traits

- [Feathered](https://www.snappit.app/explore/traits/feathered): Feathered describes animals, primarily birds, possessing a covering of feathers.
- [Social](https://www.snappit.app/explore/traits/social): Social animals live in organized groups, cooperating for survival benefits such as foraging, defense, and raising offspring.
- [Omnivorous](https://www.snappit.app/explore/traits/omnivorous): This trait identifies organisms whose diet includes both plant and animal matter.
- [Arboreal](https://www.snappit.app/explore/traits/arboreal): Arboreal animals live primarily in trees, utilizing them for shelter, food, and protection from predators.
- [Colorful](https://www.snappit.app/explore/traits/colorful): Colorful describes organisms or objects displaying a wide range of bright and distinct colors.
- [Forest](https://www.snappit.app/explore/traits/forest): Forest habitats are terrestrial environments dominated by dense tree cover, supporting a high diversity of plant and animal life.
- [Diurnal](https://www.snappit.app/explore/traits/diurnal): Diurnal animals are primarily active during daylight hours, typically resting or sleeping at night.
- [Keystone Species](https://www.snappit.app/explore/traits/keystone-species): Describes a species whose presence and role have a disproportionately large effect on its environment.

## Collections

- [Birds](https://www.snappit.app/explore/collections/birds)

## Safety

**Danger:** 1/5 · Very low

Always watch birds from a distance and don't disturb their nests.

## Frequently Asked Questions

### How to identify Acorn Woodpecker?

Compare the silhouette, bill shape, tail length, wing bars and markings around the eyes. The same small brown bird at your feeder can look quite different in breeding plumage, winter plumage or its first year. Bird Identifier: upload a photo and compare the visible details.

### How long is Acorn Woodpecker?

21-23 cm

### What is Acorn Woodpecker's wingspan?

42-45 cm

### How much does Acorn Woodpecker weigh?

0.065-0.085 kg

### How long does Acorn Woodpecker live?

5-16 years

### What does Acorn Woodpecker eat?

These clever birds eat mostly acorns and other nuts, but also enjoy insects, fruits, and tree sap.

### Where is Acorn Woodpecker usually found?

Forests

## Where to spot

- [Arastradero Preserve](https://www.snappit.app/guides/places/arastradero-preserve) — California, US · Nature Reserve
- [Arroyo Conejo Open Space](https://www.snappit.app/guides/places/arroyo-conejo-open-space) — California, US · Park
- [Atchison Village](https://www.snappit.app/guides/places/atchison-village) — California, US · Neighborhood
- [Benbow Lake State Recreation Area](https://www.snappit.app/guides/places/benbow-lake-state-recreation-area) — California, US · State Park
- [Black Diamond Mines Regional Preserve](https://www.snappit.app/guides/places/black-diamond-mines-regional-preserve) — California, US · Nature Reserve
- [Blake Garden](https://www.snappit.app/guides/places/blake-garden) — California, US · Botanical Garden

[View all places to see Acorn Woodpecker](https://www.snappit.app/guides/where-to-see/acorn-woodpecker)

## More Birds

- [Black-crowned Night Heron](https://www.snappit.app/explore/black-crowned-night-heron) (*Nycticorax nycticorax*)
- [Anna's Hummingbird](https://www.snappit.app/explore/annas-hummingbird) (*Calypte anna*)
- [Great Egret](https://www.snappit.app/explore/great-egret) (*Ardea alba*)
- [Blue Jay](https://www.snappit.app/explore/blue-jay) (*Cyanocitta cristata*)

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Source: [Acorn Woodpecker: Facts & Places to See — Snappit](https://www.snappit.app/explore/acorn-woodpecker)