Acorn Woodpecker

Acorn Woodpecker

Kingdom
Phylum
Class
Order
Family
Genus
SPECIES
Melanerpes formicivorus
Population size
7.5 mln
Life Span
16-17 yrs
WEIGHT
65-90 g
LENGTH
19-23 cm
WINGSPAN
35-43 cm

Acorn woodpeckers are medium-sized birds famous for their unique behavior of storing acorns in holes of trees. Adult birds have a brownish-black head, back, wings and tail, white forehead, throat, belly, and rump. Their eyes are white. There is a small part on the small of their backs where there are some green feathers. Adult males have 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, Acorn woodpeckers take a few flaps of their wings and drop a foot or so. White circles on their wings are visible when in flight.

Di

Diurnal

Om

Omnivore

Ar

Arboreal

Al

Altricial

Te

Terrestrial

Ov

Oviparous

Mo

Monogamy

Po

Polygynandry

So

Social

Do

Dominance hierarchy

No

Not a migrant

A

starts with

Distribution

Geography

Acorn woodpeckers are found from Oregon, California, and the southwestern United States, south through Central America to Colombia. They don't migrate and live year-round in forested areas with oaks, open oak groves near the coast, mixed forests, oak-pine canyons, and foothills.

Acorn Woodpecker habitat map

Climate zones

Habits and Lifestyle

Acorn woodpeckers have a complicated social structure; they live in family groups which raise young, gather food, store and guard it all together. Acorn woodpeckers, as their name implies, depend heavily on acorns for food. In some parts of their range, such as California, they create granaries or "acorn trees" by drilling holes in dead trees, dead branches, telephone poles, and wooden buildings. They also drill holes in the thick bark of mature living trees. These holes, always above the snow line so that the acorns can be retrieved in winter, can be observed in the hundreds on large trees. They do not harm the tree. 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. The acorns are visible, and a group defends its granary against potential cache robbers like Steller's jays and Western scrub jays. Acorn woodpeckers will also spend their daytime sallying from tree limbs to catch insects, eating fruit and seeds, and drilling holes to drink the sap. These master hoaders communicate with each other vocally and their call sounds almost like they are laughing.

Seasonal behavior
Bird's call

Diet and Nutrition

Acorn woodpeckers are omnivores. They feed mainly on insects but also acorns, fruit, seeds, nuts, and drink sap. Occasionally they may eat eggs of other birds.

Mating Habits

MATING BEHAVIOR
INCUBATION PERIOD
11 days
INDEPENDENT AGE
2 months
BABY NAME
chick
BABY CARRYING
5 eggs

Acorn woodpeckers range from monogamous pairs to breeding collectives, sometimes called "coalitions" - a social system when offspring receive care not only from their parents but also from additional group members, often called helpers. Cooperative collectives may also contain groups with multiple breeding males and females (polygynandry). With Acorn woodpeckers, cooperative breeding occurs in two ways: coalitions and family groups. Coalitions of adult Acorn woodpeckers nest together, localizing to storage granaries. Additionally, adult offspring often stay in their parents' nest and help raise the next generation of woodpeckers. Breeding coalitions consist of up to seven co-breeding males and up to three joint-nesting females. However, most nests are made up of only three males and two females. Nesting groups can also contain up to ten offspring helpers. Acorn woodpeckers nest in large cavities excavated in a dead tree or a dead part of a tree. Each female lays about 5 eggs. 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. Once all the females start to lay, they stop removing eggs. Incubation lasts about 11 days. The chicks are altricial; they hatch blind, naked, and helpless. The young fledge at 30-32 days of age and become independent when they are 2 months old.

Population

Population threats

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. These birds are also sometimes killed because they cause damage to fruit crops.

Population number

According to Partners in Flight resource, the total population size of the Acorn woodpecker is 7,500,000 breeding birds. Currently, this species is classified as Least Concern (LC) on the IUCN Red List and its numbers today are increasing.

Fun Facts for Kids

  • Acorns are such an important resource to the California populations of Acorn woodpeckers that they may nest in the fall to take advantage of the fall acorn crop which is a rare behavior in birds.
  • In parts of their range Acorn woodpeckers do not construct a "granary tree", but instead store acorns in natural holes and cracks in the bark. If the stores are eaten, the woodpeckers will move to another area and can even fly from Arizona to Mexico to spend the winter.
  • The breeding coalitions of Acorn woodpeckers are typically closely related. The males are often brothers, and the females are usually sisters. However, inbreeding is rare and co-breeders of the opposite sex are almost never related.
  • Woodpeckers belong to the family Picidae, which also includes the piculets, wrynecks, and sapsuckers. Members of this family are found worldwide, except for Australia, New Guinea, New Zealand, Madagascar, and the extreme polar regions.
  • When feeding, woodpeckers take insects and their grubs both from living and dead trees by excavation. These birds may hear sounds of their prey from inside the timber indicating where it will be productive to create a hole.

References

1. Acorn Woodpecker on Wikipedia - https://en.wikipedia.org/wiki/Acorn_woodpecker
2. Acorn Woodpecker on The IUCN Red List site - https://www.iucnredlist.org/species/22680813/92880196
3. Xeno-canto bird call - https://xeno-canto.org/702503

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