Acorn Woodpecker

Melanerpes formicivorus

birdwatching in bosque de niebla

Quick Facts

  • Scientific Name: Melanerpes formicivorus
  • Family: Picidae
  • Known Nicknames: California Woodpecker, El Carpintero Bellotero
  • Average Length: 19–23 cm / 7.5–9.1 in
  • Average Weight: 65–90 g / 2.3–3.2 oz
  • Wingspan: 35–43 cm / 13.8–16.9 in
  • Key Feature: Clown-like facial pattern with a white forehead, cream throat, and bright red crown
  • Primary Diet: Omnivore (Primarily acorns, insects, tree sap, and fruit)
  • Range: Western United States and Mexico through Central America to the Northern Andes of Colombia
  • Habitat: Oak and pine-oak woodlands, savannas, and suburban areas with mature oak trees
  • Social Structure: Highly Social (Complex cooperative breeding groups)
  • Nesting/Breeding: Cavities excavated in large dead or living trees, often reused for years
  • Conservation Status: Least Concern (LC)
  • Population Trend: Stable

The Acorn Woodpecker (*Melanerpes formicivorus*) is a striking and highly social bird easily recognized by its "clown-faced" appearance, featuring a vibrant red crown, white forehead, and piercing pale eyes set against a sleek black-and-white body. Renowned for its extraordinary industriousness, this species is famous for creating "granary trees," where family groups drill thousands of precisely sized holes to store individual acorns for winter consumption. These birds live in complex communal groups that exhibit cooperative breeding, working together to defend their massive food stores and raise their young. With their distinct, laughing "waka-waka" calls and their unique habit of wedging nuts into bark, Acorn Woodpeckers are both the engineers and the lively guardians of oak woodlands throughout western North America and Central America.

Habitats & Distribution

This species is distributed throughout the coastal and mountainous regions of the western United States, extending from Oregon and California southward through Mexico and Central America to the northern Andes of Colombia. Its range is closely tied to the presence of oak trees, which provide its primary food source. Within this geographical area, it occupies various elevations, from sea-level coastal forests to high-altitude montane woodlands. The primary habitat consists of oak and mixed oak-conifer forests, particularly in areas where multiple species of oaks coexist to ensure a stable acorn supply. These birds are also frequently found in suburban areas, urban parks, and open woodlands, provided there are suitable trees for creating granaries. They require large, mature trees—both living and dead—for nesting and for drilling the thousands of storage holes used to cache acorns for the winter months.

Behaviours & Reproduction

These birds are renowned for their highly social and complex cooperative breeding systems, often living in stable groups of up to 15 individuals. A central aspect of their behavior is the creation and maintenance of communal granaries—trees or structures riddled with thousands of holes specifically drilled to store acorns for winter survival. Within these groups, a strict hierarchy exists, yet the members work collectively to defend their territory and food stores against intruders. Their reproductive strategy is characterized by polygynandry, where multiple breeding males mate with multiple breeding females within the same group. This leads to communal nesting where all females lay their eggs in a single cavity. To ensure their own offspring have the best chance, females may engage in egg-tossing behavior, removing eggs laid by their counterparts until all breeding females begin laying simultaneously. Non-breeding helpers, typically offspring from previous years, assist in incubating the eggs and feeding the chicks, which significantly increases the survival rate of the communal brood.

Diet

The Acorn Woodpecker follows an omnivorous diet primarily characterized by its extraordinary reliance on acorns, which it stores in massive communal granaries created by drilling thousands of individual holes into trees or utility poles. While these nuts serve as a vital winter food source, the birds also consume a significant amount of insects, particularly flying ants, beetles, and flies, which they often catch in mid-air. Beyond these staples, they supplement their nutrition with fruit, seeds, tree sap collected from small pits they drill, and even flower nectar. A particularly fascinating aspect of their feeding behavior is the meticulous maintenance of their storage sites; as acorns dry and shrink, the woodpeckers move them to smaller, tighter-fitting holes to prevent theft by squirrels or other birds, demonstrating a sophisticated level of long-term food management and social cooperation.

Colors

Acorn Woodpeckers display a bold, clown-like facial pattern featuring a bright red crown, white forehead, and yellowish throat framed by a black mask. Their upperparts are glossy black, contrasting with a white belly and a black-streaked breast. Distinctive white patches on the wings and a white rump become visible during flight, while their pale, creamy-white eyes provide a striking focal point against their dark plumage.

Fun Facts

Acorn Woodpeckers are the ultimate avian architects, best known for creating "granary trees" by drilling thousands of individual holes to store a massive winter supply of acorns—sometimes up to 50,000 in a single trunk. These birds are incredibly meticulous; as acorns dry and shrink, they constantly move them to smaller, tighter-fitting holes to prevent theft by squirrels or other birds. Living in complex social groups, they practice cooperative breeding where multiple adults share mates and collectively raise young in a single nest. Despite their specialized diet, they are also skilled flycatchers, often seen launching from branches to snatch insects mid-air, and they possess a distinct, laughing call that sounds like a cartoon character.