Acorn Woodpecker

Melanerpes formicivorus

Order:
Piciformes
Family:
Picidae
Sections

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Photos from this Account

Female Acorn Woodpecker (13 November).

Medium-sized black-and-white woodpecker with distinctive red crown, glossy black and white head, white eyes, and white rump and wing patches. Throat is variably yellow. Females of all ages except Juveniles have a wide black band separating the red crown from the white forehead.

Male Acorn Woodpecker (24 November).

Males of all ages have a solid red crown that directly adjoins the white forehead.

White-headed Woodpecker (left) and Acorn Woodpecker (right).

Acorn Woodpecker is sympatric with White-headed in portions of Oregon and California and shares large white primary-patch and black back, but is easily distinguished by substantially different head pattern, white rump and lower underparts, and very different vocalizations.

Juvenile Acorn Woodpecker (31 May).

Juvenile plumage in both sexes is similar to male Definitive Basic Plumage but is softer, duller, and less glossy overall. The red crown patch is less extensive caudally, the belly is less cleanly white, the breast streaks are muddier, and the plumage is generally softer. Iris is dark, becoming white within the first 2-3 months. The Preformative Molt of inner primaries begins before fledging.

Formative male Acorn Woodpecker (29 January).

Formative male and female plumage similar to Definitive Basic plumages except primary coverts uniform in wear and becoming worn and brown by winter or spring; back feathers and replaced inner upperwing coverts glossy black, contrasting with flatter brownish-black retained outer coverts; secondaries uniform in wear, with tertials becoming worn by spring; outer primaries and rectrices retained juvenile, narrower, more pointed. Here, most or all upperwing median coverts are replaced formative feathers whereas most or all greater coverts are retained juvenile feathers.

Formative male Acorn Woodpecker (29 December).

Outer primaries and rectrices retained juvenile, narrower, more pointed, and relatively more worn, the outermost large rectrix (r5) usually with 2-4 rows of pale spots or bars. By December the iris usually becomes white, although often not as bright white, or with pinkish tinge, as found in older birds.

Second Basic male Acorn Woodpecker (15 October).

Second Basic Plumage is similar to Definitive Basic Plumage except that some juvenile primary coverts and secondaries are retained, brown, and very abraded compared to replaced feathers. Retained juvenile secondaries occur in a block of 1-6 feathers among s2-s8; here s4-s6 or so have been retained. Retained primary coverts usually include 5-8 consecutive medial feathers, forming paler panel or badge on upperwing; here the outer two coverts have been replaced but any retained juvenile feathers are obscured by the outer greater coverts.

Second Basic female Acorn Woodpecker (26 January).

Second Basic Plumage is similar to Definitive Basic Plumage except some juvenile primary coverts and secondaries are retained, brown, and very abraded compared to replaced feathers. Retained juvenile secondaries occur in block of 1-6 feathers among s2-s8; here s5-s6 have been retained.

Definitive Basic male Acorn Woodpecker (4 November).

Primaries and secondaries black or brownish black with less gloss than wing coverts; base of primaries white across both webs, the white becoming more extensive proximally, forming a conspicuous patch in flight. Rump and uppertail coverts white, sometimes with narrow black shaft streaks; tail black or brownish black with less gloss than back. Definitive Basic Plumage separated from Second Basic Plumage by having basic primary coverts and secondaries, without retained juvenile feathers. Here it appears that all primary coverts and secondaries were replaced during the previous prebasic molt.

Definitive Basic male Acorn Woodpecker (1 July).

Definitive Basic Plumage can also be characterized by mixed generations of older and newer primary coverts and secondaries, the retained feathers not contrasting markedly with the replaced feathers and usually not found in the same patterns as retained juvenile feathers in younger birds. Here the secondaries appear to be uniform (of a single generation) but two retained basic primary coverts can be seen, those corresponding to p7-p8.

Definitive Basic female Acorn Woodpecker (11 January).

Definitive Basic female is similar to Definitive Basic male except black band separates red crown from white forehead. Breast with variable black band, usually broken up with white spots or streaks, the center of the band at border of throat marked by a small area of black feathers with red tips in some birds. Note that the outer 5-6 primary coverts are basic, without retained juvenile feathers, identifying a bird in Definitive Basic Plumage.

Definitive Basic female Acorn Woodpecker (25 February).

Bases to inner webs of secondaries white with variable black bars distally; underwing coverts white with black marks and streaks. Lower breast, sides, and flanks white, variably streaked black; ventral region white. Undertail coverts white with black streaks or droplet-shaped marks. Note that the 5th secondary from the outside (s5) on this bird's left wing is slightly browner, indicating a retained basic feather and Definitive Basic Plumage.

Leucistic Acorn Woodpecker.
Leucistic Acorn Woodpecker.

Nonmelanic leucism occurs at a frequency of about 0.1%.

Female Acorn Woodpecker with aberrant crown coloration.

Occasional individuals of both sexes in California and elsewhere have been recorded with golden yellow, rather than red, crowns.

Female Acorn Woodpecker; San Diego, California, United States.

Presumably subspecies M. f. bairdi. Resident from southern Oregon south through northern Baja California. Adult female with nape red; forehead patch broad and white; throat pale yellow; chest solid black; black flank streaks broad; black mantle with green gloss; irides white.

Male Acorn Woodpecker; Monterey, California, United States.

Presumably subspecies M. f. bairdi. Adult male with crown red.

Female Acorn Woodpecker; Santa Cruz, Arizona, United States.

Presumably subspecies M. f. formicivorus. Resident from southern Arizona and New Mexico south through Mexico to the Isthmus of Tehuantepec. Center of chest is streaked black (not solid).

Male Acorn Woodpecker; Coconino, Arizona, United States.

Presumably subspecies M. f. formicivorus.

Female Acorn Woodpecker; Baja California Sur, Mexico.

Presumably subspecies M. f. angustifrons. Resident in mountains of southern Baja California Sur. Chest streaked black, forehead narrow and yellowish, and irides dark; averages smaller.

Male Acorn Woodpecker; Baja California Sur, Mexico.

Presumably subspecies M. f. angustifrons.

Female Acorn Woodpecker; San José, Costa Rica.

Presumably subspecies M. f. striatipectus. Resident in the mountains of Costa Rica and Panama. Throat is deep yellow (not pale) and black mantle has a blue gloss (not green).

Male Acorn Woodpecker; San José, Costa Rica.

Presumably subspecies M. f. striatipectus.

Female Acorn Woodpecker; Caldas, Colombia.

Presumably subspecies M. f. flavigula. Resident in the Andes of Colombia. Adult female with nape black.

Male Acorn Woodpecker; Antioquia, Colombia.

Presumably subspecies M. f. flavigula. Adult male with crown black.

Example of Acorn Woodpecker habitat: Hastings Reservation, Monterey County, California.

Mostly blue oak savannah.

Example of Acorn Woodpecker habitat: Hastings Reservation, Monterey County, California.

Valley and blue oak woodland.

Example of Acorn Woodpecker habitat: Hastings Reservation, Monterey County, California.
Example of Acorn Woodpecker habitat: Belize, Belize.
Example of Acorn Woodpecker habitat: Cartago, Costa Rica.
Acorn Woodpecker flycatching.

Generally captures insects by flycatching high above the canopy or by gleaning off tree limbs.

Acorn Woodpecker with acorn.

Acorns usually removed singly from trees, but Acorn Woodpeckers may also break off twigs containing up to 3 acorns at once or eat particularly large acorns in situ.

Acorn Woodpeckers foraging on bananas.
Acorn Woodpecker foraging for flower nectar.
Acorn Woodpecker storing acorn in granary tree.

The habit of storing nuts in individually-drilled holes in granaries is unique to this species.

Acorn Woodpecker storing acorn in granary tree.

An individual granary tree may contain only a few or as many as 50,000 holes, each of which is typically filled with an acorn in autumn.

Acorn Woodpecker granary tree.

An individual granary tree may contain only a few or as many as 50,000 holes.

Acorn Woodpecker granary tree.

Almost any dead or living tree with deep, dry bark may be used as a granary. This individual is using a palm tree.

Acorn Woodpecker granary tree.

Holes are reused annually, accumulate with time, and may eventually be drilled in almost every available limb of a granary tree, although preferred sites are those on the underside of limbs and other partially protected sites.

Felled granary tree exposing a large acorn store.
Acorn Woodpecker at Red-naped Sapsucker sap holes.
Acorn Woodpecker at hummingbird feeder.
Acorn Woodpeckers drinking.

Frequently drinks from water collected by holes in trees. Also drinks occasionally from springs and other groundwater sources.

Acorn Woodpecker drinking.
Acorn Woodpecker vocalizing.
Acorn Woodpecker in flight.

Flight is usually undulating with dips, during which the wings are partly closed and pressed against the sides of the body, interspersed with short periods of flapping and an upward sweep before alighting.

Acorn Woodpecker in flight.
Acorn Woodpecker sunbathing.

Sunbathes on warm, sunny days; birds sit with their wings partially spread out and apparently fall asleep for up to several minutes at a time.

Acorn Woodpecker bathing.
Acorn Woodpeckers defending nest cavity.
Acorn Woodpeckers interacting.
Acorn Woodpeckers interacting.
Group of Acorn Woodpeckers.

Highly social, usually lives year-round in cohesive social units.

Acorn Woodpecker excavating hole.

Excavates its own nest holes in whatever large trees are available.

Acorn Woodpecker at nest hole.
Acorn Woodpecker at nest hole.
Adult Acorn Woodpecker feeding young.

All group members continue to feed remaining nestlings as well as free-flying juveniles after the first chicks have fledged.

Acorn Woodpecker (cover image).

Recommended Citation

Koenig, W. D., E. L. Walters, P. B. Stacey, M. T. Stanback, and R. L. Mumme (2019). Acorn Woodpecker (Melanerpes formicivorus), version 2.0. In The Birds of North America (P. G. Rodewald, Editor). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/bna.acowoo.02