In all seasons, they prefer insects, whenever they are available. They will also eat insects/arthropods any time of year, with insects becoming their primary food during the breeding season. From winter through summer, they supplement their forage with sap (usually from wells they make themselves). In general, Acorn Woodpeckers eat acorns from about August through May, but more so in the fall, as the crop ripens. Sometimes they hawk for insects in the manner of the Red-headed Woodpecker or Lewis's Woodpecker, another close relative.This female Acorn Woodpecker was photographed in Pima County, Arizona on 25 April 2009. Acorn Woodpeckers also consume insects, sap, and fruit, and occasionally eat grass seeds, lizards, and bird eggs. In fact, they rarely stray far from oaks and do best in areas with various oak species, which allows the birds to increase their chances both to take advantage of good crop years and survive crop failures. Researchers believe that this arrangement works well for species with limited suitable habitat, or food resources that fluctuate in availability from year to year - conditions that also favor having a well-stocked acorn granary nearby.Īs their name implies, Acorn Woodpeckers rely heavily upon acorns for food. This kind of cooperative breeding system is rare, occurring in only 9 percent of bird species. Young adults remain with their parents for several years to help raise successive broods, but eventually they disperse to other territories. Photo by Jean-Edouard RozeĪll members of the colony share in incubation duties, and all pitch in to feed the chicks when they hatch. Acorn Woodpecker tending a granary in California. Coming a little late to the party has benefits in this case: A female laying the final clutch may wind up having more of her eggs incubated. Although this behavior seems counterproductive, it may be beneficial, resulting in all chicks being roughly the same age and size. In-synch egg-layers, however, produce a clutch totaling three to seven eggs. When egg-laying is not synchronized, females often destroy each other's eggs. If more than one female in a colony breeds, they lay eggs in the same nest cavity. (Each territory contains other cavities used as nightly roosting sites.) The nest cavity is sometimes located in the granary tree, and the group may use the same nest cavity for several seasons. The colony works together to excavate a nest cavity in a dead or living branch of a large tree, or in a dead tree. This communal lifestyle precludes the necessity of courtship and pair-bonding displays, as adult males mate with any or all of the group's female breeders. Colonies have one to three breeding females and up to eight breeding males, as well as young birds from previous broods. Like the Pinyon Jay, another social, nut-loving bird, the Acorn Woodpecker lives, breeds, and nests in groups. Why do Acorn Woodpeckers take such drastic measures to store food? This caching is actually an effective strategy for surviving the winter, allowing the birds to skip the perils of migration and stay on the same territory year-round.īreeding and Feeding Parental Perils and Communal Concerns Sometimes these woodpeckers choose more unusual storage spots: One Arizona landowner discovered that these industrious birds had stashed 485 pounds of acorns in his wooden water tank! In some parts of its range, the Acorn Woodpecker does not create a "granary tree," but instead stores acorns in natural holes and cracks in bark. Since the acorns are visible, the Acorn Woodpeckers also must defend their larder against potential cache-robbers such as Steller's Jays, White-breasted Nuthatch es, and Spotted Towhee s. Granary maintenance takes up a significant amount of this woodpecker's time, as acorn stocks need to be constantly turned and moved to different holes as they dry and shrink. A Bushel of BirdsĪ group of Acorn Woodpeckers is known as a "bushel" - a perfect description for this bird's unusual habit of squirreling away large quantities of acorns in granaries or "acorn trees." Some of these granary trees have up to 50,000 holes - drilled, stocked, and maintained by extended Acorn Woodpecker families. It's a medium-sized bird, bigger than a Downy Woodpecker and a bit smaller than its close, but more easterly, relative the Red-headed Woodpecker. The eye-catching Acorn Woodpecker's head is boldly patterned in black, white, and red, punctuated with wild-looking white eyes that give it a clownish look.
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