![]() ![]() With only six years of data the results are preliminary, but the general conclusion is clear: acorn production is highly synchronous over large geographic areas for at least several of the species. Currently encompassing 16 sites from Shasta to San Diego County, the survey involves visually counting acorns of over 950 trees of 7 species of oaks. In order to address this issue, Jean Knops of the University of Nebraska and I initiated the California Acorn Survey in 1994. This brings us to the question of geographic synchrony in acorn production within and between species of California oaks. Whereas, if the acorn crop is not synchronous within and between species, they may only have to travel a few miles before coming to an area with lots of acorns where they could survive through the winter. If the acorn crop was poor and synchronous both among individuals of the same species and across species over a large geographic area, there would be few acorns anywhere nearby and the birds might have to travel a very long distance before finding an area where there were enough acorns to survive. How far they have to go presumably depends on how geographically synchronous the acorn crop is within and between species of oaks. However, in poor years, the birds are forced to abandon their territories and wander off in search of acorns elsewhere. In good acorn years, acorn woodpeckers not only reproduce extremely well the following spring but may even successfully breed in the fall, fledging young as late as early November. Indeed, such “storage trees” or “granaries” have been reported to contain up to 50,000 acorns or more! Holes are used over and over each year and accumulate with time. More dramatically, they harvest acorns in large numbers and store them in special trees in their territories in which the birds have drilled holes, each of which can hold an individual acorn. Acorn woodpeckers eat acorns directly off trees in the fall as acorns mature. No species is more intimately associated with oaks than the acorn woodpecker, a common resident of oak woodlands throughout California. As shown by the National Audubon Society’s climate scenarios map, an increase of +3 degrees Celsius could result in population loss across part of the species’ range, but climate change might provide favorable conditions elsewhere.Oaks ‘n Folks – Volume 15, Issue 1 – March 2000 In addition to loss or degradation of mature oak trees, other threats to present population levels include slow oak forest regeneration, the introduction of European Starlings and–depending on location–a warming climate. ![]() While Washington’s populations are considered critically imperiled by Nature Serve, it is not a state-listed species since it is considered a peripheral species due to range expansion. Nature Serve’s overall species ranking is G5 (secure) but they rank the species as vulnerable in Oregon. The Oregon Department of Fish and Wildlife lists Acorn Woodpeckers as a sensitive species in the Willamette Valley and Klamath Mountains due to conversion and loss of oak habitats. As a species highly associated with oak habitats, there is concern for the species within regional or local areas and ongoing habitat loss and other environmental change elevate concerns about the species. While not the only bird species to utilize or store acorns, this species certainly takes it to the extreme!Įven with a global breeding population estimated at 5 million birds, there is still a need to conserve this iconic woodpecker. According to the Cornell Lab of Ornithology, these storage areas may have up to 50,000 acorn holes in them.īird Note also tells us that utility poles, fence posts, or the sides of barns will do in a pinch when a tree isn’t available. ![]() ![]() They spend a significant amount of their time associated with granary trees–trees in which they bore holes or use natural notches and cracks to store acorns. While other woodpeckers are usually seeking insects when they drill into trees, the Acorn Woodpecker feeds mostly on flying or terrestrial insects, seeds, and fruits as well as high-caloric acorns which they store for winter. In a win-win arrangement, the woodpeckers are also helping distribute acorns that may seed new oak trees. In California and Oregon, and slightly into Washington, they are associated with oaks in the genus Quercus, often the Oregon white oak or the black oak. They prefer oak woodlands with a more open understory and rely on mature oaks for both food storage and nest sites. The Acorn Woodpecker is an oak woodland specialist, relying on oaks for food, shelter and nest cavities. ![]()
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