Graduate Thesis Or Dissertation
 

Aspects of the geographic ecology of the Acorn Woodpecker (Melanerpes formicivorus)

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/5138jj44s

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  • Population and habitat characteristics of Acorn Woodpeckers (Melanerpes formicivorus) were examined in oak stands (Quercus garryana) in Benton County, Oregon. Characteristics of eight oak stands not containing Acorn Woodpeckers were also examined. The data were used to determine which factors might be related to woodpecker presence and abundance within the northern extension of the range of this species. Population size varied from 2 to 8 individuals with a mean of 4.25 birds per group. All were resident populations with communal storage limbs for acorns which are used as a winter food. During winter months, birds were also observed flycatching and possibly ground-feeding and gleaning for food. Neither the area of the home rance nor the number of trees in the home range were significantly correlated to the number of woodpeckers living in an area. Rather, the number of dead limbs in the home range was the best single indicator of woodpecker number. The number of storage limbs was related to the number of dead limbs in the home range. Trees in oak stands containing Acorn Woodpeckers were larger, in diameter and had more dead limbs than trees in oak stands not containing woodpeckers. The density of trees in stands occupied by woodpeckers was lower than the density of unoccupied stands. These three factors are important to the availability of resources on which the Acorn Woodpeckers depend: acorns for winter food and dead limbs for storage and nesting. An hypothesis for the recent extension of the Acorn Woodpecker range into northern Oregon is that it is related to the development of oak forests in the Willamette Valley. Prior to settlement in the 1840's, oak savannas were maintained by periodic ground fires. The control of these fires after settlement has allowed the development of mature oak forests which provide suitable habitat for Acorn Woodpeckers.
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