Title page for ETD etd-91597-204823


Type of Document Master's Thesis
Author Harding, Sergio R. III
Author's Email Address sharding@vt.edu
URN etd-91597-204823
Title The Dynamics of Cavity Excavation and Use by the Red-Cockaded Woodpecker (Picoides Borealis)
Degree Master of Science
Department Biology
Advisory Committee
Advisor Name Title
Haas, Carola A.
Jenssen, Thomas A.
Walters, Jeffery R. Committee Chair
Keywords
  • red-cockaded woodpecker
  • cavity
  • excavation
Date of Defense 1997-09-25
Availability unrestricted
Abstract
Quantification of cavity excavation produced strong empirical support for the

ecological constraints model for the evolution of delayed dispersal in the cooperatively

breeding red-cockaded woodpecker. The long times required for cavity excavation select for competition over

breeding vacancies in established territories and against excavation of cavities in

unoccupied habitat. Duration of excavation varies between woodpecker populations, but

may require over 13 years in longleaf pine and over 10 years in loblolly pine. Duration of

excavation is extremely variable. Much of the variation is due to variation in effort by

excavating woodpeckers, which is in turn partially related to the need for new cavities in relation

to the number of available cavities on a territory. An average of only 11 % of an

individual's time budget is devoted to excavation, and only one individual per group

makes significant contributions to excavation. Once completed, cavities are used for

periods that may exceed fifteen years. Cavities in longleaf pine are used for significantly

longer periods than cavities in loblolly. Whereas cavities no longer used as nests are

abandoned altogether in loblolly, they are still roosted in for many years in longleaf.

Final abandonment of longleaf cavities appears to be related to cavity loss.

Quantification of cavity turnover revealed that three of the study populations were stable

in cavity numbers over the study period, while a fourth underwent alarming declines.

The continued use of restrictors and artificial cavities, and the protection of old-growth

upon which the woodpeckers depend for excavation, are recommended.

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