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A Suggested Role for Predaceous Birds and Ants in the Population Dynamics of the Western Spruce Budworm

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To study predation processes in the population dynamics of the western spruce budworm (Choristoneura occidentalis Freeman), whole tree exclosures and sticky barriers were used to exclude avian predators, predaceous ants, or both from 9-m-tall, open-grown trees on one site in northcentral Washington and four sites in central Idaho. From instar IV to adults, samples were taken to estimate budworm density per m² of foliage. At the lowest budworm density (1.7 instar IV per m² of foliage), 10 to 15 times as many adult moths were produced on trees protected from both birds and ants as on control trees. Even when instar-IV density was 25 insects per m² of foliage, adult density continued to be ca 2 times higher on protected trees than on controls. Birds alone or ants alone were usually sufficient to greatly dampen the high survival rates observed when both groups were excluded. For the places and times studied, bird and ant predation clearly exerted a major influence on the population dynamics of the western spruce budworm. Forest Sci. 29:779-790.

Keywords: Predation; population dynamics

Document Type: Journal Article

Affiliations: Research Associate, College of Forestry, Wildlife and Range Science, University of Idaho, Moscow, Idaho 83843

Publication date: 1983-12-01

More about this publication?
  • Forest Science is a peer-reviewed journal publishing fundamental and applied research that explores all aspects of natural and social sciences as they apply to the function and management of the forested ecosystems of the world. Topics include silviculture, forest management, biometrics, economics, entomology & pathology, fire & fuels management, forest ecology, genetics & tree improvement, geospatial technologies, harvesting & utilization, landscape ecology, operations research, forest policy, physiology, recreation, social sciences, soils & hydrology, and wildlife management.
    Forest Science is published bimonthly in February, April, June, August, October, and December.

    2015 Impact Factor: 1.702
    Ranking: 16 of 66 in forestry

    Also published by SAF:
    Journal of Forestry
    Other SAF Publications
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