Abstract
Abstract Birds consume large numbers of the western spruce budworm (Choristoneura occidentalis), a forest insect which defoliates economically valuable stands. We estimated the economic value of bird predation on two stands in north-central Washington by substituting the cost to spray with insecticides to produce the same mortality rate as birds cause. It would cost at least $1,820 per square km per year over a 100-year rotation. This figure may be used to appraise the value of individual predator species, such as the voracious evening grosbeak (Hesperiphona vespertina), to evaluate the cost-effectiveness of biological control with birds, and to assess silvicultural treatments and other practices which affect both bird and insect numbers.
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