Birds of Indian Subcontinent

Measuring Predator Impact of Woodpeckers on Spruce Beetles

Publication Type:Journal Article
Year of Publication:1972
Authors:Koplin, JR
Journal:The Journal of Wildlife Management
Date Published:1972
ISBN Number:0022541X
Keywords:Dendrocopos, Dendrocopos pubescens, Picidae, Picoides, Picoides pubescens, Picoides tridactylus
Abstract:A deterministic model incorporating food requirements of free-living woodpeckers (Picidae), average number of prey per woodpecker stomach, population density of woodpeckers, and air temperature as inputs, and yielding number of prey consumed as output, was formulated to predict predatory impact of three individual species of woodpeckers on endemic, epidemic, and pan-epidemic populations of larval spruce beetles (Dendroctonus obesus). Resultant predictions compared favorably with estimates made by measuring relative survival of larvae inside and outside of woodpecker exclosures. The model predicted that northern three-toed woodpeckers (Picoides tridactylus) were the most effective and downy woodpeckers (Dendrocopos pubescens) the least effective picid predators of larval spruce beetles. It is speculated that the graded predatory effectiveness-the result of differential functional and numerical responses of woodpeckers to density of spruce beetles-was related to foraging adaptations characteristic of each species. The combined predatory impact of the woodpeckers was least effective on endemic and pan-epidemic populations of spruce beetles and most effective on epidemic populations. It is also speculated that decreased predatory effectiveness on endemic populations is related to the availability of alternate prey and to adaptations of woodpeckers for utilizing them, and that decreased predatory effectiveness on pan-epidemic populations is related to the limitations imposed by nesting territoriality on the numerical response of woodpeckers to prey density.
Short Title:The Journal of Wildlife Management
Scratchpads developed and conceived by (alphabetical): Ed Baker, Katherine Bouton Alice Heaton Dimitris Koureas, Laurence Livermore, Dave Roberts, Simon Rycroft, Ben Scott, Vince Smith