The mating season ritual causes the poles to rot, rendering them unsafe for engineers to climb, and needing replaced.
The woodpeckers have struck in Argyll and the Highlands, as natural nesting sites become rarer.
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A BT spokesman said yesterday: "In most cases phone services are not affected by the damage."
A British Trust for Ornithology spokesman said installing a fake large black woodpecker to poles would scare off the smaller birds.