Nuthatches typically establish extensive feeding territories that are much broader than their nesting territories. They make a significant contribution to the health of trees in this territory by gleaning pest insects, insect eggs and larvae that live on or in tree bark. Because they travel downward on the bark, they often find insects that woodpeckers miss.

They particularly relish the larvae of the spruce budworm and control many other pest insects as well:

Lunch For Nuthatches
Ants	Caterpillars	Moth eggs	Spiders
Beetles	Insect cocoons	Scale insects	Weevils