When we walk in the forest, we are dazzled and soothed by the leaves and needles of the trees above and around us. These surfaces — the photosynthetic factory of the forest — gather sunlight and pull carbon from the air to build themselves and all of the organisms that depend on trees.
When trees reach into the sky to form a canopy layer in the forest, the interacting crowns create a remarkable maze of three-dimensional spaces between and on the branches. The surfaces of these branches and leaves, known as the canopy, can be considered a habitat niche with specialized functions for many species of wildlife. Animals that live in trees — “arboreal” species — feed on the cones and seeds that trees produce. The surfaces of needles and branches also are home for insects, and hunting grounds for their predators. This complex habitat contains varying opportunities for wildlife to make a living by hunting insects, eating lichens, gathering seeds, or other taking specialized actions.
Birds in the canopy
Birds are the most obvious species to utilize this habitat niche, with rich varieties showing up at different times of the year. Some are resident, remaining in the same, or nearby, habitats year around, while others are migratory. Many of our migratory birds come back from the neo-tropics (that is, Central America and even South America) for breeding season, and return south in the fall.
Different birds can use different portions of canopy at different times. Dense canopies, for example, can provide thermal cover for overwintering chickadees or Stellar’s jays where they roost on a cold winter night. These same fronds can provide abundant insects for flycatchers, such as the western wood pee wee, and western tanagers to feed upon when they return from Central America for the summer. Golden-crowned kinglets nervously flit about these same branches throughout the year hunting tiny insects.
Our glorious migratory songbirds arrive between March and May to take advantage of the explosion of insect life in our temperate summer growing season. Research suggests that migratory birds, such as the Townsend’s warbler, western tanager or various flycatchers, may key on deciduous trees for the insects living there, because it is most similar to the broad-leafed forests where they spend the winter. Conifers have more consistent habitat features; with their needles present year-around, confers provide habitat for year-round residents such as chickadees and nuthatches.
These tiny avian powerhouses will glean insects from the surfaces of leaves (conifer needles are leaves too) throughout the canopy, often travelling in mixed species flocks and moving from tree to tree communicating with small chips and calls. Try “Phishing” when you hear one of these flocks nearby and see what happens. (That is, go “PSHHH, PSHHH, PSHHH” over and over until your mouth is tired and dry. It imitates a distress call among small birds and you will be amazed how close some of them will come!). Many eyes make it easier to spot predators, such as Cooper’s hawks, which make these travelling mixed flocks advantageous.
Tomorrow: A look at some of the aboreal mammals of Pacific Northwest forest .
Caring for the Canopy
If you own a small forest woodland, advice and resources to keep your forest and its canopy healthy are as close the nearest DNR stewardship forester or WSU extension forester. Call one of us to arrange a site visit or to get additional information on how to provide wildlife habitat while managing your forestland.
This article was written by Ken Bevis, a DNR Stewardship biologist. It originally published in Forest Stewardship Notes, a quarterly e-newsletter produced by DNR and Washington State University Extension.
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