Nature Watch: Life in Dead Trees

About the author: Steve Ellis is a naturalist and Land Trust member who enjoys sharing his love of the natural world. His blog series, “Nature Watch,” will appear each month in “Habitchat,” chronicling native plants and wildlife you can expect to see during that particular time of year. We thank Steve for sharing his passion, illustrating the importance of island conservation.

Overview

The race to reproduce in the avian world accelerates quickly in April. Mates are being chosen and territories defended.

For woodpeckers, the process can be a long one as a tree cavity needs to be hollowed out. The process is shortened if a snag is selected. It’s much easier to cut into dead wood rather than a living tree.

A snag is a standing dead tree. The name derives from being “snagged” or caught in an upright position.

Snags have great impacts on the forest community. Over 100 vertebrate species in Washington use snags in some ways.

Many birds perch atop dead trees. Bald Eagles, hawks, owls, ravens, flycatchers and swallows use them as lookout posts.

Snags are used as caching spots. Squirrels, chipmunks, deer mice, Steller’s Jays and others create food pantries in snags for later consumption.

A variety of invertebrates, mosses, lichens and fungi find sustenance in the dead wood material or use the snag as a place to anchor above the crowded forest floor.

Bird nesting is a critical function of snags. Woodpeckers are primary cavity nesters, meaning they cut holes in the wood for nesting spaces. Bird species that use abandoned woodpecker holes are secondary cavity nesters. Examples of these include owls, chickadees, wrens and nuthatches.

Several mammal species enjoy woodpecker holes too. Bats, squirrels and raccoons are also secondary cavity users.

Snags continuously shed tissue to the forest floor. This process helps cycle nutrients back into the soil to be used by other flora species.

The value of any given snag depends on its location, cause of death, and the tree species. A snag in a forest, protected by live trees from adverse weather, decomposes slowly and will be used for a greater period of time. Snags in exposed areas weather quickly and soon topple in a strong wind. Trees killed by root rot aren’t well anchored and will soon fall. Those killed by other diseases or by insects will have a longer career as a snag.

There’s a disparity between the expected survival time of snags of various tree species. Western red cedars are the champions and may stand for 75 years, while the thick-barked Douglas-firs stay upright for 45.  Western hemlocks can manage 15 years, and most alders usually fall before the 10-year mark.

The value of snags cannot be overstated. Small cavity-nesting birds such as chickadees and wrens range through the forest, preying on insects which are harmful to living trees and shrubs. Owls and bats also provide this type of pest control.

A look at a list of wildlife species shows the diversity found in snags. Species such as flying squirrels, Wood Ducks and Hooded Mergansers are often found nesting in snags. Simply put, there’s an amazing amount of life in dead trees.

The drumming sound of a Northern Flicker can be heard more than a mile away. Photo by Steve Ellis.

Fauna: Northern Flicker (Colaptes auratus)

This is the most commonly seen and heard woodpecker species in our region.

Flickers are 12 to 13 inches in length, with a wingspan of 20 inches. They have a long bill and a gray face.  The male has a red ”mustache” mark on the cheek. The back and wings are brown with dark barring. Below, flickers have a black bib and black dots on a pale background. The undersides of the tail and wings are salmon pink in the west, and yellow in eastern North America. A white rump patch rounds out the field marks.

Northern Flickers will be drumming in April to attract mates and establish breeding territories. This drumming can be heard more than a mile away. They like branches on snags as a drum, but they’re also partial to the metal flashing on our roof.

They communicate with their voices as well. A loud, clear Kee–er call is used to maintain contact between mates or parents with their offspring. The name flicker comes from what’s known as the long call,  Wicka-wicka-wicka, which can continue for five seconds.

Unlike most other woodpecker species, flickers find a majority of their food on the ground, where they forage for ants and beetles. They choose areas that are bare or have short grass and forbs. Tall grass is shunned because they can’t see approaching predators.

Berries, other fruits, and seeds are consumed in the fall and winter months.

Flickers create a new nest hole each year, often in a snag. Additional cavities are excavated for roosting.  This ensures there are many places for secondary cavity users. Northern Saw-whet Owls, squirrels and silver-haired bats are some of the beneficiaries of flicker-carved cavities.

They have an undulating flight, accomplished by alternating flapping and then folding the wings to the body. It’s a highly-efficient flight pattern that also shows the white rump patch.

Another behavior to watch for is the duel or “wicka-dance.” Two birds of the same sex face off against each other, either on the ground or atop a tree branch. The birds angle their bills upward and wave them back and forth while calling. It’s mostly ritualistic and rarely ends in blows. This is done for defense of territory or mate.

Flickers bathe in dust and practice anting. The latter is accomplished by lying on an anthill or crushing ant bodies and spreading the result over its wings and body. It’s presumed the formic acid in ants might be a deterrent for parasites.

Watch for Northern Flickers in every forest type and in open areas. They adapt well to suburbs.

These birds are highly attractive and fun to observe. We should also remember their contributions to pest control, the scattering of seeds from berries, and their legacy of leaving nesting opportunities for a multitude of other creatures.

Find red-belted polypores on a snag while walking through an old growth forest. Photo by Martha Ellis.

Flora: Red-belted Polypore, a.k.a Northern Red Belt (Fomitopsis mounceae)

This hoof- or shelf-shaped fungus is a mainstay of our forests, growing mostly on snags but also on living trees. It’s a polypore, a group of fungi that produce woody fruiting bodies commonly termed “conks.”

Red-belted polypores can be solitary or in small groups. The body is yellowish when young, then becomes brown with a reddish zone near the margin as it ages. Individuals also become bumpy or warty in maturity. The underside is white to yellowish. Colors among the population can vary greatly. When young, some individuals closely resemble a fried egg, sunny side up.

Polypores are detritivores, consuming the cellulose of decomposing wood. They are responsible for brown rot, decaying wood which turns brown in color and breaks into cubical chunks. (This is not the brown rot which affects fruit.)

One of the odd features of red belted polypores is their use of a process called guttation. When soaked, the conk exudes water droplets on its upper surface, which can be seen long after a good rain is over.

Polypores’ consumption of wood cellulose is an important agent of nutrient cycling in forests. They also aid in the absorption of carbon dioxide.

Walk any path through a secondary or old growth forest and you should be able to discover red-belted polypores on a snag and the cubical brownish remains left by brown rot on the forest floor. These are signs of renewal, as Nature tears down the old and makes ready for rebuilding.

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