F e a t u r e

Douglas fir Creating a Wildlife Snag makes a very Seattle Audubon took the recommendations of good, long-lasting Keith Geller and the Garden Committee and snag. We expect decided to take action to reduce risk from the . that the Seattle They also took a suggestion from the ’s Audubon snag report and, rather than removing the entire tree,

will last at least decided to create a so-called snag or wildlife tree to twenty years, and preserve habitat for birds and other creatures. It will perhaps much remain for a time as a structural element and serve longer. The arbor-

as a science lesson in the native garden. ist will monitor photo by Scott Baker Although many birders are well aware of the im- A branch is left to it and at some point, as it begins to deteriorate, serve as a wildlife portance of snags for nesting sites and food sources, may reduce its height again for safety reasons. perch. many city dwellers are not. Most tree removals in We hope that the many nature lovers who fre- urban are complete, resulting in a loss of quent the site will be observing the progress of the habitat for bird species that rely on them. snag and keeping a close watch for the first tenants. The Seattle Audubon tree was intentionally reduced in size to a point where it is unlikely to fall over or break under a wind load. We cut the tree in a manner that imitates a tree broken in a storm, to How Old Is the Snag Tree? disguise the fact that the tree was artificially cut. Se- attle Audubon’s snag has a few living branches on The snag tree appears to be older than the build- it. These were left to keep some energy flowing into ing, which was built in 1949. This is somewhat the trunk to slow the deterioration of the remaining surprising, because back then, the tendency was tree, and to lessen the visual impact of the change. to bulldoze everything and begin anew. A passer-by, on seeing the process, asked if this We counted 86 annual growth increments was not “tree topping.” Tree topping ruins a tree’s (tree rings) in the of the tree at the height natural form and causes many other problems over of the last trunk cut. This count averaged 6.8 time. Topped Douglas firs tend to grow back vigor- years per inch of trunk radius. The radius near ously and often develop multiple new tops that are the base of the tree is 19” x 6.8 = ~129 years! weakly attached to a decaying trunk. We won’t let This is an estimated maximum the tree grow back in such an unwieldy manner. In- age for the tree. We don’t know stead, as we manage our snag, we’ll prune off some what conditions were for the of the expected new growth. young tree so the age calculated Snags are quickly colonized by and fungi cannot be considered highly ac- that begin to soften the wood during the slow pro- curate. Still, it’s probably safe to cess of decomposition. Primary excavators, includ- say that the tree is over 100 years ing woodpeckers and predatory insects, create cavi- of age. ties, which are then utilized by chickadees, owls, You can read other things, mammals, and pollinators such as orchard, too, in the tree’s rings. You can mason, and honeybees. We will do several things to see that the tree was stressed help speed up this process. We’ll cut some cavities at the time the building went into the tree to attract birds. Normally, it would up, when traffic over its roots

take several years for the tree to be developed in increased and part of its water photo by Keith Geller supply was cut off. And many, many years later, This stump this manner by fungi and woodpeckers. We’ll also will remain in cut in a “bat slit” to attract bats. Bats often shelter when the native garden was started, the tree the garden as under the bark as it begins to slough off. benefited from the destruction of the lawn and an educational the addition of natural mulch. tool.

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