Woodpeckers

Here in the Evergreen area we live in close proximity to six species of woodpeckers that annually excavate a new cavity for each year’s nest.  These are the Williamson’s Sapsucker, Red-naped Sapsucker, Downy Woodpecker, Hairy Woodpecker, American Three-toed Woodpecker, and Northern Flicker.  After selecting a tree with the right degree of resonance – indicating heart rot, it generally takes them anywhere from one to four weeks to get their cavity excavated, with some species accomplishing the task faster than others.  

For Williamson’s Sapsuckers, it takes them 3-4 weeks to excavate a cavity, almost always excavating a new hole every year, and they have been known to use the same tree their whole life, riddling it with up to 40 holes.  The majority of nests in our area are in aspen with ponderosa pine less frequently used.  Similarly, Red-naped Sapsuckers also prefer aspen, and will often return to the same tree, occasionally even using the same cavity as a prior year.  Since the two sapsuckers have similar nest-site preferences, it is thought that they avoid competition by selecting nest sites on the basis of nearby foraging habitat, Williamson’s choosing nest sites in areas close to conifer-dominated forest that has few aspens, while Red-naped choose aspen and willow-dominated areas.

Downy Woodpeckers always excavate a new hole each year, taking about 1-3 weeks, and the female tends to choose the site.  Similarly, Hairy Woodpeckers take up to 3.5 weeks. Both of these species use a variety of trees, though higher in the foothills there appears to be a preference for aspen.

Three-toed Woodpeckers chose conifers over aspen, helping them secure a site in close proximity to their preferred food, the larvae of coniferous bark beetles.  They can get their cavity excavated in as little as ten days, as can Flickers, who use a variety of trees, and often use their cavity from the previous year.

Chickadees and Nuthatches

Five additional species also excavate cavities for nesting, and, as with the woodpeckers, they too seek out weak or dead trees.  These are Black-capped Chickadee, Mountain Chickadee, Red-breasted Nuthatch, White-breasted Nuthatch, and Pygmy Nuthatch. Black-capped Chickadees almost always excavate a new hole, with a definite preference for aspen and other deciduous trees.  If not excavating their own hole, they prefer natural cavities over nest boxes.  Red-breasted Nuthatches also prefer aspen, but will also use conifers.  Pygmy Nuthatches only excavate about half of their own holes, preferring Ponderosa. Often these same birds, except for the Red-breasted Nuthatch, use pre-existing natural cavities or old woodpecker holes; often modifying existing holes but not excavating the cavity on their own.

Secondary Cavity Nesters

Birds such as Mountain Chickadees and White-breasted Nuthatches that use old holes created by other birds, are known as secondary cavity nesters.  Additional secondary cavity nesters in our vicinity include Flammulated Owls, Northern Pygmy-Owls, Boreal Owls, Northern Saw-whet Owls, Wood Ducks, Barrow’s Goldeneyes, American Kestrels, Tree and Violet-green Swallows, House Wrens, Western and Mountain Bluebirds, and European Starlings.  A few additional local species use natural cavities that were not excavated by other birds.  These include Turkey Vultures, Barn Owls, Belted Kingfishers, Cordilleran Flycatchers, Northern Rough-winged Swallows, Brown Creepers, and House Sparrows.

Both primary and secondary cavity-nesters can sometimes become attracted to using nest boxes, and these may be critical to the survival of species in areas where natural cavities are lacking.  Homeowners and land management agencies may want to rightfully consider leaving a few old cavity riddled snags in place rather than removing them.  We can see the significant contribution made to the local bluebird and swallow populations by the nest boxes erected at Elk Meadow, Alderfer-Three Sisters, and elsewhere in our area.

Another important use of nest boxes is that larger, woodpecker-sized ones can be placed near houses with the purpose of providing an alternative nest site and dissuading the woodpeckers from excavating a hole in the house.  When a woodpecker taps on a house the resonating sound indicates a hollow within the siding that might make a good cavity for a nest, just like a tree with heart rot, so providing them with an option can be a wise idea for homeowners.