Nature Watch: Going Undercover
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.
Our conifer forests are generally described as having an upper story or canopy (treetops), an understory of deciduous shrubs and ground cover. Winter’s wind-driven rains push some bird species towards the safety of the plants that are carpeting the forest floor. In December, going undercover is a safe bet.
Ground cover’s composition depends on soil type and the amount of precipitation. Our typical species are salal, ferns, short Oregon grape, mosses and a few wildflowers.
Bird species such as sparrows, towhees and wrens not only find shelter in ground cover but also rich food resources. Berries, insects and other invertebrates are augmented by numerous seeds that have filtered down from the canopy and understory.
Ground cover isn’t just a haven for the 10 to 12 bird species sheltering there. Small mammals and some amphibians such as Pacific chorus frog also find protection under ferns and other plants.
The ground cover is important for the health of our forests. It prevents rain and deer hooves (and human feet) from compacting the soil atop the roots of trees and understory bushes. The taller flora reciprocate by sheltering the ground cover from the worst of December’s stormy weather.
Flora: Sword Fern (Polystichum munitum)
Sword fern can be found in many of our local forests and is a major component of the ground cover.
This evergreen gets its name from the lance-shaped fronds (leaflike part of the fern) that rise from the woody root structures known as rhizomes. Frond stalks can be up to five feet long and each frond bears dozens of parallel narrow leaflets (pinna). A double row of round spore casings forms on the underside of each leaflet.
The preferred habitat for sword ferns is moist forests. In well-shaded locations, the fronds grow out horizontally. In more open settings, the fronds are erect.
Sword ferns shelter invertebrates, amphibians, small mammals and birds. Deer browse the frond tips and squirrels use them to line their nests.
Fauna: Pacific Wren (Troglodytes pacificus)
If any bird species personifies ground cover, it’s the Pacific Wren. The scientific name, Troglodytes, means “cave dweller,” and these little dynamos are very much attached to dark places.
Pacific Wrens are all of four inches long, with dark brown upper parts and white on the throat and breast. They have thin, slightly downcurved bills, and short, upturned tails.
In spring, this tiniest of the ground-dwelling birds has one of the longest songs. It’s best described as a long series of trills and other notes. They often use a sharp, two-note “chip-chip” call when disturbed.
Pacific Wrens are often found beneath sword ferns and salal, as well as in brush piles and wood piles. They consume insects and invertebrates, and may be tempted by suet feeders. In turn, they are preyed on by small owls.
Local numbers of this perky little species are increased every winter by individuals that have dropped down from the North Cascades.