Neighborhood Naturalist Winter 2016-17 by Neighborhood Naturalist

neighborhood naturalist CORVALLIS, OREGON — WINTER 2016-17

Western Sword Fern T he undergrowth at Forest Dell Park was covered in frost, and ribbons of mist rose where sunbeams illuminated the forest floor. This park was almost as lush and green as if it were in June, due in part to Western Sword Fern. It’s ubiquitous in our area, but it’s anything but banal. It’s a competitive survivor that benefits the gardener, wildlife, and native landscapes. It has an elaborate life cycle and an extraordinary natural history.

Western Sword Fern is native only to the Pacific Northwest, home to the largest temperate rainforest in the world. Throughout much of the forest, sword fern is the dominant undergrowth, and it’s common even where it doesn’t dominate. Anywhere that’s moist and shady with loamy soil is likely to have sword fern, except for areas that have a deep winter snowpack. Fundamentally a shade lover, it can also tolerate full sun for periods of the day. It grows in some of the world’s wettest forests, but also withstands our long, dry summer and early fall. As a perennial that can live for many years, it has a tendency to grow into a mounded structure with young fronds growing out of the center, and heaps of old and dead fronds around the edges. Under ideal conditions, older plants can grow to five feet high, eight feet wide and support a hundred living fronds or more. Western Sword Fern is tough and hardy, persisting among introduced,

article and illustrations by Don Boucher photography by Lisa Millbank

invasive plants. Clumps of sword fern and their fibrous roots help to reduce soil erosion in forests impacted by logging, fire, and landslides, and sword fern can colonize disturbed areas quickly. Being a fern, it has no flowers or seeds, and instead, reproduces by the ancient method of casting millions of microscopic spores to the wind (see an illustration of the process on the next page). How can such an ancient plant be so successful? First, it’s not as primitive as it may seem, and secondly, it has robust genes. Ferns were some of the first vascular plants, and were part of the world’s earliest forests. Though they managed to survive a few mass extinctions, many groups of ferns died out when flowering plants emerged in the Cretaceous Period, about 80 million years ago. Western Sword Fern is among a group of ferns that adapted and diversified during this botanical revolution, and they’ve kept pace with evolution ever since. They took advantage of niches within the new ecosystems. Many took to the forest canopies as epiphytes. A local example of this is the Licorice Fern, which grows among thick moss mats on trees. Others, like the sword fern, proliferated on shady forest floors. Of the world’s modern fern species, many frequently selffertilize. Though it enables a single individual to reproduce

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Western Sword Fern Life Cycle Many plants spread vegetatively or by seed, but sword fern disperses spores. Unlike seeds, fern spores aren’t ready to grow into mature plants. Instead, they’re the start of a multi-step reproductive process. Even though it’s extremely unlikely that any one spore will result in a fern, sword fern is able to dominate landscapes.

The little grains of the sorus are tiny, but they aren’t actually the spores. They’re sporangia, capsules that contain the microscopic spores.

When mature, the sporangia forcibly pop open, scattering spores to the wind. Most mature by midsummer. Some overwinter, and mature in early spring.

Sorus

Sporangium

Sori

Archegonium Produces an egg

A spore grows into a haploid plant (one set of chromosomes), called a gametophyte or prothallus. It grows to about 1 cm wide, and has numerous structures for sexual reproduction. The female structures are called archegonia, and the male structures are called antheridia.

Egg

Sperm Gametophyte

6 The sporophyte matures into the familiar fern plant. Pictured here is the underside of one frond. Some individual plants can produce tens of millions of spores.

Antheridium Produces sperm

Sporophyte

A young diploid plant (two sets of chromosomes), called a sporophyte, grows out of the archegonium on the gametophyte.

Gametophyte

When the coil-like sperm are released from the antheridium, they need wet conditions to swim. One finds its way into an archegonium and fertilizes the egg. Typically, the sperm from one gametophyte will swim to a nearby gametophyte to fertilize the egg. It’s rare for a gametophyte to fertilize itself.

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by itself, it also results in low genetic diversity. Inbreeding makes ferns less adaptable to changes in the environment, and causes genetic problems. Some ferns avoid these problems by having extra sets of chromosomes that let each plant contain more genetic variety. Not so for Western Sword Fern. When the wind-borne spores germinate and grow into gametophytes, mechanisms exist that prevent them from self-fertilizing. So, almost every young sword fern is the product of two individual gametophytes. This primeval plant has a healthy genetic diversity that rivals some of the seed-bearing plants.

used sword fern to cover or layer food for storage, and to line cooking pits. Reportedly, they used various parts of the plants as a medicine for ailments like diarrhea, sore throats, tonsillitis, and sores. It was used to treat pain during labor, or to treat pain in general. Peeling and cooking the rhizomes for food was probably limited to times of desperation.

Older sword ferns are mound-like, with numerous dead fronds.

Young sword fern plants have oval leaflets edged with coarse teeth.

John Kallas, author and instructor on wild edibles, experimented with slow-cooking various parts of sword fern in water. He found that most parts were tough and astringent, and only small portions were barely edible. He then rendered the cooking water for days, and produced a There are closely related species that aren’t found in syrup that resembled molasses. While people have reported the Willamette Valley, but in the adjacent mountains. eating sword fern with no ill effects, I haven’t found any Narrow-leaved Sword Fern is found mostly in the Cascades research analyzing the potential toxicity of it. Given the and southwest Oregon, and sparsely in the Coast Range. fact that many fern species are toxic, and the impracticality It looks similar, with smaller, narrow fronds. Growing of processing sword fern to eat, it’s probably unwise to in rocky habitats, it withstands much drier conditions. consume it. Mountain Holly Fern, also a smaller plant, is found high in the Cascades and southwest Oregon. It has toothy leaflets It might not be too tasty for humans, but Western Sword and grows on rocky slopes. Fern is eaten by wildlife, especially the Aplodontia—the only creature that eats it as a staple. The Aplodontia (also Throughout the Northwest and beyond, sword fern is called Mountain Beaver or Sewellel) is a secretive, rabbitcommonly planted for landscaping, and it thrives anywhere sized, burrowing rodent that lives deep in the Pacific in western Oregon, from the coast to the Cascades. Once Northwest rainforests. Roosevelt Elk may eat sword fern established, it’s an attractive, easy-to-maintain ground in quantity during winter and spring, and Blacktail Deer cover that stays green year-round. Western Sword Fern is will also nibble at it throughout the year. It can be used sold at local nurseries, and you can plant it in any shady by wildlife in other ways. Black Bears will use the fronds spot with moist, well-drained, fertile soil. You can also to line their winter dens. The masses of live and dead grow Western Sword Fern from a piece of rhizome. Whole fronds provide excellent cover for small creatures, such as plants transplant well, but keep in mind that larger plants salamanders, that dwell on the forest floor. have extensive, fibrous roots that are difficult to excavate. Some industrious gardeners propagate them from spores. Western Sword Fern keeps our forests floors lush and It’s a time-consuming process, but it can produce a big green, even during the coldest and dreariest winter days. crop of young ferns. Maybe you have a place like Forest Dell Park in your neighborhood, or take a trip to a fern-lined hiking trail. Its uses extend beyond gardening. People make holiday Plant a fern in your yard, or just enjoy this fern that is not wreaths with it, and florists use the deep green fronds in only an iconic feature of the Northwest’s landscape, but is their arrangements. Historically, some Native Americans lovely and fascinating as well. ó

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Western Sword Fern

Sword fern has simple fronds that are once divided, or pinnate. It’s a characteristic shared with Licorice Fern and Deer Fern.

Lady Fern

Many of our other ferns, like this Lady Fern, are twice or three times pinnate.

Deer Fern

The young fronds of Deer Fern have a uniform, coiled fiddlehead shape. Western Sword Fern

The sword fern is so named because the shape of the leaflet, or pinna, resembles a sword, with a widened base that looks like the sword’s hilt. Pictured here is a leaflet from a mature plant, which has a finely serrated edge.

Western Sword Fern

The young fronds of sword fern unfurl in a loose and irregular fashion. Western Sword Fern

Licorice Fern

Sword fern leaflets are connected to the frond stalk at a single point. Sword fern tends to grow on the ground. The bases of Licorice Fern leaflets are so broad that they touch one another. Licorice Fern grows most often on trees.

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Pacific Wren article and photography by Lisa Millbank

Pacific Wren scampers over the gnarled root wad of a fallen tree, almost more mouse than bird. Tiny and brown, he vanishes into his shadowy world of ferns and rotting logs. But when a shaft of winter sunlight brightens the woods, he scales a mossy stump and delivers his incomparable song. The tumbling, rollicking torrent of notes is the sound of the deep forest, as much as the sound of wind in the conifers and the rush of rocky streams.

Pacific Wrens live in forests from southern Alaska through much of California, ranging east to Montana. A few small populations exist in places like the Black Hills of South Dakota, parts of Utah and Arizona. Throughout their range, many Pacific Wrens remain in the same territory or general vicinity year-round, but we know that others migrate varying distances. Those breeding in the high-elevation forests of interior British Columbia and the Cascade Range must escape the harsh winter by migrating Though drab at a glance, his rich brown plumage is southward or to coastal locations. It’s hard to imagine these dotted with fine speckles and subtle barring, and his pale little birds flying hundreds of miles, but some of them eyebrow markings give him an expressive look. His tail is certainly do. only a stub, but like most wrens, he often holds it upright. In western Oregon, Pacific Wrens start showing up in Until recently, this familiar forest dweller was known wooded city parks and riverside thickets in autumn, and as the Winter Wren. The wrens from our region, their exactly where they come from is a bit mysterious. We can grayer counterparts in eastern North America, and similar assume that some of these winter visitors are from the Eurasian wrens were all considered one species. Differences nearby Cascades, but some could be long-distance travelers in plumage, song, and habitat preference had long been from Canada. observed, but modern genetic research helped to confirm that these wrens were indeed three separate species. In Even in winter, Pacific Wrens find plenty of prey in the 2010, the American Ornithologists’ Union announced forest understory. They aren’t picky about what kind of the split, and the Pacific Wren was formally recognized. invertebrates they eat, and their diets include everything Neighborhood Naturalist, Winter 2016-17 v14 #4 • page 5

To the untrained human ear, these subtle differences are lost in the rapid-fire jumble of notes, almost too fast to comprehend. The creativity of this tiny virtuoso is not so apparent to the casual listener. Still, it’s very easy to identify Pacific Wrens by ear, since no other forest bird has such a long, fast-paced and complex song. What kind of meanings do these intricately composed songs convey to other Pacific Wrens? Much is still unknown about the function of vocal repertoires in songbirds, but it’s presumed to advertise the male’s fitness to both prospective mates and rival males. In some bird species, the size of a male’s repertoire of songs and the songs’ complexity correlate with the quality of the territory he defends. And though the female Pacific Wren doesn’t sing, she’s highly attuned to all of the elements of male song. No one knows just what she’s listening for, but it seems evident that song complexity and variety must be one of the primary factors she considers when looking for a mate. Pacific Wrens will sing year-round, but much less in winter. As trilliums and yellow violets begin to open in the forests, Pacific Wrens begin to ramp up their singing and prepare for breeding season. Like many wren species, male Pacific Wrens build multiple nests within their territories. Birders often call the unused nests “dummy nests,” but What sets them apart from all other wrens, and for they may have important functions. One possibility is that that matter, all other local songbirds, is the Pacific Wren’s peerless singing ability. Young males start off just like most other songbirds in our region, learning their songs in their first year, and spending months practicing and perfecting them. It’s also common for some songbirds to have a vocal repertoire of different songs, mostly learned from neighboring males. But the Pacific Wren takes song complexity, length and variety to the extreme. from beetles to millipedes, ticks to snails. In the winter, they’ll sometimes include seeds in their diet, perhaps when invertebrates are harder to find. The Pacific Wren’s diet closely parallels that of other wren species.

A singing male gives a 5- to 10-second burst of song, with a specific introduction and conclusion. Bird song researcher Donald Kroodsma studied Pacific Wrens in McDonald Forest, and determined that a song could consist of 100-300 separate notes. When he analyzed “song units”—the individual trills and brief whistled notes that make up the song—Kroodsma found that a male could build new song types by combining these units with introductions and conclusions. Yet the components of a song aren’t put together at random. Researcher Beatrice Van Horne recorded Pacific Wrens at Cascade Head, and concluded that specific types of song units are put together in certain sequences, and that a wren’s repertoire of songs may change over time as he incorporates new song units. A male Pacific Wren probably doesn’t have a fixed number of songs that he sings, rather, he improvises and composes according to a set of “singing rules,” utilizing his personal collection of song units.

A Pacific Wren nest of sticks and moss in a tree cavity

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they may distract nest predators, such as Douglas Squirrels, making it less likely that the real nest will be discovered, but research has not confirmed this. It’s also possible that Pacific Wrens use some of the dummy nests for roosting sites. What we do know is that the male Pacific Wren shows a prospective mate the various nests he’s built within his territory, and she’ll choose the one she likes best from among them. On occasion, a male Pacific Wren may have more than one female nesting in his territory. Early one April, Don and I witnessed a female Pacific Wren evaluating, and seemingly accepting, a nest shown to her by a male. He’d built this nest in a crevice near the base of a dead tree. When the female entered the nest a few times, the male sang quietly nearby. As she continued to inspect the nest, the male’s excitement built until he could barely contain himself. He danced and quivered on a branch, flapping his wings, while spreading his stubby tail and waving it from side to side. He paused to collect moss from a tree trunk, possibly as part of his display. Watch a video and listen to the sounds of the Pacific Wren www.neighborhood-naturalist.com

From what we could see, the male had built this nest from uniformly-sized sticks and topped it with a moss cup. He’d placed the tiny entrance hole at the top of the cavity, just big enough to admit a wren. If the female was happy with this nest, she would take on the job of lining it with feathers or animal hair before laying eggs. Though they prefer to nest in cavities, Pacific Wrens also nest in the root wads of logs, and even create hanging nests of moss. I’ve watched a male working on a hanging nest high in a Bigleaf Maple, where a slab of moss was draped over some branches. The nest was roughly spherical, and the little fellow was busily carrying additional moss inside.

Pacific Wrens are still common birds across vast areas of forest in the Northwest, despite the negative effects that some forms of logging have on their breeding habitat. Their preferred habitat is mature or old-growth coniferous forest, but they also breed in younger forests with the right kind of understory structure. Pacific Wrens may benefit when foresters leave snags, slash piles, root wads and other woody debris in thinned forests. Take a hike through low-elevation woodland this winter, and you’re likely to hear the sharp chp! or doubled chp-chp! call notes of the Pacific Wren. When a rare sunbreak occurs, listen for the loud and unmistakable song of this little maestro, the voice of the northwestern forest. ó

The female lays 5-7 eggs and broods them for a little more than two weeks. The almost-naked hatchlings can hardly lift their heads at first, but grow very quickly on a steady diet of invertebrates. By the time they’re about 17 days old, they’re ready to leave the nest for the first time. For several weeks thereafter, the young wrens are fed by their parents as they learn to find prey on their own, and the family roosts together. Even after breeding season is over, Pacific Wrens will sometimes roost in old nests during cold weather. In some cases, they’re willing to share—on a cold night in 1924, 31 of them were found sleeping together in a nest box in Washington. Each wren probably has several roosting sites it can use depending on the temperature and other factors.

A fledgling Pacific Wren beginning to search for its own food without the help of its parents

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Willamette Valley Wrens Pacific Wren

Present year-round. Typically breeds deep in shady conifer forests. In winter, they can be found in any type of wooded area.

Bewick’s Wren

Present year-round. Fairly common, and lives in brushy habitats in open forests, parks, suburbs and in the countryside.

House Wren

Migrates here to breed. Found in forest clearings, oak savanna and the countryside; in brushy habitats near clearings.

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Marsh Wren

Found year-round in cattail marshes and dense vegetation in wetlands; less common in winter.

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