EAGLE’S ROOST NATURE TRAIL
come to your senses
The path before you is a portal to the natural world, a haven to immerse yourself in the sights, sounds, and
smells of the Lemhi River riparian corridor.
The trail is a naturally changing exhibit, different each day of the year –tranquil and reflective, yet dynamic
and vibrant with life. Along the trail, interpretive signs will guide you in discovering the many facets of a
riparian ecosystem.
The self-guided trail follows a 1/3-mile footpath along the river’s edge, gentle enough for people of all ages
and fitness levels. The nature trail connects to the main Interpretive Trail at either end.
Before proceeding, take a moment to come to your senses. Take a breath of fresh, clean air. Smell the
earthy-resin scent of the cottonwoods. See the dappled sunlight on the Lemhi River. Listen for the sparkling
song of the yellow warbler. The Eagle’s Roost Nature Trail beckons you to explore at your leisure.
OSPREY
the perfect fisherman
Ospreys are found worldwide, wintering or breeding on every continent except Antarctica. They are
the only North American raptor to feed exclusively on fish, so are closely tied to water. In Idaho,
ospreys build nests high atop trees or platforms near rivers, lakes, and reservoirs. Their bulky stick
nests can weigh up to 1,000 pounds.
Ospreys are well-equipped to capture fish. Long, curved claws and barbed pads on the soles of its
feet help it grasp slippery fish. A reversible outer toe allows the bird to seize its prey with 2 toes
forward and 2 back, providing extra stability. The osprey carries its catch head first, in a streamlined
position, to its feeding perch or nest.
Osprey pairs arrive on nesting territories in early April. The female lays an average of 3 eggs and
does most of the incubating. The male devotes his time to providing up to 6 fish per day for the
growing chicks. By early August, the chicks are fledged and learning to fish on their own. By early
September, the family has migrated south towards wintering grounds in Mexico and Central and
South America.
(Add text: L&C documented the “Fishinghawk” on their journeys, correctly noting it was the same
species that occurred in the eastern U.S. )
THE AMERICAN BEAVER
ecosystem engineer
In recent years, biologists have come to recognize certain animals as ‘keystone’ species. In the language
of architects, a ‘keystone’ is the uppermost and last stone placed in an arch that locks all other stones in
place making the structure stable and strong. In the animal kingdom, a keystone species is a species
whose abundance and ecological role has a dramatic effect on other species in an ecosystem. In North
America, the beaver is a classic keystone species.
The beaver’s ability to change the landscape is second only to humans. In a short span of time, a
beaver dam can alter a fast-running forest stream into ponds, wetlands, and meadows rich with
biodiversity. Their skills as foresters and engineers help to recharge the aquifer, purify and store water,
and prevent large-scale flooding.
Prior to 1900, an estimated 60 – 200 million beaver populated North America. Their influence once
touched every watershed on the continent. By the early 1900’s, a booming trade in beaver pelts and
wide-scale draining of wetlands for farmlands led to the near extinction of beaver.
Through decades of conservation efforts, beaver have rebounded to an estimated 10 million across the
continent. Today beaver are welcomed in many natural areas as their beneficial role as “ecosystem
engineer” is understood and appreciated.
A BIOMASS OF BUGS
whirling, buzzing, singing, chewing, vibrating with energy
Three out of four creatures on Earth are insects, so it is no wonder insects are considered the most
successful lifeform on the planet. Experts have identified more than 1 million species worldwide and
estimate there may be as many as 10 million.
Despite their small size, insects play a vital role in natural ecosystems, recycling organic matter into
soil and furnishing food for other creatures. They are important plant pollinators, bio-indicators of
environmental health, and natural enemies of harmful insect pests.
Insects supply a major source of protein for fish and wildlife in the Lemhi River corridor. Aquatic
insects, such as the mayfly and caddisfly, are favorite fare for trout and the American dipper, the
only songbird that swims to catch its dinner. The mosquito is a staple for swallows, nighthawks,
snakes, frogs, fish, dragonflies, and bats. In just one hour, a bat can catch and eat 1,200 mosquitoes!
DEAD TREES & LIVING CREATURES
beauty in the eye of the beholder
Dead and dying trees—called ‘snags’—are essential to wildlife and forests. In Idaho, about 50 species
of birds and 25 species of mammals nest or shelter in snags.
‘Primary excavators’ are birds that chisel into trees, living and dead, for nest sites. Examples are
woodpeckers and nuthatches. ‘Secondary cavity users’ are other animals, such as bluebirds, chickadees,
wrens, owls, bats, and flying squirrels, that use cavities abandoned by primary excavators.
Snags and logs are important links in the food chain. Insects infesting snags and logs become food for
birds and mammals, which become the prey of hawks, snakes, weasels, and other predators. They are
also used as communication centers for certain bird species. Northern flickers use snags as drumming
posts to declare their territory. Likewise, ruffed grouse use elevated “drumming logs” to perform their
peculiar courtship display.
THE LIFE OF A RIVER
where the only constant is change
The water coursing before you is a powerful force of change. From snow and rain captured high in the
mountains, it collects and moves as streamflow and groundwater to the Lemhi Valley floodplain.
Peak spring flows scour and till the stream channels, forming new gravel bars, pools, and riffles. Flood
waters carry fresh nutrients and sediments to nourish new seedbeds of cottonwood and willow. Without
natural flooding, the regeneration of these forests would not occur.
High spring flows transport organic debris, such as fallen trees and rootwads, which serve to anchor
streambanks and create pools and protective cover for fish. Swift currents also cool water temperatures,
increase oxygen levels, and mix essential organic matter into the food chain. These conditions favor the
unique life cycles of chinook salmon, steelhead, and other aquatic wildlife in the Lemhi River.
STEELHEAD
icon of western rivers
Of all the ocean-going fish in Idaho, the steelhead remains the most prized among anglers for its
challenging behavior and rainbow-dappled beauty. Steelhead are a native type of rainbow trout
known as ‘anadromous’—a fish born in freshwater streams that migrates to the ocean to feed and
grow, then returns to fresh water as an adult to spawn. Unlike its anadromous cousin the
chinook salmon, steelhead can spawn more than once.
In the Lemhi and Salmon rivers, steelhead spawn from mid-April to late June. With powerful
flexes of her body, the female uses her tail as a shovel to dig a nest in the river gravels. The male
fertilizes the eggs as she releases them in the nest. She swims upstream a few feet and begins
again, using the river’s current to carry gravel over the newly-deposited eggs. The series of
gravelly nests is called a ‘redd.’
The eggs hatch in early to midsummer. Young steelhead spend 2 years in their natal streams
before their 900-mile journey to the Pacific Ocean. After 1-3 years in saltwater, steelhead return
to the upper Salmon River by October and winter over to spawn the following spring.
“MESSY” HABITAT IS GOOD HABITAT
a sign of nature’s creative genius
There is a saying that “a messy desk is a sign of creative genius.” In the natural world, “messy” habitat is
indeed nature’s sign of creative genius.
Messy habitat contains many layers of trees, shrubs, grasses, and fallen wood, creating a tangle of lush
vegetation with a complex structure. All these different layers provide habitat niches to an amazing
diversity of plants and animals.
Thatchy grasses and low shrubs create nesting habitat for song sparrows. A fallen log conceals a shy
western toad. Standing dead trees house roosting bats and a family of American kestrels. Even last year’s
cattail stalks provide the perfect hunting perch for a dragonfly.
Besides housing wildlife, messy habitat feeds them as well. Leaf litter and plant stems shelter an amazing
array of insects and spiders. In turn, these tiny creatures help pollinate plants or become prey for other
wildlife.
Neat and tidy may be okay for certain human environments, but out in nature, “messy” is simply brilliant.
MEADOWS FOR MEADOWLARKS
keeping a common bird common
Few bird songs are as distinctive as the bubbling, melodic song of the western meadowlark. In Idaho, it is
a common bird of native and cultivated grasslands. Meadowlarks – and a suite of other grassland bird
species – are well-adapted to prairie life. Most are ground feeders and nesters, weaving dried grasses into
bowls hidden among larger grass clumps for shelter and camouflage.
During the past quarter century, grassland birds have experienced more widespread population declines
than any other North American bird guild. Declines are attributed to habitat loss and fragmentation from
urban development, conversion of native grassland to cropland, forest encroachment, and early and midseason cutting of hayfields.
In the Lemhi Valley, pastures and hayfields have long replaced the native grasslands. But these private
ranchlands continue to provide critically important breeding habitat for northern harriers, sandhill cranes,
Wilson’s snipe, short-eared owls, savannah sparrows, and the locally rare bobolink.
Keeping common birds common, like the meadowlark, means supporting conservation programs that
benefit our local ranchers and farmers.
RESERVOIRS OF LIFE
off-channel habitat
Off-channel habitat refers to ponds, sloughs, oxbows, wetlands, and other backwater areas within a
river’s floodplain that connect to the main channel.
Protected from the swift current of the Lemhi River, this quiet slough is a bountiful oasis of plant and
animal life. Dense wetland vegetation slows and filters surface and ground water, trapping sediments
and nutrients, which in turn enrich the food chain.
Shallow freshwater ponds create ideal nurseries for invertebrates, fish, and amphibians, such as the
spotted frog and western toad. By summer, the nurseries become teeming cafeterias for hungry belted
kingfishers, mink, raccoons, and great blue herons. Millions of hatching insects are gleaned on the wing
by swallows, flycatchers, and bats.
Because of their abundant plant and animal life, wetlands also attract people.
RIBBONS OF GREEN AND GOLD
cottonwood forests – overflowing with biodiversity
From fluffy white seeds the size of a rice grain grew the towering cottonwood trees before you. These forest
elders have survived floods, scouring winter ice flows, livestock and wildlife grazing, fire, disease, and beaver
pruning. The one thing cottonwoods could not survive without is water.
Cottonwood forests grow in riparian areas – the land immediately surrounding creeks, streams, rivers, and
wetlands where vegetation is strongly influenced by the presence of water. In the arid Intermountain West,
riparian areas comprise less than 1% of the landscape, but they are the single most productive type of habitat,
benefiting the majority of Idaho’s wild species, from amphibians to elk.
Nearly half of Idaho’s 242 species of breeding birds use riparian areas as their primary nesting habitat.
Cottonwood forests, in particular, offer “high-rise” habitat for canopy- and cavity-nesting birds. These luxuriant
corridors act like a web across the landscape, to link patches of critical habitat along migration routes.
CHINOOK SALMON
an arduous journey to the ocean and back
One of nature’s most remarkable migrations happens in the river channel before you. In early spring,
year-old chinook “smolts” born in the upper Lemhi River begin a 900-mile journey to the ocean. On the
way, their physiology changes so they can live in salt water.
When the rivers of the Columbia River Basin were running free, Lemhi River smolts could reach the sea in
about 8 days. Today, their journey lasts several months as they navigate past 8 huge dams. The smolts
spend 1-3 years feeding in the food-rich waters of the Pacific Ocean.
Triggered by maturity, genetics, and day length, adult salmon begin their migration to natal waters.
Through a mysterious process known as homing, adult salmon cue on a trail of familiar scents to their
home stream. On this return trip, their bodies undergo radical changes to acclimate to fresh water and
prepare for spawning.
In May, adult chinook migrate upstream past this very spot to their spawning grounds in the mountain
streams of the Lemhi Basin – an 1,800-mile arduous trek to complete their life cycle.
EAGLE’S ROOST NATURE TRAIL
come to your senses
The path before you is a portal to the natural world, a haven to immerse yourself in the sights, sounds, and
smells of the Lemhi River riparian corridor.
The trail is a naturally changing exhibit, different each day of the year –tranquil and reflective, yet dynamic
and vibrant with life. Along the trail, interpretive signs will guide you in discovering the many facets of a
riparian ecosystem.
The self-guided trail follows a 1/3-mile footpath along the river’s edge, gentle enough for people of all ages
and fitness levels. The nature trail connects to the main Interpretive Trail at either end.
Before proceeding, take a moment to come to your senses. Take a breath of fresh, clean air. Smell the
earthy-resin scent of the cottonwoods. See the dappled sunlight on the Lemhi River. Listen for the sparkling
song of the yellow warbler. The Eagle’s Roost Nature Trail beckons you to explore at your leisure.