Autumn Leaf Color Change

Click for a closer view of Fall color in Logan Canyon, Courtesy and Copyright Linda Kervin
Fall color in Logan Canyon
Courtesy & Copyright 2007 Linda Kervin

In autumn, the days shorten noticeably and chilly dawns become the norm across most of Utah. Leafy plants now prepare for winter. Their summer of intense metabolic activities gradually give way to winter’s dormancy. Photosynthesis and respiration shut down as nutrients and sugars are withdrawn from leaves, to be shunted to the stem and roots for storage. But how do they anticipate the change in seasons so that they are ready for the rigors of winter?

Photosynthetic plants have a diverse array of pigments that they use to capture energy from most of the spectrum of visible sunlight. Chlorophyll is the most abundant, but its light gathering effectiveness is limited to a narrow band of the light spectrum. Plants employ many additional pigments to capture the energy available from other wavelengths of sunlight. These accessory pigments are brilliantly colored but masked by the sheer abundance of green chlorophyll.

Click for a closer view of Fall color in Logan Canyon, Courtesy and Copyright Linda Kervin
Fall color in Logan Canyon
Courtesy & Copyright 2007 Linda Kervin

One of these pigments, phytochrome, serves as a timekeeper for the plant. When phytochrome absorbs energy in the red band of sunlight, it helps to activate a number of developmental processes in the plant. As the nights lengthen in the fall, there are fewer hours of sunlight to activate the phytochrome and so it transforms to inhibit those same developmental processes.

One result is that chlorophyll is broken down and its components are moved to storage for use in the following spring. Essential nutrients, such as nitrogen and phosphorus, are likewise withdrawn from foliage for later use. With chlorophyll gone, the other colorful leaf pigments are revealed. Now maples, aspens, sumacs and more blaze for a few weeks of riotous glory.

This is Linda Kervin for Bridgerland Audubon Society.


Photos: Courtesy & Copyright Linda Kervin

Text: Linda Kervin and Jim Cane, Bridgerland Audubon Society

Additional Reading:

Chemistry of Autumn Leaf Color, How Fall Colors Work, Chemistry,

Why Do Leaves Change Color in the Fall?, Anne Marie Helmenstine, Ph.D., Chemistry,

“Autumn: a season of change” (2000) by Peter J. Marchand,

Where to see autumn leaves in Utah:

  • U.S. 89, Logan Canyon, Brigham City to Logan, Logan to Bear Lake
  • State Route 39, Monte Christo Summit, east of Huntsville
  • State Route 190, Big Cottonwood Canyon, east of Salt Lake City, including Guardsman Pass
  • State Route 210, Little Cottonwood Canyon, east of Salt Lake City
  • State Route 92, the Mount Timpanogos loop a.k.a. the Alpine loop, north, east of Provo
  • State Route 150, the Mirror Lake road, east of Kamas
  • U.S. 40, Daniels Summit, east of Heber City
  • Vernal, Red Cloud Loop (See
  • Flaming Gorge – Unitas, State Route 191 and State Route 44
  • State Route 132 Payson to Nephi, the Nebo Loop
  • State Route 31, the Wasatch Plateau, east of Fairview
  • State Route 12, over Boulder Mountain, between Torrey and Boulder (likely the most spectacular of all)
  • The La Sal Mountain loop, east of Moab
  • The Abajo Mountain loop, west of Monticello
  • The canyons of the Escalante River, Grand Staircase-Escalante National Monument, southeast of Escalante

List sources:
Aspens and Fall Foliage in Utah, Jeffrey Otis Schmerker, 2001,

Ogden Valley Business Association,

Fall Colors Tour, Utah in the Fall is a blast of color!,

National Forest Fall Color Hotline, 1-800-354-4595,

Nesting Season

Lark Sparrow Nest, Courtesy & Copyright © Jim Cane, Photographer
Lark Sparrow Nest, June
Courtesy & © Copyright
Jim Cane, Photographer 

While we swelter in summer’s heat, the southward shorebird migration has begun. But some songbirds find this a perfect time to nest. We think of spring as nesting season and for the majority of birds it is. But there are some birds nesting almost year round in Utah.

Living organisms are impelled to maximize the number of successful offspring they produce. Therefore, they tend to reproduce during times of plenty, because the breeding season is strenuous. Males compete for mates and territory and females produce eggs. Both parents may guard the nest from predators and feed the young. Many birds feed nutrient rich insects to their nestlings so nesting season is timed to coincide with the greatest abundance of insects, usually spring in temperate and arctic climes.

American and Lesser Goldfinches are one example of birds who do things differently. (Lesser Goldfinch. Kevin Colver: Songbirds of the Southwest Canyon Country) Instead of insects, they feed their young a regurgitated milky seed pulp. Therefore, they time their nesting for greatest abundance of seeds, especially sunflower and thistle, which is in the summer.

Other birds prefer one type of nut. These include Pinon Jays and crossbills. Abundant pinon nuts trigger Pinon Jay nesting. (Pinon Jay. Kevin Colver: Songbirds of the Southwest Canyon Country) If they have enough nuts cached from the previous season, they will nest in late winter, even while snow blankets the landscape. In years with a bumper crop of pinon nuts, they will also breed in late summer to take advantage of the plentiful food. Good conifer cone crops determine when and where crossbills nest, which can be almost any time.

Great-horned Owls are one of the first to nest each year. (Great-horned Owl. Kevin Colver: Songbirds of the Southwest Canyon Country) You can hear courting pairs hoot back and forth in midwinter. They may incubate their eggs while covered in snow, and if the temperature is too frigid, the eggs freeze and the young die. Many predatory birds nest early, perhaps to insure that the young learn how to proficiently hunt before winter.

The drive to reproduce is inviolable and birds take advantage of whatever season gives them the greatest chance for success. For every nesting bird there is a season.

Thanks to Kevin Colver for the use of his bird recordings.

This is Linda Kervin for Bridgerland Audubon Society and Wild About Utah.

Images: Jim Cane, Bridgerland Audubon Society
Audio: Kevin Colver,
Text: Linda Kervin, Bridgerland Audubon Society

Additional Reading:

Gardening for Hummingbirds

Heuchera, hummingbird host. Courtesy and Copyright Jim Cane, Photographer
Courtesy & © Jim Cane, Photographer

Penstemon hummingbird host Courtesy and Copyright Jim Cane, PhotographerPenstemon eatonii
Courtesy & © Jim Cane, Photographer


At long last, summer has returned as have the hummingbirds who zip around my garden, visiting flowers and chasing off intruders. (Kevin Colver: Songbirds of Rocky Mountain Foothills. Broad-tailed Hummingbird) Hummingbirds are a delight in the yard and so we plant flowers specifically to attract and feed them. In general, hummingbirds prefer long tubular flowers especially those that are red, orange or violet. But not all these flowers are created equally.

Hummingbirds visit flowers for their nectar which fuels their flight. Their long tongue reaches well beyond the tip of their needle like bill when they lap up nectar; capillary action then draws the sweet liquid up tiny grooves along the length of the tongue.

Floral nectar evolved to attract potential pollinators. The floral nectary is generally found inside the flower, at the base. When probing for nectar, floral visitors brush by the reproductive structures. Pollen adheres to parts of their body and then at the next flower of the same species, some pollen sticks to the female stigma. This transfer is pollination.

Many nectar-rich flowers grow well in Utah gardens. In the xeric garden, Penstemons are a good choice, as are Red Hot Pokers and Zauschneria, sometimes called Hummingbird Trumpet. In more moist sites, red flowered Heuchera is popular. Some red flowered cacti and Trumpet Creeper are good choices, as are Agastache and many Salvias.

Watch which flowers hummers visit. They will check out many blooms, but the ones they routinely return to are the ones yielding generous nectar. Many flowers produce little or no nectar, including some that look to us like good hummingbird flowers. Also, many horticultural hybrids and doubled flowers produce paltry amounts of nectar.

To encourage hummingbirds to remain in your garden, you can grow trees and shrubs for cover. Nectar is only part of their diet. For protein, they regularly eat insects and spiders small enough for their tiny bill so a garden free of insects is not desirable. They also appreciate a place to perch where they can digest, wait for a tasty insect to fly by and keep an eye out for potential rivals. So grab your trowel and lets feed those hummers.(Kevin Cover: Songbirds of Rocky Mountain Foothills. Broad-tailed Hummingbird)

This is Linda Kervin for Bridgerland Audubon Society.


Images: Courtesy
Text: Linda Kervin, Bridgerland Audubon Society

Additional Reading:

Hummingbirds and How to Attract Them, Washington Department of Fish & Wildlife,

Hummingbirds 101, The Hummingbird Society,

Coro Arizmendi Arriaga, Maria del, Hummingbirds of
Mexico and North America, In Spanish and English, CONABIO, 2014,

Medusahead Rye

Medusahead Rye Infestation
Courtesy and
Copyright © Steve Dewey

Courtesy and
Copyright © Steve Dewey

Courtesy and
Copyright © Steve Dewey

Weedy plants of old world origin threaten natural areas throughout the United States. An invading plant colonizing a completely new area often lacks the insects, diseases and herbivores that kept it in check back in its native homeland. If the introduced plant grows and spreads vigorously, it can spell disaster for the native inhabitants of its new home. With no natural controls in place, it may outcompete native plants and greatly diminish biodiversity. Disturbed or degraded habitats are most susceptible to invasion by Eurasian weeds.

Utah hosts many invasive weeds causing problems throughout the state. One Eurasian grass threatening sagebrush habitat and rangeland is medusahead rye. Medusahead rye probably came to the United States as a seed contaminant in the 1880’s. The seed head is heavy, so on its own, cannot spread far. But the seeds do have a ticket for dispersal: tufted hairs which cling and readily attach to livestock and vehicles. Once on site, medusahead grows vigorously, crowding out other plants.

Medusahead tissue contains abundant silica which slows its decomposition. The accumulation of dead material forms a dense thatch that smothers other plants. This dry thatch layer can also fuel wildfires. In addition, the gritty silica makes medusahead unpalatable, so both domestic and wild grazing animals avoid eating it. Infested ranches can lose 3/4 of their grazing capacity.

Sage grouse are already in trouble due to habitat loss, and medusahead has invaded more than 10 million acres of the sage brush that sage grouse call home. Once invaded by medusahead, sagebrush habitat is very difficult to restore. The best hope is to prevent or at least hinder its spread through management using controlled burns, herbicides and careful grazing. Non-native, invasive plants are among the most serious threats to our natural world and the habitats and species we know and love.

This is Linda Kervin for Bridgerland Audubon Society.


Images: Courtesy Steve Dewey &
Center for Invasive Species and Ecosystem Health, University of Georgia
Text: Linda Kervin, Bridgerland Audubon Society

Additional Reading:

The United States National Arboretum. formerly

National Invasive Species Information Center.

Forest Service Employees for Environmental Ethics.

Utah State University Cooperative Extension.