What are “vernal pools”?

I am originally from California, but I had never heard of them until recently, and yet they are (or were) omnipresent in the range/grasslands throughout the Central Valley of California. What are they? Well, we learned all about them on our field trip to the Merced Vernal Pools and Grassland Reserve at the University of California-Merced, thanks to Chris Swarth, former Director of the Reserve.

Canada Geese graze at the edge of one long pool that still has a few flowers blooming.

Vernal pools are unique, ephemeral ecosystems that develop in the spring where winter rains puddle in grass and range lands that have a hard clay pan impermeable to water drainage below the soil surface. Pools can range in size from several feet to several acres, and in depth from several inches to a foot or more.

As the water evaporates from the pool, a unique ecosystem blooms (literally) and develops with a complex food web of protozoans, diverse species of invertebrates, and plants that draws amphibians, birds, and mammals to it until it dries up in mid-summer, and becomes quiescent and dormant until the next winter rains.

This particular pool had a dense mat of coyote thistle growing around the edge and mossy looking plants and small yellow flowers called Goldfields in the center.

Coyote thistle is a spiky plant with purple tinged flowers, and looks just like a miniature thistle.

A dense mat of Goldfields filled the center of this pool, with a lone, lilac-colored Sidalcea flower still blooming. More than 30 common grasses, sedges, and flowering annuals are endemic to central California’s vernal pools (found nowhere else).

Vernal pools can actually thrive in a rangeland where cattle walk through them, creating little microcosms of deeper mini-pools within the larger pool. There, small communities of pool fauna and flora can flourish longer before drying out. However, estimates of 50-80 % of historic vernal pool habitat has been lost when rangeland has been converted to agriculture.

Yellow mariposa lilies were blooming at the edge of this vernal pool.

It looks like a poppy, but it’s a lily, Calochortus luteus.

Horned Larks were common everywhere on this grassland, and we heard and saw Western Meadowlarks as well.

Ground squirrels are probably numerous, but we only saw one, shyly peaking out from the grass flower spikes.

Looking at this scene, you might think it’s just a sea of grass transected by a few ATV trails, but differences in the underlying soil layers makes the rangeland a patchwork of pools and grass.

Stock pods are man-made and hold water much longer than the vernal pools.

I’m told that rangelands are so extensive in this particular part of the Central Valley of California (near Merced) that it’s possible to ride/walk through them from the area in this photo to Yosemite Park whose snowy mountain tops you can just barely see in the distance! It’s refreshing to be in the middle of such a tranquil landscape of waving grasses as far as one can see.

Earth day 2024 — challenges and hope

It’s easy to be cynical about the multitude of challenges to sustaining life on earth, but there are promising steps toward meeting some of those challenges, and today is a good day to think about them.  I posted some of the blog below back in 2016, but the message is even more important today, on Earth Day 2024, when we should stop and reflect on how we impact our world.

Things we worry about — illustrated by photos from past blog postings

Warming climate, rising sea levels, and disappearing coastlines directly threaten human habitation, as well as that of wildlife in those areas.

Violent weather: tornadoes, hurricanes, and thunderstorms with high winds threaten people and wildlife.

Lack of winter snowpack reduces the spring/summer water flow in rivers necessary for grassland and desert plants and wildlife to prosper.

Changes in rainfall and river flow impact fish and invertebrate populations and the wildlife dependent on them. 

Rising average air temperatures make the local climate unsuitable for plants (and animals). For example, the Cape Floral Kingdom at the tip of South Africa is doomed if temperatures rise much because there is no more southerly retreat for them.

Rising ocean temperatures, coupled with increased acidity of ocean water due to higher CO2 content threaten invertebrates, such as coral.  Coral bleaching (due to the loss of their symbiotic algae) has increased dramatically in reefs all over the world in the last decade.

Habitat loss, as more acreage is converted to farmland, impacts wildlife and native plants, resulting in local extinctions.

Changes in weather patterns affect crop harvest and food production.

The consequences of our actions threaten all life on earth if they are not corrected.  In my lifetime I have seen the corrections being made, albeit perhaps too slowly:  recycling materials, conserving water, “green energy” technology to reduce carbon dioxide release, reducing chemicals, pesticides, fertilizers, etc. released to the environment, reducing air pollution (I grew up in the smog-filled Los Angeles basin in the 1950’s when it was really hard to breathe in the summer). 

A new day, another chance to correct our impact on Mother Earth.

We don’t have to wait for technology and policy to solve our environmental problems.  Not just today on Earth Day, but every day, let’s think about the global consequences of our local actions so we can be a part of the solution to these challenges.

The Rio that is no longer so Grande

The Rio Grande is the fourth-longest river in North America and runs almost 1900 miles from its origin in south-central Colorado through the cities of Albuquerque and El Paso across the Chihuahuan desert in northern and central Texas to its mouth near Brownsville, Texas, where it flows (or not) into the Gulf of Mexico. I visited that area near South Padre Island in January 2017, and was amazed at how little water there was in the “grand river”.

The narrow strip of water behind the white pelicans and gulls standing on the sand spit is the Rio Grande River emptying into the Gulf of Mexico! You can just barely see the waves of the Gulf waters where the river enters. The sandy hill beyond the river is, of course, Mexico. Photographed Jan, 2017.

Since the mid-20th century, only about 20% of the Rio Grande water reaches the Gulf of Mexico and in some years (e.g., 2000), no water flows to the Gulf at all. This is largely a result of water taken out for irrigation of farmland in Colorado and Texas and water supplied to large cities along its route, along with climate changes in the amount of precipitation.

According to my phone’s GPS, I am standing in the middle of the Rio Grande, right on the U.S.-Mexico border!

But in traveling through the arid landscape of the Chihuahuan desert in Texas in mid-winter this year, we were still able to see what the historic power of this river had carved along some of its routes in Big Bend National and State Parks.

Much of the river topography is rolling hills surrounding the river valley. In some areas, there is enough water to support a grove of cottonwoods.

In places, the river valley is surrounded by 1000-foot limestone cliffs. Grasses and willows line the sides of the river bank.

Typical topography along the Rio Grande in southern Texas

Side canyons with steep walls attest to the powerful action of the water cutting through the limestone.

A view into one of the narrow canyons along the river in the Big Bend Ranch State Park. Santa Elena Canyon is popular with canoers for its scenic beauty.

With so little water in the river and in such a drought-prone landscape, you might expect there would be little wildlife. However, Audubon’s bird inventories of the park show that more than 150 bird species spend the winter in some parts of the park. Much to our surprise, we saw at least one Roadrunner a day, (and an amazing seven of them one day) along with many other brilliantly-colored and new birds for the trip.

A pair of Roadrunners canvassed the grounds of the Cottonwood campground in the state park.

Vermillion flycatchers hunt for flying insects near water. Southern Texas is at the northern edge of their winter range.

Golden-fronted Woodpeckers, with their bright orange and red head feathers, can only be found in south and central Texas in the U.S., the northern edge of their range. Unlike most woodpeckers, these birds consume as much fruit and nuts as they do insects.

Black-tailed Gnatcatchers inhabit the driest desert scrubland in the southwestern U.S., finding enough insects there to sustain themselves without needing much water.

Rock Wrens are insect and spider specialists in the driest deserts of the southwestern U.S., finding enough food in the nooks and crannies of rocks to allow them to be completely independent of water.

Say’s Phoebes are flycatchers, hunting insects from a perch and darting out to catch them. South Texas is the northern extent of their winter range; they migrate as far north as central Canada to breed.

White-winged Doves spend the winter in Mexico and Central America, except for a small area of the Rio Grande Valley in Big Bend National Park. They can be found in brushy thickets in the desert, but are most fond of dining on the nectar, pollen, fruit, and seeds of the Saguaro cactus in the Sonoran desert.

A new bird for us was the Rufous-crowned Sparrow, a chunky-bodied sparrow with a long tail and a handsome face. The species has a very disjunct distribution, occurring along the coastal areas of California, central Texas, parts of southern Arizona and New Mexico, and the grassy slopes of the eastern and western sides of the Sierra Madre in Mexico. Hot, rocky hillsides are their preferred sites for foraging for seeds.

Ay, Chihuahua!

Literally, Oh! Chihuahua!, as in to be impressed, or terrified, or surprised by the amazing expanse and diversity of North America’s largest desert. The expression probably originated with early Spanish explorers who were cautioning others to beware of the Chihuahuan desert area and the Apaches that lived there.

The Chihuahuan desert is indeed a great expanse, extending 900 miles from Albuquerque to just north of Mexico City. It also consists of a great variety of different land formations in typical basin and range topography: broad desert valleys (basins) bordered by mesas and mountains (ranges). Medium elevation of 1000-6000 feet keeps both summer and winter days cooler than one would expect in a desert climate. Summer rains from the Gulf of Mexico monsoons provide some moisture.

Desert valley floor: prickly pear-type cactus and widely spaced creosote bushes dominate the landscape.

A little higher elevation and Yucca species mix in with cactus. There is more grass here – a great place for antelope.

In the mountain foothills, oak and juniper are added to the mix of cactus, low shrubs, and grasses.

Montane areas used to be heavily forested, with streams running down into the lower grasslands. But the hillsides were logged, and the drier microclimate makes this area suitable for just pines, junipers, oaks, and cactus.

As a result of this climatic diversity, the Chihuahuan desert has a remarkable diversity of plants and animals. For example, more than 20 species of mammals can be found throughout the Chihuahuan desert area: mule deer, pronghorn, bighorn sheep, coyote, grey fox, even wolves, in addition to jaguar, puma, bobcat, javelina, bison, skunk, coati, jackrabbits, and many species of small rodents. Driving through the area in the dead of winter, you wonder how there could possibly be that much diversity, but the landscape will change dramatically when the rains come.

It’s just mid-February, but the Texas Bluebonnets are already blooming. More wildflowers will add to the mix of roadside blooms when spring arrives.

We were not lucky enough to see all the mammalian diversity that inhabits this desert area, but here’s what we could perhaps expect to see on another visit.

Pronghorn antelope in grassy areas of the valleys.

Mule deer and White-tailed deer in the tall grasses and woodland areas.

Bighorn Sheep in the rocky outcrops and montane cliffs

Coyotes live just about everywhere. This one was a roadside coyote that might have been waiting for handouts from tourists, or it might have been sick.

Black-tailed Jackrabbits are wonderfully adapted to desert heat, with their huge big ears for radiating body heat to any cooler object they might sit near or under.

Several other large mammals used to be present in the Chihuahuan desert but were extirpated in the U.S. when large ranches were established in Texas, New Mexico, and Arizona in the 1900s. Jaguars, pumas, bobcats, even a smaller version of the gray wolf, called the Mexican Wolf, were originally part of the Chihuahuan fauna. Imagine being able to see these animals there today.

Jaguars once ranged throughout the Chihuahuan desert area all the way into southern South America. But today they have a much more tropical distribution in South America. Jaguars are the largest cat species in the Americas, and the third largest cat in the world, with a bite so strong they can pierce the shells of tortoises and the skulls of their mammalian prey, killing them instantly. This one was photographed in the Pantanal of southern Brazil.

Cougar, mountain lion, panther, or puma are widely distributed from the Yukon, across the U.S. to the tip of South America. Their diverse diet contributes to their success in a variety of habitats throughout their range; they might prefer large ungulates like deer in one habitat, capybara rodents in another, but will also eat mice, beaver, hares, raccoons, wild donkeys, etc. — basically, anything they can pounce on and kill. (Photo by Debbie Reynolds from Argentina)

Like cougars, wolves in North America are wide-ranging animals, that have spread from Asia into a variety of environments in the U.S. and Canada and become somewhat specialized to live there. Mexican wolves filled the top canid carnivore role in the Chihuahuan desert but were hunted to extinction in the U.S. Several of them were captured in Mexico in the 1970s and sent to the U.S. to start a captive breeding program. Generations later, their descendants have been reintroduced in parts of Arizona and New Mexico, and their numbers have slowly been increasing. Some were even sent back to Mexico because the population of wolves there had become very rare. However, there are less than 400 of them in the wild today.

Mexican Wolves are the smallest of the Gray Wolf sub-species, but their gene pool shows evidence of past hybridization with other gray wolves, coyotes, and possibly dogs. The conservation plan for these animals is complex.

One important feature of the Chihuahuan desert area to note is that it spans two countries, between which, historically, wildlife moved freely. At least this was true before there was a huge barrier erected between the two countries. The Wall does more than limit human movement. It prohibits the exchange of wildlife (and thus gene flow) necessary to sustain vibrant communities in both places, and it limits animals from moving north toward cooler climates in an era of record-setting heat waves year after year.

A view of The Wall running off into the distance from the Coronado National Memorial south of Sierra Vista, Arizona.

Close-up of the previous image

The Wall near Sasabe, AZ separates Mexican and American houses just a few yards apart.

How will this 700+ mile long structure impact wildlife in the Chihuahuan desert? Time will tell.

A walk in the canyon

We spent some time hiking in Ramsey Canyon, a Nature Conservancy preserve in southern Arizona near the city of Sierra Vista. This preserve is a unique and interesting place because it is located at the intersection of Sonoran and Chihuahan deserts and the junction of the Rocky Mountains with the Sierra Madre of Mexico. As a result, the preserve has representatives of all of these communities in one place.

The remains of a cabin of an early settler in the canyon.

The trees lining the creek bed shade the trail and provide a cool respite from summer heat. On this winter day after a recent snowfall here, the temperature was quite chilly.

The canyon is an elongate creek bed lined with shady sycamores, oaks, and maples and steep hillsides lined with pines, cacti, and yucca. And it has the added attraction of a very nice bed and breakfast right next door to the preserve.

The canyon hillsides can be quite dry and hot with full sun exposure.

Picturesque scenes along the creek are everywhere on the trail up the canyon.

When the creek is running, there are small waterfalls.

Birds are common all along the canyon trail in the spring and summer, but it was quiet on this cool, wintry day. Everyone’s favorite spring and summer inhabitant of the canyons of southern Arizona — the Elegant Trogon from Cave Creek Canyon.

Coatis (raccoon relatives), like many other visitors to and inhabitants of the canyons of southern Arizona, have expanded their range northward from central and South America into similar habitats in the brushy slopes and wooded areas of the Arizona canyons. (Photo by Debbie Reynolds.)

A delightful place to visit, and to support the work of The Nature Conservancy: “Together, we find a way” to preserve our world.

A Crane-derful morning

A return visit to Whitewater Draw in the Sulfur Springs valley of southern Arizona was just as exciting as the first time we visited. Once again several thousand cranes were bunched in groups around lagoons of the Rio de Agua Prieta. It’s a photographer’s dream just to stand and watch as groups of cranes break off from one area, circle in the sky, and drop down into another area, while croaking their unmistakable, prehistoric rattling bugle.

A unique formation for the fly-in.

We watched the cranes fly around for a couple of hours in the morning, then took a break for a picnic lunch, and when we returned to the lagoons, the cranes were having a mid-day break. Most of them were gathered around one edge of the lagoon in a long line. Some were sipping water, some were grooming, some were standing still as statues, but the scene was entirely different than the early morning.

Mid-day gathering at the waterhole…

Crane statues

Like most birds, cranes dip their beaks and fill their mouths with water, then tip their heads back to let the water run down their throats.

And there was very little vocalization, unlike during the morning hours. But here is one bird making some sort of announcement.

Weather drama in the grasslands

On our first visit to Buenos Aires national wildlife refuge in southern Arizona last February, we saw lots of wildlife with little effort. But the weather this year could not have been more different than last year. Cold wind kept most of the birds from appearing, and even after driving every road open to the public we never found the pronghorn antelope that are so commonly observed near the public roads.

Where are all the ducks? Where are the deer and antelope that come to this pond to drink?

At least one little bird didn’t mind the change in weather. We’ve been lucky to find Soras, members of the rail family, in this little marshy pond near the entrance of the refuge, both times we’ve visited here. These small marsh inhabitants are usually quite secretive as they probe for seeds, insects, and vegetation among the tall stems of marsh plants.

On this cold, windy day, animals were scarce. The scenery was beautiful, if a little stark with just grass and distant mountains.

A stately adult Red-tailed Hawk patiently perched on a snag, buffeted at times by wind, and really didn’t want to leave its perch.

A female Northern Harrier, as always, flew away from us.

As it turns out, the wildlife at the refuge were good predictors of the coming stormy weather, because it snowed overnight, and morning temperatures the next day were in the low 30s F. Although the dirt roads were soft and slippery, we drove back to the refuge anyway, and finally found the antelope and the deer, as well as some dramatic winter landscapes.

Snowy peaks and storm clouds made dramatic landscapes.

We found a few white-tailed deer late in the afternoon near the road.

A little sun broke through the thick storm clouds and lit up the grassy area where the pronghorn were foraging.

But the weather wasn’t done with us yet. The atmospheric river that hit Southern California in early February was probably responsible for the snowy, stormy weather that followed us in Arizona.

Sonoran desert sights

The Sonoran desert in southwestern Arizona is hot, but amazingly diverse in plant life because it receives two periods of rainfall annually and it provides subtropical warmth in the winter. In fact, some of the cacti growing in Organ Pipe National Monument on the U.S.-Mexican border can’t survive freezing temperatures.

A landscape of cacti, palo verde trees, and creosote bushes — the plants are so closely spaced it looks like a thorny subtropical forest.

Mid-winter rain makes the desert green and lush looking.

The dominant cacti are the spiny cholla (left), the tall, columnar saguaro, and the multi-stemmed Organ Pipe, which only grows here, in the U.S, but is also found across the border in Mexico.

They are well-named since their bunched, stout columns resemble the pipes of an organ. The multiple columns arise from a common stem and each stem continues to elongate over time with some reaching heights of 20-30 feet.

Two new stems are growing from the base on this plant, but it will take them several decades to reach the height where they will have flowers. Organ Pipe cacti are very slow growing and typically mature and flower only after 100 years of growth.

An interesting feature of plant growth in the Sonoran desert is the role of “nurse” plants, which are well developed trees or cacti that provide shade and protection for other young plants. You can see an Organ Pipe Cactus growing up through the shade of a Palo Verde tree on the right side of the photo, and an Ocotillo plant growing up next to an Organ Pipe Cactus in the center of the image.

Even with all the diversity of plant life in the Sonoran desert, climate is a challenge for birds and other animals, especially during the hot summer. By far the most numerous birds we saw while driving through the desert in mid-winter were the Ravens, which seem to be able to tolerate the climate and seasonal food scarcity extremely well.

Birds in the desert

Actually, we’re not seeing a lot of birds in the desert on this trip: it’s winter (food is scarce), and it’s cold! Cold enough to snow—I.e., it’s warmer in Minnesota than in Arizona right now. We have braved walking around in the rain, sleet, snow, and strong winds trying to find the birds, but they are too smart to come out to greet us in this weather. 

The Mojave desert is an intimidating place — extreme heat in the summer and extreme cold in the winter. What a challenge for a small, warm-blooded animal to exist there. How do birds manage?

The variety of plants in the Mojave desert provide many different hiding and roosting spots for small animals, and their leaves and fruits are a source of food for many birds and small mammals.

Cholla is a scary-looking plant. Its small, jointed lobes can easily break off and adhere to a careless passer-by, but it offers protection from predation to birds that nest in it, like Cactus Wrens and Thrashers. Fruit ripening on the tips of the branches are a food source for some animals.

Bladderpod is a medium-large shrub that offers some shade from desert heat. The leaves emit a pungent odor to deter herbivores from munching on it, but the flowers have lots of nectar.

On a warmer, sunnier day, we might have seen quite a variety of birds in the Mojave desert. These desert species are champions of water conservation, using scanty water resources, finding food, and building or finding protection from heat and/or cold.

Gambel Quail eat primarily seeds, but seek out succulent green vegetation and dewy leaves in the early morning hours as a source of water. They can fly to distant water holes to replenish their body water, when they get heat stressed or dehydrated.

Black-throated Sparrows can survive without access to standing water on just a seed diet. Fat-rich seeds provide a gram of water for every gram of fat metabolized, and they excrete a dry paste which also saves them some water. They supplement their seed diet with juicy insects when they are available.

Cactus wrens can also live in areas without free water available, but they eat mostly insects, fruits, and succulent vegetation to obtain enough water daily.

Verdins are tiny, distant relatives of chickadees and are primarily insectivorous, but they supplement their diet with fruit and nectar when it’s available. Verdins build a globular nest of thorns and dry leaves in thorny shrubs that they use for both raising their chicks and for a retreat from the hot midday sun in the summer or the cold days in winter.

Curve-billed Thrashers are not fussy eaters. They eat insects when available, and consume fruit and nectar or succulent vegetation and new leaves to balance their water budget. Almost all Curve-billed Thrashers build their nests in Cholla cacti, where the spines of the plant offer both protection from predators and shade in the middle of the day.

After the storms, a little sun…

And then more rain, but in the meantime, we took some walks along the beach in Cambria and at Morro Rock. When the sun comes out, so do the animals.

Morning light from the sunrise reflecting on the ocean clouds. The waves were much calmer than yesterday.

There is a nice boardwalk and trail along the beach in Cambria, great for early morning walkers.

The powerful surf yesterday might have deposited some of this driftwood, but I suspect the pile has been accumulating from several recent storms. The tide and surf was so high yesterday, it covered the sand and driftwood here.

A couple of dogs were chasing each other on the beach. It was fun to try to capture their frolicking.

I particularly like this image — from a biological point of view. Four-legged runners maximize their stride length by flexing their backs and coiling the four legs together (left dog), and then extending their backs for maximum spread of the front and back legs (right dog). The fastest runners have the greatest degree of flexion and extension in their stride, and cycle through the two maneuvers most rapidly — like cheetahs.

Morro Rock was free of fog on this day, and we took a short walk around one side to see if there were any birds.

A lone Turkey Vulture swooped back and forth over the rock face.

An Osprey caught a nice updraft and hovered over one spot on the top of the rock for several seconds. Looking for a nesting spot? Or just riding the breeze.