The Sonoran Desert

View across the valley to the Kofa Mountains

I love the desert, all of it! I treasure the big-sky views, the dryness, the unique cacti and vegetation, as well as the amazing reptiles, amphibians, birds, insects, and mammals! The area of the Sonoran Desert that I've visited many times is in the southwest part of Arizona. The average total rainfall for the area is only 5". Unlike previous years, a series of wet storms had recently passed through. It even rained when we were there last week! It was incredibly lush and beautiful, with flowering shrubs, cacti, and annuals everywhere, as well as pools of water in all the bedrock washes!!! Additionally the air was super clear, and the turquoise-blue sky was filled with beautiful dramatic clouds. My introduction to the desert happened 40 years ago, and I've been back almost every year since then! Luckily the area I travel to is protected and has remained the same all these years. We were so lucky to be there! SUCH beauty! 

Brittle Bush and Mountains

The following article describes the Sonoran Desert and is from the website at

https://www.desertmuseum.org/desert/sonora.php.

"The Sonoran Desert as currently defined covers approximately 100,000 square miles (260,000 sq. km.) and includes most of the southern half of Arizona, southeastern California, most of the Baja California peninsula, the islands of the Gulf of California, and much of the state of Sonora, Mexico. It is lush in comparison to most other deserts. Two visually dominant life forms of plants distinguish the Sonoran Desert from the other North American deserts: legume trees and columnar cacti. It also supports many other life forms encompassing a rich spectrum of some 2,000 species of plants.

The amount and seasonality of rainfall are defining characteristics of the Sonoran Desert. Much of the area has a biseasonal rainfall pattern, though even during the rainy seasons most days are sunny. From December to March frontal storms from North Pacific Ocean occasionally bring widespread, gentle rain to the northwestern areas. From July to mid-September, the summer monsoon brings surges of wet tropical air and frequent but localized violent thunderstorms.

The Sonoran Desert prominently differs from the other three North American Deserts in having mild winters; most of the area rarely experiences frost. About half of the biota is tropical in origin, with life cycles attuned to the brief summer rainy season. The winter rains, when ample, produce huge populations of annuals (which comprise half of the species in our flora)."

Bedrock Tank

 Water in the Desert!

We camped at the base of some low, rocky hills, and hiked up bedrock washes and rocky ridges during the day.  This year EVERY bedrock wash we hiked in had water in its basins.  In some areas the water was even running!  WOW!!!  Natural deep bedrock pools are called "tanks".  Local animals depend on these deep tanks for water during the hot months of summer.  The U.S. Fish and Wildlife Service has added small dams to some of these tanks to help provide year-round water for wildlife.  The natural tank pictured above is shaded from the sun, and algae doesn't grow in it easily.  In fact it was quite cold!  I wonder how long the water will last!

 Sky-Water Wash

I have never seen a flash flood, but we saw evidence of one on our hike.  In one area, huge boulders had crashed down from a cliff that bordered a wash, and 3' tall plants along the wash were bent over from a high volume of water flowing over them!  It must have been amazing to see!  There was more water in the washes than I have ever seen before!  The dramatic clouds and sky were reflected in all the pools.  I unofficially named this wash "Sky-Water Wash".  It was SO beautiful!

Arizona Toad - Anaxyrus microscaphus

In one of the pools we were surprised to find two pairs of Arizona Toads in "amplexus", the mating position of frogs and toads.  The males were on top of the backs of the females and holding on!  They were about 3" long and were pretty bumpy looking.  Arizona toads breed in pools, typically along streams and rivers.  After fertilization, strings of jelly-like eggs will be laid by the female on the bottom of the pond. Clutches range from about 3150-4280 eggs!!!  Eggs hatch in 3-6 days, and tadpoles typically metamorphose in 1-3 months, but development can be slower in cooler water or at higher elevations.  Breeding occurs over a relatively short period (10-12 days) in February-April, and is not triggered by rainfall events, but rather by warm nighttime temperatures.  Adult toads are mainly nocturnal, spending the day in sandy burrows. They enter a state of torpor and remain underground from about September to February. They may live for four or five years and the main cause of mortality is probably predation by mammals, birds, and snakes. 

That would have been amazing to come across a pool containing thousands of tadpoles!  It doesn't really sound possible!  Flash floods would definitely impact the survival rate. I wonder if lots of animals eat frog eggs or if a lot of them don't survive.  I'll have to look that up!  

Bedrock Mortar Holes - Petroglyphs

In and along the bedrock washes, there are lots of mortar holes made by Native Americans, dating from as long ago as 1,000 to 2,000 years!!!  The holes were formed by the Native Americans grinding up plants and seeds.  In some areas there are also ancient petroglyphs carved on the rocks. 

It is difficult to pin down who exactly made these petroglyphs and mortar holes.  Wikipedia states, "Patayan is a term used by archaeologists to describe the prehistoric and historic Native American cultures who inhabited parts of modern-day Arizona, west to Lake Cahuilla in California, and in Baja California, between 700–1550 A.D. This included areas along the Gila River, Colorado River and in the Lower Colorado River Valley, the nearby uplands, and north to the vicinity of the Grand Canyon."

The number of mortar holes in the area where we stayed is amazing.  I found them in many of the washes as well as in several shallow caves along the dry watercourses.  One particular north-facing cave, with a beautiful view of the Kofa Mountains, has an astounding 27 mortar holes!!!  Petroglyphs are not as common, but I have seen many of them in other areas of this desert preserve.

 

Desert Bighorn Sheep - Ovis canadensis nelsonii

Desert Wildlife

I have seen Desert Bighorn Sheep several times in this desert over the years.  I didn't think we would see any this year, as there was water available everywhere.  However, we were SO LUCKY and came across a group of 5 Bighorn Sheep while we were out hiking!  There were two young rams, two ewes, and one youngster!  You can just see part of the youngster's backside, behind the ram on the far right, in the photo below.  These beautiful sheep have been declining in population and are now currently listed as "vulnerable".  What a privilege it was to see these uncommonly seen, beautiful, wild animals!  

The following information on Desert Bighorn Sheep is from the U.S. Fish and Wildlife Service website, https://www.fws.gov/uploadedFiles/DesertBigHorn_2013_508.pdf.

 "Characteristics Desert Bighorn are stocky, heavy bodied sheep, similar in size to mule deer. Weights of mature rams (males) range from 125 to 200 pounds, while ewes (females) are somewhat smaller. Due to their unique padded hooves, bighorn are able to climb the steep, rocky desert mountains with speed and agility. Bighorn rely on their keen eyesight to detect potential predators and use their climbing ability to escape. Both sexes develop horns soon after birth with horn growth continuing throughout their lifetimes. Older rams have impressive sets of curling horns measuring over three feet long with a circumference of more than a foot at the base. The head and horns of an adult ram may weigh more than 30 pounds. The ewes’ horns are much smaller and lighter and do not tend to curl. Both rams and ewes use their horns for fighting and as tools to remove the spines from and break open cacti, which they then consume. Desert bighorn sheep live to be between 10 and 20 years old. Their age is indicated by annual growth rings in the horns. 

 Desert bighorn sheep are well-adapted to the climate of the Sonoran Desert. They are able to survive the extreme heat of summer and the cold of winter because their body temperature can safely fluctuate several degrees. Bighorn also escape the heat by resting in the shade of trees and caves during the day. Unlike most mammals, desert bighorn sheep have the ability to lose up to 30% of their body weight in water and still survive. Bighorn may go without drinking for weeks or months during the cooler parts of the year, although lactating ewes need water more often. During the hot, dry summer months, bighorn often go three to seven days without drinking, sustaining their body moisture from their food alone. After drinking up to two gallons of water in just a few minutes, they recover from their dehydrated condition.  Bighorn feed on a wide variety of leaves, twigs, flowers, forbs, grasses, and cacti. 

Mature bighorn live in separate ram and ewe bands most of the year. They gather together during breeding season (usually July-October), though breeding may occur anytime in the desert due to suitable climatic conditions. Rams battle to determine the dominant animal. They face each other and charge head-on from distances of twenty feet or more, crashing their massive horns together with tremendous impact until one animal ceases. The winning males are able to breed with the ewes. Gestation lasts about six months and the lambs are typically born in late winter. 

In the early 1900s, desert bighorn populations gradually declined. Competition from introduced animals and human activities were primarily responsible for the population decrease. Domestic cattle and sheep, as well as feral horses and burros, compete with bighorn, especially at water sources. Domestic stock also introduced diseases."

Desert Big Horn Sheep - Ovis canadensis

"Between 2000 and 2006, the number of desert bighorn sheep on the refuge declined from more than 800 animals to less than 400. As a result of the decline, transplants of bighorn sheep from Kofa National Wildlife Refuge to other areas of Arizona and neighboring states were suspended in 2005. Surveys conducted from 2007 to 2012 show little increase has since taken place. The U.S. Fish and Wildlife Service, working closely with the Arizona Game and Fish Department, has undertaken an effort to increase the number of sheep by investigating the causes of sheep mortality, controlling predation of bighorns, reducing the number of hunting permits issued annually, and identifying lambing areas that may be potentially closed to human entry during the peak of lambing season. Permanent water is being maintained in locations known to be critical to the desert bighorn sheep as well."

Desert Cottontail/Audubon's Cottontail Rabbit - Sylvilagus audubonii

Last year I saw several Black-tailed Jack Rabbits in Joshua Trees National Monument. This year I saw several Desert Cottontail Rabbits right near our campsite in Arizona!

I have never seen them there before! When the temperatures are hot, these rabbits are most active in the evening and early morning. 90% of their diet is grass, but they will also eat forbs, shrubs, cacti, domestic crops, and even the bark of fruit trees. They get most of their water from either the plants they eat or dew that forms on the plants. Females have 5 litters of 2-6 young per year. When startled they will either freeze in place, or run off in a zig-zag pattern. Unlike other rabbits, they can also swim and climb trees and brush!!! During the day they will usually rest in a "form" (shallow depression or flattened nest of grass) made by other animals, under the cover of bushes. Both the male and female have white cottontails. They have excellent hearing with their large ears!  Cottontails are preyed upon by a number of predators, including golden and bald eagles, great horned owls, ferruginous hawks, badgers, coyotes, foxes, bobcats and humans. Rattlesnakes may prey on the young.

Northern Mockingbird - Mimus polyglottos

Desert Birds

Usually where we camp, there is a large variety of birds in the area.  There is a bedrock tank, enhanced with a small man-made dam, just up the road that attracts birds and wildlife.  This year we didn't see that many different species of birds, probably because there was water available in ALL the bedrock washes, not just the one near our camp.

The predominant birds we saw and heard were Northern Mockingbirds.  First thing in the morning, they were singing their incredible repertoire of songs!  They are excellent mimics of other birds, cats, dogs, frogs, crickets, and squeaky gates etc.!  Both males and females sing, and can learn up to 150 songs in a lifetime!!!  They are widespread across the U.S., preferring to live in open areas such as farmlands.  At this time of year they feed on insects.  In winter they eat fruits and berries.

Black-throated Sparrow - Amphispiza bilineata

Every year, at our camp, we are visited by Black-throated Sparrows.  These birds are year-round desert residents.  The get enough water from the insects and succulent vegetation that they eat.  Although they aren't as vocally versatile as Mockingbirds, they have a lovely, repeated, bell-like song. 

Ash-throated Flycatcher - Myiarchus cinerascens

These lovely Ash-throated Flycatchers were also commonly seen.  They may be year-round desert residents, or may migrate as far north as Washington to breed.  They do not need to drink water, as they get enough water from the insects and cactus fruit (in season) that they eat!  They are an overall warm-brown in color with pale gray throats, and lemon-yellow bellies.  The one in the photo on the right was startled by me, and raised its crest feathers in alarm!

 Phainopepla (male) - Black-tailed Gnatcatcher (female) (?)

Phainopepla nitens - Polioptila melanura (?)

We saw two male Phainopeplas over the 3 days we were in the desert.  Surprisingly I have also seen one male Phainopepla in the foothills near my home!  The following information is from the Cornell Lab of Ornithology website, birdsna.org., and explains why these birds are seen in such different environments.

"This long-tailed, crested bird is common and conspicuous in the Sonoran Desert, where it perches atop mesquite or palo verde trees, calling with a questioning 

"Wurp?" while flicking its tail and turning from side to side. The female in gray plumage, and the male in glossy black, flutter and zigzag, especially in pursuit of flying insects. In flight, the male flashes white wing patches, a striking contrast with the shimmering black plumage which inspired the Greek name Phainopepla, or "shining robe."

The Phainopepla lives and breeds in the Sonoran Desert until it gets hot and the mistletoe berries dry up.  They then migrate to the oak woodlands and sycamore canyons of California and Arizona where they breed through July!  In the desert, mated pairs vigorously defend their territory, whereas in the oak/sycamore woodlands they live in loose colonies of 3-15 pairs!  They eat insects and berries, mistletoe being their main desert fare.

 __________

I'm not 100% sure that this is a female Black-tailed Gnatcatcher (above right), but it is the most probable species for the area we were in.  I have never seen any Gnatcatchers before!  It appears that they are year-round residents in the southwest.  They are tiny, only 4.5' long!  They primarily glean shrubs for insects, and rarely eat seeds and fruit. We watched it flitting around in this Brittlebush, whipping it's tail from side to side!  How lucky we were to see one of these tiny desert residents!

Brittlebush after the Rain - Encelia farinosa

The Blooming Desert!

This year the highways were bordered with "hedges" of blooming Brittlebush and Coulter's Globemallow!  It was gorgeous!  There were also lots of other blooming shrubs and annuals.  I've been using Edmund C. Jaeger's, 1941 edition of Desert Wildflowers as a wildflower field guide for 40 years!!  The excellent, detailed, pencil drawings (not in color) were done mainly in-the-field by the author, over a period of 25+ years!  During this time he trekked through the deserts of the southwest with a pack burro, covering over 30,000 miles of roads and trails!  Although many of the scientific names have been changed, the drawings are still incredibly accurate and extremely helpful in identifying desert plants.  I have also used the following website for up-to-date information and identification of desert plants, http://swbiodiversity.org/sienet/.  SEInet stands for "Southwestern Environmental Information Network".  

Pale-stemmed Four O'Clock - Notch-leaved Phacelia - Desert Windflower 
Mirabilis aspera - Phacelia crenulata ambigua - Anemone tuberosa

New to me this year was the Desert Windflower (far right)!  We only saw two small plants in bloom.  None of the literature says it is rare.  I was thrilled to see this elusive little anemone in a rocky crevice!  The tallest stem is bearing the large seedhead.

Coulter's Globemallow - Crucifixion Thorn - Chuparosa

Sphaeralcea coulteri - Holocantha Emoryi - Beloperone californica

Another new species we saw this year was the profusely blooming Crucifixion Thorn (center).  It was a LARGE shrub covered in  small cream-colored blossoms. Beautiful!

Beavertail Cactus - Opuntia basilaris

The Beavertail Cactus were the only blooming cacti we saw.  The Buckhorn and Teddy Bear Chollas were still in bud, as well as the Hedgehog and Barrel Cacti.  The Saguaro Cactus bloom much later, in April through June.

Sunrise in the Sonoran Desert

On the morning we left to go back home, we watched an incredible sunrise!  The clouds lit up briefly in beautiful oranges and golds, then dark gray clouds moved in and the temperature dropped!  It had rained quite heavily around 3:00 am that morning, and I had even heard an owl out in the rain!  We headed home filled with beauty, with plans to return again next year.  We are SO lucky!

We cut our desert trip short due to the Coronavirus news.  I hope you all stay healthy, and get out in nature while you have the time.  It heals all!

What new birds have arrived?

Where are the mammals?

Check back next week for the answers to these questions and more!

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