Leguminous Trees

Ironwood Pods rich in protein, calcium and iron

Most desert trees are legumes, meaning they produce pods.  (Beans and peas are also legumes.)  Masses of spring blooms gradually give way to lengthening seed pods that ripen at the height of summer.  This is just when most species are scrambling to feed families of babies. 

The crunchy fare provides sustenance for desert critters including coyotes, javelinas, Harris’s antelope squirrels, pocket mice, kangaroo rats and rock squirrels.  Some of these animals are destined to become prey for meat eaters like owls, hawks, coyotes and desert snakes.  Through this dynamic cycle, ironwood, mesquite, and Palo Verde trees set the table for wildlife.

Desert legumes also have an almost magical ability to feed the desert underground.  Desert soils are notoriously lacking in nutrients due to aridity and lack of organic matter. Legumes coexist with soil bacteria that provide surplus nitrogen to their root systems. High levels of nitrogen are essential to the development of protein, making the legume pods very high in protein.  Nitrogen helps nearby shrubs and annuals grow, which provides more forage for animals like lizards, desert tortoises and cottontail rabbits.

As a bonus, trees also create microclimates of shade where tender sprouts such as saguaro cacti grow.  Animals like jackrabbits and javelinas wait out the midday heat under the protective drape of ironwood branches.  Crawling on the branches and among the bark, a variety of insect species feed on nectars, saps and the bark itself.  As they flourish, these insects become a protein rich and often juicy addition to adult and baby bird diets. 

Mesquite beans
Palo Verde pods
Palo Verde pod factory

Charmed by Chuckwallas

Big and baggy, Chuckwallas are lizards from the iguana family.  All that extra skin comes in handy when a predator such as a red-tailed hawk or a coyote threatens.  Chuckwalla dives into a nearby rock crevice and gulps in air, blowing itself up like a balloon.  The predator finds its almost prey wedged into a tight space with no leverage to pull it out.  This is Chuck’s primary defense mechanism. 

For a few years we grew a grape vine in the backyard, and a big male Chuckwalla with a bright orange tail claimed that vine for his own.  (Only males in the South Mountains boast the orange tails.) He lounged on our block wall, nibbling leaves and sunbathing – a Chuckwalla’s two favorite activities.  I once saw him chase a smaller Chuck out of the yard.  I had no idea he could move so fast or look so scary. 

The other day I happened to see two Chuckwallas together in a rocky area where I walk. I heard a scratching noise, and saw an orange tail disappear into a crevice in a rock face.  Something moved on a sandy ledge below, it was a light-colored female.  She was completely inflated, her back humped up and her banded grey tail all contorted and sticking out at an odd angle. 

She nibbled some dried annual plants.  Then, as her body resumed its normal shape, she climbed into the branches of a small Brittlebush. She used her front feet to pull the most tender leaves down and munched on those.  Up at the crevice the male was peeking out, watching.  When I moved to reach for my camera, they both disappeared, like they were never there.

Chuckwallas are plant eaters and can store moisture from the plants they eat in fatty tissues in their tails.  The female buries six or more eggs in loose soil. I have seen more Chuckwallas than ever this year, and we even have a new backyard resident!

Pigments in plant foods make the male’s tail orange
Chuckwalla blends into the scenery
A new backyard Chuck

Tale of Two Turkey Vultures

It’s a bit weird when turkey vultures show up in your backyard, especially while a pandemic rages.   Yet, in late March, a couple of turkey vultures started hanging around on the rocky boulders behind our house.  As we sheltered at home, the massive birds loitered, preened and flew.  With their bald red heads and hooked beaks turkey vultures sure are homely, but to see them soar on broad silver wings is to feel a certain wonder.  

Pinau Merlin states in her terrific book Bird Nests & Eggs that turkey vultures scope out a potential nest site over several weeks. Satisfied by the local vibe, they mate and lay two eggs on a sheltered and inaccessible rock ledge.  We continued to see the vultures, flying overhead or sitting together, grooming. 

The time came when only one vulture was apparent.  They were taking turns sitting on the eggs!  The shift change was secretive.  One of the big birds would fly in and land on a boulder, then immediately drop into the crevice below, pulling bulky wings down after. 

Vultures soar endlessly, barely moving a feather.  But it isn’t all about grace and elegance, vultures fly to search for food.  They are looking and sniffing for the carrion, or dead animals, that make up their diet.  These are the trash collectors of the desert.

The eggs were due to hatch, and I was looking forward to seeing vulture fledglings in the next month.  But one evening late in May our neighbor Jim sent a text saying he’d seen a coyote prowling around up near the vultures’ nest.

Oh, wily coyote, tell me you didn’t! 

The next day one vulture flew in tight circles around and around the nest site.  She haunted the area for several days.  Then the turkey vultures disappeared.

Turkey vultures mate for life.  Only a limited number of adults from the total population will breed in a given year.  Maybe these two will try again next year.  We hope so. 

The the beak is the business end of this bird
The bald head is easier to clean after messy meals
TVs pee on their legs for evaporative cooling

Photo credits: Turkey vulture head Livescience.com Vulture in flight AllAboutBirds.com

Desert Tortoise

By May spring wildflowers have crisped into mere scaffoldings for seeds.  Underfoot the soil is loose and the air itself feels bone dry.  Out hiking, I descend into a dip in the Desert Classic Trail, a place where cyclists speed down and pedal madly up again. I’m startled to see a Desert Tortoise come lurching towards me.  She pitches side to side down the slick slope.  Scrape, scrape go her fin-like feet.  Once she reaches shady cover, she drops her shell to the ground and slides shiny black eyes towards me.

Hustling to safety – tortoise speed

Desert Tortoises are ancient creatures, having existed on the planet for 50 million years.  And they live long, 40 years or more.  Their reptilian features, and their awkward gait make them fascinating creatures.  These animals live underground in burrows much of the time, dormant and protected from extremes of heat and cold.  They come out in pleasant weather and cooler times of summer days to feed, to find water and to mate.  Desert Tortoise eats spring wildflowers and summer annuals that grow after monsoon rains.  She can digest dried plant material, if she has been able to find water.

Because water in the desert is rare, Desert Tortoise stores the precious liquid in her bladder, enough to get by for months.  In fact, water can make up 40 % of her body weight. This allows the tortoise to survive without drinking from winter rains until summer monsoons. 

If frightened, a tortoise will void its bladder, compromising its ability to survive.  People are urged to keep away from Desert Tortoises, and to certainly not pick them up, even if they are found on a roadway.  (I guess you stop traffic instead!) 

Arizona Department of Game and Fish handles a Desert Tortoise adoption program.  Tortoises that have been in human contact, either from illegal breeding or handling, are prevented through this program from being returned to the wild, where they may spread disease among the native populations. 

Whose Finch?

Handsome Male House Finch

Naming a bird House seems wrong.  And because it’s a commonplace urban bird, the House Finch might seem a little boring.  But consider House Finch social life.  The rather plain female keeps her colorful mate very occupied with making her happy.  At breeding season, she assesses potential partners and looks approvingly on males with the brightest coloring. 

The male has been working hard to make himself attractive. He’s in tip top shape, and has been feasting heavily on berries and fruits with strong pigmentation. These give him the brilliant red or yellow feathers that make a female sing.  She’s looking for the healthiest, best-looking guy, surely most capable of helping her raise her young.   

If her glance lingers on him, the male breaks out in fluttering flight displays and persistent song.  When she’s properly impressed, she starts right in on house hunting, touring the area for potential nests sites.  The male flutters madly after her, singing with joy.

The nest might be a remodel of an old nest, or a nest pre-owned by another species.  The couple might consider a cavity nest, or build new. 

The male can’t be complacent at this point.  He must guard his mate during egg laying and incubation and bring her the tastiest morsels of her favorite foods.  Otherwise, she may abandon the nest and look for another mate!  Both parents feed the hatchlings regurgitated seeds or vegetable matter.  These birds eat very few or no insects. 

The bright clear notes of the House Finch song string together like colorful beads.  At this time of year, it’s a beautiful backdrop to our mornings.  The House Finch is native to desert canyons of the West, where they live near water sources. Our backyard fountain is visited by a parade of the birds.

Back in 1940 some captive House Finches were put in a pet shop in New York City.  But the rascals escaped and took up urban life.  Now the clever and endearing House Finch can be found in city parks throughout the east as well as the west. 

Below see the female House Finch and various colors on males, depending on what they ate during the molt before breeding season.

Babies In Boots

Gila Woodpecker drills a cavity nest
Gila Woodpecker digs deep

This past Feburary I watched a Gila Woodpecker male, identified by the red patch on his head, creating a cavity in a saguaro.  He reared back his head and used the leverage afforded by his long tail to hammer at the green skin of the cactus, breaking through the outer layer. 

After that, things went easier.  He quickly enlarged the hole, reaching inside with his formidable beak to scrape and probe, pulling his head out to shake off the juicy bits of saguaro flesh.  Soon, the woodpecker had excavated the cavity enough that he was leaning far inside to do his work.

Once the cavity is 9-18 inches deep, the Gila Woodpecker leaves it alone to cure.  The inner parts of the saguaro callus over in a couple of months forming what is called a boot. Then the nest is ready for use.  Unless someone else moves in first, the female woodpecker lays three to four white eggs in the bottom of the bare cavity. 

Sometime in May, the eggs hatch. The parents feed their noisy hatchlings insects, berries and cactus fruit. Even after they fledge, mom and dad continue to feed and watch out for their young, sometimes caring for overlapping broods. 

Only two species of birds, Gila Woodpeckers and Gilded Flickers, make cavity nests in saguaro cacti. But many others make use of these cozy and protective hidey holes, Elf Owls, American Kestrels, Ash-throated Flycatchers, European Starlings and Screech Owls to name a few.

Desert Iguana

Desert Iguana at South Mountain Park in April

This lizard loves heat, and is out and about on even the hottest summer day.

One fast runner, the Desert Iguana bursts into explosive speed to reach the safety of its burrow when threatened.

The biggest treat for this large lizard is the yellow flower of the Creosote bush. Mmm, delicious!  The iguana crawls right up into the bush to reach the delectable treats. The leaves and flowers of the Creosote make up most of the Desert Iguana’s diet.  It also eats insects and even carrion.

The Desert Iguana digs burrows under Creosote plants, making safe hiding places.  This also helps the Creosote, as the burrows funnel water down to the plant roots when it rains. 

Desert Iguana hibernates during the chilly fall and winter months, emerging in March just as the Creosote is setting its blooms.  The iguanas breed in April or May and the clutch of 2-8 eggs hatch later in the summer. 

This Desert Iguana was soaking up the sun, and surveying its territory as I happened by. It was my lucky day as they are known to be secretive and shy.

Creosote bush stays green all summer, even with the heat. It leaves are covered with a waxy coating to keep them from drying out, and they tilt to minimize exposure to suns rays.

Saguaro and White-Winged Dove

Here’s how a cactus and bird join up to help each other out.

White-winged Doves fly to the Sonoran Desert from Southern Mexico every April.  They arrive just as the creamy blossoms of the Saguaro cactus are breaking open, releasing their sweet fragrance.  The doves replenish themselves with Saguaro nectar containing water, sugar and protein. A sports drink couldn’t be better formulated to match their needs. In return, the doves carry pollen from one tall cactus to another, ensuring the flowers will set fruit.

Saguaro flowers bloom for a single night, opening up after dark and closing when the sun is high the following day.  Nectar feeding bats get first dibs on the new blossoms.  Come dawn, White-winged Doves feast at the flowers, joined by Gila Woodpeckers and Curved-bill Thrashers.  Bees also mob the sweet blooms.

White-winged Doves mate in early May, and build their flimsy nests in the highest tree branches.  The hatching of the eggs in June coincides perfectly with the fruiting of the Saguaro. Nestlings first drink crop milk regurgitated by mom and dad, but soon transition to the pulp and seeds of the Saguaro fruits along with seeds from other desert plants.

Saguaro fruits ripen at the hottest, driest time of the summer.  The juicy fruit helps many desert animals survive until the monsoon rains arrive.  As birds feast on the fruits and fly about excreting the seeds, new baby Saguaros are planted across the desert. White-winged Dove’s digestive system is brutal on cactus seeds, but doves still help their Saguaro partners when they carry bits of dripping fruit to their nestlings.  Seeds dropped beneath nests await the promise of summer rains.

In September White-winged Doves break off the cozy relationship with their cactus cohorts and migrate back to the southern regions of Mexico.

Saguro Fruit ripening in early June
White-winged dove display
Yes, you are beautiful