Ironwood Trees Feed the Desert

Blossom Close up

Ironwood trees take center stage in late April.  The trees produce clouds of tiny orchid-like blossoms that transform the ironwood into a vision of beauty. 

These blooms also attract a buzzing swirl of Centris pallida, commonly known as digger bees.  Male digger bees detect females, still lingering in their underground burrows, and furiously dig them out. After mating the female buzzes off to the nearest ironwood and its sweet nectar laden blossoms. 

The masses of spring flowers give way to lengthening seed pods that ripen at the height of summer. This is just when most desert species are scrambling to feed families of babies. The crunchy fare is rich in nutrients and enjoyed by 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.

Desert legume trees such as ironwood also have a magical ability to feed the desert underground. Desert soils are poor in nutrients, but legumes partner with soil bacteria that provide nitrogen to the root systems. High levels of nitrogen contribute to the large amount of protein found in legume pods. Nitrogen in soil at the base of the trees encourages the growth of shrubs and annuals, which provides more forage for animals like lizards, desert tortoises and cottontail rabbits.

The protective drape of ironwood branches creates a shady microclimate where animals wait out the heat of the day. 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.

Ironwood Tree April 29

High Time for Saguaro

Curve-billed Thrasher

In springtime desert birds like Cactus Wrens and Curve-billed Thrashers perch on the domed tops of forty foot Saguaros, and their calls ring like bells in the desert air. Gila Woodpeckers and Gilded Flickers cling to Saguaros’ spiny ridges, peering into cavity nests, drumming territorial calls on the cacti’s green skin, and sending messages with their piercing cries. 

Gila Woodpecker peeks out of cavity nest
Gilded Flicker inspects cavity

Gila Woodpeckers, Gilded Flickers, Flycatchers, Screech Owls and more nest in Saguaro cavities throughout spring and summer. Some, such as the Ash-throated Flycatcher, build cozy nests inside the “boot” of the cavity, the hollow cocoon formed by resinous secretions after a woodpecker excavates. Others simply lay their eggs in the bottom of the boot.

In the first week of April, White-winged Doves show up from Mexico. With their arrival, the stately Saguaros erupt, sprouting green caps of tubular buds. Soon after, the blossoms open, spreading thick waxy petals to the night air, summoning pollinators like moths and bats.  Come morning bees and birds feed avidly on the nectar, for by afternoon the tropical looking blossoms will be closed tight again, holding in precious moisture. 

White-winged Doves migrate to the Sonoran Desert to feed on Saguaro nectar and its fruits. They raise their young on the fruits. Saguaros benefit from their company as doves spread seeds when they carry juicy fruit bits to their nests in nearby trees. Saguaro seedlings get a start in the shade the branches of these desert “nurse” trees provide. 

When the last of the fruits have been eaten, when the last summer nesters have fledged their young, when the air shimmers with heat, every animal finds shade or retreats to underground burrows. Saguaros stand stoic in the silence and wait for summer rains, their shallow roots poised to absorb even the most meager shower, while their seeds nestle in the soil nearby, anticipating moisture for germination. 

Red sunrise in August

 

Ash-throated Flycatcher

The Ash-throated Flycatcher has a call like a whistle being blown, and it always catches my attention.  Usually, the noisy flycatcher is perched at the top of a shrub or on a low branch where it watches for passing insects. I’ve seen them launch from such a perch and dart and dodge through the air in pursuit of some bug that is flying for its life. In addition to insects and spiders, this flycatcher enjoys cactus fruits and mistletoe berries. With all of these juicy items to eat, this arid-adapted bird has no need for water. 

Ash-throated Flycatchers are cavity nesters, but they don’t have the equipment to create their own cavities.  As secondary nesters, they move into holes made by other birds, in saguaros, fence posts, dead stalks of agaves and yucca plants, old Cactus Wren nests, and even pipes, mailboxes, and reportedly clothes left out on a clothesline. Inside the cavity the pair builds a platform of grasses, twigs and rootlets and then a cozy cup nest of fur and feathers for their eggs. The beautiful eggs are creamy white with purple and olive markings. Ash-throated Flycatchers raise one to two broods of up to seven young.

At South Mountain Park April 14

 

  

Stellar in Flight

The fierce looking Cooper’s Hawk

This is an animal superbly designed for flight. Cooper’s Hawks prey on other birds, and many live and hunt in forests, so they must be able to fly with extreme agility. Notice the boney ridge above the eye.  This supra-orbital ridge protects the eyeball from twigs and branches as the raptor careens through the trees. It also shades the eye from sunlight, just like a ball cap. 

With this close up you can see even the nostril is protected by bristly feathers. And did you know, a bird’s ear is below and behind the eye, and protected by the tawny ear patch feathers shown here. Short wings and a long tail also help the Cooper’s Hawk make the quick turns and adjustments necessary to survive.

Cooper’s Hawks that live in the Southwest eat mammals and lizards in addition to birds, but are very fond of Mourning Doves, Rock Pigeons and Gambel’s Quails, all birds that provide a hefty meal. The female Cooper’s is larger than the male, and since this is a bird that eats other birds, the male must be very careful during breeding season. Maybe this is why the pair sings duets during courtship and continue singing together in the mornings for the entire month of incubation of the eggs, just to stay on the same page. 

This particular Cooper’s Hawk is an education ambassador at Liberty Wildlife. He was found with a wing injury at Saint Anthony’s Monastery in Florence, Arizona, so is named Monk. Unfortunately, Monk did not heal in the top-notch form that would allow him to survive in the wild. So it is that Monk has gracefully taken on a new role. As an education ambassador, he agrees to show off for visitors at the wildlife rehabilitation facility, and in school classrooms across the state. He has been trained to sit quietly on the handler’s glove, and is rewarded with fresh meals daily.

Note the talons, this is how a raptor kills its prey
Wild Cooper’s Hawk on a light post near South Mountain

Desert Birds Come Courting

Gilded Flicker examines cavity nest

Spring unfolds quickly in the desert, and the season’s star actors are birds. After a winter of quiet, they appear on the scene in early February, acting out courtship dramas on stages such as Saguaro cacti and Ironwood trees. The first group I noticed were House Finches, singing and twirling together in the sky, chasing each other tree to tree. Their trilling songs herald the pre-spring dawn, as the male sings with vigor to his female. He will woo her, guard her and feed her while she incubates their eggs.

Male House Finch on Saguaro

   

Cactus Wrens sound like a car that won’t start

Curve-billed Thrashers shared the early season spotlight. Suddenly they were apparent, on the ground with a twig, and in a Buckhhorn Cholla cactus, checking out the site for nesting potential. Cactus Wrens also became conspicuous, belting out their churring songs from the tops of Saguaros, and even chasing each other among the rooftops on our street.   

Curve-billed Thrasher considers nest options

Next on the scene are the cavity nesters. Both Gila Woodpeckers and Gilded Flickers seem to be everywhere around Saguaros these days, calling back and forth from the tops of the stately cacti, peeking into cavities and drumming on the green cacti skin.  Choosing nests, declaring territories, cementing pair bonds, it is a busy build up to actual nesting. 

A week ago, I watched a pair of Gilded Flickers inspecting a nest high on the east side of a Saguaro.  The male first peered repeatedly into the cavity, disappeared down inside, came out and circled the ridged stem, then drummed vigorously.  When he flew off, it was the female’s turn to execute the same maneuvers.  Four flickers danced and sang together in our front yard at evening time.  Hopping from a sprawling prickly pear to the ground they bowed, stretched their beaks to the sky, flared their tails and sang in high chittering notes. It was a thrilling performance.

Most recently I’ve heard the beautiful and endlessly varied song of the Northern Mockingbird, the male sings in the morning and even in the middle of the night.  Today on my hike, I watched a playful pair on a Saguaro, flying up in the air and flashing their white wing patches, dropping from the rounded top of the cactus to one of its upraised arms.  The partner waited for his turn in the spotlight, then whistled, flew up and tumbled back down in a flutter of grey and white feathers.

All of this excitement and play is a prelude to the grueling work of feeding and protecting nestlings.  Although courtship is highly visible, nests and babies are usually kept well out of sight.     

Northern Mockingbird

Desert Mistletoe

Desert Mistletoe clumps in Ironwood Tree

We think of mistletoe as having holly-like leaves and hung with red ribbon in doorways at the holidays.

Not like that, Desert Mistletoe is one of 1000 species of mistletoe that grow worldwide. Its leaves have shriveled over eons of arid life, to mere scales on jointed twigs.  The flowers are fragrant, but have no petals, and bloom in the winter.

This plant is a parasite, it inserts rootlike haustoria under the thin bark of desert legume trees and siphons off the water and nutrients that it needs to survive. It takes 2-3 years to get established and another year of growth before fruiting. Desert Mistletoe does carry on photosynthesis, and as a perennial comes back strong every spring, living on its host for 60-70 years.

The berries are juicy and sticky, ensuring that birds carry the seeds on their beaks to nearby branches where they rub them off and the seeds stick, waiting to sprout.  The mistletoes hosted by ironwood, mesquite and acacia grow sweet berries. Indigenous peoples made a nutritious pudding of them, but mistletoe berries from plants growing on paloverde and buckthorn are bitter, inedible. 

Phainopepla, Cactus Wren, Curve-billed Thrasher and Hooded Orioles eat the berries, and others such as Black-tailed Gnatcatcher and Pyrrhuloxia nest amidst the treetop clumps of stems.  A desert tree may tolerate the growth of several mistletoes, as the species have acclimated to each other over the eons and learned a way they both could survive. 

Growing down lower in tree
Yellow blooms starting to show February 14
Spiny leaves and yellow flowers March 24

Mourning Dove

First Dove Pair of the Season February 6

Like pleasing background music, the cooing of doves adds a soft note to spring and summer in the desert. I don’t see Mourning Doves around here in the wintertime, but couples recently began showing up in the back yard, and I’ve seen them in pairs in the desert. Out there they blend so well with the ground that their movement is startling, like a bit of the earth moving. 

Doves build their flimsy nests just about any old place, not too concerned about the near presence of humans. We’ve had them nest on a ledge about 3 inches wide over the front door, on outside speaker boxes, and even on patio fan blades.   

As Mourning Doves may have six broods per season, nesting continues well into the hottest part of the summer. On days when their eggs might cook in the heat, the couple takes turns sitting on the nest. They are able to absorb heat from the surface of the eggs and dissipate it by gular flutter or panting. The nestlings are fed regurgitated crop milk for a couple of weeks and dad continues to care for the juveniles while mom starts right in on incubating the next brood.

Widespread across the U.S. and Mexico, Mourning Doves live in open country, grasslands, agricultural fields, backyards and roadsides.  Although they require plenty of water, they can survive in the desert because they are strong, fast fliers, capable of traveling ten miles a day to drink. 

Mourning Doves eat seeds, grinding them up in their tough stomachs along with sand or gravel they consume to use as internal teeth.  They are one of the most hunted bird species in North America. 

Dove Cooing
Fledgling in Palm Nest

  

Raven

Near Willcox Arizona is a water treatment/wildlife refuge called Cochise Lake. When I arrived in late morning only a couple of mallards floated in the middle of the water. As I’d made quite a detour to find this place, I was disappointed by the lack of vegetation and birds. But as I drove slowly away on the dirt track, this raven called out to me, croaking in guttural tones.   Here I am!  Look at me!  I am bird! I stopped the car, got out and had quite a visit with this raven who seemed eager to interact.

Ravens are famous for their intelligence, curiosity and playfulness. Inky black ravens soar gracefully overhead, walk on the ground with a swagger, and show off with acrobatic barrel rolls in courtship and play. Myths and stories attest to their smarts, and as scientists come up with ever more sophisticated problems for them to solve, ravens continue to amaze with their clever solutions. 

Ravens are usually seen alone or in pairs. They mate for life and the pair bond is very strong. The couple often hunts together, able to trap prey more effectively working as a team. Juvenile birds do hang together in social groups until they are old enough to choose a mate between the ages 3 to 7 years.  During this time young ravens form friendship bonds, hunt cooperatively and roost together. Outsiders are treated with suspicion and often chased away.

As omnivores, ravens eat just about anything. If the portion is too big, leftovers are carefully cached for later. Since their dietary range is so large, there is no template for a young raven as to what food looks like. They follow their parents to learn about the many tasty tidbits to be found or hunted. Their innate curiosity serves them well when they set out on their own. Ravens check out pretty much everything in their environment, because you just never know what might taste good. They are especially attracted to shiny things – bottle caps, jewelry, bits of glittering glass, but will investigate anything unusual in the landscape.  This use of inquiry ensures that in any situation unusual or rare food will be discovered.