Butterflies of the Desert

Malachite Butterfly clings to the underside of a leaf

On a recent trip to Desert Botanical Gardens I visited the butterfly tent.  Inside butterflies fluttered about lazily or perched on flowers and leaves.  Seen up close, their colors were dazzling.  Butterfly wings are covered with thousands of overlapping scales, each a solid color, creating lovely hues and the distinctive patterns of each species.

Many butterfly species are found in the Sonoran Desert. Some are residents that stay in a fairly small range centered around larval food plants, others are visitors from other areas, drawn here by weather patterns or plants.  Adult butterflies feed on nectar and are important pollinators, while the larval stage caterpillars eat green leaves and often become food themselves for birds and their young. 

Pesticides applied to landscape plants, roadsides and agricultural fields are major threats to butterflies, as is habitat destruction, particularly in riparian areas.

Gulf Fritillary caterpillars feed exclusively on passion vines while Pipevine Swallowtail larvae eat only pipevine plants
Zebra Longwing males wait for females to emerge from crysalis and mate with them immediately
Monarch Butterflies are known for their epic migrations

Ruby-crowned Kinglet

In our neighborhood grows a beautiful Cascalote tree. When I walked by on a chilly morning recently I saw hundreds of showy yellow blossoms had unfolded at the ends of the branches, and that the tree was alive with tiny birds.

Usually tiny birds around flowers are hummingbirds or Verdins, both of whom eat nectar and insects, but the one that caught my eye on this day was neither.  As I paused beneath the tree, it dipped its head and a slash of red gleamed on its crown.

This was a Ruby-crowned Kinglet, and he was in constant motion, hopping from bloom to bloom and flicking his wings. These birds eat insects, perhaps it was ants or aphids attracted to the sweet blooms that the kinglets and Verdins were eating.  Only adult males have the red crown patch which is flashed when the bird is excited.  Sometimes the ruby coloring is not visible at all.

Ruby-crowned Kinglets spend their summers in spruce and fir forests in the Northwestern United States and across Canada.  In Arizona they can be found in the northern parts of the state where coniferous trees grow.  In fall, Ruby-crowned Kinglets migrate to warmer areas, which is why I saw this one enjoying the feast at the Cascalote tree. 

Photo courtesty Manitoba Breeding Bird Atlas
Winter blooming Caesalpinia cacalaco

Wren With A Swagger

A bird with a swagger? Yes, that’s the Cactus Wren. This brash songbird makes no effort to conceal his busy occupations about the desert. Nest building is nearly a full-time job, but plenty of hunting is done as well, and Cactus Wren is always on patrol in his territory, singing from a cactus top or scolding intruders. 

Cactus Wrens choose life-long partners and live in year-round territories. They build many nests, nests for raising babies, and nests for shelter from heat and safety from nighttime predators. The spherical nests are open at one end, where a tunnel leads to the inner chamber, which is cozily lined with feathers.

These nests are usually placed in cholla or prickly pear cacti, but are also found in acacia, Palo Verde or mesquite trees. The thornier the better. Working together, a Cactus Wren pair can build a nest in one to six days, working mostly in the morning. After the youngsters have fledged, the grasses and weeds woven into the abandoned nest are popular with other bird species. In a prime location, a new nest will be built right on top of the old. 

When not nest building, Cactus Wrens are hunting. Omnivores, they eat insects mostly but also spiders, lizards, berries, fruit and nectar, some seeds, and occasionally a small rodent.  They do not drink free standing water, obtaining moisture from cacti pads and fruits. Dust baths keep their feathers clean. 

Parents raise 2-3 broods every year, feeding the 3-5 nestlings insects. Grasshoppers are a favorite food. The parents pull the wings off before feeding up to 14 grasshoppers to each nestling every day. Fledging happens in about three weeks. So strong is the nest building instinct, that the youngsters begin picking up nesting materials when they are only 12 days out of the nest. 

Nest in Saguaro
New nest on old nest in Buckthorn Cholla
Prickly pear cacti offer water and nesting sites

Boo Draws a Glance

This Red-tailed hawk perched on the rocks out back and watched Boo the cat, who was enjoying a supervised breath of fresh air. Boo was oblivious to the predator, intent instead on a wily lizard hiding in the chive patch. What a plump and juicy treat Boo would be! Red-tailed hawks eat mostly rodents, but also squirrels, and rabbits, taking prey up to 5 pounds. (Boo weighs much more!) They also hunt other birds, snakes, and lizards.  A Red-tailed hawk is one of the largest of the raptors, yet weighs only about 3 pounds.

We all observed each other with great interest. I watched the hawk through my camera lens, the hawk leveled its binocular-keen eyesight on the cat, who peered into the chives for the lizard. Boo finally gave up on the little reptile, safely hidden in its herby jungle, and I put him back in the house. The Red-tailed hawk flew to find more suitable prey.

A sprawling platform nest rests on a high ledge in the canyon near here, and a pair of Red-tailed hawks performs aerial acrobatics at mating season each year. Although Red-tails mate for life, the male woos his female every spring. I see them circling together higher and higher until they disappear in the sky. At some point in the mating dance the male drops from above and touches the female on the back with his talons. Sometimes Red-tailed hawks actually grasp each other’s talons and plummet together towards the earth, gracefully pulling out of the fall with wind whooshing through feathers. 

 

White-crowned Sparrow

Lately I’ve noticed flocks of these striking birds foraging on the desert floor, and singing in trees. White-crowned Sparrows hop around, kicking at the soil, uncovering seeds to eat. During breeding season in spring and summer, they establish and defend territories, hunting insects, caterpillars, wasps, and beetles, for themselves and for their young.   

White-crowned Sparrows are famous for their dialects, common songs that vary slightly depending on where they live. Young males learn the local songs from other males in the neighborhood when they are just 2-3 months old. Females also sing, but their songs are more limited and related to defending breeding territories and feeding grounds.

A White-crowned Sparrow’s song is key to its survival, helping to attract mates and to defend nesting territories, with a particularly vigorous song warning off other males. Dialects of White-crowns are quite distinct – imagine a Southern drawl or a Yankee twang, and the boundaries between dialect areas are sharp. Sometimes a particular White-crowned sparrow dialect is only learned by males within a several mile area, and the sparrows just on the other side of this sparrow defined boundary sing a slightly different song. Birds that live in the middle usually learn both dialects.

These distinctive dialects make the sparrows prime candidates for many types of scientific studies. Using digital recordings of White-crowned Sparrows’ songs recorded over many years, scientists report that birds in urban areas are evolving to sing at higher frequencies so as to be heard over city noise.

This sparrow can be found across the North American continent, generally breeding in the far north and wintering in southern areas.  Some stay in place all year, others undertake long migrations. White-crowned Sparrows that breed in Alaska migrate 2600 miles to winter in Southern California.

To hear the song of the White-crowned Sparrow click the link below.

https://www.allaboutbirds.org/guide/White-crowned_Sparrow/sounds

Singing White-crowned Sparrow at South Mountain

Prehistoric Insect

Orange Skimmer

Dragonflies are among the most ancient creatures alive today. Fossils of dragonflies date back to 300 million years ago, 100 million years before dinosaurs appeared on the planet.

The dragonfly hunts on the wing, capturing prey in basket traps formed by dangling, haired legs. Patrolling the edges of streams and ponds, males hunt, guard their territories and look for mates. Females hunt, receive mates and lay millions of eggs.

The aquatic juveniles hatch and grow in streams, ponds and marshes. They feed on small invertebrates, small fish and even tadpoles. Dragonfly nymphs breath through internal gills.

The juveniles live underwater for a year or longer, expanding in size and developing adult features through a series of molts. There will come a day when the nymph gorges with water and climbs out of the water, onto a rock or up the stem of a plant. The exoskeleton splits open and an adult emerges, without gills and with two gigantic eyes. The dragonfly hangs in place as new legs, wings and a long slender abdomen slowly dry and harden. Then it lifts into the air, reborn as a superbly designed flying machine.

Dragonflies are among the fastest flying insects. They are highly maneuverable, able to fly forwards, backwards, hover and turn 180 degrees. Two sets of wings beat in opposite directions, enabling remarkable feats of aerodynamics. 

Enormous eyes provide exceptional vision and allows them to avoid predators. More than 80% of the dragonfly brain is used in analyzing visual data gathered by the compound eyes. Yet for all of their incredible adaptations, adult dragonflies live only a few weeks.  In late fall they all die, while underwater the nymphs eat, grow, and prepare to take to the wing.

Look for dragonflies where there is water and sunlight

A Teapot of Towhees

Abert’s Towhee is a shy but engaging bird. This member of the sparrow family has one of the smallest ranges of any bird species, making it a prize sighting for birders; and a familiar face for desert dwellers. 

Secretive Abert’s Towhees are described in field guides as residents of thick brush in Sonoran riparian corridors, usually cottonwood and willow woodlands along rivers and streams. Yet a pair of Abert’s hangs around our back yard, kicking and pecking on the ground for insects and seeds. They shelter in the creosote and chuparosa, and sip water trickling from the cement lip of our fountain. 

The native waterways that make up Abert’s Towhee’s traditional range have mostly dried up. Growing demands on ground water have brought Arizona’s desert streams to a nonexistent or strictly ephemeral status.  Water collects in these channels after rains, but lately the amount is insufficient to bring the water table up to the surface level of the stream beds.  Suburban yards, particularly those planted with native species that attract insects and produce seeds, have proven to be havens for these displaced song birds. 

Abert’s Towhee is a homebody. He keeps to a small home range and mates for life.  In a romantic ritual, the male woos the female by feeding her seeds and the two sing duets together. Throughout the year towhee pairs forage together, calling to each other often, always strengthening their bond. The female weaves a large open cup shaped nest and decorates the outside with flowers. She lays 1-4 eggs, often raising two broods. 

Did you know if you see a group of Abert’s Towhees together you can claim you’ve seen a tangle of towhees? Or if it seems appropriate, a teapot of towhees works too. 

Hosting Hummers

The desert plant Chuparosa grows in both our front and back yards, bringing in a resident population of Costa’s hummingbirds. Costa’s is the only true Sonoran Desert hummer, well adapted to the arid environment. Hummingbirds lap nectar from tubular shaped flowers using long beaks and tongues. They also eat soft bodied insects, gleaning their small prey from foliage or seizing them in midflight. 

A hummingbird beats its wings 80 times per second, flying forward, backward, up, down and sideways. The active heart rate of this tiny being is 1260 beats per minute. This racing metabolism requires the bird to feed nearly constantly to survive. 

The key to the gorgeous iridescent colors of a hummingbird is found in the cellular structure of the feathers. The light absorbing and pancake shaped “melanosomes” within the cells of feathers are filled with tiny air bubbles that create a multitude of surfaces.  When sunlight glints off these surfaces we see the shimmering colors.

Males wear the dazzling pigments to attract females of course, and these flashy guys also put on astounding flight displays in breeding season. The Costa’s male loops 75 to 120 feet up into the sky, and rockets down at 60 mph, adding a whistling call to the descent, all to impress the watching female. After he has secured her attention and after the pair have mated, he moves on. The female builds her nest, incubates the eggs and raises the young on her own.

Costa’s hummingbirds nest early in the desert to take advantage of winter blooming plants such as the Chuparosa. In February the female begins collecting spider webs and binding together her walnut shell sized nest. She weaves small stems, leaves, bits of bark, and feathers into a cozy receptacle for her two bean sized eggs. The spider webs ensure the nest is stretchy enough to accommodate two rapidly growing nestlings. 

Although the most arid adapted of all hummingbirds, the Costa’s that visit our yard drink frequently from the trickling water of our fountain.

Male leans in to access lavender bloom
Chuparosa blooms winter to spring
Male Costa’s Shows Amethyst Colors