The Sound of Summer

A summer day in southern Arizona is anything but silent. Even if we completely eliminated the sound of humans and their machinery, the desert supplies a raucous, riotous auditory performance during the summer. Animals are emerging to metamorphose, feed or mate. In monsoon season, the diversity of the Sonoran Desert is on full audible exhibition.

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Photo: Lauren Grace Bailey

Dawn

Gambel’s quail greet the day noisily, chattering away in their gregarious covey. A peek out the window confirms the racket: male and females are scratching away in the dirt searching for seeds and insects, topknots bobbing in time. They are persistent communicators- their constant updates include information about assembly times, location reports, predator spotting, or to check in with a mate. In fact, their distinct “ka-KAA-ka” call brings humans to windows in hopes of catching a glimpse of their babies lined up in a comical crack-the-whip chain of cotton balls.

The calming and attractive sound of doves rounds out the early morning experience. Mourning, white-winged and Inca doves have successfully made the Sonoran Desert home, and are especially common around houses that have bird feeders and a consistent water source. The overlapping “coo”s of the three species creates a harmonious tune, until startled and a noisy clap of wings initiates a burst of flight. The mourning dove’s wings make a unique whistling sound, especially during take-off and landing. This may be a way to warn flock-mates that danger is imminent, although the purpose of this sound is debated.  This is especially interesting because other birds, such as owls, have feathers designed to render them nearly silent in flight.

Mid-Morning

Northern cardinals and pyrrhuloxias gossip back and forth from the mesquite trees. These thick-billed birds are remarkably similar, as are their rich songs. Cardinals do well year-round in Tucson. Their metallic chirp provides familiar staccatos in an auditory landscape, just as their bright crimson plumage and crest provide visual interest in a backyard.

The cardinal’s song is a series of two-part whistles, often ending in a slow trill, and lasting 2-3 seconds.  Both males and females will sing, “cheer, cheer, cheer” or “birdie, birdie, birdie,” but it’s the male most likely to be heard, as he will sing throughout the year.  The northern cardinal has at least 16 different calls, but the one heard most often is the loud metallic chirp used for warning. This sound is used to warn intruders to their territory, to signal that predators are near when females approach their nests, when trying to get babies to leave the nest, and when carrying food to the nest. The pyrrhuloxia’s songs and calls are similar, though slightly softer and more reedy. Both of these birds’ calls stand out from the chorus.

On the quieter side, In the dry leaves under a jojoba, rustling can be heard while whiptail lizards dig and search for prey and the buzzing flight of the green fig beetle can be heard overheard as it looks for its next juicy meal. Banded-wing grasshoppers, the incredibly common gravel colored orthopterans, can be heard as well. Not only is their stridulation loud, the scraping of the hind femora against the forewing, but also their crepitation—their short disruptive flight noises as they bounce from spot to spot evading capture.

Noon

Quiero morir cantando como muere la cigarra” (I want to die singing as the cicada dies)

– Raymundo Perez y Soto, sung by Linda Ronstadt, “Canciones de mi Padre”

The cicada gets the Sonoran Desert to itself in the heat of the day. It’s an ingenious predator-avoidance strategy. Appear when it’s so hot that no other animal can withstand the temperature. So how does a cicada do it? Same way humans do in an arid environment. Cicadas are the only insect known to have sweat pores and utilize them as a cooling mechanism. The chunky insects are losing 20-35% of their body’s water every hour and thus, feed almost continuously on plant fluid. Because xylem is so nutrient poor, the cicada must suck up copious amounts to retrieve the precious minerals and carbohydrates. The sweating cicada has an internal swamp cooler mechanism so that in an arid desert it can be out in record-setting temperatures and, by sweating, can lower its body temperature by 9°F (5°C). It is at this time that this noisy hemipteran is the most brazen in its reproductive communication attempts. Everyone is familiar with the loud buzzing of the bug in the summer heat.

Male cicadas are equipped with tymbals—noise-making membranous structures on their abdomens. Muscles control the expanding and contracting of the tymbals, while the nearly hollow abdomen amplifies the sound. Several species of cicadas live in the Sonora Desert and each has its own distinct song with which to attract a mate. In fact, it is often the song that is a distinguishing factor in cicada species identification (DNA analysis is more helpful when dealing with a preserved specimen!). The sound can be ceaseless and hypnotic and has often lulled me into a dog-day afternoon nap.

Mid-Afternoon

Each afternoon is a guessing game during the monsoon season. Will today bring an abundance or paucity of rain? The towering 40,000ft cumulus cloud that creeps over the Catalina Mountains isn’t a guarantee for everyone, but whether or not you get wet, you will likely hear this other celebrated summer sound: thunder. Lightning rapidly heats and thus expands the air, essentially creating a sonic boom in the sky. The closer you are to lightning, the louder and more urgent the thunder is—often described as a cracking sound. The further away, the more of a low rumble.

Whether a crack or a rumble, in Tucson the sound is familiar and relieving. The dry, parched desert is rewarded after a long foresummer’s wait, the smell of creosote fills the air, and animals begin to act on a singular goal. Rainfall is synonymous with reproduction.

Dusk
The romantic overture of the male spadefoot is no solemn affair. These amphibians are not known for secretive, furtive coitus; rather, males loudly and persistently advertise their bachelorhood to the neighborhood. Such vulnerable proclamations can be heard for long distances. Spadefoots are not merely tenacious for tenacity’s sake. They have a very limited timeframe in which to take their reproductive chances.

The spadefoot’s emergence from underground hibernation is sparked not by moisture but the vibration caused by rainfall and thunder. Once a year, during the monsoon season, spadefoots dig their way back aboveground to search for other amorous amphibians. The clock is ticking. The metamorphosis of the toad, from breeding and egg development, to well-nourished juvenile must happen quickly—in under a month! Egg to tadpole to toadlet to young adult can happen in as little as nine days! Why? To win the race against evaporation. Spadefoots must grow up before their pools dry up. Thus, the call of the newly emerged is essential to species survival. The males will fill their air sacs with gases pushed up from the lungs and then expel it forcefully. The sound has been described as a lamb bleating or a baby crying. It will go well into the night, if success does not come quickly.

Once a pair of spadefoots accepts one another (rather, the female accepts the male as the male seems none too choosy) they get into position in a body of water. Ephemeral pools, potholes, and swimming pools have all been hosts to spadefoot trysts. It is called amplexus. The male rides atop the female, hooking his front limbs over her “shoulders.” Both expel their gametes simultaneously. The female can lay over 3000 eggs, with the hope that just one will make it to adulthood. Spadefoots will alternate between bleating, mating and gorging themselves until the monsoon season ends.

Nighttime

The call of the coyote starts out in monosyllabic yips, shouting to pack mates. It is a literal wake-up call that slowly adds voices and builds to a crescendo. The pack prepares for a night of hunting, playing and perhaps mating. Coyotes sing to communicate, to warn, and to attract. It is a haunting alien tune, but it is not the cry of the alienated. This iconic sound ends our summer day. It is time to go to sleep.

Summer’s long-awaited symphony is a layered affair. The arrangement is improvised daily, but the ensemble and their distinct scores are familiar and complementary. Quail, insects, and thunder all do their musical part, be it providing melody, harmony, or rhythm to create the acoustic event of the year. All you have to do is open your window to enjoy a free concert.

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Photo: ASDM/Liz Kemp

Written by ASDM Education Specialist, Catherine Bartlett. 


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