Shades of Night

Jimsonweed or Sacred Datura is a type of nightshade species.

Common garden plants such as tomatoes, potatoes, and eggplants are members of the Solanaceae family, also called the nightshades. The term nightshade comes from the Old English nihtscada, which literally means ‘shades of night’. Some species grow in shady areas or bloom or become more fragrant at night. The toxic reputation of this family is due to the fact that some species are poisonous and consuming them can cause deep sleep or death, but this belief was before non-toxic tomatoes and potatoes became known staples in our diet.

Species in this family are characterized by star-shaped flowers with five petals and often yellow centers, alternate leaves with pointed tips and wavy margins, and fruits or berries containing alkaloids. These alkaloids vary by species, and are beneficial in some but toxic in others. In our area, some of the more common native nightshades include Silverleaf Nightshade (Solanum elaeagnifolium), Downy Groundcherry (Physalis pubescens), Jimsonweed (Datura wrightii), and Chile Pequin (Capsicum annuum).

Silverleaf Nightshade, also called White Horse Nettle, Trompillo, and Tomato Weed, is one of the poisonous species. It grows 1 to 3 feet tall, with silvery hairs covering its leaves, and violet-purple or white ¾ inch blooms. Its yellow fruits resemble small tomatoes and stay on the plant for months, often into winter. This nightshade blooms from April to October and can be found in prairies, plains, pastures, and roadsides. Its genus name comes from the Latin solamen meaning ‘quieting’, and alludes to the narcotic properties of several species. 

Silverleaf Nightshade

Downy Groundcherry, also called Husk Tomato, grows to about 1 foot tall, with deltoid leaves and stems covered in fine hairs, inflated, papery, lantern-like husks that cover the round green fruits, and yellow flowers with 5 greenish/brown spots at the base of the petals. It blooms from April to December and can be found on rocky ground throughout our area. Its fruits can be edible but only when fully ripe.

Downy Groundcherry

Downy Groundcherry fruit is covered in a lantern-like husk.

Jimsonweed is also known as Sacred Datura, Thorn-apple, and Angel Trumpet. Often found on floodplains, it grows to 6 feet tall, stout and branching, and is covered in spreading hairs. Its leaves are up to 8 inches long and are mostly egg-shaped with an asymmetric base, its flowers are large, white, fragrant, trumpet-shaped blooms, and its fruits are 1.5-inch, round, spiny capsules. The flowers bloom in the evening through the morning, from April to October, and it is a host plant for the Carolina Sphinx moth. Extracts from this plant are narcotic and potentially lethal if ingested. It was once important in the religious ceremonies of southwestern native peoples.

Jimsonweed Bloom

Jimsonweed Spiny Seed Capsule

Also called Chile Tepin and Bird Pepper, Chile Pequin is an edible nightshade that grows to 2 feet tall, with simple, alternate leaves, tiny white blooms, and small green fruits that turn red when ripe. These fruits are edible but on the hotter side, and are favored by many species of birds. It blooms from May to October and can be found in thickets and along rivers in well-drained soil.

Chile Pequin

Consider adding some of these shades of night in your garden. They are beneficial for wildlife as their flowers attract pollinators, their leaves provide food for caterpillars, and their mature fruits are consumed by birds and small mammals alike. 

Leaping Lizards

 

Warmer weather increases the activity of lizards

As temperatures rise and the days grow longer, it’s quite common to see different types of lizards basking in the sun, darting across driveways and sidewalks, and climbing tree trunks and other vegetation. Three common species observed this time of year include the Green or Carolina Anole (Anolis carolinensis), Plateau or Texas Spotted Whiptail (Aspidoscelis gularis), and Texas Spiny Lizard (Sceloporus olivaceus).

Green Anole - green form

Ranging from bright green to dark brown, the Green Anole possesses the ability to change color due to temperature and light. A small lizard, it has a pale colored underbelly, long claws, and a thin tail. The males have what is called a ‘dewlap’, a bright pink flap of skin that can be extended and retracted for purposes of intimidating rivals and attracting females during the mating season. These anoles are arboreal, spending most of their time in trees, shrubs, and vines, feeding on insects and spiders. While they have a small territory, the males will aggressively defend it, starting with extending their dewlap, bobbing their head, performing pushups, and ultimately ending in a chase or a wrestling match. All this posturing, patrolling, and jumping from one branch to another can make the males much easier targets for predators, however, and they tend to have higher mortality rates than the much more discreet females. If it is late spring and the right to mate is at stake, the winner will once again employ headbobbing and dewlap extension to entice the female, who will lay a single, softshell egg among the leaf litter. 

Green Anole - brown form

A male Green Anole extending his pink dewlap

A medium to large striped and spotted lizard, the Texas Spotted Whiptail is endemic to New Mexico, Oklahoma, and Texas. It grows from 6.5 to 11 inches long, typically tan brown to green-brown in color, with a pattern of seven distinct grey or white stripes that run the length of the body and stop at the tail. Light colored spots are present along the sides, the underside is uniformly light in color, and the tail is often close to three times the body length. This whiptail is highly active during the day, hunting for insects in a wide variety of habitats, and like other whiptails, is capable of tail autonomy or the ability to shed its tail to escape predation. Breeding occurs in the spring, with the female laying a clutch of 1 to 5 eggs in a separate chamber of their underground burrow, typically in moist soil, by early summer. 

Texas Spotted Whiptail

Primarily arboreal but preferring basking surfaces such as fence posts and rock walls, the Texas Spiny Lizard is quite common in all but the eastern and western thirds of Texas. A robust spiny lizard up to 11 inches long, it is grayish to olive brown with up to nine dark wavy bars spaced along its back, which gives it a very scaly appearance. Males have a narrow bright blue patch on each side of the belly, and while the females lack this coloration, they are slightly larger and paler than the males. An ambush predator, they feed on a variety of insects found on the ground in open areas or up in trees in wooded areas. Breeding occurs in the spring and summer, and mature females may lay several egg clutches per year.

Texas Spiny Lizard

As temperatures cool when evening approaches, most lizards will retreat into sheltered refuges until warming begins the next morning. As temperatures rise throughout the day, they will increase their activity levels and become leaping lizards once again!

Breaking Slumber

 

Many small creatures awaken in Spring

In the winter months in central Texas, most cold-blooded reptiles and amphibians exhibit a form of hibernation called brumation. Triggered by shorter days and lower temperatures, this state can last for days or weeks, depending on the species. Brumation differs from true hibernation in that these animals remain semi-conscious and occasionally wake up to drink but not eat. During this period, body temperature, heart rate, and respiratory rates are greatly reduced.  This state of dormancy occurs with several common amphibian species, including the Rio Grande Leopard Frog (Lithobates berlandieri), Gulf Coast Toad (Incilius nebulifer), and Green Tree Frog (Hyla cinerea).

Rio Grande Leopard Frogs are medium-sized native frogs, to 4.5 inches, greenish-brown in color with a yellowish ridge along each side of the back. They have large dark spots on the back and sides, and a wide, light-colored jaw stripe that is poorly defined and fades in maturity. Their call is described as a short, low-pitched guttural rattle, either given singly or in rapidly repeated sequences. These frogs spend the winter months resting at the bottom of ponds, lakes, or other bodies of slow-moving water, but can become active during warmer, wet periods. Since they are semi-aquatic, they can also tolerate cold conditions by burrowing into mud or soil. They tend to enter brumation just before freezing weather, and often hide in deeper water to temporarily escape extreme temperatures.

Rio Grande Leopard Frog

The Gulf Coast Toad is a native, broad-headed, mostly terrestrial toad, to 5 inches, with prominent cranial crests that form a depression on top of the skull. Their background color is brownish-yellow to brownish-gray, with broad dark lateral stripes bordered by a light stripe, as well as a light central stripe, and they are covered in numerous small whitish to orange spots. Their vocal sac becomes large and rounded when calling, which sounds like a short, flat trill repeated several times. These toads are usually dormant from December to February, hunkering down in self-dug holes, abandoned animal burrows, under logs, or in leaf litter to protect themselves when the temperature dips below freezing. While they become active as the temperatures rise in early spring, they may also burrow to survive hot, dry conditions in the summer months, and this unique behavior is called aestivation.

Gulf Coast Toad

Green Tree Frogs are smaller, native arboreal frogs, to 2.5 inches, with smooth skin, a slender, flat body, and long slender legs with large toe pads on each foot. In warmer conditions, when the frog is active, they are typically a bright green color, but they can change to a dull color during periods of cool weather or to blend in with their surroundings. They also have a long white stripe on either side of the body. Their call sounds vaguely like a honking duck and is repeated 30 to 60 times a minute. These frogs brumate in the winter months, often hiding under deep leaf litter, in tree cavities, in potted plants, or even in the corners of garages and sheds. During this time of inactivity, they slow their metabolism and sometimes survive partial freezing by producing natural antifreeze compounds called glycerol that protect their cells. They also typically choose sheltered damp spots to avoid freezing completely, and may wake on warmer, sunny winter days to move about.

Green Tree Frog

As the days get longer and temperatures begin to rise, once again we will be treated to the sights and sounds of these marvelous amphibians, as they break their winter slumber!

Butterflies in Winter

Early blooming plants like Elbowbush attract butterflies  

While butterflies are most noticeable in spring, summer, and fall, seeing them in the middle of winter is often surprising.  Most spend the winter in the egg, larva, or chrysalis stage of development, concealed in leaf litter or in other forms of vegetation, but some overwinter as adults.  

Most of the adult butterflies observed in the winter belong to the Brushfoots, a highly variable group of primarily mid-sized butterflies, some with irregular wing shapes, and many that fly with distinctively alternating flaps and glides.  In our area, the adult butterflies in this group most often seen in the winter, usually on a particularly warm sunny day, include the Red Admiral (Vanessa atalanta), Question Mark (Polygonia interrogationis), and Painted Lady (Vanessa cardui).

The Red Admiral is a common butterfly, not to be confused with any other species.  Dark above with fiery orange-red slashes and white spots on the outer part of the forewing, their flight is fast and erratic, darting out at anything crossing their path. Their larval host plants include nettles and pellitories. 

Red Admiral

Question Marks are also quite common, and their orange forewings and hindwings are sprinkled with dark brown dashes and dots, especially in the winter form (oddly, in summer their hindwings are mostly black). Their wings have irregular edges with a somewhat hooked forewing tip and a short tail on the hindwing. But their most distinctive feature is the silvery comma and adjacent dot forming a question mark in the center of the hindwing’s underside. Their larval host plants include nettles, hackberries, and elms.

Question Mark

The Painted Lady is one of the most familiar butterflies in all of the US. They are orange and black with a black patch and white spots on the forewing tips and a row of small black spots on the hindwing. On the hindwing’s underside, they have a row of four small eyespots which help distinguish them from American Lady butterflies. Their larval host plants include mainly thistles and mallows.

Painted Lady

But how do these adult butterflies survive the cold? First, they begin to enter a period of suspended development in the fall, called diapause, which causes their metabolic processes to slow down considerably. Second, their bodies produce chemicals that act as natural antifreeze, preventing their body fluids from freezing. And third, they find protected locations to shelter from the cold, such as in tree hollows, under loose bark or leaf litter, in cracks between rocks, or among dense, dry brush. 

Those butterflies that overwinter in the egg, larval or pupal development stage have hidden homes in the colder months. Some are lying in leaf litter on the ground, while others are slumbering in silk shelters on spent stems and along grass blades. While it can be difficult to spot these hidden homes, be mindful that these vulnerable creatures are asleep in our yards and green spaces, and try to hold off on removing all leaf litter and performing cut back until the beginning of spring. 

Winter Warblers

 

Warblers in winter?  Who knew!

New World warblers, often called wood warblers, are a group of birds found predominately in the Americas. They are relatively small birds with thin, pointy bills, and are famous for their diverse and high-pitched songs. Many warbler species are migratory, breeding in North America and traveling to their Central and South American overwintering grounds each fall.  But there is a certain warbler species that stops short of traveling so far south, spending its winters in the central and southeastern portions of the United States, including most of Texas. That species is the Yellow-rumped Warbler (Setophaga coronata).

While the Yellow-rumped males are most colorful during the spring and summer breeding season when they sport a dazzling mix of bright yellow, charcoal gray, black, and bold white, in winter their plumage coloring subdues, but still exhibits their trademark bright yellow rump with some yellow on the sides. Females are always duller, and may show some streaky brown, but like the males they also have a yellow rump, which is why these birds are sometimes affectionately called ‘butterbutts’.

'Myrtle' form of the Yellow-rumped Warbler

The Yellow-rumped Warbler has two distinctive subspecies that used to be considered separate species: the ‘Myrtle’ Warbler of the eastern U.S. and Canada, and ‘Audubon’s’ Warbler of the mountainous west.  The Myrtle form has a white throat and is more common here, and the Audubon’s has a yellow throat and can be found in west Texas.

'Audubon's' form of the Yellow-rumped Warbler

Like most warbler species, Yellow-rumps are active birds, even in winter, foraging for insects in open woods and shrubby habitats.  This time of year, they supplement their insectivore diet with native berries from Ashe Junipers, Poison Ivy, Greenbrier, Mustang Grape, Winter Grape, Virginia Creeper, and Roughleaf Dogwood.  However, they prefer the fruits of Wax Myrtle and Bayberry, as their digestive systems are uniquely suited to process their waxy berries, thanks to specialized microbes in their gut.  This ability allows them to remain farther north than other warbler species during the colder months. 

Winter plumage of Yellow-rumped Warbler

In winter, Yellow-rumps will join flocks and even come to feeders where they’ll eat sunflower seeds, raisins, suet, or peanut butter.  Flocks can be mixed species of other winter birds or even large groups consisting entirely of Yellow-rumped Warblers. But if another bird gets too close, they respond to the infraction by holding their body horizontally and raising their fanned tail to form a right angle to their body, indicating that they want the other bird to give them some space.

The Yellow-rumped Warbler’s flight is agile and swift, and they often call as they fly and change direction. Their sharp chips are quite distinctive, and they even call while foraging. Learn to recognize their sound and you will then be able to locate and enjoy these delightful winter warblers!

Roving Ringtails

Raccoon or Ringtail?

The common but elusive Ringtail or Ringtail Cat (Bassariscus astutus) is not a cat at all, but a member of the Procyonidae Family and a close relative of the Northern Raccoon.  The origins of its scientific name comes from bassar or ‘fox’, isc or ‘little’, and astute or ‘cunning’. In Texas, it is found mostly in the Trans-Pecos, the Edwards Plateau, and the Cross Timbers regions.   

An adult Ringtail on our back porch railing.

While ringtails are cat-sized mammals, their face is fox-like with a pointed snout, their body is elongated, and their tail resembles a raccoon.  The ears are large, and their big, dark eyes are each surrounded by a patch of light-colored fur.  The fur on their body is buff to brown-colored above and whitish below, with a spectacularly bushy, ringed tail.  This tail is often longer than their body, and is marked by a series of 14 to 16 alternating black and white rings (black rings incomplete on the underside) with a black tip.  

Close-up of the face of a Ringtail.

Mainly nocturnal but sometimes seen at dawn and dusk (crepuscular), ringtails are roving, solitary mammals that come together only to mate.  Their breeding season starts in late February and continues to mid-April, and females are in heat for only one 24-hour period during this time.  In early May to mid-June 2 to 4 cubs are born fuzzy, white-haired, and with a tail that is not yet colored with the distinctive black and white bands.  The cubs open their eyes at one month, and at four months begin hunting for rodents, insects, lizards, birds, and berries.  Ringtails are quite vocal, especially the young, and will make a variety of sounds including squeaks, chatters, grunts, growls, and hisses, with the typical call being a loud, plaintive bark.  In the wild, ringtails live an average of seven years. 

This Ringtail is eating sunflower seed that has fallen out of our bird feeders.

Ringtails can be found in our oak-juniper woodlands that have rocky areas associated with water, including riparian canyons and caves, limestone cliffs, and sometimes in man-made structures like mine shafts.  They can den in tree hollows, rock crevices, other animals’ abandoned burrows, and even seldom-used spaces in buildings.  They roam frequently, rarely spending more than three straight nights in one den.  Interestingly, the ankle joint of the Ringtail is very flexible and is able to rotate over 180 degrees, which makes them very agile climbers.  By pressing their feet against one wall and their back against the opposite wall, or by pressing both right feet against one wall and both left feet against the opposite wall, they are able to ‘stem’ or ascend/descend narrow passageways and wide cracks in the rock.  Their strong tail can provide balance for negotiating narrow ledges and limbs, and even allows them to reverse direction by performing a cartwheel!       

Getting access to our bird bath is an easy feat for the agile Ringtail!

Ringtails have many other common names, including Miner’s Cat, as they were often kept by miners and settlers as pets, to keep their cabin free of mice.  A hole was cut in a small box that was placed near a stove or fireplace, which acted as a dark, warm place for them to sleep during the day, and they returned the favor at night, hunting mice and keeping them and other rodents at bay.  In the native language of the Nahuatl Indians of Mexico, ringtails were called cacomistle, which is derived from the word tlahcomiztli meaning ‘half mountain lion.’  Whatever you call them, consider yourself lucky should you spot one of these beautiful, timid, and rarely seen nocturnal mammals!  

Observing Orbweavers

Drops of morning dew sparkle on a spider's web.

The family of spiders known for building flat, spiraled, wheel-shaped webs are called Araneidae, or the orb-weavers.  They are the most common group of spiders often founds in yards, gardens, fields, and forests.  In our area, those include the Black & Yellow Garden Spider (Argiope aurantia), Lichenmarked Orbweaver (Araneus bicentenarius), and Spinybacked Orbweaver (Gasteracantha cancriformis).  While all of these spiders produce venom, that venom is harmless to humans but helps them to immobilize their insect prey.

Also called the Yellow Garden Spider, the Black & Yellow Garden Spider is a large spider that has an abdomen with a series of pale, yellow spots on a black background, and legs that are orange at the base, black near the tips, and often held in pairs. Females are much larger than males, with up to an inch in body length. While both appear in late summer, females can be seen through December in our area.

A Female Black & Yellow Garden Spider.

While not quite as common, the Lichenmarked Orbweaver has an abdomen with a pattern of light green and reddish-brown markings and two small humps on front.  Females can grow to one inch in body length. Its legs have alternating bands of orange and brownish-black, and the coloration on its abdomen acts as a natural camouflage against the lichen-covered branches of trees where it often rests.

Lichenmarked Orbweaver, showing its characteristic green abdomen with two humps.

Often called crab spiders, one of our most distinctive spiders is the Spinybacked Orbweaver, a small, half-inch wide spider with a hard exoskeleton that has six spines around the edge.  There are many color forms, but most are yellow or white with black or dark red spines. Males are tiny and seldom seen, but females can be seen year-round. They build their webs in the morning in shrubs or low tree branches.

Spinybacked Orbweaver, yellow form.

Spinybacked Orbweaver, white form, showing relative size.

Orb-weaving spiders are one of nature’s engineers, and their process to build a web is intriguing.  They start by floating a line of silk on the wind to another surface. Once that line is secured, they drop another line from the center, forming a Y.  The rest of the web is a series of non-sticky spirals ending with a final spiral made of sticky capture silk.  The non-sticky webbing is nearly invisible, but the more visible sticky webbing is what normally traps the spider’s prey.  As such, there is always a tradeoff between the visibility and stickiness of the web.

The webs built by some orb-weavers include a vertical zigzag band of highly visible silk through the center of the web.  This is called the stabilimentum, and is most often found in the web of a Black & Yellow Garden Spider. While scientists are unsure of the exact purpose of this structure, theories include it posing as a lure to bring prey to the web, a warning for birds not to fly through the web, or as a way to camouflage the spider as it sits on the web.

A male Black & Yellow Garden Spider
rests on the web's stabilimentum.

Many orb-weavers build a new web on a daily basis.  They often hide during the day and become more active in the evening, when they consume the old web, rest for a bit, then begin spinning a new web in the same general location. Consider all that hard work the next time you think about destroying a web!

 

Fall Fliers

 

Fall-blooming Blue Mistflower and White Boneset attract late season butterflies.

Butterflies are frequently thought of as insects that fly primarily in the spring and summer seasons.  This is because the emergence of many butterfly species is unimodal, which means that their numbers increase as environmental resources increase.  These resources are defined as their host plants and nectar plants, which also become available during these warmer seasons.  

However, there are some species that have bimodal emergences, or increases in numbers in both the spring/summer and fall seasons.  It is thought that the division of offspring between two different emergence times may have evolved to avoid producing all offspring at one time.  This approach would reduce the risk of species mortality in case of potential fluctuations in habitat quality. 

Whether they be unimodal or bimodal, butterfly species typically exhibit a tightly synchronized adult emergence in order to help them locate mates. Further still, some species are present in low numbers during most of the year, but their numbers increase during the fall.  In central Texas these species include the Tailed Orange (Pyrisitia proterpia), Julia (Dryas iulia), Common Mestra (Mestra amymone), Queen (Danaus gilippus), and White-striped Longtail (Chioides albofasciatus).

In the fall, the Tailed Orange is in its winter form, yellow with brown lines and blotches below and a noticeably pointed hindwing edge.  Its summer form is unmarked yellow below and the hindwing edge is less pointed. It flies late summer through fall, and uses senna species as its host plant.

Tailed Orange, winter form

The fast-flying Julia is mostly orange above and orange to brown below, with the female being a duller orange than the male and having a dark forewing band.  Its longwing shape is quite distinctive and it prefers woodland edges and gardens where it uses passionvine species as its host plant.

Julia, male

A slower, flat-winged flyer, the Common Mestra is pearly white above with a pale orange border on its hindwing, and mostly pale orange below with a thin, white spotband.  It is most often seen from June to November, and it uses noseburn species as its host plant.

Common Mestra

The Queen butterfly is often confused with monarchs, as it also uses milkweed species as its host plant.  Rich dark brown to deep orange above with white spots in the black wing margins, it lacks the strong black veining on the wings like monarchs, and can be found in any open habitat usually visiting flowers.

Queen

Straying into our area from south Texas, the White-striped Longtail is a dark brown butterfly with very long tails, and a prominent white stripe on the underside of its hindwing.  It usually perches with its wings closed, and uses various legume species as host plants.

White-striped Longtail

One way to increase your chances of seeing these fall fliers in your yard is to provide native plant species that bloom in late summer and well into fall. These plants include Frostweed, Gregg’s Mistflower, Blue Mistflower, White Boneset, Lindheimer’s Senna, Plateau Goldeneye, and Texas Lantana.  And remember, fall is the perfect time to plant!

Furtive Fledglings

 

Mixed woodland of oak and juniper in Central Texas is the only breeding habitat
for the Golden-cheeked Warbler.

As the temperature rises and late spring turns to early summer, many bird species are in the throes of caring for newly hatched nestlings (still in the nest) or fledglings (just out of the nest).  As you hike through our oak-juniper forests in the western part of Austin, you just may run across young families of our endangered bird, the Golden-cheeked Warbler (Setophaga chrysoparia).

Adult Golden-cheeked Warblers arrive at their breeding grounds by mid-March, returning largely to the same areas each year and nesting from April to May. They are socially monogamous, with the males arriving before the females to establish their territory. Courtship behavior, rarely observed, involves the female collecting nesting material as the male sings a soft, twittering version of his song, flicking and spreading his wings and tail and sometimes bringing nesting material to the female. 

A male Golden-cheeked Warbler sings from a juniper to establish his territory.

The female chooses the nest site, often in a branched fork of an Ashe Juniper or Live Oak tree, and the nest is built in 4 days, camouflaged by bark strips from mature juniper trees and secured by spider silk. Females lay 3-4 eggs and for the first 3 days she broods or sits on the eggs continuously, being attended to and fed by the male. The eggs hatch in approximately 12 days, and the nestlings are altricial or born helpless and requiring significant parental care.  

Female Golden-cheeked Warblers typically don't have black throats,
but the ones that do are called 'bearded females'.

However, they leave the nest only 8 or 9 days after hatching, staying in the vicinity of their attendant parents, but usually huddled together and partially hidden in the trees. They continue to be cared for by both parents, who actively search for caterpillars and other insects in the foliage to bring directly to the fledglings.  

A fledgling Golden-cheeked Warbler.

The most obvious way to spot these furtive fledglings is by listening for the family group.  As a parent nears with food in its beak, the fledglings chip rapidly and flutter their wings, begging and hoping to be the one who gets the morsel of food.  They grow quiet once the parent takes off to forage again.  Once they get a bit older, they start to follow their foraging parents begging for food, eventually becoming more confident in their ability to fly and learning to forage for themselves. As they become even more independent, the young join the adults in mixed-species flocks in the woodlands before migration begins in July and early August.

This Golden-cheeked Warbler fledgling caught its own food!

If you hear or see a Golden-cheeked Warbler family foraging and feeding in our mixed woodlands, consider yourself lucky.  Of the nearly 360 bird species that breed in Texas, the Golden-cheeked Warbler is the only one that nests exclusively in Texas, so each one is a native Texan! 

Requisite Night

 

Light pollution is nearly non-existent in Big Bend,
allowing for spectacular star-filled night skies.

Most environmentally-minded individuals recognize the more talked about threats to our native wildlife, such as habitat fragmentation/loss, invasive species, and climate change, but not as many are aware of the dangers posed by light pollution. Up until the mid-1800s, humans and animals lived under night skies solely lit by the moon. Electric outdoor lighting became common in the early 20th century, but its use spread quickly, and the global extent of modern light pollution became clear.  

By 2016, it was possible to measure nocturnal artificial light with the advent of a comprehensive global satellite measurement system. Researchers found that more than 80% of the world’s population lived under light-polluted night skies, or skies where the glow of artificial light is significant enough that the stars disappear from view.  In the US and Europe, it was found that 99% of residents live under light-polluted skies.

Light pollution exposes animals to many dangers, including predators, starvation, exhaustion, and disorientation. Artificial light, like roads and fences, can create barriers that fragment habitat.  Slow-flying bats avoid feeding in or passing through illuminated areas for fear of predators such as owls and other birds of prey. Artificial light near their roosts can also delay their emergence at dusk when their insect prey is most abundant.  If they never leave their roost since it always appears to be light, they can even starve to death.  

Artificial nocturnal light can also lure animals in and lead to their destruction.  Many species of migratory songbirds are attracted to brightly lit structures at night, circling them, sometimes colliding into them, or becoming disoriented enough to lead to a depletion their energy stores which ends in exhaustion and the inability to complete their journey.  In some bird species, artificial light at night interferes with their ability to use natural polarized light from the sky to calibrate their internal compass.

Artificial light at night attracts insects, like this Luna Moth, 
and can disrupt normal behavior patterns.

Light pollution is also one of the many factors contributing to the rapid decline of insect populations.  Moths and other nocturnal insects orient themselves by moonlight, and this instinctual tendency is interrupted by artificial night light, luring them in to fly incessantly around a bright light, causing exhaustion, exposure to predators, and the potential to miss courtship cues from mates.  This is especially true for fireflies, as artificial night light can cause them to alter or cease their mating flashes.  Studies have also shown that light pollution can harm diurnal insects like monarchs, who flit and flutter all night when exposed to excessive light when they should be resting, and causing them to be disoriented from their migration route.

Light pollution facts and some easy solutions.

Unlike other environmental threats to wildlife, simple solutions to artificial nocturnal light exist.  The best solution is to have no nocturnal lighting other than natural conditions. If a light at night is truly needed, the amount that spills into wildlife habitat can be reduced through dimming, downward shielding, or switching to motion-activated lights. Studies are also showing that lights in the warmer color tones are less disruptive than bright white lights.

Travis Audubon promotes the Lights Out Initiative for Austin.

Austin is one of several cities across the US that participates in the migratory bird friendly Lights Out Initiative, which asks residents to turn out all non-essential lights from 11pm to 6am every night during spring migration (March 1 – June 15) and fall migration (August 15 – November 30).  This is one of many ways we can prevent light pollution from overpowering our native wildlife. Turn out your lights when they are not needed, and welcome the requisite night!