Monday, April 17, 2017

The Zen of Wrens

Carolina Wren, Thryothorus ludovicianus

Wrens are small to medium-sized birds, generally drab in color, typically grayish-brown with barring in the wings and tail.  But oh, when they sing, they have loud, melodious, and often complex songs!  Active and vocal, they frequently carry their tails in an upright position, and have adapted well to the presence of humans.  Some of the species of wrens that can be found in our area include Carolina Wren (Thryothorus ludovicianus), Bewick’s Wren (Thryomanes bewickii), and Canyon Wren (Catherpes mexicanus).

Deep cinnamon brown above and warm buff below, with a white throat and prominent white stripe above the eye, the Carolina Wren is a vivacious bird common in moist woodlands and wooded suburbs.  Males sing year round and are known to have a repertoire of about 32 songs, the most common being ‘cheery cheery cheery!’ and ‘teakettle-teakettle!’ This bird is routinely seen around yards, garages, porches, and woodpiles, often nesting in those same places.  Pairs stay bonded year around, and often raise multiple broods a year.

Bewick's Wren, Thryomanes bewickii

A subdued brown and gray bird with a white eye stripe, gray-white underparts, and a long tail barred with black and tipped with white spots describes the Bewick’s Wren.  It typically flicks its tail from side to side or fans it as it skulks through tangles of branches and leaves, searching for food. Nimble and acrobatic, it often hangs upside down from tree branches and leaves. While it favors dry, brushy areas, it is often found inhabiting gardens, residential areas, and parks.  The male has a repertoire of up to 22 songs, usually beginning with two or more high, quick notes, dropping into a lower, buzzy phrase, and ending on a high trill.  Courting birds normally form monogamous pairs.

Canyon Wren, Catherpes mexicanus

The Canyon Wren has a white throat and breast, chestnut belly, brown back flecked in black, and a bright rufous, barred tail.  It prefers areas with rocky cliffs, canyons, outcrops, and boulder piles but it will often build its nest in stone buildings or chimneys.  This wren has a slightly flattened skull and a vertebral column attached higher on the skull, and these adaptations allow it to thrust its bill forward into tight cracks without bumping its head.  While its repertoire consists of only 3 songs, its most common is an exquisitely beautiful descending cascade of liquid notes.

Wrens are mainly insectivores and are often found hopping about, climbing short walls and tree trunks, or making brief flights to search out and glean insects from crevices and cracks.  In fact, their family name Troglodytidae is derived from troglodyte, meaning ‘cave-dweller’, generally referring to the places in which they forage.  Their fairly long and slender, straight to slightly decurved bills assist them in exploring every nook and cranny for insects and spiders.

This spring, take the time to listen to the highly variable, sweet sounding, rollicking songs of these little birds.  Get in tune with their amusing antics, and discover for yourself the zen of wrens!

Wednesday, February 22, 2017

Three Terrific Trees

Mexican Plum in full bloom
Trees are often planted for their ornamental value, or to provide shade, but there are many other reasons to plant them.  They improve air quality by producing oxygen and storing carbon, which offsets the harmful byproducts of burning fossil fuels.  They can moderate the effects of sun and wind, reduce air conditioning costs, and clean the air by trapping dust and pollen.  Trees can also be credited with increasing property values, lowering our heart rates and reducing stress, and providing shelter and food for many types of wildlife.

In Central Texas, three terrific trees that are native to our area include Escarpment Black Cherry (Prunus serotina var. eximia), Mexican Plum (Prunus mexicana), and Carolina Buckthorn (Frangula or Rhamnus caroliniana).  All three of these trees are medium-sized, deciduous, display fall color, and benefit wildlife by producing fruit.

Escarpment Black Cherry blooms
Escarpment Black Cherry is a distinct variety of Black Cherry, found only on the calcareous soils in our wooded hill country canyons, slopes, and floodplains.  Up to 50 feet tall, this tree is prized for its attractive silvery trunk and branches, five-inch long clusters of showy white blooms that occur in March and April, juicy summer fruits, and vivid yellow to red fall foliage.  While the small dark red to purple-black cherries it produces are edible, the rest of the plant is not, and the cherries are often eaten first by birds.  Several butterflies, including Viceroy, Eastern Tiger Swallowtail, Two-tailed Swallowtail, Red-spotted Purple, and Striped Hairstreak use this tree as their host plant. 

Escarpment Black Cherry fruit
Often called the ‘star of our native plums’, Mexican Plum is easily recognizable in spring, as it is an early bloomer.  Before the leaves appear, white to pale pink, five-petaled flowers cover the 15 to 35 foot tall tree from February to April, and they are extremely fragrant, attracting several species of native bees and butterflies.  Plums up to one-inch wide turn from yellow to mauve to purple as they ripen July through September, and they are edible for humans and wildlife alike.  Thick, five-inch long leaves provide food for the Eastern Tiger Swallowtail and Cecropia Silkmoth, and turn a showy shade of orange in autumn. Mature trunks are a beautiful satiny blue-gray with horizontal striations, typical of most fruit trees.

Mexican Plum fruit
A flowering Carolina Buckthorn
Lesser known is the Carolina Buckthorn, an understory tree 12 to 15 feet tall, with oval, shiny green leaves and small yellow clusters of blooms produced near the leaf stems in May and June. It prefers bottomlands, canyons, and streamsides, and in light shade it is airy and tiered.  Bright red fruits turn to black when ripe, and are relished by many birds and mammals.  The leaves stay green into late fall, turning various colors from yellow-gold to bronze-sienna as the weather cools. Carolina Buckthorn is also the host plant for Spring Azure, Gray Hairstreak, and Painted Lady butterflies.

Carolina Buckthorn berries
Consider adding one or all of these terrific trees to your property.  While the best time to plant trees in Central Texas is in the fall, it’s never too late to plan for future enhancements to your native landscape!

Monday, January 23, 2017

Winter Chorus

Clear and bell-like, consisting of a single, quickly repeated note, the call of the male Strecker’s Chorus Frog (Pseudacris streckeri) is unmistakable.  In the midst of winter, especially in the peak calling season from January to early March, multiple males call at the same time, their alternating notes resulting in an unexpectedly delightful winter chorus rising up from the canyons!

Reaching an adult length of 1 to 1.5 inches, this largest chorus frog is identified by a stout gray, brown, olive, or green body, a dark brown mask-like stripe through the eye and a dark spot under the eye, dark longitudinal stripes along the back, and a deep golden or orange color in the groin. Males are slightly smaller than females and have greenish-yellow vocal sacs.  The genus Pseudacris comes from the Greek pseudes meaning ‘false’ and akris meaning ‘locust’, and is likely a reference to the repeated rasping calls of most chorus frogs, which are similar to and can be mistaken for those of an insect.

Although Strecker’s Chorus Frog is mainly a nocturnal frog, its call can be heard day or night. Males call as they hang on to or sit on vegetation, or from the bank above the water’s surface. Typically feeding on insects, this chorus frog is seen most often in moist woodlands, rocky ravines, near streams or in swamps.  While its range includes portions of Kansas, Illinois, Missouri, Oklahoma, Arkansas, and Louisiana, the individuals in Texas are of the subspecies P.s. streckeri, and occur in most counties in the eastern half of our state.

Aside from its distinctive winter chorus, Strecker’s Chorus Frog is also distinguished by its ability to use its forelimbs to burrow headfirst, unlike other amphibians that typically use their hind legs to back into a burrow.  It burrows deeply in sand or mud and hides under rocks and woody debris to protect itself from heat and predators, emerging mainly after heavy rains. Following these rains, it migrates a short distance to a preferred breeding site.

Strecker’s Chorus Frog is a cold-tolerant, winter breeding frog, breeding anytime between November and March when rains are adequate. While most frogs prefer to breed in flowing water, Strecker’s Chorus Frog prefers still, clear, temporary water bodies such as ditches, ponds, and pools in wet weather creeks.  Females attach their small, jelly-covered clusters of eggs to vegetation below the water’s surface, and the time to hatch, while water temperature dependent, is usually just a few days.  Tadpoles take around two months to transform into adult chorus frogs.  In spring, at a time when most other frogs are just beginning to seek their breeding ponds, Strecker’s Chorus Frogs terminate their breeding activities.

Named after John Kern Strecker, Jr (1875 – 1933), a Texas naturalist and Curator of the Baylor University Museum (renamed the Strecker Museum in 1940 in his honor), this chorus frog with its peculiar and unusual habits and haunting winter chorus might have been a perfect candidate for “Strecker’s Cabinets of Curiosities”!  

If you’d like to see and hear the chorus for yourself, check out the video at

Saturday, January 7, 2017

Flowers of Ice

While many plants can be damaged or killed by freezing temperatures or frost, this varies by the type of plant and tissue exposed to these conditions.  In our region, there is a plant called Frostweed (Verbesina virginica), which is commonly found in low-lying areas near streams, creeks, canyon bottoms, and in dappled shade at woodland edges. 

For much of the year, Frostweed goes unnoticed while it grows tall and leafy, the top of each of its stalks crowned by clusters of small white flowers.  It begins to bloom in the August heat, and continues until first frost, well into fall.  In fact, this leggy plant is a rare late-season nectar and pollen source, as its blooms are a magnet for fall migrating hummingbirds and Monarch butterflies, as well as a host of other insects.

However, it is with the first frost or sub-freezing temperatures that this plant really puts on an unexpected show.  When temperatures dip, the water contained in each plant stem expands, causing the stems to crack.  Via capillary action, more water is drawn through the cracks, freezes when it hits the cold air, and forms long curls of ice, reminiscent of petals of an intricate flower or of a delicate, abstract sculpture.

These very delicate ice forms are fleeting in nature, and can only be found in early morning, as the rising temperature of the day quickly melts them away.

Sunday, December 4, 2016

The Preserves Around Us

Golden-cheeked Warbler, Setophaga chrysoparia
One of the main reasons Austin is such a wonderful place to live is because it is interlaced with a patchwork of preserves, which together comprise the Balcones Canyonlands Preserve (BCP) System.  In 1992, voters in the City of Austin passed Proposition 10, approving $22M in bonds for the sole purpose of acquiring and improving lands to protect air and water quality, conserve endangered species, and provide open space for passive public use. Jointly owned and managed by the City of Austin, Travis County, the Lower Colorado River Authority, the Nature Conservancy, the Travis Audubon Society, and private landowners, the BCP’s ultimate goal is to set aside 30,428 acres that contribute to the quality of all life here in Austin. 

A multi-agency conservation effort that operates under a regional permit issued under the Endangered Species Act by the U.S. Fish & Wildlife Service, the BCP consists of several tracts of land in western Travis County.  It is important to note that a ‘preserve’ is different than a ‘park’, and is set aside for the purpose of maintaining a natural state rather than developed for recreational use.  The BCP protects prime habitat for the endangered Golden-cheeked Warbler, a bird species that is found only to breed within Central Texas’ specialized mix of native, mature Ashe Juniper (often incorrectly called ‘cedar’) and stands of Live, Spanish, and Shin oak trees.  This type of mixed oak-juniper woodland grows mainly on our moist steep-sided canyons and slopes, providing the warbler with the food, water, and nest-building material it needs to breed.  

Black-capped Vireo, Vireo atricapilla
In addition to the Golden-cheeked Warbler, 7 other endangered species make the preserve system their home, including the Black-capped Vireo, Tooth Cave Ground Beetle, Tooth Cave Pseudoscorpion, Tooth Cave Spider, Kretschmarr Cave Mold Beetle, Bone Cave Harvestman, and Bee Creek Cave Harvestman.  These last 6 species are called karst invertebrates, arthropods that spend their entire existence underground in karst formations.  These karst features, such as caves, sinkholes, cracks, and crevices, were formed by the dissolution of calcium carbonate in limestone bedrock by mildly acidic groundwater.  Over 70 other rare plant and animal species also exist on the preserves, making this region one of the most biologically diverse areas in the country. As such, Central Texas is happily home to more habitat conservation plans than any other region in the United States.   

These wild and beautiful areas require management plans in order for them to remain pristine habitats.  This includes establishment of secure boundaries and rules for access control, maintenance of appropriate trails, species monitoring, habitat enhancement, and – last but not least – public education and outreach to promote good neighbor relations.  As Austin residents, we can do our part to become stewards of these unique habitats.  While in the preserve system, we can stay on marked trails, travel only on foot, and “take only photographs, leave only footprints.”  In our neighborhoods, especially those that border preserve tracts, we can landscape with native plants, remove invasive plants, eliminate pesticide use, be responsible pet owners, practice water conservation, and always respect preserve boundaries.

Most importantly, we can all minimize further negative impacts on the fragile habitat that surrounds our neighborhoods by caring for the preserves through volunteering.  Some of the activities you can become involved with in the preserve system include long-term habitat restoration, gathering and planting native seeds, removing non-native invasive plants, leading guided hikes, and learning about and sharing your knowledge of the native plants and animals that make this such a special place to live.  For more information, visit the Balcones Canyonlands Preserve website at  

Monday, September 26, 2016

Discovering Blacklighting

A large Polyphemus Silkmoth, Antheraea polyphemus, is always a 
welcome visitor.

Lepidoptera is the order of insects that includes both butterflies and moths.  While over 180,000 species of these insects have been identified worldwide, recent estimates suggest that this order may have more species than previously thought, and is among the four most speciose orders, along with Hymenoptera (sawflies, wasps, bees, & ants), Diptera (true flies, mosquitoes, gnats, & midges), and Coleoptera (beetles).  Of the approximately 180,000 known Lepidoptera species, some 160,000 are moths, with nearly 11,000 of them found in the United States, and many are yet to be described.

The Imperial Moth, Eacles imperialis, is another silkmoth that may 
come to a blacklight in Central Texas.

Carolina Sphinx, 
Manduca sexta

Small Heterocampa Moth, 
Heterocampa subrotata

With such huge numbers and such a diversity of species, how does one go about studying moths? A good place to start is while knowing that most moths are creatures of the night, they are also attracted to light.  The reason for this behavior is unknown, although one theory is that moths use a form of celestial navigation called transverse orientation.  They attempt to maintain a constant angular relationship to a bright celestial light, like the moon.  But since the moon is so far away, and the angle change is negligible, the moth appears to travel in a straight line.  This theory is tested when moths fly near much closer sources of light, such as a porch light or a campfire.  The angle to the light source changes constantly as the moth flies by, so the moth instinctively attempts to correct it by turning toward the light, thereby producing its erratic flight.

Cellar Melipotis, 
Melipotis cellaris

Giant Leopard Moth, 
Hypercompe scribonia

White Palpita Moth
Stemorrhages costata

Cisthene unifasc
Melonworm Moth, 
Diaphania hyalinat

Paler Diacme Moth, 
Diacme elealis
Eggplant Leafroller Moth, 
Lineodes integra

Ragweed Plume Moth, 
Adaina ambrosiae
Swag-lined Wave, 
Scopula umbilicata
Southern Emerald Moth, 
Synchlora frondaria

One way for the moth to keep a constant angle to a stationary light source is by becoming stationary itself, effectively being ‘trapped’ by the light rather than ‘attracted’ to it.  Those interested in studying moths have taken advantage of this fact, and have developed a method called blacklighting to attract and photograph moths.  The first step is to set up a light source, and either an ultraviolet light (also known as a blacklight) or a mercury vapor  light can be used. Mercury vapor is now the preferred source, as it provides a different spectrum of light than a blacklight, although a blacklight emits a greater spectrum of light.  Moths can see waves of light that humans cannot, so providing them with different spectrums will generally produce the greatest response. The light is carefully hung or positioned in front a vertical white sheet, which the light bounces off to produce a big, concentrated, glowing mass, while also providing a safe surface for the moths to land.

The blacklighting setup is positioned out of the wind and typically near a boundary between wooded and open areas.  The light is turned on at dusk and left on all night, as different species of moths are most active at different times.  After taking the desired photographs with a digital SLR with a macro lens and flash, the light is turned off and the sheet is given a vigorous shake to scatter the remaining moths.  After all that was done to ‘capture’ them with light for observation and photography, it would be a shame for them to become easy  quarry for insect-eating birds or other predators!   

Another opportunistic predator at a blacklight is this Mediterranean Gecko, which 
has captured an Underwing moth.

Friday, August 5, 2016

Sun Trackers

This time of year, the most notable family of plants are the Heilianthus, or sunflowers.  From the Greek ‘helios’ or sun and ‘anthos’ or flower, these plants are usually tall annuals or perennials that during their growth phase exhibit a subtle behavior in the daylight hours.  This behavior, called heliotropism, is the ability for the young flower buds and leaves to gently tilt toward the sun, tracking it as it moves across the sky. By the time the flower heads mature, they are stationary but generally facing east to greet the rising sun.

Sunflowers are typically tall plants with one to multiple flower heads, consisting of bright yellow ray florets or flowers, surrounding yellow or maroon disc florets.  In wild or native species, the rough and hairy stems are normally branched, and the leaves are often sticky and lance or heart-shaped. Sunflowers also exhibit phyllotaxis, or the arrangement of leaves on a stem that forms a distinct pattern, in this case a repeating spiral.  Additionally, the disc florets also display a phyllotactic pattern, one that creates the optical effect of criss-crossing spirals in the flower’s center.

Common Sunflower (Helianthus annuus)
In our area, the two most abundant sunflowers are the Common Sunflower (Helianthus annuus) and the Maximilian Sunflower (Helianthus maximiliani).  Blooming from May to October, the Common Sunflower grows on dry soils, especially in disturbed areas.  It can reach 1.5 to 8 feet tall, and various parts of the branched stems can be either green or dark purple.  The heart-shaped leaves are coarse and covered in rough hairs, and grow from 2.5 to 10 inches long.  Up to 4 inches across, the flower heads have yellow ray flowers and reddish brown disc flowers.  As their scientific name suggests, these plants are annuals.

Maximilian Sunflower (Helianthus maximiliani)
Maximilian Sunflowers, on the other hand, are perennials that bloom in September and October. They grow 1 to 6 feet tall in colonies on both the dry ground of prairies and the moist ground of roadside ditches and other low places.  Shorter, rough hairs cover the narrow lance-shaped leaves, which average 2 to 4 inches long.  The 1.5 to 3 inch wide flower heads have yellow ray flowers surrounding yellow disc flowers, with numerous flower heads growing along the unbranched stems.

Aside from their aesthetic value to humans, sunflowers are generally palatable to deer and numerous species of birds eat their seeds.  Their flower heads support nectaring bees, and they are the food plants for several butterfly species such as the Bordered Patch and Silvery Checkerspot.  When mixed with other native annuals, these sun trackers provide good cover for many species of wildlife, and would be a great addition to your native wildscape.