Friday, August 21, 2015

Mysterious Migration

Wandering Glider, Pantala flavescens

Fall migration season is upon us, and that usually conjures up thoughts of songbirds and hawks using the central flyway through Texas to make their way south to the subtropics and tropics for the winter.  However, birds are not the only ones who migrate, and while much has been said about the complex, annual migration made by Monarch butterflies, the record for the longest insect migration (twice the distance of the Monarch) belongs to a dragonfly species, the Wandering Glider (Pantala flavescens).  In fact, dragonfly migration has been suspected for over 100 years, and up to 50 of the world's 5,200 dragonfly species are thought to migrate (about 16 out of 326 in North America), but not much is known about where they are coming from or where they are going.  

Green Darner, Anax junius

In Texas, there are several species of dragonflies that migrate in addition to the Wandering Glider. They include the Common Green Darner (Anax junius), Black Saddlebags (Tramea lacerata), Variegated Meadowhawk (Sympetrum corruptum), and Spot-winged Glider (Pantala hymenaea).   Cooler nights seem to trigger the dragonflies' journey south, and like birds, they build up their fat reserves before setting out.  They may use the lay of the land as a navigation guide, and some scientists speculate that they have an internal magnetic compass, as those that fly off course and out to sea appear to realize their mistake and reorient themselves.  

Black Saddlebags, Tramea lacerata

Dragonflies migrate during daylight hours, and green darners have been found to break their journeys every three days to rest and feed, using oak and juniper trees as stopover sites.  Like monarchs, the full migration circuit takes multiple generations to complete, as it is the offspring of the generation that traveled south in the fall that is migrating north again in the spring.  

Variegated Meadowhawk, Sympetrum corruptum

Swarms of dragonflies can create one of nature's most impressive spectacles, with tens to hundreds of thousands of individuals streaming southward along lakeshores, mountain ridges, and coastlines.  Even with the origins and destinations poorly known, the migration in the fall is more noticeable than that in the spring, presumably because the spring event occurs over a wider front and a longer period of time.  However, migration is the only explanation for how dragonfly adults appear in early spring in places where their nymphs or larvae from the previous year or years have not yet emerged.

Spot-winged Glider, Pantala hymenaea

The ecological role of migrating dragonflies is another facet of the mystery yet to be resolved. Since several species use the same migration strategies and timing as migratory birds, traveling at the same times and concentrating in the same places, it is likely that certain bird species are exploiting the abundance of dragonflies as a source of fuel for their own migration.  More research is being done to solve these mysteries, most notably the Xerces Society’s Migratory Dragonfly Partnership initiative, which uses “research, citizen science, education, and outreach to understand North American dragonfly migration and promote conservation.”    

Sunday, August 9, 2015

Traveling Tarantulas

Relatively common throughout Texas, the Tarantula (Aphonopelma sp.) is Texas’ heaviest and largest spider.  Typically, the head and legs are dark brown, and the abdomen is brownish-black. Coloration varies between individuals as well as between the 14 different species found in Texas. Identification of individual species is difficult, however, and is often performed only on mature males under a microscope.

Tarantulas are typically found in grasslands and semi-open areas, and use burrows, natural cavities under stones or fallen logs, spaces under loose tree bark, and even old rodent holes as shelters.  They are also capable of digging their own burrows, and often line them with webbing, placing a few strands across the front to help detect passing prey.  Laying several hundred eggs in a hammock-like web constructed inside the burrow, females will guard them until they hatch. Females have lived in captivity for over 25 years, while males rarely live over two or three months after reaching maturity.   
Like many animals, tarantulas molt their exoskeletons several times as they grow.  The skin on the hard upper shell and abdomen splits, and the tarantula begins the process of squeezing through the opening.  Most of the time, tarantulas molt while positioned on their backs, twitching, stretching, and kicking until the entire exoskeleton has been cast off.  After they have wriggled free of their old skin, this discarded exoskeleton is a perfect replica of the spider, minus its head and fangs. 

Other insects such as crickets, beetles, grasshoppers, cicadas, and caterpillars form the basic diet of the tarantula.  They inject their prey with a poison when they bite, which liquefies the prey’s insides, making it easier to ingest.  While they can climb, they are usually restricted to the ground, where the majority of their prey is found.  The hairiness and large size of tarantulas often evokes concern, but the bites of Texas species are not serious to humans.  Tarantulas maneuver quickly to face whatever disturbs them, often raising up on their hind legs and stretching out their front legs in a threatening posture.  They have also been observed rapidly brushing the top of their abdomen with their hind legs to dislodge hairs that can be used to irritate the attacker’s eyes or skin.

For a few weeks late in the summer or early fall, one of the most spectacular spider events occurs in Texas.  Not well understood, this phenomenon is often called a migration, but it may be related more to mating rather than seasonally motivated movement.  Males actively wander to seek out females, and can travel 50 miles in search of a mate.  Populations seem to follow a boom and bust cycle, depending on weather patterns and the availability of food, but a good year can be a sight to behold if summer rains have been plentiful.  While the males are out searching, females wait in their burrows for a suitor to appear.  Larger and more robust, the female does not always accept any male that comes along, and will kill and eat males that are deemed unsuitable. 

Tarantula Hawk
As formidable as they may seem, tarantulas are not without their own enemies.  In fact, in late spring and early summer they are routinely hunted by female Tarantula Hawks as food for their larvae.  Belonging to a group of spider wasps in the genera Pepis and Hemipepsis, tarantula hawks are large, 2-inch long wasps with iridescent blue-black bodies and bright, rust-colored wings.  This vivid color combination is a form of aposematism or warning coloration, a type of advertising signal to both predator and prey that these species are potentially harmful.  These wasps have the ability to deliver a powerful sting, and their long legs have hooked claws for grappling their victims.  

Flying low over the ground, the female tarantula hawk will find a tarantula and sting it, which paralyzes the spider but does not kill it.  She then drags the inert tarantula into her burrow or transports it to a specially prepared nest, where she lays a single egg on the spider’s abdomen, then seals the opening to the burrow as she leaves.  When the wasp larva hatches, it creates a small hole and enters the spider’s abdomen, where it feeds voraciously, avoiding vital organs to keep the spider alive as long as possible.  After several weeks the spider dies, the larva pupates, and then it emerges from the spider’s abdomen to continue its lifecycle.

Thursday, July 2, 2015

Keep Austin Wild

Golden-cheeked Warbler
As Austin and surrounding areas grow and expand, encounters with urban wildlife become increasingly frequent, especially during the spring and summer breeding seasons.

Wild animals often make their homes in or around our homes, and they can be unwelcome and even destructive.  Be aware that trapping is not always the answer, and should only be used as a last resort.  Unless the source of the problem is eliminated (uncapped chimneys, holes in decks or attics, pet food left outside), another animal will likely move into the same spot.  Additionally, during spring and summer, you may trap a mother whose babies will be left orphaned if she is removed.

Eastern Cottontail
Trapping is also quite stressful for animals, and they often injure themselves when trying to escape.  They can be exposed to the elements and left trapped for an unknown number of hours or days, without food or water.  If they are relocated, they may have trouble finding food, water, or shelter, as they will be disoriented in their new environment.  They can also be considered intruders by the resident animal population, and be driven away or attacked, with a very uncertain outcome.

Nine-banded Armadillo
To avoid all of these situations, there are humane solutions to prevent common wildlife problems before they occur.  These include installing L-shaped mesh barriers under decks, sheds, and around gardens, adding bungee cords to trash can lids or keeping the cans inside the garage until collection day, capping the top of the chimney, installing mesh covered attic vents, taking pet food indoors overnight, and adding squirrel-proof baffles to bird feeders.

If you do run across wildlife babies, remember that they cannot digest cow’s milk properly, so they should be brought to Wildlife Rescue as soon as possible.  Fawns are often left alone and curled up in the grass for up to 10-12 hours while their mothers forage, so if their mouth is warm, bottom is clean, and they are not being overrun by fire ants, leave them alone.  Young feathered birds are frequently found on the ground and belong there, as it is natural for them to fledge the nest and learn to fly, feed, and avoid predators, all under the watchful eyes of their parents, who are likely nearby.  Unfeathered baby birds can be safely united with their parents by creating a makeshift nest, nailing a small plastic bowl as high as you can reach onto a tree, first poking a few small drain holes in the bottom, adding some dry grass or leaves, and placing the nestlings in it.  Within a few hours, the parents should return to resume feeding them.

Recently, the National Wildlife Federation ranked America’s largest cities based on three criteria for wildlife: percentage of parkland, citizen action to create wildlife habitat, and school adoption of outdoor learning in wildlife gardens.  Austin, Texas was named as “the clear-cut (#1) choice as America’s best city for wildlife, boasting the most Certified Wildlife Habitats (2,154), most certified Wildlife Habitats per capita, and most Schoolyard Habitats (67).  Famous for its Congress Avenue Bridge that’s home to 1.5 million bats, the City of Austin is certified as a Community Wildlife Habitat.  Its residents not only want to Keep Austin Weird – they’re the best in America at keeping their city wild.”

Black-capped Vireo nest
However, as more and more of our landscape is bulldozed and developed, we leave less and less for the native animals that call it home.  The least we can do is be cognizant of these changes, prevent conflicts when possible, and learn to treat our native wildlife as humanely as possible! 

Friday, June 12, 2015

Serious About Salamanders

Jollyville Plateau Salamander

Humans often wonder why efforts are made to protect biodiversity and save endangered species.  Biodiversity is defined as the variety of life in the world or in a particular habitat or ecosystem, and preserving it provides us with tremendous and vital benefits.  Among others, these benefits include air purification, medicines for better health, fresh water, pollination of crops, carbon sequestration (or storage), and preserving the fertility of the soil. 

Forests purify our air by filtering particulates and regulating the composition of the atmosphere. They act as massive carbon reservoirs, essential to the Earth’s global carbon cycle, and significantly contribute to regulating the global climate. Natural forest soils, with their active microbial and animal populations, have a higher content of total nutrients and biomass, supplying the right nutrients to plants in the right proportions.  Soils and wetlands also act as a filter for water, helping to reduce nitrogen loading, which is a significant form of pollution that occurs as a side effect of development in many parts of the world.  

Roughly 50% of the medicines currently available are derived from natural products.  Of these, at least 120 chemical compounds derived from 90 different plant species are critically important drugs in use around the world today.  Many flowering plants rely on a great variety of animals to pollinate them, including one third of the world’s food crops.  In the U.S., it has been estimated that honeybees alone pollinate approximately $10 billion worth of crops.    

Recently, the U.S. Fish and Wildlife Service protected the Austin Blind Salamander (Eurycea waterlooensis), and the Jollyville Plateau Salamander (Eurycea tonkawae) in addition to a total of 4,451 acres of critical habitat.  These salamanders live no where else in the world, and saving them is also an important step for our region’s long-term water quality and health.  They cannot survive in waterways polluted with pesticides, industrial chemicals, and other toxins, so they are excellent indicators of the health of the environment.

Austin Blind Salamander

The Austin Blind Salamander has external feathery gills, a pronounced extension of the snout, no external eyes, and weakly developed tail fins.  It occurs in and around Barton Springs, which is fed by the Barton Springs segment of the Edwards Aquifer.  The conditions that threaten this species include degradation of its aquatic habitat from pesticides and fertilizers, as well as low flow conditions in the aquifer and the springs.  The Jollyville Plateau Salamander is physically similar to the Austin Blind Salamander, but has generally well-developed eyes, except for some cave-dwelling forms that exhibit eye reduction, head flattening, and loss of color.  Typically, their habitat is spring-fed, and they occur in depths of less than one foot of cool, well-oxygenated water.  While this salamander lives in the Jollyville Plateau and Brushy Creek areas, significant population declines have been observed, likely as a result of degrading water quality from rapid urban development. 

Perhaps one of the most fundamental benefits of saving endangered species is an aesthetic one, as the loss of biodiversity impoverishes our world of natural beauty, both for ourselves and for future generations.  It is yet another good reason for us to be serious about salamanders!  

Tuesday, March 31, 2015

Lovely Lupines

Texas Blubonnets, Lupinus texensis

Bluebonnets are often thought of as the ‘floral trademark of Texas’, akin to the shamrocks of Ireland, the cherry blossoms of Japan, the roses of England, and the tulips of Holland.  Loved for centuries, bluebonnets were described by early explorers as they roamed the vast prairies of Texas, planting them around the Spanish missions by early-day priests, and making them the subject of several Native American folk tales.  Technically known as ‘lupines’ or ‘lupins’, bluebonnets received their present-day common name due to the shape of the flower petals, which resembled the bonnets worn by pioneer women to shield their faces from the sun.

Bluebonnets are part of the legume or bean family, and like other members of this family they offer nitrogen-fixation through their root system’s symbiotic relationship with Rhizobia bacteria.  This gives them the useful ability to grow in poor, disturbed soils, and bring much-needed nitrogen back to these soils as they decompose.  Ironically, bluebonnets are all in the genus Lupinus, which is Latin for ‘wolf-like’, from the original but erroneous belief that these plants ravenously exhausted the soil.

In our area, bluebonnets normally bloom between March and April, but the timing and extent of the blooms depends on the amount of rain received the previous fall and winter.  The flower is purple to blue in color, about half an inch long, with a white spot on the upper petal or banner.  This banner spot acts as a target to attract the bumblebees and honeybees that pollinate the flower. When the pollen is fresh and sticky, the banner spot is white, and is seen by the bees as reflected ultraviolet light and appears to them as a good landing spot.  But as the flower and its pollen age, the banner spot turns yellow and then reddish-magenta, and is ignored by the bees, whose vision cannot see red.  The decline in bee populations has a direct effect on how many seeds a bluebonnet can produce, because bluebonnets cannot self-fertilize.  Each plant has the potential to produce hundreds of seeds, but often only a small number result, due to the recent decline in the number of bee pollinators.

A rare pink Texas Bluebonnet

Infrequently, both white, and more rarely, pink bluebonnets can occur naturally.  In fact, there is a legend associated with how the pink bluebonnet came to be.  Many years ago, in a spring wildflower field near San Antonio, children came across a pink bluebonnet on their way to Lenten devotion at the mission church.  Their grandmother told them the story of Texas, when it was a remote province of Mexico.  After a terrible Mexican dictator overthrew their Constitution, a war broke out between the brave new Texans and the Mexican troops.  The troops eventually overwhelmed the Texans, and much blood was shed and lives lost.  Several years later, the grandmother saw her mother place a pink bluebonnet in a vase by the statue of the Virgin Mary. She said she found it by the river, where “it had once been white, but so much blood had been shed, it had taken a tint of it.”  Interestingly, the only place in the state where the original native pink bluebonnets were found was along the side of a San Antonio road not far from the original mission. 

Big Bend Bluebonnet

Texas has 6 state flowers, more or less, and they are all bluebonnets.  In the spring of 1901, the Texas Legislature selected a state floral emblem after much debate and consternation.  Both the cotton boll and prickly pear cactus were hardy contenders, but the National Society of Colonial Dames of America won the day, and the Sandyland Bluebonnet (Lupinus subcarnosus) was selected and passed into law on March 7th.  And that’s when the bluebonnet war started.  The Sandyland Bluebonnet is a dainty little plant growing in the sandy hills of coastal and southern Texas, and many thought it was the least attractive of all the bluebonnets.  They wanted the Texas Bluebonnet (Lupinus texensis), which was a showier, bolder bloomer.  For the next 70 years, the Legislature was encouraged to correct its oversight, not wanting to get caught in another botanical trap or offend any supporters.  As politicians often do, they solved the problem with clever maneuvering by creating an umbrella clause, and in 1971 added the two species together, plus “any other variety of bluebonnet not heretofore recorded” (including potential species not yet discovered), and lumped them all into one state flower.

Long before the bluebonnet became the Texas state flower, many stories existed about its origins. Some believed it was a gift from the Great Spirit, and that it arrived with rain after a young, orphaned girl sacrificed her precious doll in the hopes of bringing a terrible drought to an end. Whatever you believe, look for these lovely lupines during our central Texas spring!    

Wednesday, March 25, 2015

The Buzz about Bees

There are over 1000 species of bees native to Texas, and this remarkable diversity is attributed to the high number of flowering plant species found in a multitude of habitats throughout the state.  Central Texas is home to at least 185 of these species, many of which inhabit our yards, gardens, and public green spaces.  Bees often get confused with other flying insects, mainly flies, wasps, and sometimes hawk moths.  Flies and wasps, in particular, have similar sizes, colors, and even stripes.  How can you begin to tell the difference?  

In general, bees have longer, thinner antennae, large eyes on the side of the head, four wings (although all four can be hard to see), at least partially fuzzy bodies, and can carry loads of moist pollen on their legs or abdomens.  Flies, on the other hand, have short, thick antennae, large eyes in front of the head, two wings, minute body hairs, and while pollen can stick to their bodies they don’t carry loads.  Finally, wasps have narrow bodies often with a pinched abdomen, very few body hairs, little to no patterns or designs in their exoskeleton, and like flies, don’t carry pollen loads.

Groups of bees that you will commonly see include metallic green bees, honey bees, bumble bees, and carpenter bees. Metallic green bees have an obvious metallic green exoskeleton, but care must be taken to use other methods of identification, as there are also metallic green flies and wasps.  Honey bees buzz as they fly from flower to flower, with a fuzzy thorax and striped abdomen, but while quite common and numerous, are a non-native bee imported from Europe.  

Our biggest native bees are the bumble bee and the carpenter bee.  Bumble bees have a robust body size and shape, mostly black with some yellow or white stripes.  Their entire body is fuzzy, and they fly around in a ‘bumbling’ pattern, making a low buzzing sound.  When landed, they fold their wings neatly over their abdomen.  Carpenter bees are mostly all black, some with a little gold or brown, and the top of their abdomen lacking hairs.  They are fast fliers, sometimes hovering like flies, and make a fairly loud buzz.  Upon landing, they keep their wings splayed apart.

Native bees could fill the important pollinator role currently held by the declining population of non-native European honey bees.  While there is still some debate as to the cause of this decline, there is no debate about the heavy reliance we have on bees pollinating many of our food crops.  Native bees offer an efficient alternative because they are resistant to the mites thought to be harming the honey bees, and because they do not live in collective hives but live singly in nest holes and tunnels, which are not at risk of being overcome by Africanized bees.  Further, native bees and their behavior have evolved so that their actions on a flower actually trigger pollination, so it is possible to find a native bee species that is evolutionally ‘tailored’ to assist a specific crop.  Now that’s something worth buzzing about!

Sunday, March 1, 2015

Spring Heralds

Texas Redbud, Cercis Canadensis var. texensis

Nature has a way of letting us know when spring has arrived in the hill country of central Texas.  In addition to increasing temperatures, the awakening of birds, butterflies, and native plants are among the harbingers that mark the arrival of the season.

More than half of the birds recorded in Texas are migrants.  Returning north in the spring to exploit the more productive temperate regions, they come in search of abundant food supplies, longer daylight hours, and less competition for nesting space. Texans have the advantage of being situated in the path of two flyways or principal routes used by North American birds – the Mississippi Flyway and the Central Flyway – and of the 338 species of North American species listed as Neotropical migrants, 333 are documented for Texas.

Chuck-will's-widows, Caprimulgus carolinensis, lay their eggs on the ground in the spring

Listen for the song of the Chuck-will’s-widow (Caprimulgus carolinensis), which sounds just like its name, rising up from the canyons in the twilight and pre-dawn hours.  Delight in the acrobatic flight of a Scissor-tailed Flycatcher (Tyrannus forficatus), a pearl gray and white bird with salmon-pink underwings and very long outer tail feathers, whose return coincides with the leafing out of the native Honey Mesquite (Prosopis glandulosa var. glandulosa) trees. Marvel at the nest-building skills of the Cliff Swallows (Petrochelidon pyrrhonota), who zoom down to creek beds gathering mud to build colonies of gourd-shaped nests under our bridges and overpasses.  And watch for the Western Kingbird (Tyrannus verticalis), a gray bird with a pale breast and yellow belly, whose raucous calls are heard in between bouts of insect-chasing from perches high in our neighborhood trees.

Scissor-tailed Flycatcher, Tyrannus forficatus

The sweet scents of early-blooming native plants catch our attention and the attention of many pollinating insects.  Some of the most fragrant include the Texas Mountain Laurel (Sophora secundiflora), whose glossy, evergreen leaves form the perfect backdrop for huge clusters of deep purple to whitish flowers, up to ten inches long, that smell like grape Kool-Aid.  Or the less common Mexican Plum (Prunus mexicana), a beautiful small tree identified by its numerous and intensely fragrant white blossoms, which like the pink blossoms of the Mexican Buckeye (Ungnadia speciosa) and the Texas Redbud (Cercis Canadensis var. texensis) and the yellow blossoms of the Elbowbush (Forestiera pubescens), appear on the tree before the leaves begin to emerge.  

Mexican Plum, Prunus mexicana
Elbowbush, Forestiera pubescens

Many of these native plants provide nectar for several species of bees, and are nectar and/or larval food sources for spectacular butterflies such as the Giant Swallowtail (Papilio cresphontes), Two-tailed Swallowtail (Papilio multicaudata), Great Purple Hairstreak (Atlides halesus), Juniper Hairstreak (Callophrys gryneus), Long-tailed Skipper (Urbanus proteus), and Henry’s Elfin (Callophrys henrici).

Henry's Elfin, Callophrys henrici
Juniper Hairstreak, Callophrys gryneus

Wildflowers will soon begin to grace our fields and roadsides, starting with the famous Texas Bluebonnet (Lupinus texensis), intermingled with Indian Paintbrush (Castilleja indivisa), pink Evening Primrose (Oenothera speciosa), Winecup (Callirhoe involucrata), and Indian Blanket or Firewheel (Gaillardia pulchella), to name a few.   These swaths of multi-colored gems not only delight the eye and provide the perfect setting for those upcoming Easter family photos, but they are a key element of the hill country ecosystem, and should be protected and propagated for the visual enjoyment and habitat value they provide all living things.          

Prairie Paintbrush, Castilleja purpurea var lindheimeri

As the weather warms, take the time to go outside and discover for yourself the distinctive essence of a central Texas spring.  As Lyndon Baines Johnson, one of our more famous Texans said, “The beauty of our land is a natural resource.  Its preservation is linked to the inner prosperity of the human spirit.”  Celebrate it!