South Texas Part V: A Stop for a Sand Sheet Endemic

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Amelia’s Sand Verbena blooms in the South Texas Sand Sheet

The South Texas Sand Sheet occurs across a handful of South Texas counties.  It consists of layer of loose sand that was blown inland from the Gulf of Mexico in the Holocene.  The sand sheet is home to a suite of endemic plant species.  Perhaps the most spectacular is the Amelia’s Sand Verbena (Abronia ameliae), which can be found nowhere, save the South Texas Sand Sheet.

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Amelia’s Sand Verbena

While returning home from the Rio Grande Valley we passed through the sand sheet.  I began seeing splashes of a deep pinkish purple passing as a blur at 75 miles per hour.  Finally after seeing a large field of pink I shouted “STOP!”  And my dad, despite his better judgement pulled over into the right of way of the busy highway and backed up to the spot that caught my eye.

The Amelia’s Sand Verbena was blooming en masse.  It was great to see such a rare, range-restricted plant thriving.  Recent rains may have helped provide such a spectacular bounty of flowering plants.  Growing among the sand verbena were a number of other South Texas specialties, including Rio Grande Phlox (Phlox glabriflora).

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Amelia’s Sand Verbena

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Amelia’s Sand Verbena and Rio Grande Phlox bloom in the South Texas Sand Sheet

It was a cool, overcast morning, so there were not many pollinators around.  We did however notices a stealthy predator nestled within the amble flowers on the inflorescence of one of the sand verbenas: a Crab Spider.

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A Crab Spider hidden in the blooms of an Amelia’s Sand Verbena awaits a meal

Seeing these South Texas Sand Sheet endemics was the perfect ending to an incredible trip full of biodiversity.  I was sad that it was coming to an end, but I took comfort in the fact that there were many other natural wonders still waiting to be explored.

 

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South Texas Part II: Into the Thornscrub

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Common Pauraque

Beyond the South Texas coastal dunes, marshes, and prairies lies a unique, biodiverse community dominated by a variety of shrubs and small trees.  Variably referred to as South Texas brush country, mezquital, and Tamaulipan thornscrub, this semi-arid, subtropical community occurs in South Texas and the Mexican states of Tamaulipas, Nuevo Leon, and Coahuila.  It is home to plants and animals found nowhere else on earth, and in South Texas, marks the northern extent of several Latin American species that just barely enter the United States.

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Tamaulipan Thornscrub with blooming Lady Finger Alicoche alongside Strawberry Pitaya.

The Tamaulipan thornscrub in the Rio Grande Valley of South Texas is one of the United State’s premier birding locations.  My parents and I have made a number of birding trips here in the past, drawn in by the promise of catching a glimpse of one of these South Texas specialties.  During this trip the birding was fairly slow, but we did see many of the typical Rio Grande Valley species including Plain Chachalacas (Ortalis vetula), White-tipped Doves (Leptotila verreauxi), Green Jays (Cyanocorax yncas), Long-billed Thrashers (Toxostoma longirostre), Altamira Orioles (Icterus gularis), and Olive Sparrows (Arremonops rufivirgatus).  Unfortunately these species did not present me with any good photo ops.  I did luck out, however, when we found another Valley specialist, the Common Pauraque (Nyctidromus albicollis) roosting alongside a trail.  These members of the nightjar family are nocturnal and rely on their camouflage to roost on the ground during the day.  It was nearly invisible among the dried leaves and sticks littering the earth.  I utilized the dense natural debris to create the window effect seen on the photo at the start of this blog entry.

Many mammal species also reach the northern extent of their range in deep South Texas.  Unfortunately many of them are now gone.  The last Jaguar (Panthera onca) in Texas was killed in the Tamaulipan thornscrub in the 1940’s.  There are some that still hold onto hope that there may be a few Jaguarundi left in the Rio Grande Valley.  Though there have been no verified sightings in many years, there have been unverified reports.  Ocelots (Leopardus pardalis) are still hanging on in the brush country, though they are now rare, and protected under the Endangered Species Act.  In our explorations of the thornscrub we observed a number of mammals including White-tailed Deer (Odocoileus virginianus) and Collared Peccaries a.k.a. Javelinas (Tayassu tajacu).  The only mammal I was able to photograph was the little Eastern Cottontail (Sylvilagus floridanus) pictured below.

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Eastern Cottontail

There are many reptile and amphibians whose United States distribution is also limited to the Rio Grande Valley.  Being an amphibian enthusiast, I was disappointed that we missed the heavy rains that brought out such rarities as the Mexican Burrowing Toad (Rhinophrynus dorsalis) and White-lipped Frog (Leptodactylus fragilis) by just a couple of days.  These species are explosive breeders that emerge to breed after heavy rains.  I did spend some time looking for the beautiful Speckled Racer (Drymobius margaritiferus), a primarily Latin American species that is known from only a couple of sites in South Texas.  I struck out on the snakes, but was able to photograph a couple of the areas conspicuous lizards: the Texas Spiny Lizard (Sceloporus olivaceus) and the Rose-bellied Lizard (Sceloporus variabilis).

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Texas Spiny Lizard

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Rose-bellied Lizard

The Rio Grande Valley is also world famous for its butterflies.  While we observed many species, the only one I obtained a decent photo of was the Common Mestra (Mestra amymone).

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Common Mestra

The Tamaulipan thornscrub is named for the typically thorny shrubs and small trees that dominate the community.  Typical species of this community include Mesquite (Prosopis gladulosa), Chaparro (Ziziphus obtusifolia),  Whitebrush (Aloysia gratissima), Texas Paloverde (Parkinsonia texana), Texas goatbush (Castela erecta), Saffron Plum (Sideroxylon celastrinum), Blackbrush Acacia (Vachellia rigidula), Corona de Cristo (Koeberlina spinosa), Guayacan (Guaiacum angustifolium), and Ebano (Ebenopsis ebano).  These shrubs form often impenetrable thickets.  On some sites, particularly as one moves further west in the Rio Grand Valley the shrubs may become more scattered, forming dense clumps with areas of exposed gravel and caliche.  It was in areas such as this where we observed the rare Baretta (Helietta parvifolia).

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Texas Paloverde

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Texas Paloverde

Occasionally growing in the crooks of mature Ebano, a real botanical treasure can be found.  The epiphytic bromeliad Tillandsia baileyi, commonly known as Bailey’s Ball Moss barely enters the United States in South Texas, where it is rare.  It is much more striking than other members of its genus, which includes the familiar Spanish Moss (Tillandsia usneoides).

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Bailey’s Ball Moss

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Bailey’s Ball Moss

A conspicuous component of the South Texas brush country is the Anacahuita or Mexican Olive (Cordia boissieri).  Its bright blooms illuminate the native brushlands, and it is a popular native ornamental in South Texas.  The tree was reportedly utilized by native cultures and Spanish settlers to make jellies and dyes.  The leaves can be brewed in a tea that may help with rheumatism and various ailments of the lungs.

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Anacahuita

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Anacahuita

Many invertebrates can be found utilizing Anacahuita leaves and flowers.  The Wild Olive Tortoise Beetle (Physonota alutacea) is found exclusively on these small trees.

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Wild Olive Tortoise Beetle

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Wild Olive Tortoise Beetle

Many pollinators also frequent the blooms.  They due so at their own risk, however, because predators lurk beneath these flowers.  We observed this crab spider (Mecaphesa sp.) awaiting an unsuspecting victim.

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Crab Spider

South Texas is also home to a variety of native lantana species.  Brushland lantana (Lantana achyranthifolia) could occasionally be found scattered about the thornscrub.

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Brushland Lantana

We also observed a couple of species of heliotrope, including the widespread Seaside Heliotrope (Heliotropium curassivicum), and the more range restricted Scorpion Tail (Heliotropium angiospermum) which occurs in South Texas and southern Florida.

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Seaside Heliotrope

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Scorpion Tail

Fiddleleaf Tobacco (Nicotiana repanda), a species of central and southern Texas, was also fairly common.

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Fiddleleaf Tobacco

Shrubby Blue Sage (Salvia ballotiflora) occurs in the U.S. only in southern and western Texas.

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Shrubby Blue Sage

Over the millennia, the meanders of the Rio Grande has slowly changed course, leaving in their wake old depressional oxbow scars.  The scars eventually filled with rainwater and runoff and developed a unique flora.  Known as Resacas these unique wetlands provide habitat for a host of rare plant and animal species.  We observed many Least Grebes (Tachybaptus domincus), another bird species whose U.S. distribution is restricted to South Texas in them.  We also observed the rare Runyon’s Water-Willow (Justicia pacifica) here.

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Runyon’s Water Willow

As one moves further west along the valley, one begins to notice more and more of a desert influence.  I observed many familiar species that I have photographed in West Texas including Snapdragon Vine (Maurandella antirrhiniflora) and Cenizo (Leucophyllum frutescens).  The latter blooms in response to rainfall and humidity.

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Snapdragon Vine

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Cenizo

I observed Purple Groundcherry (Quincula lobata) here.  These showy groundcover primarily occur in the southwestern United States.

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Purple Groundcherry

I also observed Bearded Prairie-Clover (Dalea pogonathera) here.  This member of the pea family is primarily a species of the Chihuahuan Desert.

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Bearded Dalea

South Texas is also home to a few woodsorrel species that do not have the typical “lucky clover” leaf.  Pictured here is Peonyleaf Woodsorrel (Oxalis dichondrifolia).

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Peonyleaf Woodsorrel

The open caliche hills were home to the beautiful Berlandier’s Nettlespurge (Jatropha cathartica), which is restricted to South Texas and adjacent Mexico.

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Berlandier’s Nettlespurge

The most spectacular element of the Tamaulipan thornscrub, however, were the cacti.  These famed succulents were my main target in South Texas, and I was fortunate to observe many species.  Though my next two blog posts will be dedicated to the incredible diversity of South Texas cacti, I have decided to provide a preview of things to come below.

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Lady Finger Alicoche (Echinocereus pentalophus)

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Glory of Texas (Thelocactus bicolor)

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Heyder’s Pincushion Cactus (Mammillaria heyderi)

South Texas Part I: Along the Coast

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Coastal Dunes with Beach Morning Glory

When I was developing my 2017 list I added several species that were contingent on a spring break trip to Big Bend.  Unfortunately I did not plan ahead enough, and by the time I tried to make arrangements out west everything was already booked up.  Fortunately there are so many biodiversity hot spots in Texas that it was not hard to find a substitute.  We decided on the varied subtropical habitats of Deep South Texas.  Here one can encounter a suite of endemics and Mexican specialties that are found nowhere else in the country.  It may come as no surprise that immediately after posting my 2017 list I began thinking about my 2018 list, in which I planned to include many of the South Texas specialties.

So Carolina and I began an adventure with my entire family: my brother, Seth, my mom, Jolynn, and my dad, Jack.  We traveled south in two vehicles intent on seeking out plants, birds, herps, and good food.  Our first couple days were allocated for time along the coast, from Port Aransas to South Padre.

The South Texas coast contains several extensive dune fields, primarily along the barrier islands.  Some are ever shifting, and some have been stabilized with vegetation and debris.  One might be surprised to find plants clinging to life in these sandy wastelands, however several species thrive in these shifting sands.  The most conspicuous species during our trip was the Beach Morning Glory (Ipomoea imperati), which is a coastal specialist ranging from the Atlantic Coast from North Carolina to Florida to the Gulf Coast of Florida to Texas.  We enjoyed the view from the base of the dunes as Sanderlings (Calidris alba), Ruddy Turnstones (Arenaria interpres), Willets (Tringa semipalmata), and Black-bellied Plovers (Pluvialis squatarola) chased the receding waterline only to swiftly retreat with each incoming wave.

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Beach Morning Glory

Beyond the dunes lie a variety of habitats including wet and dry prairies and marshes.  Marshes vary from saline to brackish to freshwater, depending on the influence of tidal waters.  We spent time exploring some high quality saltmarshes, one of my favorite communities, where we observed several bird species including Long-billed Curlews (Numenius americanus), Marbled Godwits (Limosa fedoa), Spotted Sandpipers (Actitus maculatus), Greater Yellowlegs (Tringa melenaleuca), American Oystercatchers (Haematopus palliatus), Clapper Rails (Rallus crepitans (formerly R. longirostris)), American Coots (Fulica americana), Common Moorhens(Gallinula chloropus), Osprey (Pandion haliaetus), Redheads (Aythya americana), Northern Pintails (Anas acuta), Blue-winged Teal (Anas discors), Black-bellied Whistling Ducks (Dendrocygna autumnalis), and Mottled Ducks (Anas fulvigula). Mottled Ducks are coastal specialists that range from Florida to central Mexico.  These close relatives of the Mallard have experienced population declines throughout much of their range as coastal habitat has been lost to development and sea level rise.

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Mottled Duck

The marshes were also home to a variety of wading birds including American Bitterns (Botaurus lentiginosus), Roseate Spoonbills (Platalea ajaja), White Ibis (Eudocimus albus), Green Herons (Butorides virescens), Great Blue Herons (Ardea herodias), Great Egrets (Ardea alba), Snowy Egrets (Egretta thula), Reddish Egrets (Egretta rufescens), Yellow-crowned Night-Herons (Nyctanassa violacea), Black-Crowned Night-Herons (Nycticorax nycticorax), and some cooperative Tricolored Herons (Egretta tricolor) and Little Blue Herons (Egretta caerulea).

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Tricolored Heron

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Little Blue Heron

A number of songbirds were also present.  We observed several Common Yellowthroats (Geothlypis trichas) and scores of Red-winged Blackbirds (Agaleius phoeniceus) and Great-tailed Grackles (Quiscalus mexicanus).  The Grackles were particular tame, and would perch on the boardwalk support posts mere feet away from us.

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Great-tailed Grackle

Slight variations of topography along the coast result in vastly different vegetative communities.  On small sandy crests and ridges dry prairies and scrublands persist.  These prairies are dominated by a variety of grasses and forbs.  The most visible member of this community is the Spanish Dagger (Yucca treculeana).  These stately yuccas are common in these dry prairies, and in the United States are restricted to southern Texas, New Mexico, and Arizona.

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Spanish Dagger

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Spanish Dagger Flowers

Along the wetter transition zone between marsh and prairie Carolina spotted a pair of Texas Feathershanks (Schoenocaulon texanum).  These bizarre members of the lily family can be found in south, central, and west Texas and southwest New Mexico.

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Texas Feathershank

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Texas Feathershank

The contact zone between the dunes and coastal prairie also harbor an interesting flora.  Arkansas Lazy Daisy (Aphanostephus skirrhobasis) is a widespread species of the south central states that can be common in this community.

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Arkansas Lazy Daisy

The lazy daisy is popular with pollinators, and coincidentally with their predators like this crab spider (Misumenoides formosipes) that awaits a hungry pollinator to fall into its trap.

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A crab spider awaits an unsuspecting pollinator

American Bluehearts (Buchnera americana) was also fairly common in this community.

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American Bluehearts

I have always been a fan of milkworts.  I was delighted to see several White Milkworts (Polygala alba), which we don’t have in East Texas.

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White Milkwort

Texas Palafox (Palafoxia texana) is primarily restricted to southern Texas.  Its brilliant pink blooms added a splash of color to the primarily brown grasses of the coastal prairie.

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Texas Palafox

I observed this wasp, Campsomeris tolteca (thanks to Seth Patterson for the ID), feeding on the nectar-rich flowers of the Texas Palafox..

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Campsomeris tolteca

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Campsomeris tolteca

Scattered along the coast are a series of woodlots primarily dominated by Live Oak (Quercus virginiana and Quercus fusiformis) and Hackberry (Celtis laevigata).  Here we observed a variety of Neotropical Migrant birds including Yellow-throated Vireos (Vireo flavifrons), Northern Parulas (Setophaga americana), Black-and-white Warblers (Mniotilta varia), and Yellow-throated Warblers (Setophaga dominica).

These woodlots are also home to Drummond’s Hedgenettle (Stachys drummondii).  This member of the mint family is restricted to the Texas Coast and the Rio Grande Valley.

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Drummond’s Hedgenettle

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Drummond’s Hedgenettle

Stachys drummondii

County Level Distribution for Drummond’s Hedgenettle from http://www.bonap.org

The wealth of biodiversity along the coast was not limited to land.  We observed a variety of shells, jellyfish, and dead fish along the shore, as well as a number of dolphin pods on the move offshore.  The most exciting encounter of the trip, however, came in the form of this juvenile sea turtle, which I believe is a Mexican Green Sea Turtle (Chelonia mydas).  Thanks to a tip from my good friend John Williams, we were able to observe several foraging just offshore.  Despite the cool morning, 40 mile per hour winds, and spitting rain, everyone enjoyed watching this rare marine reptiles as they surfaced for a breath before returning to the depths.

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Green Sea Turtle

The South Texas Coast was good to us, however the trip had only begin.  Next we would be venturing into the South Texas Brush Country, famed for its biodiversity and specialty species that can be found nowhere else in the country.