The Nature Writers of Texas

The best nature writing from the newspaper, magazine, blog and book authors of the Lone Star State . . .

Thursday, May 29, 2008

Our Ever-changing Butterfly Populations
by Ro Wauer

One of the fascinating facts about butterflies is their ever-changing populations. In any field or garden, butterfly species present may change significantly from one day or one week to the next. In a sense, the ever-changing population is one of the more exciting facets about butterfly-watching. In my garden at Mission Oaks near Mission Valley, probably a pretty good representation of the entire region, black swallowtails can be present for a few days and then totally disappear and pipevine swallowtails can be commonplace a few days later. And at about the same time, a few giant swallowtails put in their appearance. The butterfly scene can change dramatically.

Another population change that I have experienced in the last few weeks is the shift from cloudless sulphurs to large orange sulphurs. These two species are similar at first sighting, but the cloudless sulphur is usually lemon yellow with scattered white spots edged with red, while the large orange sulphur is orange-yellow with a dark line running from the tip to the center of the wing. Both perch with folded wings.

The reasons for changes in butterfly populations vary, but it primarily relates to emergence, the act of an adult butterfly leaving its chrysalis and flying free. Emergence depends upon weather conditions and time of year. Some species, such as falcate orangetips and Henry’s elfins, fly only in early spring. Others, such as soapberry and oak hairstreaks, appear a little later in spring. Still other species wait to emerge in late summer or fall. The emergence times depend so much upon when pertinent larval foodplants become available. In many cases, emergence can include dozens or even hundreds of individuals, thus significantly changing population numbers.

Almost any time of year, except during really cold periods in winter, I can pretty well depend on daily finding a few butterfly species in my yard. Some the more dependable species include little yellow, dusky-blue groundstreak, gray hairstreak, gulf fritillary, common buckeye, Carolina satyr, white and tropical checkered-skippers, and fiery skipper. Eastern tiger swallowtail, checkered white, orange and lyside sulphurs, southern dogface, great purple hairstreak, mallow scrub-hairstreak, Reakirt’s blue, queen, bordered patch, phaon and pearl crescents, question mark, common mestra, funereal duskywing, clouded and dun skippers, and Celia’s roadside-skipper, are also found year-round, but their appearance can never be expected.

Some of the late summer and fall species may be primarily composed of strays from further south, although because of the changing weather pattern, many of those that once were considered more tropical species are now able to find an adequate niche further north. During the last few years I have discovered several species that had not previously been recorded in the central Gulf Coastal area. Examples include yellow and white angled-sulphurs, Mexican yellow, tailed orange, Lacey’s and lantana scrub-hairstreaks, red-bordered metalmark, soldier, brown longtail, Mazans scallopwing, white-patched and violet-banded skippers, and Erichson’s white-skipper. How many of these latter species were able to find proper larval foodplants is anyone’s guess; only time will tell.

But perhaps the white-striped longtail, a long-tailed skipper with a white slash across the hindwing, best represents our changing butterfly populations. When I first established a garden to attract butterflies in the mid-1990’s, white-striped longtails were found only in the Lower Rio Grande Valley. But by 2000 and 2001 they were suddenly found almost daily during much of the year. Their larval foodplants – wild peas and other legumes - are plentiful in the area, and so they moved northward and are now recorded through much of coastal Texas. They are considered a true invader and now a highly successful resident. Ever garden should have one!

Thursday, May 22, 2008

Carolina Wren Youngsters Are Out and About
by Ro Wauer

The first brood of Carolina wrens already is out and about. They are spending the majority of their time searching for bugs and spiders in every conceivable hole, crack and cranny on and around our backyard deck. There are at least four of the poorly marked fledglings, with a stubby tail and white eyebrows. They all seem extremely busy but yet slightly unsure of the best techniques for finding food. All the while the adults perch nearby, apparently letting their youngsters learn on their own. When one of the youngsters gets close enough, however, the adult will pick up a bit of food and feed its young. But the youngster’s uncertainty can be rather humorous to anyone watching their antics, whether it involves walking up and down a tree trunk, probing into a flower pot, or investigating the underside of a birdbath.

Our Carolina wrens have been in breeding mode a good part of the spring. It was first evident by the adult’s increased and more vigorous singing. They sang from numerous sites, ranging from flowering plants on the deck to the chimney top. Singing began to subside when nest-building activities began. Then we watched the adults gathering nesting materials that they carried to at least two sites. One was located in a pan in the open garage adjacent to the deck. The other was situated under the deck in an out of sight location. This was the nest that eventually produced the four youngsters.

An examination of the ingredients of the garage nest included an amazing array of materials. Although most was grasses and tiny twigs, pieces of string and thread, bits of paper and plastic, and a couple of tree branches larger than an adult bird were also present. How a bird the size of a Carolina wren, only two-thirds the size of a robin, was able to haul such a load and place it strategically on a nest located six feet above the floor is a wonder.

The Carolina wren is one of our most common resident birds. Like cardinals, they are year-round residents. They can be commonplace around our homes and yards inside and outside the cities. They are our largest wren, about six inches in length. Adults possess a rust to buff plumage, with fine black streaks across their wings and short tail, and bold white eyebrows, one of their most distinguishing features. Although Carolina wrens are common throughout the eastern half of Texas, from Brownsville to Texarkana and west to San Angelo and Abilene, they are not found in the far west or to the north. They are truly wrens of the eastern and southern portions of North America and south into Mexico.

A Carolina wren’s nesting process, from egg-laying to fledglings, requires only about two weeks. Nest-building can vary considerably, depending on weather conditions and the availability of materials. And when the youngsters are finally out and about, it will take only another two to three weeks before they can hardly be separated from the adults. But these few days offer some really special observations to anyone with the time and inclination to watch.

Thursday, May 08, 2008

Summer Tanager Numbers are on the Increase
by Ro Wauer

For the third year, summer tanagers are singing about my neighborhood at Mission Oaks, and on a recent breeding bird census between Schroeder and Mission Valley, I recorded three singing summer tanagers for the first time. The increased numbers of this charismatic species is most welcome, although why it has begun to frequent oak woodland areas of Victoria, DeWitt and Goliad counties are unknown. Although it’s regular Texas breeding range includes most of the southern half of Texas, it usually prefers broadleaf woodlands like those found along the river floodplains instead of oak woodlands.

Male summer tanagers possess bright red plumage, except for the red-brown wings, while females are yellowish with a yellow-green back. Both sexes possess a rather large pale bill. And although they are not often easily seen, because of their habit of staying in the upper foliage of broadleaf trees, their songs and calls usually give them away. Summer tanager songs resemble that of the American robin, with a series of sweet, clear phases, but faster and more deliberate. And their call is a dry spit-a-chuck, pit-a-tuck, or pit-tuck. Sometimes they will give an extended series of calls.

The summer tanager male that is currently utilizing my yard may be the same individual that was present there during the previous two summers. My current yardbird is an adult male in full breeding plumage. The earlier individual had not yet developed full adult plumage, but was mottled with red and yellowish plumage. And I had the impression that it was a juvenile bird that had not yet found a mate, but working hard to attract a lady tanager. It sang loudly during most of May and June, but seemed to loose interest by mid-summer. And it spent considerable time at my birdbath, sitting in the water splashing itself with water. It stayed until September, and then disappeared, only to return the following April; easily recognized due to its unchanged plumage pattern.

Three other tanager species do occur regularly in Texas. The one that probably is best known is the scarlet tanager, a bird of the eastern forests, and is only an occasional migrant through South Texas. The western tanager is a bird of the western forests that is only rarely found in our area. The hepatic tanager is a bird of the Southwestern woodlands, fairly common in the Davis and Guadalupe mountains of West Texas. All are easy identified. The scarlet tanager male is also bright red, but it has coal black wings and a yellow bill; females are greenish-yellow with darker wings. The male western tanager is yellow and black with a red face and cap. The hepatic tanager male is a liver-red color with dark streaks on the wings and a black bill; females are yellowish with a black bill.

Tanagers primarily are tropical species that occur in the tropics, usually south of the United States. There are 28 tanager species in Mexico, and 216 species in South America. I suppose that we are fortunate to find a tiny percentage of that number in Texas. Our birds are neotropical species that come north to court and raise a family, but the majority returns to their tropical habitats soon afterwards where they spent most of their life.

Thursday, May 01, 2008

The Yellow-flowering Retama Is a Symbol of Early Summer
by Ro Wauer

The fragrant and bright yellow flowers of our native retama have begun to bloom, another symbol of late spring or early summer in South Texas. This lovely little tree, with its thorny, green bark, can grow to 35 feet. Its drooping foliage, rounded crown, and compound leaves (tiny leaflets on a long flat stem) also help with identification. And by late summer, light brown to reddish, narrow pods, 2 to 4 inches long, appear.

Our ratama, known to scientists as Parkinsonia aculeate, occurs in Texas from the Gulf Coast west to El Paso, mostly in moist areas. A closely related tree known as Texas paloverde, or Cercidium texanum, occurs from Del Rio west along the Rio Grande to El Paso and westward through Arizona. Texas paloverde has smaller pods and a shorter flower stem than retama. The two flowering trees look very much alike. In Mexico they collectively are known as “palo verde” (Spanish for “green stick”), due to their green bark. Also in Mexico, the two trees are often called “lluvia de oro,” meaning “shower of gold.”

Both trees are members of the pea or legume family that comprise over 500 genera and more than 10,000 species in all parts of the world. Retamas prefer moist sites and often are common in riverbeds and at springs. In the Texas Big Bend country, the presence of a retama can be an indicator of water.

Because of their attractive appearance, retamas often are used for landscaping. Ornamentals rarely grow more than 20 feet in height. Also due to its all around attractiveness, retama has been named the city tree of Corpus Christi. Flowering plants also make good bee-trees, due to their sweet, nectar-laden flowers. Hummingbirds are attracted as well, and in Mexico it is a larval foodplant for a little green hairstreak butterfly, Clench’s greenstreak.

Paul Cox and Patti Leslie, in their book, “Texas Trees: A Friendly Guide,” point out that “livestock browse the foliage and branches during hard time. Bees are attracted to the flowers, and the pods are sought after as food by deer and other animals. In earlier times the pods were pounded and made into course flour by Indians. In Mexico a tea brewed from the branches and leaves is used in the treatment of diabetes and as a fever remedy.”

Whether the retama is a wild tree growing along the riverbeds or is maintained in our gardens, it is among our loveliest and most cherished plants.