The Nature Writers of Texas

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

Sunday, February 24, 2008

Cliff Swallows Are Returning to South Texas
by Ro Wauer

One sure sign of spring is the arrival of cliff swallows. These little birds build their mud-pellet nests under highway bridges and similar structures throughout South Texas. Colonies of from 35 to 200 individuals can usually be found at all the area’s concrete bridges and overpasses. They arrive in South Texas by early March and leave their nesting sites by the end of August. A few migrants can usually be found through October. Our cliff swallows spend their winter months in South America.

Nest-building is an amazing activity. Although some cliff swallows may only refurbish an old nest, most began anew by constructing a retort- or gourd-shaped structure (tubular entrance to a spherical cavity) from thousands of tiny mid pellets that they paste together literally one a time. They congregate at mud puddles or along the banks of streams to gather mud that they shape into round pellets in their beaks. They then methodically construct their nests. Construction time lasts for four to fourteen days, depending upon the availability of mud, distance to the source, and an adequate food supply. They then line their nests with grass and feathers, and the females lay four or five spotted eggs. Fledging occurs in 21 to 24 days.

Biologists have discovered that cliff swallows practice “intraspecific brood parasitism,” by laying eggs in nests other than their own. And, surprisingly, some individuals can transport their eggs to another nest. They may even toss out an egg, presumably to replace it with their own. As many as twenty-five percent if all cliff swallow nests in a colony may be parasitized.

Cliff swallows are one of the square-tailed swallows, in comparison with the long-tailed barn swallow and fork-tailed tree, bank, and rough-winged swallows. Cliff swallows possess a buff-colored rump and cheeks, pale forehead, and blackish throat and back. They are most closely related to cave swallows, which we also have in South Texas. While cliff swallows nest in open places, cave swallows building their nests in twilight sites, such as in the entrance to caves, in culverts, and other closed structures. Cave swallow nests are cup-shaped instead of gourd-shaped

All swallows are insect-eaters, taking millions of flying insects daily. One report stated that 35 cliff swallows collected in the vicinity of cotton fields in Texas had consumed 687 boll weevils, averaging 19 in each bird’s stomach. Beetles of all types are readily consumed. Other food types include ants, bees and wasps, flies, and a number of true bugs. Various small fruits are also eaten after the nesting season.

Cliff swallows are wonderful neighbors for a number of reasons. Not only do they eliminate many of our insect pests, but they provide one more reason to admire and wonder about our natural environment.

Monday, February 11, 2008

Where did all the monarchs go?
by Carol Cullar, February 11, '08

October is Monarch Month all across South Texas. Starting around the 9th the skies are generally filled with the flutter of hundreds of thousands, if not millions of these colorful creatures in dedicated flight toward the south southwest, steering an uncharted course toward an unseen, but certainly not unsensed destination. Then again, not.

Take this past year for example. Monarchs zipped through Maverick County on the 18th-19th of October and by the 21st. they were gone. Perhaps as few as 50,000. Only the ragtag stragglers came through after that, begging the question, “Where did Maverick County’s usual plethora of monarchs go?” What happened to the 180,000 migrants we were expecting?

This past week, Francisco Luna Contreras, spokesperson for PROFEPA [Mexico’s environmental protection agency] announced that the overall area of December’s monarch population in the Transvolcanicos of Central Mexico was 1.5 hectares smaller than the area calculated at this time last year.

This interesting factoid presents quite a few questions for us: How does one measure 200 million butterflies, all densely packed and clinging to trees in rugged canyons above 9,000 feet elevation on the side of a cinder cone volcano—albeit, an extinct one? It wasn’t until the deadly snow of ’02-03 that scientists began to get a handle on that one. They counted the dead on the forest floor in a square meter and 6 inches deep and extrapolated the numbers based on the thickness of the dead zone and its area.

What we learned from that macabre task was that previous population estimates were low by several tens of thousands per tree, if not millions per forest. At that point researchers realized it was more accurate to give up on a head count (or proboscis count) and rely on the area into which the monarchs had condensed. In late December of each year the monarchs manage to shuffle about within their colonies and condense even further, so another measurement of their area will be taken late January/early February.

For the present, the total area of all the colonies within the Reserva de la Biosfera de la Mariposa Monarca, some 56,000 hectares (a hectare is 2.6 acres) of forest and high meadows in the states of México and Michoacán, is 4.6. They expect the January area to be 4.1, which is the typical consolidation percentage.

Last year’s figures were 5.6 with the early figures at 6.6. In the last fifteen years, only the years of 2000/2001 and 2004/2005 were smaller than this year. These were due to die offs in the Reserva caused by severe weather.

Fortunately, so far this season there have been no freezing rains or snows to reduce the population. The current survivors have only to weather the next four weeks before they began their trek back north to this part of Texas. [Between February 28th and March 15th all the monarchs will begin to mate and struggle northward looking for milkweed in South and Southwest Texas.]

Another question or two: Why was the migration through here in October so small and short and quick? What factors determine the migration route through the Central Flyway and the numbers arriving in the Reserva each fall?

Three nations are interested in actively seeking answers to these questions. It will be noted that Sr. Luna Contreras was quick to mention that Mexico had no responsibility for the numbers arriving at her doorstep, but was willing to concede that reduced numbers in the colony around Contepec might in fact be attributed to local logging in the region, although Mexico is working harder each year to protect the forests and huge Oyamel fir trees vital to the sheltering of the monarchs.

Luna Contreras eagerly pointed to factors in the monarchs principle breeding grounds in the North Central U. S. and southern Canada as possible determinants for the reduced numbers.

It’s a fascinating and complex topic. A circle without end. Here are the primary factors:

1)Monarchs arriving in the spring from Central Mexico need to be met with abundant milkweed and few predators in South Texas. These conditions are contingent on rainfall and man. High rainfall encourages the growth of milkweed, but also gives a boost to the fireant population. Fireants destroy 98% of the monarch breeding population in SW Texas. Pesticide applications to remove fireants also impact monarch larvae in negative ways. Humans are in charge of the roadside mowing schedules throughout the region. Herbicides in pastures to knock out shrubs and weeds also take their toll on the availability of milkweed. Recent research has determined that size of the successful Generation One monarchs in this region determines the entire U. S. population east of the Rockies for the coming year.

So how could humans improve those conditions? No-mow regions along roadsides from January through early May would promote increased monarch numbers, as would fireant eradication through non-pesticide means. Garden plantings of native milkweed, other than the Tropical or Mexican milkweed would be of tremendous benefit.

2)North of San Antonio and reaching to the Plains in Canada, the increased use of GMO crops like Bt corn and soybeans has seriously threatened the number of milkweeds available in the primary breeding grounds. Another factor in this region is occasional cool, wet summers, which slow the lifecycle and therefore reduce the number of monarchs hatched in a single season.

Thousands of individuals have joined the Monarch Waystation Program to install butterfly havens and native plant gardens in this region to counterbalance deleterious agribusiness practices in the Corn Belt.

3)And then there is the fall weather pattern during the migration. For example, this past summer of 2006 saw favorable weather conditions for a healthy summer population in the North Central states. Migration progressed nicely out of Canada, Minnesota, Michigan, Iowa in late September. BUT then the jet stream got involved, and a huge dome of high pressure stalled out over the Central U.S. Monarchs by the millions began to pile up in Eastern Kansas and Oklahoma. They typically wait for a norther to blow them south, conserving energy expenditures. Hundred of thousands built up in commercial sunflower fields, nectaring and fattening up for the long haul. They waited and waited. Finally, a front came through, blowing fiercely to the southeast.

Monarchs that would have arrived in Maverick County around October 9th to the 12th, instead were blown into East Texas and Louisiana. When they struck the Gulf, they were compelled to turn along the Coast and fly back toward the southwest. Monarchs from the Central Flyway were forced to join the more heavily diseased monarchs from the Eastern migration. Two things happened. One: They added many hundreds of miles to the distance they were forced to fly. Two: The number of days they perforce had to travel were greatly increased. At roughly 24 miles per day one can see that an additional 500 miles would create considerable delay.

Evidently, fat storage plus distance plus timeline is somehow locked into the genetic clock each migratory monarch is committed to. Research has shown that monarchs that fail to depart their latitude in a timely manner or are delayed by other factors can experience a shutdown of their timing apparatus and the migratory imperative switches off. Even extreme warm weather in South Texas in late October can trigger them out of their reproductive diapause and into reproductive mode. Once that happens, the impetus to migrate is lost.

Dr. Orly Taylor of the U. of Kansas Entomology Dept. has long claimed, “If it’s the Coast; then they’re toast.” Dr. Taylor’s fifteen year migratory study, based on tagging monarchs with a small wing sticker, has shown that Coastal monarchs do not arrive in Michoacán and the Reserva. It is possible, these monarchs are over-wintering in as yet undiscovered colonies or the smaller colonies on the flanks of Popocatepetl east of Mexico City. But they don’t make it to Michoacán.

So where did the few monarchs who blustered out of here on a rough wind October 20th come from? It’s possible they were the leading edge of the migration that had actually made it south of the developing high pressure before it stalled out to the north. But they still arrived a full ten days later than normal.

One thing is clear. In four weeks the whole, vast, complex engine will power up, fluttering out across the continent one monarch at a time, beginning the cycle of life for this fragile creature yet again.

Sunday, February 10, 2008

Spring is in the Air
by Ro Wauer

I have long been smitten with spring. I have even wondered if my late-March birthday, right after the spring equinox, is somehow related to my love of spring. Maybe I was introduced to spring as a tiny baby, imprinted with that glorious time of year. One of my earliest memories is a song I learned as a youngster, “When It’s Springtime in the Rockies.” For growing up in the Rocky Mountains – the Grand Tetons were visible from the edge of town – I anticipated spring all winter, so that I could hike the Teton trails and see, smell, and feel springtime in the Rockies.

Anticipation of spring is evident for peoples throughout the world. Spring profoundly influenced the ancients and played a significant role in mythology, folklore, and art. In America, spring in marked by an abundance of festivals, weddings, special days such as Arbor Day and May Day – and spring cleaning.

Numerous authors and philosophers have expressed their anticipation of and joy over spring. There is a Chinese proverb stating that “spring is sooner recognized by plants than by men.” Author Thomas Wolfe wrote that “spring has no language but a cry.” Anne morrow Lindbergh wrote: “Today I went out. It smelled, it felt, it sensed spring. I had for the first time faith – not intellectual belief, but a sudden feeling of turning tide. Yes, there will be spring.” And humorist Dorothy Parker observed, “Every year, back spring comes, with nasty little birds yapping their fool heads off, and the ground all mucked up with arbutus.”

The revelations of spring vary from subtle nuances that only a seasoned naturalist can detect to much more obvious clues, such as a purple martin returning to its ancestral nest box, the discovering of the first violet or bluebonnet of the season, or hearing the roar of a territorial alligator. Clues are all around us if we so much as open our eyes and see the signs of the new season.

For South Texas, there are a host of spring heralds, ranging from birdsongs to new wildflowers to those more subtle indicators such as the scent of fresh earth to the taint of onions to the sweetness of huisache blooms. My spring usually comes as a trickle when the January days are mild. Most obvious, perhaps, are the scattered songs of cardinals and mockingbirds. It seems that the full songs of these two full-time residents are first to express their enthusiasm for the coming season. Those vocal signals urge me to look more closely at some of the shrubs and trees. And on close inspection, I often can find a few groundcover herbs in flower – bluets, prostrate lawnflowers, tenpetal anemones, and yellow woodsorrels – several shrubs have buds that are close to fulfillment – agarito, coral honeysuckle, and redbud. But one shrub, the viburnum, may produce its drooping, white-flowering blossoms as early as the last of January. And by taking up a watch nearby, I am likely to find a few early butterflies: cloudless sulphur, little yellow, gray hairstreak, gulf fritillary, common buckeye, and American lady.

Yet these signals of the new season are, for me, only indicators of better things to come. But it is now only a short wait for the northbound migrants to appear, for our purple martins, chimney swifts, and painted buntings to return, and the summer butterflies that utilize our abundant flowering plants to appear. It was Richard Hovey who, in 1898, wrote: “Spring in the world! And all things are made new.”

Sunday, February 03, 2008

Spring Means Romance for Skunks
by Ro Wauer

While driving from Mission Valley to town this week, I discovered four skunk road-kills along that 15-mile stretch. The same drive during most of the year produces very, very few road-killed skunks, although an occasional raccoon or cottontail can be expected. But it is the time of year when our striped skunks are out looking for mates. And apparently, the hot-blooded males pay little head to traffic when crossing the roadways. Also, perhaps, because of their behavior of standing their ground and relying on their nauseous fluid for protection rather than running away.

Striped skunks are normally shy creatures that venture out of their dens only during the nighttime to search for food. But their diet can include a vast array of prey, ranging from insects such as grasshoppers and beetles, various snakes and amphibians, to small rodents, such as mice and rats, to crabs, and an occasional bird and their eggs. They also feed on various fruits. Although skunks usually are good neighbors, they occasionally invade chicken coops when hungry or trying to feed a litter.

The striped skunk is easily identified by its black body with a narrow white striped that runs from the top of its head backward along its back, like an elongated V. About the size of a house cat, striped skunks can appear almost anywhere, from our fields and woodlands to even our residential areas. Nocturnal in behavior and rarely encountered, they are more often detected by scent than they are seen.

Three skunk species occur in South Texas: the fairly common striped skunk and the very rare spotted and hognose skunks. The spotted skunk is the smallest of the three and can be identified by numerous white markings, while the hognose skunk, about the same size as the striped skunk, has an all black back and tail and a longer snout.

All skunks possess scent glands with an obnoxious odor that they can spray at an antagonist when disturbed. Although it may seem that the typical skunk odor is commonplace, they spray only as a last resort. The scent glands, located near the base of the tail, are normally activated only after the animal warns the intruder first. It first will audibly strike the ground with its forefeet and even make short rushes at its enemy before actually using its potent spray. It finally will bring its rear around toward its enemy, with its tail erect, and then discharge fine yellow, oily droplets through small ducts that open just inside the anus. These glands are encased in muscles that can be voluntarily controlled by the animal when the situation demands it. The jet may travel 12 feet, and the powerful scent may be detected miles away during favorable weather. Also, the scent from droplets that touch immediate objects, animals, plant or trap, can remain for weeks.

Skunks normally live a solitary existence, only pairing up during their spring breeding season. Their gestation period lasts for 42 to 63 days. The litter of four to ten young is born blind and finely haired. The youngsters open their eyes in about 21 days, and they are weaned in six to seven weeks and taken on hunting trips by the mother during the end of that period.

Skunks are carnivores that belong to the Mustelidae Family, along with various weasels and the badger, wolverine, ferret, and otters. All possess scent glands, but only the skunks are able to spray their obnoxious fluid any distance.