The Nature Writers of Texas

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

Thursday, June 25, 2009

White Ibis is a long-legged water bird
by Ro Wauer

An adult white ibis is a very clean-cut, distinct bird, although young of the year are rather ratty looking. Adults possess all white plumage except for black wingtips and a bright red face and long curved bill, with a blackish tip, and long red legs. The adult plumage gives them a rather royal appearance. The plumage of young birds is mottled with brown, although they too possess a reddish bill and legs. It is not too unusual this time of year to see adults and youngsters together, feeding in shallow water along the coast or at inland wetlands, such as mudflats and flooded pastures, or flying about in family groups. They are one of our more social birds, feeding and roosting together, sometimes in rather large colonies.

Ibis are waders that glean their food with their long curved bill, either in water or on more solid ground. Their diet consists primarily of crabs, crayfish and snails, but they also will take fish and snakes and almost any small creatures, including insects, that they find. Feeding behavior is rather interesting. Kent Rylander, in his “Behavior of Texas Birds,” wrote that “they walk leisurely through the shallows, sweeping their long, decurved bills from side from side as they probe the bottom mud for crustaceans (especially crayfish), worms, and other animals.” He also states that “this ibis is a nonvisual, tactile forager: it places its partially opened bill in the water or bottom sediment, then snaps it shut when it partially detects prey. Prey taken from the water’s surface, mud, or short grass habitats are generally located by sight. White Ibises also steal food items from one another.”

Nesting birds often gather in huge, dense colonies with as many as a thousand or more nests. One colony on Galveston Islands contained 20,000 breeding pairs in 2001. Most nests are built with numerous sticks, lined with green leaves, in low shrubbery, but other nests may be placed higher on low trees around water areas. Nests may be usurped by their neighbors, and a colony can raise a great racket when squabbling among themselves. Young leave the nests in about three weeks and follow the adults to choice feeding sites.

White ibis are primarily found in Texas along the Gulf Coast, but they are casual visitors considerable distances inland. They even are considered accidental in the Trans-Pecos. In recent years, breeding birds have expanded their range further inland. Generally, white ibis in Texas can be expected only during the summer months, but they seem to be staying all winter long more and more often.

Three species of ibis occur in Texas: white, white-faced, and glossy. And the roseate spoonbill is closely related, all within the family Threskiornithidae. White and white-faced ibis are reasonably common in wetlands in the Golden Crescent, but glossy ibis, a bird that once was found only along the eastern Gulf Coast, is gradually increasing in numbers. And the roseate spoonbill is far more numerous along the coast, rather than venturing very far inland.

Thursday, June 18, 2009

Courtship Feeding
by Ro Wauer

Cardinals and a few of my other yard birds are currently feeding one another. Much of that, of course, is an adult bird feeding one of its babies. Fledglings will follow their parents about for a considerable time, depending on how long the adults feel it is necessary. Some birds, like roadrunners, as soon as their youngsters can feed themselves, will lead their offspring away from their nesting territory and essentially loose them. Some humans need to do the same.

But there also is a lot of courtship feeding still underway. That is the behavior of one of the adults, usually the male, feeding his mate or his potential mate. In cases where the female takes the lead in courtship, such as with some sandpipers, the female will feed the male. This behavior is considered part of avian courtship, and it may start very early in the breeding season and may last for a few weeks after the last nestlings have fledged.

Early courtship feeding is a way for the dominant individual to attract a mate and develop a bond. This pair bonding, or the honeymoon period, may last for a considerable time, or at least until copulation occurs. Although courtship feeding is likely to continue, the individuals will also feed themselves. Ornithologists believe that courtship feeding not only forms a bond but also tends to maintain the health of the female and leads to greater nesting success. The number of eggs and clutch weight are partly determined by the female’s nutritional status. As Paul Ehrlich and colleagues wrote in “The Birder’s Handbook, feeding of the female “seems apparent that he is increasing his own reproductive success by keeping her fat and healthy.”

Males usually continue feeding the female through much of the nesting process or at least until the nestlings require both adults gathering food on a full time basis. Then the feeding behavior changes dramatically. As the nestlings grow and demand more and more food, feeding by the adults become all consuming. This is the time of year when more nutritional foods are necessary. For the majority of songbirds, such as cardinals, wrens and mockingbirds, insects and other small creatures become essential. Some studies suggest that songbirds must consume up to 80 percent of their weight on a daily basis. Adults with nestlings must therefore capture an amazing amount of food for themselves and young each and every day.

Once the young are fledged, in spite of the fact that they will continue to beg food from the parents, their diet begins to change from insects and other highly nutritional food to other things like seeds and fruit. Young cardinals for instance will very soon join their parents at seed feeders. And by late summer fruit usually becomes part of their daily diet. It is interesting that even some Neotropical flycatchers, species that nest in the United States and Canada where they specialize in insects, will switch to a diet dominated by fruit on their wintering grounds in the tropics.

The majority of songbirds that we find in our yards must feed constantly, especially when feeding young. During a normal day, however, most songbirds feed most heavily during the early morning hours, again during mid-morning, and then again in the late afternoon prior to going to roost for the night. Seed eaters that frequent seed feeders follow the same pattern, but they also are constantly on the lookout for insects and other more nutritious creatures. All birds are opportunists!

Thursday, June 11, 2009

Our Mysterious White-tailed Visitor
by Ro Wauer

Betty saw it first, and she called me to the kitchen window from where we could see the tiny fawn that was lying in the shade of one of the backyard planters. It was almost impossible to believe that the mother white-tailed deer had left her fawn so very close to the house, about 40 feet from our kitchen window. We immediately grabbed our cameras and began to photograph our tiny visitor. At first it had its head turned away, tucked alongside its body, and the only sign of life was an occasional ear flick. Through binoculars we could see that it was dry; it apparently had been cared for by its mother.

About 30 minutes after our first discovery it raised its head and turned in our direction. More photos! It seemed to be gaining strength, moving about a little and even nibbling at its side. And in another 20 minutes or so it began to stand. It took another few minutes to stand fully upright; it looked like a little spotted body on amazingly long legs. It seemed to teeter a bit, and then take a few steps. It may have seen our movement inside the house because it slowly walked away around the side of the planter and out of sight.

We finally walked outside, trying to follow it and to position ourselves so that we could take some additional photos. We high hope that its mother would suddenly appear and guide it away from our yard and into the brushy area beyond. But instead, it walked only another 100 feet and again laid down in the shade of another planter box. It stayed there for another half-hour or so, even when I walked to within a few feet while watering. Eventually we again approached it to get some close-up photos. But that was more than it could put up with, for it suddenly jumped up and ran at full speed away and out of our yard toward the brushy area beyond.

The entire episode left us with numerous questions. Where was the mother during all of this? Why had she left her baby in our yard so near the house? And why had she not made some effort to return or coax it away?

We first found the fawn right after returning from our morning walk, at about 10am. Had we frightened the mother away when we left or returned to the house? We did not approach the fawn at all during the first period. We did watch to make sure some predator stayed away. The most likely predator would be a large dog that might wander into our backyard for a drink at one of the birdbaths. Yet we also understood that fawns do not have a scent to attract predators. And we understood that mother deer regularly leave their young in a safe place for considerable time. We wondered if she had a second fawn elsewhere, and was not concerned about the safety of our mysterious baby. Did she consider our yard safe?

I know that we will never fully understand what we experienced, but that is all part of Mother Nature’s mystic. We only wish the best for our little fawn. We hope that it found its mother and that she was able to feed and care for it, and that she will nurse it to a healthy youngster. Maybe we will see it again when it returns to enjoy one of our birdbaths.

Thursday, June 04, 2009

Robber Flies Are Deadly Predators
by Ro Wauer

It’s been said that robber fly predation on other insects can be compared with peregrine falcon predation on birds. Both are dramatic predators that take a significant number of prey. Although dragonflies also take numerous insect prey, including other dragonflies, from what I have observed in recent weeks, robber flies are far more successful in catching prey. And a close-up look at one of our many robber flies is rather scary. I am surprised that one of the horror movies, so common today, has not been developed around a monster robber fly.

Although robber flies can vary considerably in size (some tropical species can be more than a foot in length) and bodies, they all possess extremely long spiny legs, bearded face, piercing mouthparts, large eyes, hollowed out area between the eyes, and a bristly humped thorax. Some are stout like bees while others are long and narrow with a very long abdomen. And the various species, of which there are about 1000 in North America, utilize a wide range of habitats, from our yards to the beach to desert scrub and even grasslands. They can be found perched on the ground, on branches and leaves, or on various structures.

Robber flies will eat almost any flying creatures they can catch. Some of their prey can be considerable larger than they are, and one’s daily diet may include everything from bees and wasps to grasshoppers, butterflies, beetles, and other flies. Most hunt from perches where they wait for passing prey, and some species actually establish a flight territory that they defend from other robber flies. They possess a mobile head that can move about in various directions. When seeing a passing prey, they will immediately give chase and catch it in mid-air. They may even fly ahead and intercept the prey from an angle. They will then fly to a shady perch, holding the prey in their long spiny legs, and consume their catch by sucking their prey dry with hypodermic-like mouthparts.

The robber fly life cycle is rather ordinary. The females lay eggs on or just beneath the soil surface. Upon hatching the larvae (tiny, slightly flattened worms) crawl about in the soil and feed on tiny arthropods. Some species may remain in the larval stage for a full year, but most at least stay as larvae through the winter months. By spring, the larvae feed on decaying vegetable matter and the larvae of other insects. And by late spring or summer they pupate and wriggle to the surface where the adults emerge.

Robber flies are members of the Order Diptera or flies, a huge group of insects that includes everything from mosquitoes, wasps and bees, to house flies. What separates robber flies from most of the other flies is their aggressing predatory behavior. During some periods of the year they seem to be especially common, and I have often wondered if their numbers actually control populations of some other flying species. During a recent visit to the Lower Rio Grande Valley, I found several robber flies that had captured butterflies. Although they often are difficult to photograph when perched, they seem to allow a much closer approach when feeding on prey. I realize that robber flies have every right to coexist with all the other native insects, but I must admit that I am bothered when I find one with a butterfly firmly gasped in its long spiny legs.