The Nature Writers of Texas

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

Sunday, September 30, 2007

Bald Eagle Time Again in South Texas
by Ro Wauer

It is again time for the annual arrival of bald eagles into South Texas. Southern bald eagles normally return to their ancestral nesting sites in September to November from their summering grounds in the north. They will remain through the winter months, nest in midwinter, and leave in March or April. Young birds may linger into early May, but all of the adult birds and their offspring usually are long gone before the heat and humidity of summer truly sets in. Only rarely does one remain year-round.

The bald eagles that nest in South Texas, along the coastal plain from Nueces County to Houston, and around lakes in northeastern Texas, are members of the southern bald eagle race, rather than the northern race of bald eagles that nest north of the state and as far away as Alaska. All bald eagles are long-lived and mate for life, although if one of the pair dies, the remaining bird will usually take a second mate. Adult nesters construct huge stick nests in trees usually located along waterways. Sometimes those stick nests, which may have been used for twenty or more years, become so large that they literally break down the tree branches. One nest was measured at 10 feet across and 20 feet deep.

Females normally lay two or three large, bluish white eggs, but more than two hatchlings are an exception. Incubation takes thirty-four to thirty-six days, and the nestlings are fed by both parents for about three months before fledging. So by the time the southern youngsters are flying, it is time for them to go north. More often than not, the adults will leave ahead of the uncertain youngsters.

Although bald eagles take advantage of available carrion, their diet is rather broad. Wayne and Martha McAlister write in their book, A Naturalist’s Guide: Aransas, that “food items found in the nests on the Aransas generally confirm the eagle’s diet of fish and waterfowl: flounder, mullet, red drum, a white pelican, many American coots, pintails, scaups, and numerous grebes; swamp rabbits and cottontails, and one armadillo that may have been picked up as carrion. One adult eagle was seen in flight carrying a struggling scaup duck in its talons. Another was observed over Dunham Bay dive-bombing an osprey in an apparent attempt to make it drop its fish.”

Adult bald eagles are truly magnificent birds, with a snow-white head and tail and a huge yellow bill that are stark contrasts to its chocolate brown body. Its general appearance as a fierce predator also is in contrast to its true character, that of a timid carrion feeder. But anyone who has watched one of these magnificent creatures for any length of time cannot help but be impressed. In fact, Congress declared the “American eagle,” instead of the wild turkey that Benjamin Franklin preferred, as our “national bird” on June 20, 1782.

Yet in spite of the bald eagle being established as our national emblem, North American populations declined precipitously during the 1950s and 1960s, primarily as a result of egg-shell thinning caused by pesticides and heavy metals that the birds absorbed through contaminated fish and other foods. The birds were listed as endangered by the United States and Canada in 1963, and DDT, one of the most long-lived and widespread pesticides, was banned for use in the United States and Canada in 1972. Since then, bald eagle populations have made a remarkable recovery throughout their range. And last year it was delisted.

Today, one can observed one of our national birds in winter in several South Texas locations. Best bet sites include a variety of fishing sites such as Coletoville Reservoir, Lake Texana, and various points along the Guadalupe and San Antonio rivers. And Dupont Victoria has constructed an observation platform along the north entrance road to the plant where as active bald eagle nest can be seen. What’s more, the public is welcome!

Sunday, September 16, 2007

Red-tailed Hawks Are Almost Everywhere
by Ro Wauer

During a recent trip to California I was surprised how different those red-tailed hawks are from those that occur in South Texas. Although I had lived in California for many years, even started my birding life while living in the northern Bay Area, I had forgotten those differences. Although both areas produce birds with a rufous to brick-red tail, a frontal view is quite different. The California birds are typical of red-tails in much of the West as well as those in the northern and eastern U.S. Those birds typically possess cream-colored underparts with cinnamon or blackish streaking on the side of the breast and a broad band of dark barring and streaking across the belly. The South Texas red-tails, a subspecies that occurs from the Trans-Pecos east to the Gulf Coast, possess white underparts; the breast is often shiny white in the right light. All red-tails have a rather distinct call, a raspy, descending “tseer,” often heard in Western movies. They call most often when disturbed to irritated.

Our red-tailed hawk is the Fuertes subspecies, the largest of all the red-tail subspecies. If the two birds were sitting side-by-side, the Fuertes red-tail would be noticeably larger and whiter. The back of all the adult red-tails is blackish or dark brown with mottled gray patches. That mottled appearance helps to identify red-tails that are sitting with their back to you even from a distance. The other broad-winged hawks that occur in our area regularly - Harris’s, broad-winged, red-shouldered, and white-tailed - are quite different in appearance. Even in flight, they are very different. First and foremost, only red-tails possess a red tail. Harris’s hawks possess chestnut shoulders, but their tail is white with a broad black band. White-tailed hawks also possess chestnut shoulders, and their tail is immaculate white except for a narrow black band near the tip. And the red-shouldered hawk, our most common full-time resident hawk, has a many-banded tail and reddish shoulders and banded underparts.

The red-tailed hawk is the most widespread species of North American hawks with a range that extends coast to coast, south to Panama, and northwest through most of Canada to Alaska. Unlike our red-shouldered hawk, that frequents wooded areas, red-tails prefer open country with scattered trees as well as arid lands. Nesting, that normally occurs from late February through late June, usually occurs in the crotch of large trees with a commanding view. But some individuals also utilize cliffs with pockets large enough to hold a nest and high enough so that it cannot be reached by predators. The nests, the largest of all hawk nests, are bulky structures of sticks and twigs, and lined with bark, twigs and leaves. They sometimes utilize old nests of other raptors. Females lay one to five eggs, both adults feed the nestlings, and fledgling occurs in 45 to 46 days.

Red-tail diet consists primarily of rodents, such as mice, rats, ground squirrels and prairie dogs, but they also will take other prey, such as amphibians, crayfish, fish, and even insects, whatever the land provides. Hunting red-tails utilize open country where they soar at moderate heights in search of prey. They can stalk their prey from the air, usually from 100 to 500 feet, or they can search for prey from some strategic perch such as a treetop, telephone pole, or fence post. Once a prey is located they may either dive on it or approach from a lower side angle. They then pin the prey to the ground with their large curved talons, kill it with a swift bite of the bill, and then either carry it off to a waiting family or to eat it elsewhere, or they may even feed right on site. Unlike a few other raptors, such as caracaras and eagles, red-tails normally feed only on their own kills.

In spite of their abundance throughout Texas, including being fairly common in all the open areas of the Golden Crescent, red-tailed hawks are worthy of our admiration.

Sunday, September 02, 2007

Male Hummingbirds Are Early Migrants
by Ro Wauer

It seems impossible that some of the southbound fall migrant birds are already arriving in south Texas. Only a few short weeks ago we were watching the hordes of northbound migrants that were passing through our area en route to their nesting grounds to the north. And now, barely four to six weeks later, some of those same birds are heading south to their wintering grounds in Mexico and Central America. Although the majority of the neotropical migrants are still feeding young far to the north, a few, such as several of the male hummingbirds and a number of shorebirds, are already back in Texas.

It has been said, and truthfully so, that male hummingbirds are little more than brightly colored “promiscuous rakes.” They have little or no home life. In spring they migrate north to ancestral breeding grounds where they establish territories, which they may defend against other hummers to their death, performing fascinating aerial displays to attract the ladies, mating whenever the opportunity occurs, and heading south as soon as all the available females are on a nest.

It is the female hummingbird that selects the nest site, builds the nest, incubates the two or three eggs, and feeds the nestlings. Male hummers are long gone halfway through the nesting season. They search out lush mountain meadows with lots of wildflowers, where they usually remain until late summer or fall. Sometimes male hummers passing through South Texas will find suitable conditions to keep them in one place for a few weeks or, rarely, into fall and even all winter.

Shorebirds share similar behavior. Many of the shorebirds that we observed along the South Texas coastline in March and April continued northward to northern Canada or Alaska. Although some shorebirds are like hummingbirds, with males departing their breeding grounds soon after mating, others are caring parents. But the great number of shorebirds that utilize the northern tundra to nest experience a short summer and extremely long days that permit a faster nesting cycle. Many nestlings are feed twenty hours a day, and many of the young are precocial (capable of a high degree of independent activity from birth): they follow their parents about, feeding on the abundant tundra insects within hours of hatching.

The long days and abundant food leads to a very swift completion of their nesting cycle. So the coastal wetlands in Texas, like a narrow part of a North American hourglass, experience great numbers of southbound shorebirds by mid-summer. And wherever masses of shorebirds are found, raptors are not far behind.

Of the hundreds of post-nesting birds that can be found in South Texas in late July and early August, my personal favorite is the rufous hummingbird. Its arrival somehow represents a very distinct change in the characters that utilize our yards. The summer resident ruby-throated, black-chinned, and the larger buff-bellied hummingbirds are less territorial and aggressive. Only the much larger buff-bellied hummer dominates a male rufous hummer. But it is the rufous hummingbird that controls the choice patches of flowers and a favorite feeder that were earlier utilized by the resident ruby-throat and black-chinned hummingbirds. Even in September, when the yard can be filled with 50 to 100 southbound ruby-throated hummers, the one or two rufous hummers that have managed to stay are dominant. Rufous males are pugnacious characters with a personality all of their own!