On the Wing, Over Prairie and Sea

Peregrine Falcon. Photo by David Powell

They’re coming soon, to a forest or shrub stand near you! In fact, many are already here. September is just about the best month to look for migrants winging their way south toward their wintering grounds. It is an especially good time to look for those uncommon species, like Yellow, Canada, Prairie, or even Chestnut-sided Warblers that nest in the northern forests, but winter in Central or South America.

The good news is that huge numbers of migrants can be found in any area with a good supply of insects, often in mixed flocks that just might include that target bird on your wish list. Just about anywhere with good stands of shrubs beneath the cottonwood canopy should host more than enough birds to satisfy your birding appetite. Just find a likely patch and stop and listen. Shortly, you should begin hearing the little chips that tell you songbirds are around. At this time of year, only one thing is on their minds – food! Their entire focus is to add as much fat reserve as possible to help them survive their long migration.

Just as all species look and sound different, their feeding styles vary too. Yellow-rumped and Wilson’s Warblers are very active feeders, flitting about at all levels from ground level to canopy tops. Watch for motion in the leaves that indicates a songbird is actively feeding. For others, like MacGillivray’s Warbler and Common Yellowthroat, a forceful chip note arising from near ground level in dense vegetation reveals their presence. Still others, like our resident Virginia’s and Grace’s Warblers, tend to skulk in the vegetation, moving slowly and deliberately, often evading detection. And, lastly, there are those that never make a sound, like Warbling Vireo. Luck has to be on your side to detect them.

Although the songbirds moving south through New Mexico have a land-based migration, many species in eastern North America have evolved to migrate over the Gulf of Mexico. Their southbound journey exactly coincides with hurricane season. Have you ever wondered how birds cope with the wrath of Mother Nature at her most ferocious? So far in 2008, Gustav, Hannah, and Ike have affected an already perilous journey, one in which there is no natural respite for an exhausted bird.

It is clear that hurricanes have a devastating effect on migrants caught in the storm, with some estimates of hundreds of thousands dead as a result of a single powerful hurricane. Seabirds, in particular, have nowhere to seek shelter on the open waters. Birds caught up in these storms are blown far off course, often landing in inhospitable places or simply arriving too battered and weak to survive. Although the toll may be extreme on individuals, healthy bird populations are able to withstand such losses, and have evolved to do so. However, severe storms can have devastating consequences for endangered species. Such was the case in 2007, when all 18 endangered Whooping Crane youngsters drowned in their protective cage in the lowlands of Florida following an unexpected storm surge.

There is evidence that birds are sensitive to changes in air pressure and instinctively take shelter. A sharp drop in barometric pressure indicates a big storm is on the way. Some birds fly away from the storm’s path, while strong-flying birds, like the Peregrine Falcon, fly ahead of the storm. In 1998, a second-year, female peregrine was captured in Virginia, and fitted with a satellite transmitter. Scientists monitored her migration southward to Venezuela, including during the extreme weather created by Hurricane Mitch. The peregrine initially followed a track that would have taken her island hopping along the eastern Carribean. As Mitch’s winds altered the normal southerly flow that aids migrating birds, she was pushed toward the west into the open waters of the Gulf. Suddenly, over open water, the falcon appeared to stop for nearly two hours, apparently taking refuge on a ship. For the next three days, she moved against the prevailing winds in a direct line toward Galveston, at a speed of ~10 miles per hour, again presumably on a ship. She rested near there for six days before departing in a southeasterly direction, again possibly hitching a ride on a ship based on her average departure speed. She arrived in Venezuela approximately five weeks later after a sojourn in the Yucatan Peninsula.

Although, much has been published about the effect of Hurricane Katrina, little has been written about its impact on avian migrants. One study, conducted by U.S. Geological Survey scientists, used radar ornithology to measure the effect of the storm on migrant use of lowland forested wetlands of the Pearl River and upland pine-dominated woodlands near Slidell, LA. Their study used archived Doppler weather radar data to measure bird use of this particularly important stopover location. What they found was that for the 3 weeks following Katrina, when virtually all vegetation had been stripped in the wetlands, the birds foraged in the less heavily damaged pine uplands. However, about five weeks after the storm, when much of the surviving forest in the Pearl River bottoms began to sprout new foliage, a corresponding increase of migrant use of the lowlands was documented.

Ultimately, the real threat to birds may not be from Earth’s natural forces, but rather human alterations to the planet that reduce or eliminate surge-protecting coastal wetlands and warming ocean waters that generate increasingly more powerful storms.

Death of a Songbird

Western Meadowlark. Photo by David Powell

I caused the death of a songbird. Certainly more than one bird, and possibly a hundred or more, died because of me. I didn’t mean to do it. In fact, I was oblivious to their silent suffering and desperate demise. It was the winter fruits and vegetables that did it, those seemingly healthy foods that the doctor recommends. They make up a large part of my diet throughout the year. I have a particular fondness for grapes, bananas, asparagus, peppers, and that standard American staple, coffee.

One of the indicators of the changing season is the annual return of bird song. Many of us look forward to the return of our feathered friends from their wintering grounds. We take for granted that their song will fill the spring air with cheerful sounds. But, each year, as we continue to demand out-of-season fruits and vegetables, fewer and fewer songbirds return. Just as the Bald Eagle, Peregrine Falcon, and Osprey were the proverbial canaries in the coal mine that warned us of the dangers of DDT, and changed pesticide use in the United States, today’s songbird populations are an important environmental indicator.

Land management plans in North America now include provisions designed to protect migratory songbirds, including virtually all federal, and most state plans. Many land managers have changed the way they manage to allow for the needs of songbirds and other wildlife, and support research to develop methods to maintain healthy populations. Ambitious projects are underway to permanently protect large swaths of acreage for birds, particularly grassland and boreal forest species. Because of their role as environmental indicator species, avian conservation measures have become part of global efforts to protect biodiversity, not just for birds, but for all life.

Many of our summer residents winter in Central and South America, where highly toxic pesticide use has caused steep declines in bird populations. Pesticide use has increased 500% since the 1980s in Central America as these countries have increased their production of crops to fuel our demand for fresh produce during the winter. The chemicals include monocrotophos, methamidophos, and carbofuran, all of which are rated Class I toxins by the World Health Organization, are highly toxic to birds, and are either restricted or banned in the United States.

In some cases, the poisonings are indirect such as the 1995 deaths of 20,000 Swainson’s Hawks on the pampas of Argentina. Farmers had sprayed monocrotophos, an organophospate on their fields to control grasshoppers, the primary food item of wintering Swainson’s Hawks. Thanks to the efforts of the American Bird Conservancy and other organizations, Novartis (formerly Ciba-Geigy), a major manufacturer of this pesticide, has agreed to phase out production and sale of monocrotophos. Additionally, a major effort has taken place to educate farmers about the benefits of these insect eating hawks and other birds that help keep insect populations under control.

In other instances, birds like the Bobolink, meadowlarks, and other grain eating birds are viewed as pests as they feed on the crops intended for humans. They are directly poisoned to minimize crop damage. The Bobolink, in particular, has suffered a 50% decline in the last 40 years, according to the Breeding Bird Survey.

Americans, however, shouldn’t feel too smug about our environmental record when it comes to pesticides. On a global scale, over 5 billion pounds of pesticides are used annually for agriculture, forest and rangeland management, disease control, and on private properties. In the United States alone, we use 1.2 billion pounds each year. Many of the most toxic chemicals, including DDT, have been banned in our country. However, the U.S. continues to export DDT as well as other pesticides known to be hazardous to the environment and to human health. Conservative estimates place the of the number of birds killed in the U.S. each year due to pesticide ingestion at 67 million. This represents 10% of the 672 million birds annually exposed to pesticides in our country alone.

South of our border, human pesticide exposures continue despite workers’ improved awareness of the dangers. Most Central American countries have few regulations for effective controls for pesticide use, and in 1998, (most current figure available) almost 6,000 human poisonings were reported in Central America. Ironically, while we have increased our reliance on winter produce, Mexico, a major importer of that produce, has increased its dependence on pesticides. It is currently the second largest pesticide importer in Latin America.

We have effectively created a circle of poison in which pesticides outlawed in the U.S. because of documented toxicity are exported to Third World Countries that use them to grow the crops that are, in turn, sold to the American consumer. Testing by the U.S. Food and Drug Administration shows that produce imported from Latin American countries is three times as likely to violate Environmental Protection Agendy standards for pesticide residues., Some, but not all pesticide residues can be removed by washing or peeling produce, but tests by the Center for Disease Control show that most Americans carry traces of pesticides in our blood. We, however, show few if any signs of that oxicity. It just may be that our beloved songbirds might be the first indicator of threats to our health.

As American consumers, our most effective tool is our wallet. Next time you shop, buy locally grown foods wherever possible. Not only will you reduce your pesticide exposure, you will be purchasing food with a smaller carbon footprint.

Purchase organic, shade-grown coffer. Most mass produced coffee is heavily treated with fertilizers, herbicides, fungicides and insecticides. Shade grown coffee is grown beneath a canopy of tropical trees, which provide shade, essential nitrogen, and leaf litter for fertilizer.

Organic bananas should on your list. Although our pesticide exposure from bananas is minimal because we peel the fruit, bananas are grown with one of the highest pesticide loads of any tropical crop.

Purchase produce such as melons, green beans, tomatoes, bell peppers, and strawberries only if they are not grown in Central America.

The birds, and your great grandchildren will thank you for it.

Big Black Birds a.k.a. Nature’s Clean-up Detail

Photo by David Powell


In my mind, they are among the first harbingers of spring. Each year, beginning in mid-March, my eyes are drawn skyward daily, searching for their dark form, soaring aimlessly above. I record this event faithfully each year, and my records show that our Turkey Vulture (Cathartes aura) friends return from their wintering grounds around March 15 each year, just in time for Saint Patrick’s Day celebrations. This year it happened on March 17, only not in the cerulean blue open sky, but on KOAT-TV, on the news! They ran a wonderful story, showing one of the first big black birds to return. My first sighting occurred a few days later, on March 21, at 8:30 a.m. in the Rio Grande bosque during a songbird survey. First one large black shape caught my eye, followed by another. Ultimately, ten birds took flight from their night roost in snag along the river bank. I knew that spring was on the way despite the dreadfully windy days of late.

Often unappreciated, vultures perform a vital role in the Earth’s food chain, that of the scavenger. Their scientific name, Cathartes, means purifier. Until very recently, they were considered to be a raptor even though they almost never kill their food, preferring instead to eat carrion. DNA studies conducted within the last ten years have proven that this species is more closely related to the stork family. Unlike other birds of prey, Turkey Vultures have a highly developed sense of smell, and can locate concealed carcasses beneath the forest canopy. Vultures tend to forage alone, but keep a keen watch on the activities of other vultures nearby. A discovered carcass may attract numerous vultures to the site, along with the other, much smaller western scavenger, the Common Raven. Even Golden Eagles are sometimes found at carcasses, and indeed, nearly all species of raptors scavenge when live food is scarce. Vultures, including the Black Vulture which does not occur in New Mexico, are responsible for the removal of tons of animal carcasses in North America each year.

Generally acknowledged as a beneficial scavenger, Turkey Vultures were accorded protection in many states even before the Migratory Bird Treaty Act was passed in 1918. They are; however, still persecuted in some areas and have been trapped, shot, and poisoned by ill-informed humans who fear that they may spread disease among livestock, or kill newborn calves, although direct kills of young are almost certainly due to another avian predator. Over 100,000 vultures were killed in Texas in the mid-1900's by baiting walk in traps with carrion, and the species is also vulnerable to steel leg-hold traps such as the ones that were responsible for the deaths of two gray foxes in Jemez Springs in February 2006.

The population of Turkey Vultures is generally stable in the U.S., particularly as increased education about the benefits of this species has reduced persecution. The greatest causes of mortality for this species today are collisions with automobiles and aircraft, and electrocution on power poles. Collisions with military aircraft are particularly serious, costing the U.S. Air Force 21.6 million dollars, 3 crashed aircraft, and 2 fatalities between 1989-1992. Records of collisions with power lines are rare, and Turkey Vultures often forage directly beneath power lines on carcasses of other less adept species; however, electrocutions occur when the bird perches on power poles, and two body parts, such as wings, or a wing and a foot, touch separate energized portions of the structures, causing electricity to arc between them. Their winspan (63-71 inches), which is smaller only than that of eagles, makes them particularly susceptible to electrocution when the fleshy wrist tissue spans two energized wires.

One of my first and most memorable close encounters with Turkey Vultures happened in the Jemez Mountains. A friend and I were attempting yet again, to find a way to hike to the top of Virgin Mesa without driving around to the west side. We struggled through the increasing steep terrain of the tent rocks, where each step forward was countered by a half slide back. Then, just as we were about to admit defeat, several vultures took flight right over our heads. Their presence was impressive as they wheeled buoyantly on the wind, above and around us oblivious to the limitations of the land-locked humans below. I wondered then, if they nested on the cliffs above us, and they may have been doing just that. They do not build nests, but utilize caves and crevices in cliffs, like the escarpment on Virgin Mesa, and other mesas in the Jemez Mountains. By the time this reaches you, these remarkable black birds should have returned to their mountain home.