Texas Raptors & Their Prey

— This article by Jerry Cates was first published on 20 February 2019, and was last revised and expanded on 23 April 2019. Copyright Bugsinthenews Vol. 18:02(01)

Eastern Screech Owl maternity nest in Austin, Texas

Maternity nest of four Eastern Screech Owl (Otus asio) chicks, deep in a hole excavated by nature and animals, high in the cleft of a tree, in the midst of a residential yard in south Austin, Texas. The hole, which opens to the sky, is invisible from the ground, had gone undetected for years while it served as home for multiple generations of screech owls. Three chicks are visible in the photo; the fourth had fallen out to the ground, but was rescued by the author and — after consulting with wildlife biologists familiar with this species — returned to the nest later. Note the chicks’ gray coloration. Eastern Screech Owls are found in gray and red color phases, sometimes in the same brood. The chick’s birth color is retained into adulthood and throughout the owl’s life. Most gray phase specimens are found in the northern portions of this owl’s native range, while the reddish phase is more common in the southern U.S. For some reason, however, the gray phase is also common in southern Texas.

The world’s magnificent Raptors, or birds of prey, symbolize traits that most humans venerate: freedom, wisdom, strength, and courage… Mankind’s cultures have tended to revere them as special animals with extraordinary powers that extend way beyond our puny capabilities. Who doesn’t thrill at the sight of eagles, hawks, ospreys, kites, kestrels and harriers in flight? We marvel at the uncanny precision of our hawks, falcons and eagles when, while plying the skies with watchful eyes, they spy minuscule prey from afar, then swoop down at lightning speed to snatch their quarry from riverbanks, meadows, tree limbs, and waterways… all in the wink of an eye.

At night, in the moonless dark of a forest glen, we watch with bated breath as a huge, ghostly owl, all but invisible in the blackness, paces its domain aloft on silent wings. It dodges trees, rocks, and hillocks we scarcely see, then suddenly descends into the brush. We discern a muffled “squeak” before the owl launches skyward, its talons clutched about a now-silent form whose protests are forever quenched.

Traveling down our highways, we chance upon the recumbent corpse of an animal that had taken up combat with a motorized vehicle and lost. Holding court about its sad remains, a company of vultures gathers, each waiting a turn to rip putrefying flesh from the vanquished animal’s bones. Nearby, still others bear silent — though impatient — witness, their common, ministerial garb proclaiming them all the undertakers of the animal kingdom. As with the hawks and eagles, we recognize the stark majesty they illustrate so well.

What would life be like without these dark-robed creatures presiding over death? What if they had not the gift of flight, nor eyes that spy their pungent quarry miles in the distance, or were absent the keen olfactory organs that guide them to ferret out prizes the eye cannot yet see? What if it took twice or three times longer to purify the ground upon which the objects of their gustatory affections lie? We suspect we know the answers… Those answers give us pause, and make us thankful…

Poets and scribes, in secular and sacred writings, have long extolled the raptor’s kingly style. In song, verse, and prose they inspire a deep and envious appreciation, one drawn from a well buried deep in mankind’s collective soul. Now our skies are filled with manmade contraptions that feebly imitate the still-mystic feats of our feathered friends, but which evoke no more than a fraction of the reverence attached to the originals they mimic. Surely the awe filling our bosoms with each raptor’s sighting will never wane, but will forever thrill each generation of humanity that marches into the future.

Professions of Love Contrasted with Brute Actions…

Ah… if only mankind’s actions, as a whole, mirrored our outward professions…

Despite our deeply-felt respect for these animals, we too often mistreat the raptors we claim to revere. Sometimes the insults are intentional, hurled by those who neither know nor care about the consequences. More often, though, the injustices are dispatched by perpetrators who are unaware of the cruelties their actions have wrought. After all, only rarely are they carried out with willful intent.

Still, history faithfully chronicles our misdeeds, whether intentional or not, and that record tells a chilling story. It shows how we nearly brought widespread extinction upon many raptor species with the worldwide use of DDT. By luck we came to our senses — in the early 1970’s — in the nick of time. But as Mark Twain is alleged to have said, history, even when it doesn’t repeat the past with precision, still rhymes. Today we risk visiting a similar fate on our raptors with the unbridled dispensing of powerful, bio-accumulative rodenticides.

Rats & Mice, the Other Side of the Raptor’s Story…

Where raptors abound, so do their prey. The latter consist, in the main, of mammals in the taxonomical order Rodentia, one of the most prolific orders of animals known. The nearly 2,000 species of rodents that are presently recognized worldwide comprise about 40% of all living mammals. 68 rodent species are known to be found in Texas, and 24 of these are found in the central portion of the state, all fully capable of invading yards, landscapes, and man-made structures.

Rodents are distinguished from other mammals by the kinds and arrangements of their teeth: all rodents have a single pair of upper, and a single pair of lower incisors that are separated, from several pairs of chewing teeth, by a large gap (diastema). The chewing teeth of typical mice consist only of molars, while squirrels and their allies, jumping mice, and cavylike rodents have both molars and premolars. Rodent incisors grow continuously from birth to death, and have chisel-like cutting edges.

Rodent Biology, with Particular Attention to Urban Environments…

Despite the fairly large number of rodent species found in Texas, only three of them are regularly found in urban settings. These are the brown rat (also known as the Norway rat, with the taxonomical name Rattus norvegicus), the black rat (also known as the roof rat, with the taxonomical name Rattus rattus), and the house mouse (Mus musculus).

None of these three species is native to North America. They apparently were introduced to this continent from Europe, arriving as escapees from the ships of European explorers, and as hitch-hikers in goods shipped via those ships. All three species are able to migrate over long distances in search of food and shelter. Each is also able survive in a wide variety of environments, eat just about anything that they find even remotely nourishing, and reproduce at almost mind-boggling rates. It is a testament to all of these attributes that, within one or two centuries after arriving here, at least two of these three species could be found practically everywhere, often in relatively large numbers.

One of these three, the black, or roof rat (Rattus rattus) is not quite as enamored with colder climates as the brown rat and the house mouse. Too, the black and the brown rats tend not to get along that well in contested territories, with the brown rat the larger, more aggressive, and more successful of the two. As a result, while the brown rat is distributed throughout North America, the black rat is only common in the southern states, in all those states on the Pacific coast, and in those on the Atlantic coast south of New Jersey. In Texas, the black rat is very common throughout South, East, and Central Texas, but is much less common in north Texas, the Trans-Pecos, and the Panhandle.

The reproductive rates of these rodents illustrate, perhaps better than anything else, how they were able to spread out, from where they were first introduced, to just about every corner of the North American continent. All three reproduce throughout the year, and although their lifespans, in the wild, tend to average less than twelve months for the two species of rats, or about two years for house mice, during those lifespans they can produce a bounty of offspring. Brown and black rat females typically produce 3-6 litters a year, are able to become impregnated again within hours after giving birth to a new litter, and thus are capable of producing as many as 12 litters annually under favorable conditions. House mouse females, by comparison, can produce 6-10 litters in a lifetime, spaced 30-50 days apart.

Gestation periods for black and brown rats range from 21-25 days, and their young become sexually mature within three months of birth. Both the brown and black rats have typical litter sizes of 6-12 young (sometimes as many as 22 have been recorded); house mouse litter sizes typically range from 5-6 (with up to 13 recorded).

The extraordinary survival rate of these three species of rodents is also tied to their tendency to associate with human congregations. For this reason they have long been described as “commensal” rodents. That word, commensal, is derived from the Medieval Latin term commensalis, meaning “to eat from the same table.” The expression “commensalism” was first applied in 1876 by the Belgian zoologist Pierre-Joseph van Beneden. He intended the term to apply to cases where one organism interacted with another such that the one gained a benefit without harming or otherwise affecting the other. However, in the case of these rodents and their interaction with humans, the term appears to be misapplied. While the rodents certainly benefit, their human hosts pay a huge price as a result.

Part of the price we pay for sharing “the same table” with these three species of rodents has to do with the amount of foodstuffs they both eat and contaminate. Studies published by the United Nations estimated that, in 1982 in the U.S. alone, urban rats caused an economic loss of $13 billion (Almeida, 2013), simply by contaminating the food we eat. Others (Kowitt, 2016) suggest that food-borne pathogens — many of which are linked to rodents — result, in the U.S. alone, in an economic loss of $55 billion annually. The costs, both economically and on the medical side of the issue, are enormous.

In recognition of these costs, vigorous efforts aimed at eliminating the threats these rodents pose have been as important a part of human history as our interactions with these rodents themselves. In conjunction with those efforts, however, have come another cost: that associated with the agents and methods we’ve used in our rodent control programs. Some of those costs affect humans directly. Others affect primarily the animals — such as raptors — that prey on rodents and become poisoned from rodenticides the rodents have consumed.

Certain rodenticides pose untoward risks of secondary poisoning to raptors, no matter how they are used. Others, if used in an undisciplined manner that allows rodent populations to spike on a regular basis, are no better. A few, used in conjunction with a carefully crafted, monitored, and science-based rodent control program, pose little or no risk at all. Some of these, in fact, can play a part in the nobler goal of protecting and helping raptors thrive within the ecosystems they serve.

Three Steps to Protect Raptors from Rodenticides…

We need to know which kinds of rodenticides to use, and how to use them. That knowledge is the first step toward protecting non-target animals.

The second step, which is just as important as the first, is to secure rodenticides in containers that are so tamper-resistant as to make them nearly impervious to pets and children. That’s not as easy as it appears. Despite claims by their manufacturers to the contrary, there are at present no off-the-shelf rodent bait stations that truly achieve that objective.

At EntomoBiotics Inc., for example, we modify the off-the-shelf rodent bait stations we use to make them more secure. Still, we remain unsatisfied because those modifications — though effective — add considerable labor and time to the servicing process. That dissatisfaction has led to the creation of new designs — presently undergoing extensive field testing — that meet our security objectives without increasing servicing costs.

The third step toward protecting non-target animals, including raptors, is to perform fully-disciplined rodent control processes. What was earlier referred to as undisciplined baiting procedures — by homeowners and pest management professionals alike — that allow rodent populations in a locale to see-saw back and forth, from few to many rats and mice in an unremitting cycle, characterizes the typical rodent control programs carried out today.

When rodent predators in a locale are regularly treated to a Smörgåsbord of poisoned rodents they, too, can become poisoned from the food they eat. Some of those poisons have lengthy half-lives, allowing them to accumulate in the predators’ bodies. Unless kept below certain thresholds, those accumulated poisons produce sickness, and may be fatal.

The 4th Dimension, Dosage Mangement, and Rodent Control…

Viewed in this light it becomes easier to understand how important the fourth dimension — time — figures in the scientific analysis of risk. That kind of analysis often comes to the fore in human medicine. With practically every life-saving medication, dose-related issues dictate how it must be metered in precise ways. Failing that, achieving the positive outcome that is sought, while avoiding potentially negative results, cannot be guaranteed.

Can we do that with rodenticides? That is, can we meter them precisely, the same way we meter medicines to humans? Absolutely. But to do that we have to approach this subject the same way we approach all science-based projects. For example, we should weigh all the rodenticides as they are being placed, then weigh the residue, later, when the stations they are placed in are serviced. When that is done with all the rodent stations within a locale, it becomes possible to ascertain the the maximum amount of a particular rodenticide that those stations have added to the environment over time.

Simultaneously, an assay should be made of the number and kind of rodent predators within that same locale. From those two bodies of fact it becomes possible to establish the risk, to each predator, that the potential consumption of every rodent poisoned by those rodenticides poses.

It is fortunate that, today, many people are awakening to the unintended collateral effects of over-the-top, modern-day do-it-yourself and professional pest control zealotry. Rational rodent control may not be as intuitive as some believe, but the more light that is shown on the subject the better we understand how to do it right, and how to avoid costly mistakes. Righting past wrongs, even on a small scale, has had an immediate, restorative effect. As a result, raptor populations everywhere are on the rebound, as pockets of enlightened folks contribute time, finances and intellect to become their protectors.

We can, and must, do more. Still, we cannot expect a greater fraction of our fellows to join our throng until they comprehend the beneficent gifts these awesome creatures bestow on all mankind. Only then will humanity as a whole be so moved as to insist on curbing every insult directed their way.

So, with that worthy goal as the foundational purpose of this paper, let us now dig deeper into the biology of our raptors…

The Raptors of Texas…

We confine our study here to the raptors of Texas, that is, to those raptors that are native to the state, or that spend some time here at some period during the year. The definition of “raptor” is often restricted to those birds of prey within the taxonomical family Accipitridae. In this paper, however — following the convention used by a number of avian biologists — we will refer to all birds of prey, including vultures that feed primarily on carrion, as raptors.

A few other birds, though not considered raptors by any stretch, have diets with such a high percentage of rodents as to suggest they should be discussed as well. It could be argued that even birds that are primarily terrestrial but that subsist mostly on insect, reptile, and rodent prey, should also be included. The Greater Road Runner (Geococcyx californianus) is one of those.

The common denominator distinguishing raptors from other birds is their predatory behavior, one that leads to the conspicuous consumption of omnivorous animals such as commensal rodents. The environmental toxins that bioaccumulate in these omnivores are passed on to their predators, magnifying the toxic bioaccumulation found in the prey. As a result, birds of prey are more likely — as a group — to be affected by such poisons than practically all other animals on earth.

All raptors are members of the taxonomical class Aves (from the Latin avis, meaning “a bird”), but are grouped under several avian families, as described in what follows below. A brief description of each raptor species is provided on this page. These are to be followed, when time permits, by separate pages on each species, replete with photography of the birds themselves, their nests, and other pertinent features related to them.

Three Important Notes on Perspective…

— First: The Details of Raptor Violence and Raptor-on-Raptor Predation are Ghastly…

As you read through the accounts that follow, try not to be shocked by some of the native predatory habits of these birds. Each is a dedicated carnivore. As such, they all go about their daily lives killing and eating other animals. Some — such as the Osprey — restrict their selection of prey to fish. Most, however, are not that picky.

Many raptors include other birds in their diet. In general songbirds are high on their list of preferred avian prey, even if they are just as fond of rodents. Some, notably the falcons, mercifully kill their prey with lightning speed, using a notched ridge on their upper beak known as the tomial tooth to snap their spines, rendering them lifeless the instant they are caught. Others, particularly owls, large hawks and eagles, take their prey alive, then dismember and consume them, often while they are still conscious (Fowler et al., 2009).

This unmerciful behavior is not surprising to those who study bird evolution. Modern animals typically reflect in their behavior the genetic roots of the past. Raptors are no different, and the same is true for practically all birds, including those that we think of as vegetarians. Many bird enthusiasts are shocked to find that only the geese subsist mainly on a vegetable diet, and that even they will eat insects when the opportunity arises. All other birds are at least rapt insectivores that show no more mercy to their insect prey than raptors show to their bird and rodent prey. Many, like the raptors, are strict carnivores. As one would expect, their ancestry tells the tale.

The raptors, along with all other birds, are believed by most paleontologists to be the last remaining remnants of the carnivorous therapod dinosaurs. Though the exact lineage is not yet fully understood, as more fossil evidence is unearthed the linkage between theropods and modern birds only strengthens. Modern raptors, like their ancient, now-extinct ancestors, have to employ a vicious, no-holds-barred modus operandi to survive. Nobody would expect a meat-eating dinosaur to treat its quarry with mercy. Seen in that light, the violent, dispassionate behavior of modern raptors is, perhaps, somewhat easier to comprehend.

In an ironic twist of fate, it happens that many raptors readily kill and consume other rodent-predator raptors. Prey in any form is still prey, and they show no more mercy toward their own kind than to the rodents that both of them prey upon. For example, the Great Horned Owl, which is one of the more prolific rodent predators, preys on Screech Owls (which also prey on rodents). Incidentally, this trait is not employed as an afterthought. The Great Horned Owl is considered the Screech Owl’s most dangerous and persistent enemy.

— Second: The Need for Vigorous Rodent Control Justifies Overlooking Our Raptors’ Less Admirable Traits…

We celebrate raptors because serious rodent control is not an option. It is a non-negotiable imperative to which anyone who has knowingly fallen victim to a rodent-borne disease will attest. It is a historical fact that many of the most destructive plagues and epidemics affecting mankind are known to have been linked to rodents and their parasites. The bubonic plague, known as the Black Death because of the appearance of its victims’ cadavers, was caused by a strain of the bacterium Yersinius pestis carried by infected rats brought to Constantinople on granary ships from Egypt. It killed from 25-50 million Europeans from 542-750 c.e. At its peak during this period the death toll was so great that ordinary life, including the harvesting of crops in the fields, came to a stop for a lack of healthy human workers.

Since that first plague several pandemics followed, killing millions more. The interesting thing about those later pandemics is that the strain of Yersinius pestus associated with them was not a derivation of that causing the first plague, but was from a strain that originated in the dry plains of Central Asia. The common denominator in both was the rodent carrier of the bacterium.

Today, we know that rodents continue to carry a long list of infectious agents capable of sickening and killing humans, our livestock, and our companion pets. Still, we typically underestimate how important rodent control is to maintaining human health. There are several explanations for this, but one in particular stands out: Much of the time our rodent-associated maladies are not recognized as such. Thus we can’t place the blame where it belongs.

Whether we understand it or not, though, rats and mice pose serious epidemiological risks to humans and our companion pets. They and the ticks, fleas, mites, and lice with which their exterior bodies are infested are all efficient carriers of serious, non-trivial human diseases. Inside their bodies, and by extension their urine and fecal pellets, lurk another long list of microorganisms and helminth parasites (worms) capable of causing morbid, even mortal, diseases.

Wild Rats and Mice present a Genuine, Existential Threat to Humans, our Livestock, and our Companion Pets…

The lesson is obvious to those who have studied the subject carefully. Allowing rats and mice to nest, feed, defecate, and urinate in our homes and yards exposes us to a wide range of maladies. Children, elderly, the infirm, and pets are most at risk to the ravages of these diseases, but the risks to healthy adults follow close behind.

The linkage to our pets is a particularly insidious one… Dogs and cats sniff out rodent latrines, often licking up their urine stains and masticating and swallowing their pellets. In the process the pathogens carried by rodents are efficiently transferred to the pets we love so much.

Contaminated and/or infected pets are capable of transferring those pathogens to every member of the household. What the dog or cat gets into eventually gets around to the rest of the family. When the family pet wants to lick, rub, or cuddle, it cannot be denied. The joy that comes from intimate acts of bonding with our pet is one of life’s greatest pleasures. Making sure that we do all we can to keep our pets free of rodent pathogens is a crucial work we should — but often do not — take very seriously.

While some rodent borne diseases are life threatening, many just make us miserable. Some of those miseries are short-lived, but a host of others lead to long-term quality of life issues. Their origins are not obvious, though, and that makes it difficult for us to point fingers at the rodents that brought them to us in the first place. I mention that because, when we are unaware of where our miseries originate, we cannot connect the dots. That makes it much too easy to overlook the importance of avoiding exposure to wild rodent activity.

Chances are, if we really knew about all the negative health effects of living with wild rats and mice nearby, we would be shocked into taking action. Do you sometimes wonder how some of your irritating maladies arrived at your figurative doorstep? Often, more than likely, they arrived at your literal doorstep, and local wild mice and rats worked the deliverance. Yet — because rats and mice are nocturnal and are usually not seen even when they are present in large numbers — we rarely make the logical connection.

Making the Dot-to-Dot Connections…

What should we do about that? Surely it is wisdom to make the dot-to-dot connections and, in recognition of what those interrelationships tell us, to do all that is reasonable to mitigate such exposures. Keeping rats and mice away is the best possible way to do that, without question.

So, here’s the big question: how should we keep rats and mice away? Well, for one thing, Mother Nature provides a very obvious way, one embodied in the raptors that eat rats and mice “for a living.” That singular trait makes them heroes despite their long rap sheet of less admirable habits, such as killing and eating at least as many songbirds as rodents, and regularly making lunch of other raptors as well. We honor our raptor heroes by protecting them from harm, in every way possible.

Earth Island Institute‘s (EAI) educational project known as Raptors Are The Solution, or RATS, teaches about birds of prey and the dangers posed to them by rodenticides. EAI is so invested in that concern that one of the most passionate objectives of the RATS project is to eliminate rodenticides from use everywhere, worldwide.

It is easy to understand and empathize with that passion. Some rodenticides are unnecessarily toxic. All rodenticides presently on the market can be, and often are, misused in ways that pose hazards to non-target animals including raptors and even humans. Most rodent bait stations are too easy to unlock, are easily broken into with their locks intact, and can be shaken and manipulated in a way that dislodges and spills out their bait contents without unlocking them.

For all those reasons we must stamp out careless, undisciplined, and irresponsible rodenticide use where we live, work, and play. Responsible rodenticide use must employ rodent bait stations that are next to impossible to be unlocked by children or broken into by dogs, and whose contents cannot be shaken out with their locks intact.

All those measures are within our reach, yet the RATS project proposes to eliminate rodenticides altogether. On the surface, that approach, for the naive who have not drilled deeply into the subject, seems very straightforward and logical. No more rodenticides means fewer raptor poisonings, which means more raptors, which means fewer rats and mice. Makes sense, right? Maybe, but — then again — maybe not.

Rodenticides are not very much different from many of the medicines used today to cure humans and animals of serious maladies. In fact, the active ingredients in many of our modern rodenticides are also used in human medicines, despite the fact that, when misused, they can lead to human disease and death (Eason, 2018).

Dosages matter. When dosage restrictions are ignored for most of today’s celebrated medications, the results can be devastating. Yet, properly dosed and administered, those same medications improve health and save lives. In the case of rodenticide use, the saving of lives takes place indirectly, by eliminating the vectors that spread disease, but the end result is just as real and just as pertinent. Imagine what would happen, today, if modern medicine was forced to cease using all medications that are toxic if improperly dosed or administered…

— Third: Raptors, Alone, Cannot Keep Urban Rodents Under Control…

There is no question that raptors have a legitimate role in rodent control. As you read through the accounts that follow, below, that fact will become abundantly clear. What may not be as clear is that, while raptors are part of the solution, they are not THE solution. Even those associated with the RATS project acknowledge this. On the RATS website that very point is made, though with descriptors that can be misleading. Raptors, the website asserts, though still “the” solution, are not “the entire” solution, so other measures must also be taken to help them out.

To further that end, the RATS website posts a list of six explicit steps that homeowners and renters should follow to discourage rats from taking up residence near their homes. So, does this mean that if you eliminate rodenticides, and follow those six steps, your rodent problems are over? That’s the implication, but — unfortunately — it is wrong.

Let’s assume you, your neighbors, even your whole community outlawed local uses of rodenticides and followed the six steps posted on the RATS website religiously. The extra raptors in your skies, the ones now added because irresponsibly dispensed rodenticides no longer put a portion of them in early graves, would be able to keep rats and mice out of your yard and home, right?

Many wish that were so, but it isn’t. Rats and mice reproduce too fast in urban environments for any solely-natural control method to keep up. In fact, they also reproduce too fast in suburban and wilderness areas for raptors to keep up, too. I’m often called to farms and ranches throughout Texas to help farmers and ranchers deal with rodent infestations that erupted “out of nowhere.” While there I often am treated to regular sightings of healthy, well-fed hawks, eagles, harriers, kites, and other raptors. These birds of prey had clearly been taking advantage of the rodent bounty there, without making an appreciable dent in the population of rats and mice.

That’s good news for raptors, by the way. It would not be good for them if they were so good at their trade that they could greedily wipe out most of the rodents they rely on for food. Rodents constitute the main food supply for most of our raptors; if they were capable of decimating that food source, they’d be in serious trouble.

Where rodent populations are high raptors thrive and stick around. Where rats and mice are in short supply, raptors suffer until they relocate to places where rodent prey is more plentiful. That natural dynamic was aptly illustrated during the 7-year drought that — in the early years of the new millennium — devastated all of Texas and our neighboring states. During that time mice and rats were in short supply in our meadows, forests, and wilderness areas. As expected, the raptors, snakes, raccoons, skunks, and opossums, all of which depend to some extent on a regular diet of rats and mice to stay alive, were just as scarce.

Yet, in our urban environments, commensal rats and mice thrived despite the drought. There, the chance introduction of just a couple of wild rodents — even in the midst of a devastating drought — can and often does, almost overnight, lead to a huge population of rodents in our yards and homes. With that population explosion comes, inexorably, all the epidemiological risks we discussed earlier. That’s not acceptable, no matter how you look at it, but — and this is the crux of the matter — raptors alone can never keep that from happening.

So, What is THE Solution?

So, if raptors are a serious part of the solution, but in all honesty cannot be considered THE solution to the problem of rats and mice, what is? Unfortunately, much as we may wish it wasn’t so, the only consistent, lasting control method known to man is the use of rodenticides.

The right rodenticide, placed in a secured, tamper-resistant container that cannot be accessed by children or pets, provides one of the most humane methods known to man for exterminating rodents. They are much more humane than snap-traps, for example, because more than 25% of the time the rodent that triggers a snap-trap is not killed outright; often only a limb or part of the rodent’s head is caught in the trap, and the hapless, conscious, and hurting rodent suffers for hours or days before death finally comes.

Electrocution traps, a relatively recent innovation, may be as humane as rodenticides (the jury is still out on that), but they have to be serviced immediately after the rodent is electrocuted, and with that service comes the need to come into close contact with a rodent carcass and the ectoparasites that have escaped its body.

Most electrocution traps loudly boast that they make it possible for the user to “Never touch a dead rat again!” That may be true, but rodent ectoparasites are still able to leave the electrocuted rodent and attack anyone who comes near afterward. If the servicing individual does not properly treat the electrocution device and surrounding area with sterilants and vermicides, the risk of contamination can be severe.

Further, and perhaps most important, electrocution traps cannot be used outside. They come into play only after rodents have breached a home or a business. Waiting until that happens invites all the epidemiological risks that come with rodent infestations in spades. So, though electrocution traps do have a place in rodent control, the drawbacks associated with their use narrow those places significantly…

Finally, lest we forget, it would be hard to imagine anything less humane than the experience of being dismembered alive by a raptor.

… The Solution, Used Judiciously…

It must be repeated that rodenticides should be used judiciously, scientifically, carefully. and safely. They must not pose a risk to raptors and it is, indeed, possible to design and implement a methodology that protects raptors from harm. Further, it cannot be overemphasized that — like raptors — rodenticides are still not THE solution, but only part of it, so their use must be augmented with a list of well-defined habitat modifications (a list much longer than the one posted on the RATS website) that convert landscapes, yards, homes and businesses from rodent havens to places that do not attract or nurture them.

Of course, doing all that is not easy. In fact, the challenges to doing the job right, identifying obstacles in the way, and recognizing the risks involved, are as daunting as any of the challenges faced by the pest management industry today. Yet, with the proper motivation and dedication, all those challenges can be met, the risks can be mitigated, and the obstacles can be overcome. Achieving all those objectives is, in fact, what the EntomoBiotics Inc. Enhanced Ecosystem Monitoring, Management & Control (E2M2C™) program seeks to accomplish…

A Quick Note on Taxonomical Terms used in the Following

With many taxonomical names, a suggested pronunciation is provided. There is a good reason for this: If you can pronounce these sometimes-quite-long words, they actually come alive; if you cannot even imagine how to pronounce them, they acquire a poisonous kind of mystery that stunts learning by making them appear out of the intellectual reach of the reader. Don’t let that happen. Try to speak these words as you read along, and in the process of doing so, own them for yourself. If you fear you might “murder” the word, put such thoughts away. Taxonomy is a written, not a spoken, science. The pronunciation of a particular taxon is almost never sacrosanct. There is no really wrong, or truly right way to say these words. Within reason, anyone can pronounce a given taxonomical name any way one wishes, though a few loose rules have been adopted over time. The author does not pretend to have a lock on all those rules, but believes it is more important to help the reader feel as comfortable with the taxonomical terms presented than to fret about any mistakes he might make in the process…

Hawks and Eagles are members of the taxonomical family Accipitridae (pronounced ack-sih-PITT-trih-dee, from the Latin word accipiter, pron. ack-SIH-pih-tur, meaning “a hawk”); within this family are found the ospreys, eagles, kites, harriers, long-tailed hawks (accipiters), and broad-tailed hawks (Buteos, members of the genus Buteo, a Latin term, pron. BYEW-tee-oh, meaning “a buzzard,” which is the word used in Europe for these hawks, and does not refer to vultures, as has long been erroneously applied to the latter in the New World.)

The total number of birds of prey in the family Accipitridae known to be found in Texas varies according to the authority consulted. In John L. Tveten’s “The Birds of Texas” (Tveten, 1993) the number is 15, while in John H. Rappole & Gene W. Blacklock’s “Birds of Texas: A Field Guide,” (Rappole et al. 1994) the number is 26.

  1. Osprey (Pandion haliaetus): Though somewhat sexually dimorphic (the female is slightly larger), both sexes of this species are about the same size. Adult size (head to tail) ranges from 20-25 inches/51-64cm; wingspan ranges from 59-67 inches/150-150cm (Wheeler, 2018). This is a large, diurnal (day-active), piscivorous (fish-eating) bird, the osprey is found on all continents except Antarctica. Though most often found along coastal shorelines, this bird travels extensively throughout its range, fishing rivers, creeks, lakes, and streams. During the winter months it can be found along the Gulf coast and the Rio Grande Valley. It does not prey on mammals, and thus is not at risk from terrestrial placements of rodenticides. However, mercury residues in ospreys tested in Charlotte, NC, recently showed high levels (15.09mg/kg, 15 times the health threshold of 1mg/kg of body weight) for three specimens of this species, undoubtably due to high mercury levels in the fish they’d preyed upon. The same study also found mercury levels above the health threshold in a red-shouldered hawk and an eastern screech owl.
  2. Hook-billed Kite (Chondrohierax uncinatus): This species is omitted by Tveten because it rarely intrudes into the south Texas counties of Hidalgo and Starr from its native range of north Mexico to southern South America. According to the Audobon Society, it was first seen in Texas in 1964, and has been seen in south Texas with regularity, usually in pairs or in family groups, since 1975. It feeds primarily on tree snails, supplemented with frogs, salamanders, and insects. “Tree snail” is a label applied to tropical air-breathing terrestrial snails with shells that live exclusively in trees. Most tree snails subsist exclusively on the fungal growths infecting tree trunks and limbs.
  3. American Swallow-tailed Kite (Elanoides forficatus): Size, head to tail, 20-25 inches/51-64 cm; wingspan 57-54 inches/119-137cm (Wheeler, 2018). This is an aerial hunter that feeds on flying insects, arboreal frogs, lizards, reptiles, and nestling birds (Wheeler, 2018). Though a rare transient along the Texas Gulf coast two decades ago, the previous population decline appears to have stabilized, and now may be on the increase. This raptor appears to be primarily insectivorous, feeding mostly on flying insects such as dragonflies and cicadas. It will also snatch snakes, nestling birds and eggs from the treetops it skims over. In its wintering grounds of South America, it is often observed eating fruit.
  4. Black-winged Kite (Elanus caeruleus): Also known as the Black-shouldered Kite, but because that name causes confusion with an Australian kite with the same common name, the Black-winged version is now preferred (adding to this confusion, however, is the use of this same common name for another unrelated species, Milvus migrans). It is a broad-ranging bird that ranges over much of the Americas, Africa, and Asia, and is considered one of the most common raptors within this range. It is a small, diurnally active bird of prey, with long wings, creamy white, gray, and black plumage, and forward-facing owl-like eyes with red irises. It flies slowly, much like a harrier, while foraging, but often hovers over meadows and grasslands, its wings only slightly moving, as kestrels are wont to do. Its prey includes grasshoppers, crickets, cicadas, lizards, rats, mice, birds, snakes and frogs; in Africa, studies have shown that 80% of this bird’s prey consists of rodents; a typical adult consumes at least 2 mice a day, which would represent 25% of its average 250g body weight. This author remembers one memorable sighting, fifteen or so years ago in Fort Worth, Texas, when a black-winged kite snatched a sparrow from a tree limb less than five feet away, then flew up into a nearby tree to dismember and consume its meal.
  5. White-Tailed Kite (Elanus leucurus): Though somewhat sexually dimorphic (the female is slightly larger), both sexes are about the same size. Size (head to tail) 14-16 inches/36-41cm; wingspan 37-40 inches/94-102cm (Wheeler, 2018). According to one authority (Wheeler, 2018) this raptor is fairly to locally common in Texas, with a permanent range that includes the Gulf Coast, portions of the Rio Grande Valley, and small pockets along major rivers and lakes.
  6. Snail Kite (Rostrhamus sociabilis): subsists almost exclusively on aquatic apple snails. Accidental intruder into south Texas, and rarely observed.
  7. Mississippi Kite (Ictinia mississippiensis): Though somewhat sexually dimorphic, inasmuch as the female tends to be slightly larger, both sexes are about the same size. Size, head to tail, 12-15 inches/30-38 cm; wingspan 29-33 inches/74-84cm (Wheeler, 2018). This gregarious raptor roosts, feeds, and migrates in flocks, and often nests communally. It is an aerial hunter, subsisting mostly on flying insects, tree-inhabiting amphibians, lizards, and nestling birds; it rarely captures terrestrial rodents. It is an uncommon summer resident in most of the panhandle, central, and east Texas including the Gulf Coast outside of its core breeding areas, but is a locally common summer resident in some portions of Texas; in west Texas, and inland to the Rio Grande valley; in the Trans-Pecos it is rarely sighted.
  8. Bald Eagle (Haliaeetus leucocephalus, from the Greek roots ἅλς, hals = “sea”; αἰετός, ai-EE-tos = “eagle”, λευκός, loo-KOS = “white”, κεφαλή, keff-HALL-ee = “head”): Females are larger; adults of both sexes range in length, head to tail, 27-37 inches/69-94cm. The Bald Eagle was approved by th U.S. Congress as our national emblem on 20 June 1782, edging out the Golden Eagle based on two considerations. First, the Golden Eagle, which is found throughout the Northern Hemisphere, had already been honored as the national emblem of a number of other nations. Today, following a trend that continues unabated, the Golden Eagle remains the most common national symbol worldwide, including the nations of Scotland, Afghanistan, Egypt, Germany, Spain and Mexico (the eagle honored by Austria and several other nations is the Black Eagle). Second, and perhaps more germane, the Bald Eagle is only found in the New World, and here its range is confined to the Northern Hemisphere, where it can be found throughout the continental U.S., southern Alaska, most of Canada and Greenland. Further, it is considered by many avian biologists as the largest of the true raptors found in North America, being on average 455 grams heavier than the Golden Eagle, though the latter on average has a wing span some 3 cm greater than that of the Bald Eagle. Arguments against its selection as the U.S. national emblem included the assumption that rather being primarily a hunter — as is the Golden Eagle — the Bald Eagle is thought by some to be primarily a scavenger. That assertion, and other similar negative claims regarding the Bald Eagle’s behavior, are much in dispute, but once led to a regular slaughter of this bird by hunters who believed they were performing a public service by taking out as many Bald Eagles as they could. That practice was brought to a halt, but not before Bald Eagle populations had been decimated throughout the U.S. It is fortunate that their populations have rebounded once they were accorded protection from wanton destruction. Though listed as Endangered on March 11, 1967, this raptor was down-listed to Threatened some 28 years later, on July 12, 1995, and delisted entirely 12 years afterward, on 8 August 2007. Today the Bald Eagle is recognized as a skilled aerial and perch hunter that feeds mainly on live prey during the nesting season, but often scavenges in other seasons; fish is its main prey, but waterfowl, jackrabbits, and large rodents such as prairie dogs are also taken in areas away from water. In Texas, Bald Eagles — which are monogamous and mate for life — nest from October to July; their large nests, which females construct with help from their mates, is made of large sticks covered with Spanish moss, and is re-used year after year with regular amendments of added materials. They can be found in isolated pockets year-round throughout the northern half of the Texas panhandle, and in central, north, and east Texas, with breeding populations concentrated in southeast Texas along the Gulf Coast, and non-breeding and wintering populations concentrated in the Panhandle, and in Central and East Texas.
  9. Northern Harrier (Circus cyaneus): Sexually dimorphic, with the size of the male, head to tail, 16-18 inches/41-46cm, and a wingspan of 38-43 inches/97-109cm; the size of the female, head to tail, is 18-20 inches/46-51 cm, and a wingspan of 43-48 inches/109-122cm (Wheeler, 2018). Also known as the Marsh Hawk, this is an aerial hunter that preys on rodents, hares, rabbits, small to mid-size birds and large ducks; it sometimes consumes amphibians, reptiles, and large insects; it readily consumes carrion in the wintertime (Wheeler, 2018). This is a common winter resident throughout Texas, arriving in September and remaining through March. It forages in a distinctive way, flying low over meadows and open areas, mostly gliding but flapping its wings from time to time, then hovering with flapping wings when spying prey.
  10. Sharp-shinned Hawk (Accipiter striatus): Sexually dimorphic and distinguishable in the field with practice, with the size of the adult male, head to tail, 9-11 inches/23-28cm, and a wingspan of 20-22 inches/51-56cm; the size of the female, head to tail, is 11-13 inches/28-33 cm, and a wingspan of 23-26 inches/58-66cm (Wheeler, 2018). This is an aerial and perch hunter of songbirds (Wheeler, 2018). It is a common winter resident throughout Texas.
  11. Cooper’s Hawk (Accipiter cooperii): Sexually dimorphic, and separable in the field, with the size of the adult male, head to tail, 14-16 inches/36-41cm, and a wingspan of 28-30 inches/71-76cm; the size of the adult female, head to tail, is 16-19 inches/41-48cm, and a wingspan of 31-34 inches/79-86cm (Wheeler, 2018). This is an aerial and perch hunter of songbirds and small upland game birds, rodents, and lizards (Wheeler, 2018). Like the Sharp-shinned Hawk, this is common winter resident throughout Texas except for the panhandle, where it is scarce; it is a permanent resident of the inland regions of north, east and south Texas.
  12. Northern Goshawk (Accipiter gentilis): Sexually dimorphic, sexes not easily distinguished in the field, with the size of the adult male, head to tail, 18-20 inches/46-51cm, and a wingspan of ?? inches/??cm; the size of the female, head to tail, is 21-24 inches/53-61 cm, and a wingspan of ?? inches/??cm (Wheeler, 2018).This is an aerial and perch hunter of Snowshoe Hare, Ruffled Grouse, squirrels, large passerines and woodpeckers, and waterfowl (Wheeler, 2018). It is a winter resident of the Trans-Pecos and western panhandle of Texas.
  13. Crane Hawk (Geranospiza caerlenscens):
  14. Common Black-Hawk (Buteogallus anthracinus): This is a perch hunter of fish, amphibians, reptiles, small mammals, birds, and large insects (Wheeler, 2018). It is an infrequent summer resident of small pockets scattered throughout the state.
  15. Harris’ Hawk (Parabuteo unicinctus): This is a perch hunter that takes prey as large as jackrabbits but mainly eats rabbits, quail, songbirds, and lizards (Wheeler, 2018). It is a permanent resident of the Texas Hill Country, northeastern Trans-Pecos, central and south Texas.
  16. Gray hawk (Buteo nitidus): This is a perch hunter that feeds primarily on lizards but also eats small birds, rodents, and large insects (Wheeler, 2018). It is very common in north Mexico, and is a permanent resident of small pockets along the Rio Grande Valley of Texas.
  17. Roadside Hawk (Buteo magnirostris):
  18. Red-shouldered Hawk (Buteo lineatus): Size of the adult male and female, head to tail, is 15-19 inches/38-48cm, with a wingspan of 37-42 inches/94-107cm; females are larger than males (Wheeler, 2018). This is mainly a perch hunter that eats small mammals, amphibians, reptiles, invertebrates, small birds, fish, insects, and carrion (Wheeler, 2018). The Eastern subspecies (Buteo lineatus lineatus) is a common winter resident of the eastern half of Texas, but is not a permanent resident anywhere within the state; the Southern subspecies (Buteo lineatus alleni) is a permanent resident of much of the eastern half of Texas, and a winter resident of central, east, and south Texas as well (Wheeler, 2018).
  19. Broad-winged Hawk (Buteo platypterus): Females are larger, with adults of both sexes having a head-to-tail length of 13-17 inches/33-43cm, and a wingspan of 32-36 inches/81-91cm. This is a perch hunter, perching on exposed and concealed objects, including utility poles and wires; it eats small amphibians, insects, reptiles, and rodents that it catches on the ground or on outer branches in direct flight, rarely by diving (Wheeler, 2018). It is a common summer resident of far east Texas, less frequently a summer resident of portions of central Texas.
  20. Short-tailed Hawk (Buteo brachyurus): This is strictly an aerial hunter of sparrow-to-Jay-sized birds, chipmunks, and lizards (Wheeler, 2018). It is an infrequent summer resident of small pockets of east, south, and west Texas.
  21. Swainson’s Hawk (Buteo swainsoni): Females average larger, with adults of both sexes having a head-to-tail length of 17-21 inches/43-53cm (Wheeler, 2018). This is a perch and aerial hunter of open-area small rodents and large insects such as grasshoppers, small birds, and reptiles (Wheeler, 2018). It is a common summer resident of the Texas panhandle and west, central, and south Texas.
  22. White-tailed Hawk (Geranoaetus albicaudatus): This is a perch and aerial hunter of amphibians, reptiles, small mammals, and terrestrial birds; it readily eats carrion (Wheeler, 2018). It is a permanent resident of the Gulf Coast of Texas, a winter resident of south Texas, and an infrequent summer resident of small areas throughout the state.
  23. Zone-tailed Hawk (Buteo albonotatus): This is a low-altitude aerial hunter of terrestrial lizards, small birds, and rodents (Wheeler, 2018). It is a summer resident of scattered pockets throughout the southern half of Texas, and a winter resident of scattered pockets within that range.
  24. Red-tailed Hawk (Buteo jamaicensis): Females average larger, and juveniles are longer than adults because of typically longer tails, with adults ranging from 17-22 inches/43-56cm, head to tail (Wheeler, 2018). This is a perch and aerial hunter of small to medium-sized amphibians, birds, mammals, and reptiles (Wheeler, 2018). The Eastern subspecies (Buteo Jamaicensis borealis) is a permanent resident of the Texas panhandle, north, central, and east Texas, and a winter resident of the southern half of Texas excluding the Trans-Pecos; Krider’s Red-tailed Hawk (B. j. kriderii) is a winter resident of central and east Texas; the Western Red-tailed Hawk (B. j. calurus) is a winter resident of all portions of Texas, and a permanent resident of some portions of the northwestern Trans-Pecos; Harlan’s Red-tailed Hawk (B. j. harlani) is a winter resident of central, north, and east Texas; Fuertes Red-tailed Hawk (B. j. fuertesi) is a permanent resident of southwestern Texas, and a winter resident of the southern tip of the state;
  25. Ferruginous Hawk (Buteo regalis): Females average larger, with adults of both sexes ranging in length, head tail, 20-26 inches/51-66cm. This is a perch and aerial hunter of ground squirrels, prairie dogs, rabbits, hares, terrestrial birds, insects, reptiles, and carrion (Wheeler, 2018). It is a common winter resident of the Texas panhandle, west, central, north, and south Texas.
  26. Rough-legged Hawk (Buteo lagopus): Females average larger, with adults of both sexes ranging in length, head to tail, 18-23 inches/46-58cm. This is an aerial and perch hunter of small rodents (Wheeler, 2018). It is a winter resident of the Texas panhandle, the Trans-Pecos, north and central Texas,
  27. Golden Eagle (Aquila chrysaetos): This is a perch and aerial hunter, with mated pairs hunting cooperatively; spring and summer prey includes mammals, from rabbits to small deer, large waterfowl, upland game birds and birds as large as the Great Blue Heron; fall and winter prey is primarily carrion (Wheeler, 2018). This is an uncommon winter resident of the Texas panhandle and west Texas, with some local permanent residents in those areas as well.

Caracaras and Falcons are members of the taxonomical order Falconiformes (fowl-kahn-uh-FOHR-mees), and the taxonomical family Falconidae (fowl-KAHN-uh-dee, from the Latin word Falco, meaning “a falcon”). A comparative genome analysis published in 2008 provided evidence that the caracaras and falcons are more closely related, genetically, to parrots and passerines than to other raptors. In 2011, an analysis of transposable element insertions shared between falcons, passerines and parrots but absent in the genomes of other birds, confirmed the genetic relationships evidenced in the earlier study. Worldwide the Falconidae family presently contains around 60 species of diurnal birds of prey, divided into two subfamilies. The subfamily Polyborinae (polly-BOHR-enn-ee) contains the caracaras and forest falcons, and the subfamily Falconinae, which contains the falcons and kestrels.

Texas has three (Tveten, 1993) or six (Rappole et al., 1994) birds of prey in this family.

  1. Crested Caracara (Polyborus plancus): This raptor subsists primarily on carrion, but will take small prey dislodged by fire or plowing as well (Wheeler, 2018). It is a permanent resident of south Texas, and in small pockets of central, north, and east Texas.
  2. American kestrel (Falco sparverius): This is a perch and aerial hunter of large insects, small rodents, songbirds, reptiles, and amphibians (Wheeler, 2018). It is a permanent resident of the Texas panhandle, north Texas, portions of central east Texas, and the Trans-Pecos, and a winter resident throughout the state.
  3. Gyrfalcon (Falco rusticolus): This is a perch and aerial hunter of birds up to the size of geese, and mammals to the size of hares (Wheeler, 2018). In Texas, it has only been sighted in the city of Lubbock.
  4. Merlin (Falco columbarius): This is an aerial hunter of small birds and large insects (Wheeler, 2018). The Taiga Merlin (Falco columbarius columbarius) is a winter resident of central, north, south, and east Texas; Richardson’s Merlin (F. c. richardsonii) is a winter resident of the Texas panhandle, north, central, west Texas, and the Trans-Pecos; the Black Merlin (F. c. suckleyi) is a rare winter resident of the Gulf Coast of Texas.
  5. Aplomado Falcon (Falco femoralis): This is a predator of birds ranging from sparrow to Mourning Dove in size, of large insects such as cicadas, and — especially along the Gulf coast — of crustaceans and amphibians (Wheeler, 2018). It is a permanent resident of the Gulf coast, and areas in the Trans-Pecos.
  6. Peregrine Falcon (Falco peregrinus): This is an aerial hunter of small songbirds, shorebirds, large ducks, and small mammals (Wheeler, 2018). In Texas, the Arctic Peregrine Falcon (Falco peregrinus tundrius) is a common winter resident of the Gulf Coast; and the Anatum Peregrine Falcon (F. p. anatum) and Eastern Peregrine Falcon (n.s.d.) are common winter residents of north, central, east, south Texas and the Trans-Pecos.
  7. Prairie Falcon (Falco mexicanus): This is a perch and aerial hunter that feeds mainly on passerines, small game birds, and mammals as large as rabbits during the non-breeding season; feeds readily on carrion. It is common winter resident of much of Texas, excluding the eastern half of the state; permanent residency occurs in pockets in the northern panhandle and the Trans-Pecos.

American or New World Vultures are members of the taxonomical family Cathartidae (kuh-THAR-tuh-dee, from the Greek word καθαρός, pron. KATH-uh-rohs, meaning to cleanse, purify). This family is confined to the Western Hemisphere, and contains seven species in seven genera, divided into two groups of five vultures and two condors. The condors are the largest flying land birds in this hemisphere; neither species is found in Texas.

Of the five species of vultures found in the Americas, two — the black vulture and the turkey vulture — are found in Texas.

  1. Black Vulture (Coragyps atratus): This species is not sexually dimorphic, so both sexes are about the same size. Size, head to tail, 23-28 inches/58-71cm; wingspan 53-63 inches/135-160cm (Wheeler, 2018). This vulture is aptly named, being clothed in black feathers, with — at all ages — a naked, black-skinned head and upper neck, white legs, and six white wingtip fingers visible in flight. Distinguished in flight habits from the Turkey Vulture in that it normally does not soar, but glides at low levels with its wings held flat, while alternately flapping its wings. It is common to the eastern half of Texas, less common in the western half.
  2. Turkey Vulture (Cathartes aura): Like the black vulture, this species is not sexually dimorphic, so both sexes are about the same size. Size, head to tail, 24-28 inches/61-71cm; wingspan 63-71 inches/160-180cm (Wheeler, 2018). This vulture is black, with — in the adult — a naked red-skinned head and upper neck (the head and neck in recently fledged and early stage juveniles range from a dark gray, to a dark reddish gray), and with pale, silvery feathers at its underwing wingtips. It is a common resident throughout Texas in the summertime, and a permanent resident of the eastern half of Texas year-round.

Owls are members of the taxonomical order Strigiformes. The order is divided into two families, the Strigidae (true or typical owls) and the Tytonidae (barn owls).

Barn Owls, members of the taxonomical family Tytonidae, is composed of 12 species. Only one of these is regularly found in North America:

  1. Common Barn Owl (Tyto alba): This tawny and gray owl, with large dark eyes, a white face with features reminiscent of a monkey, and long legs, is common to the eastern half of Texas, less common in the western half of the state.

True, or Typical Owls, members of the taxonomical family Strigidae (from the Latin word strix, meaning “screech owl”). This large family, which is represented on all continents except Antarctica, is subdivided into 25 genera embracing about 200 living species. They are nocturnally active, with large heads, shortened tails, and eyes surrounded by disc-shaped feather contours specially positioned to amplify and direct sounds to their ears. Feathers covering their bodies are soft, with downy bases, and those on the leading edge of each wing are serrated, all of which features work to facilitate silent flight. Their large eyes and quiet demeanor in the presence of humans convey a sense of contemplative wisdom, and give rise to the kindred notions that they can see well even under extremely dark conditions, but are visually impaired in the daytime; neither notion is correct, however.

Texas is home to either six (Tveten, 1993) or sixteen (Rappole et al., 1994) true or typical owl species:

  1. Flammulated Owl (Otus flammeolus): Found principally in the Trans-Pecos region of Texas, where it is a rare summer resident.
  2. Eastern Screech-Owl (Otus asio): Found principally in the eastern half of Texas, less often in western half of the state, rarely in the Texas panhandle. Distinguished from the Western Screech-Owl by having a pale-colored bill, while the Western Screech-Owl has a darker bill.
  3. Western Screech-Owl (Otus kennicottii): Found principally in the Trans-Pecos region of Texas.
  4. Great Horned Owl (Bubo virginianus): Found throughout Texas, where it is a permanent resident. See the author’s article on the humane exclusion of this species of owl from a commercial structure in Austin. Texas (2012).
  5. Snowy Owl (Nyctea sandica): This owl is primarily found in the northern polar regions of the Old and New World, and is but a casual winter visitor to Texas, arriving in north and central areas of the state in December, but departing by early March.
  6. Northern Pygmy Owl (Glaucidium gnoma): A casual transient in the Guadalupe Mountains National Park, Culberson County, Texas, where it resides from April to May in the springtime, and August to September in the fall.
  7. Ferruginous Pygmy Owl (Glaucidium brasilianum): This small, long-tailed owl is a rare permanent resident in the Lower Rio Grande Valley of Texas.
  8. Elf Owl (Micrathene whitneyi): This small, short-tailed owl is an uncommon summer visitor to the Big Bend region of the Trans-Pecos, rarely sighted in the Lower Rio Grande Valley.
  9. Burrowing Owl (Athene cunicularia): This is a long-legged, terrestrial owl that is often associated with prairie dog towns. It is a common summer resident of the western half of Texas, less commonly found in the eastern half of the state.
  10. Mottled Owl (Ciccaba virgata): This is rarely found in south Texas, specifically in Hidalgo County, where it is considered an accidental visitor.
  11. Spotted Owl (Strix occidentalis): This large, dark-eyed owl is a rare permanent resident of the mountains of the Trans-Pecos.
  12. Barred Owl (Strix varia): This large, dark-eyed owl is similar in appearance to the Spotted Owl; it is commonly found throughout the eastern half of Texas, and is a common permanent resident of portions of the Texas Gulf Coast, particularly in the vicinity of Sinton and Corpus Christi.
  13. Long-eared Owl (Asio otus): A medium-sized owl with yellow eyes and long ear tufts, similar in appearance to the Great Horned Owl. It is a rare winter resident in Texas, where sparse sightings have been made throughout the state, usually during the period from November to April.
  14. Short-eared Owl (Asio flammeus): A medium-sized owl with short ear tufts and yellow eyes. It is a crepuscular forager that paces low over open meadows and fields in much the same manner as the Northern Harrier (Circus hudsonius or Circus cyaneus hudsonius), or Marsh Hawk. It is an uncommon winter resident of the eastern third of Texas, sighted mostly from October through April.
  15. Northern Saw-whet Owl (Aegolius acadicus): This small, dark brown, white-spotted, yellow-eyed owl is a casual winter visitor to the northern half of Texas.

This paper is a work in progress. Please bear with us as it is fleshed out…

Taxonomy: The taxonomical hierarchy presented below is currently fleshed out to the owls in general, and thence to the Great Horned Owl. The remaining links are now in the process of being added. Note that taxonomical hierarchy is always in flux, though perhaps never in the past as it has become in the last few decades. Fleshing the presently-accepted hierarchy out below is an impossible task, because many of the clades that apply to this work are in dispute, not only in terms of acceptability but also with regard to their placement within the hierarchy. Rather than choose only those that are fully accepted by most taxonomists, the following includes many of those that are considered, by some, to be questionable.

Traditional taxonomy grouped the raptors into four families in a solitary order, Falconiformes. Many avian taxonomists felt, however, that this group was paraphyletic, a term derived from the two Ancient Greek words παρά (PAHR-ah) = “beside, near”, + φῦλον (FOO-lawn) = “genus, species”, which refers to the presence of two or more monophyletic subgroups (e.g., genera, species) that are not descendants of a unique common ancestor.

Evidence accumulated in the last three decades of the previous century indicated that the New World vultures, in the Cathartidae family, were less related to other raptors than to storks and herons in the Ciconiiformes family. Eventually that connection, too, was discredited, though without bolstering the relationship with the Falconiformes. Now most taxonomists group the New World vultures in their own order, Cathartiformes, which is not closely associated with raptors, storks, or herons, though — In 2007 — the American Ornithologists’ Union’s North American checklist returned the Cathartidae family to the lead position in Falconiformes, while noting that it is “probably misplaced” there.

A. The taxonomical hierarchy applicable to all birds:

  • Kingdom Animalia (ahn-uh-MAYHL-yuh) — first described in 1758 by the Swedish taxonomist Carolus Linnaeus (23 May 1707 – 10 January 1778), using the Latin word animal = “a living being,” from the Latin word anima = “vital breath”, to refer to multicellular, eukaryotic organisms whose body plans become fixed during development, some of which undergo additional processes of metamorphosis later in their lives; most of which are motile, and thus exhibit spontaneous and independent movements; and all of whom are heterotrophs that feed by ingesting other organisms or their products;
  • Phylum Chordata (kohr-DAY-tuh) — animals that have, at some point in their life cycle, a hollow dorsal nerve cord, pharyngeal slits, an endostyle, and a post-anal tail.
  • Clade Dinosauromorpha (dye-noh-sahr-oh-MOHR-fuh) is a clade of archosaurs that includes the clade Dinosauria (dinosaurs), and all animals more closely related to dinosaurs than to pterosaurs. Birds are the only surviving dinosauromorphs.
  • Clade Dinosauriformes (dye-noh-sahr-eh-FOHR-mees) — a clade of archosaurian reptiles, including dinosaurs and their most immediate relatives. Dinosauriformes have shortened forelimbs and a partially to fully perforated acetabulum, the hole in the hip socket traditionally used to define dinosaurs;
  • Clade Dracohors (DRAY-coh-horz) — a clade of dinosauriform archosaurs that includes dinosaurs and silesaurids. The oldest known dracohorsian, Asilisaurus, dates to approximately 245 million years ago, during the Anisian age of the middle Triassic period.
  • Clade Saurischia (saw-RISS-kee-əh), from the Greek σαῦρος (SAW-rohs) = ‘lizard’ + ἴσχιον (ISS-kee-ohn) = ‘hip joint’; one of the two basic divisions of dinosaurs, the other being Ornithischia. This term originally designated an order, but is now considered, by most paleontologists, as an unranked clade;
  • Subphylum Vertebrata (vurr-tuh-BRAY-tuh) — chordate animals with backbones and spinal columns;
  • Class Aves (AAH-vays) — Birds, i.e., vertebrate, endothermic (warm blooded), bipedal (two-legged), tetrapod (four-limbed), egg-laying animals covered with feathers and fitted with wings that usually confer the faculty of flight. With around 10,000 living species, they are the most speciose (rich in species) class of tetrapod vertebrates, regarded by paleontologists as the only clade of dinosaurs to have survived the Cretaceous–Paleogene extinction event that took place 65.5 Ma ago.
  • Clade Neoaves (NEE-oh-aah-vays) — a clade embracing almost 95% of all modern birds, excluding only the Paleognathae (ratites and their kin) and the Galloanserae (ducks, chickens and their kin). Diversification of the neoavian groups occurred after the Cretaceous–Paleogene extinction event. Resolution of their interrelationships is incomplete and controversial.
  • Subclass Neornithes — modern birds having feathers, a beak without teeth, that lay eggs with hardened shells, exhibit a high metabolic rate, have a four-chambered heart, and a strong but lightweight skeleton. The forelimbs of all modern birds are modified to function as wings and most are capable of aerial flight. The digestive and respiratory systems of all modern birds are specially adapted to the necessities of flight. Many birds, e.g. corvids and parrots, are highly intelligent animals capable of the manufacture and use of tools, as well as transmitting cultural knowledge from one generation to the next;

B. Orders applicable to Raptors:

  1. Accipitriformes (includes the eagles, Old World vultures, secretary-birds, hawks, harriers, etc) – 47–0 Mya, Late Eocene–Present;
  2. Falconiformes (includes the falcons and caracaras) – 50–0 Mya, Early Eocene–Present;
  3. Cathartiformes (includes the New World vultures) – 41–0 Mya, Middle Eocene–Present;
  4. Strigiformes (includes the barn owls and true owls) – 30–0 Mya, Early Oligocene–Present;
  • Order Strigiformes (Wagler, 1830) — Owls, most of whom are solitary and nocturnal, that typically hunt small mammals, insects, other birds, and fish; characterized by small beaks, wide faces, large binocular eyes; divided into two families: typical or true owls (Strigidae) and barn-owls (Tytonidae); the order was first described by the German ornithologist Johann Georg Wagler (1800-1832) in 1830 while he was director of the zoological museum at the University of Munich, a position he’d held since 1926; he worked extensively on avian collections from Brazil, and died in 1832 from an accidental but self-inflicted gunshot wound while in the field collecting specimens; apparently Wagler crafted the order’s name using the same Greek word, for screech owl, στριξ (pron. “strix” or “strige”) that Vigors had applied to the family name of the true owls five years previously;
  • Family Strigidae (Vigors, 1825) — typical (true) owls, presently represented by 25 genera and 189 species; these vary significantly in size, from the smallest Elf Owl, to the Eurasian Eagle-Owl, the latter being a hundred times larger; all typical owls share a similar body plan, with large heads, short tails, cryptic plumage and round facial discs surrounding the eyes; most are arboreal, though some burrow into the ground; all secure their food on the wing; their wings are large, broad, rounded and long; as with other birds of prey most exhibit reverse sexual dimorphism, wherein females are larger than males; the family name was first described in 1825 by the Irish zoologist/politician Nicholas Aylward Vigors (1785-1840), who merely applied the Greek word for screech owl, στριξ (pron. “strix” or “strige”); the name is today juxtaposed with the Tytonidae (crafted by the American ornithologist Robert Ridgeway in 1914 from the Greek τυτω “tyto”, meaning a night owl), the barn owls; Vigors co-founded the Zoological Socety of London in 1826, and later founded what eventually became the Royal Entomological Society of London in 1833.
  • Genus Bubo (Duméril, 1805)  Horned owls; classically this genus includes all the North and South American horned owls and Old World eagle-owls, but the number of species within the genus is in dispute; the generic name was first described in 1805 by the French physician, zoologist, and ornithologist André Marie Constant Duméril (1744-1860), applying the Latin name Bubo, which simply means “owl”;
  • Species Bubo virginianus (Gmelin, 1788) — the large Great Horned Owl or Tiger Owl native to and the most widely distributed true owl of the Americas; body length 18–27 inches (46–69 cm); wingspan 40–60.5 inches (101–153 cm); weight 0.72 to 2.55 kg (1.6 to 5.6 lb); adults exhibit large ear tufts, reddish, brown or gray faces with white throat patch; iris of eye is yellow; horns adorning head crown are tufts of feathers; underparts light in color with brown barring; upper parts of mottled brown; legs and feet entirely feathered to talons.


Questions? Comments? Corrections? Let us know your thoughts: email jerry.cates@entomobiotics.com.

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