Owls: A Guide to Every Species in the World

By Marianne Taylor

Discover the fascinating and mysterious world of owls with this stunning full-color, encyclopedic visual guide that explores all 225 known species, packed with maps, photographs, illustrations, informative scientific details, and a bonus 35½" x 12" accordion poster illustrated with the true-to-size wing span of the largest owl, overlayed with the wing span of the smallest owl and several owls in-between.

Humans have long been fascinated by owls. From prehistoric cave paintings to popular modern children’s stories, these magnificent predators have been seen as harbingers of good fortune and impending disaster, as icons of fear and wisdom, and as the powerful sidekicks of magic-makers, including the beloved Harry Potter. Scientists have faced tremendous challenges trying to document the lives of these solitary, nocturnal, and highly elusive creatures. New species are still being discovered, as are new insights into the habits of even the most familiar varieties.

Visually spectacular and authoritative, Owls includes full descriptions and maps of key viewing locations for all 225 owl species in the world, and is illustrated with drawings and stunning full-color images from some of the leading wildlife photographers from around the world which capture these birds’ breathtaking beauty and power. The book also features a special section on the art of hiding—a highly honed skill set of the owl.

Throughout, Marianne Taylor provides a wealth of detail on each type of bird’s hunting and breeding behavior, habitat, and conservation. Inside, are dozens of fun facts, such as:

• Only nineteen of the 225 known species of owls are found in North America;
• Owls can be found on all continents except Antarctica;
• Owls, like humans, have binocular vision;
• Owls cannot turn their eyes, but are able to rotate their heads up to 270 degrees;
• Owls are carnivorous and are known to eat rodents, small mammals, nocturnal insects, fish, and other birds.

Lavishly illustrated and educational, this breathtaking volume is essential for readers interested in natural science, devout birders, professional ornithologists, and all owl lovers.

• Language: English
• Publisher: Open Road Integrated Media
• Release date: Nov 22, 2016
• ISBN: 9780062413895

Marianne Taylor

Marianne Taylor is a writer and editor, with a lifelong interest in science and nature. After seven years working for book and magazine publishers, she took the leap into the freelance world, and has since written ten books on wildlife, science and general natural history. She is also an illustrator and keen photographer, and when not at her desk or out with her camera she enjoys running, practicing aikido, and helping out at the local cat rescue center.

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Introduction

Owls have long held a particular fascination for people. It’s hard to think of any living things that are as familiar and yet as mysterious. When we look into their forward-facing eyes we see, or think we see, intense and humanlike expressions—from profound thoughtfulness to comical astonishment. No wonder we see more representations of owls than any other birds in our day-to-day lives, as charming characters on-screen and in books, and as decorations for our houses and yards.

However, the way most owls live their lives means that it is a truly rare experience to encounter one in the wild. The archetypal owl is nocturnal, and an inhabitant of dense woodland, hidden in time and space. When it hunts, it flies on cushioned, soundless wings, giving nothing away, and bringing sudden, violent death to its oblivious prey. Its cryptic plumage renders it invisible by day, blending into its background of forest colors and patterns. Only its mournful, far-carrying calls in the dead of night reveal it is there at all.

Over the millennia, a rich fund of owl-related myth, legend, and lore has been passed down the generations. Rigorous scientific study of the birds has gained momentum in the last couple of decades, and in many cases the truth about owls and their lives has proved no less astonishing than the old stories. However, of the world’s 220 or so owl species, many are still virtually unknown and have only ever been glimpsed by a lucky handful of people, much less properly observed and studied. With the destruction of wild habitats proceeding at a frightening pace, learning about how these wonderful and irreplaceable birds live and what resources they need from their habitats is more important now than ever.

Owl evolution and taxonomy

Animal evolution can be pictured as a constantly growing, spreading tree. Taxonomy is our attempt to categorize different kinds of twigs and branches, and put names to them all.

Evolution

All birds evolved from a lineage of dinosaurs known as theropods, of which the most familiar example is the fearsome Tyrannosaurus rex. Theropods were bipedal dinosaurs, most of them much smaller than the mighty T. rex, and it is now believed that most, if not all, had at least some feathers on their bodies. The earliest feathers were probably small, soft, and simple, supplying a means for the animals to control their body temperature, with larger, color-bearing feathers coming later. Theropods evolved other birdlike traits, including internal air sacs connected to the lungs and to air spaces in the bones and the habit of building nests and incubating their eggs. The best known transitional fossil between theropod dinosaurs and modern birds, the magpie-size Archaeopteryx, shows well-feathered wings that would have permitted flight, and an arrangement of body feathers similar to that of modern birds. It also resembled modern birds in its skull structure, its large brain, and its inner ear anatomy. However, it retained a number of dinosaur features, including a bony tail, a flat instead of keel-shape breast bone, teeth, and claws on its forelimbs.

Archaeopteryx lived about 150 million years ago. Over the next 50–100 million years, some theropod descendants lost their teeth and bony tails, and as their bodies grew lighter and their feathers stronger, they became more powerful fliers. Nearly all modern birds (including owls) belong to the most successful of these lineages, the Neoaves, which diversified greatly and made use of many habitats in many different ways. The fossil record indicates that Neoaves directly ancestral to owls were present on the Earth some 57 to 65 million years ago, making the group one of the oldest of all bird lineages.

A great diversity of fossil owls have been discovered and described, some of them assigned to families that are now extinct. Some of these prehistoric owls were different to modern owls—for example, the extinct family Sophiornithidae were ground birds that chased their prey on foot. Fossil owls belonging to the modern owl families Tytonidae and Strigidae date back at least 20 million years. Initially, Tytonidae was the larger and more diverse group, but Strigidae came to dominate in more recent times.

However, Tytonidae does include some extremely widespread species, so in terms of global coverage, the two families are close to equal. Together, the two owl families’ diversity and almost global distribution makes for a real evolutionary success story, every bit as impressive as that achieved by the 300 or so species of day-flying birds of prey.

This dinosaur fossil clearly shows full-length flight feathers, as well as reptile traits, such as teeth, claws on the forelimbs, and a bony tail.

Corbis/Xinhua/Xinhua Photo

Him or her?

There is usually little or no difference between males and females in terms of plumage. The most marked exception is the Snowy Owl, in which the female’s more heavily mottled plumage helps camouflage her on the nest, which may be in an exposed situation. Among diurnal species, such as the Burrowing Owl, males are often paler, because they spend more time outside the nest and become slightly bleached by the sun. As with the diurnal birds of prey, it is usual for female owls to be larger and heavier than males. This may be because the female’s greater strength is useful for defending the nest against predators and intruders. Meanwhile, the smaller and more agile male spends his time hunting and can keep up a constant supply of small prey for the chicks. Once the chicks are larger, better able to defend themselves, but also much hungrier, the female leaves them and joins the male as food provider.

The order Strigiformes

Owls form the taxonomic order Strigiformes and are not closely related to the other great orders of predatory birds, the Accipitriformes (hawks, eagles, kites, harriers, and buzzards) and the Falconiformes (caracaras and falcons). These are often collectively known as raptors or diurnal birds of prey to distinguish them from the owls. The closest relatives to the owls are probably the nightjars and their allies (order Caprimulgiformes), which share with the owls a nocturnal habit and well-camouflaged plumage but have different body shapes and more aerial habits. The order Strigiformes is subdivided into two families—Tytonidae (the barn owls and bay-owls) and Strigidae (all the rest).

The two owl families break down into a number of groups of closely related species (genera—singular genus), and with a little experience, it is usually easy to tell which genus a particular owl probably belongs to, because of a range of traits common to all the members of that genus. However, there are also a number of odd owls out that are the only members of their genus.

The male Snowy Owl has almost pure white plumage, so he is easily told apart from his dark-barred mate. Young owls are mottled for camouflage.

Shutterstock

Tytonidae

The owl family Tytonidae contains just two genera—Tyto (the barn owls) and Phodilus (the bay-owls). The barn owls are medium-size birds with long wings and legs, and they have heart-shape faces with the bill set much lower than the eyes. Their plumage usually combines shades of yellow-gold and gray and the facial disk is well defined. Many are open-country birds that hunt on the wing, but there are also some darker, shorter-winged forest species. The bay-owls also have long, heart-shape faces with a big space between eyes and bill, but they are squatter and shorter-legged than barn-owls.

Strigidae

Within Strigidae there are about 25 genera, but the majority of species belong to one of the following. The genus Otus holds the scops-owls, which are small, slim, insectivorous owls with pointed ear tufts. They occur in only the Old World, and in the Americas they are replaced by the genus Megascops, the screech-owls, which are similar but on average larger and more predatory. The eagle-owls, genus Bubo, are the largest of the world’s owls. They are bulky, powerful birds with prominent ear tufts (with the exception of the Snowy Owl). The other main genus of owls with ear tufts is Asio, known as the eared owls, with just few species but including some that have wide distributions. These are medium-size, slim owls that often live in open country and hunt in flight.

The pygmy-owls make up the genus Glaucidium. These small, round-headed owls are forest birds with whistling calls and a propensity to take large prey for their size. Somewhat similar but larger and leggier are the little owls, genus Athene. The small genus Ciccaba, of the Americas, contains some of the most strikingly marked owls in the world, while Strix, the wood-owls, unites a range of medium to large, round-headed, and intricately plumaged woodland owls, noted for their highly nocturnal ways and classic hooting voices. The small genus Aegolius contains some widespread small but fiercely predatory forest owls, which are perhaps the most perfectly adapted of all to a strictly nocturnal lifestyle. Finally, Australasia and southeast Asia are home to the hawk-owls or boobooks, genus Ninox, which are slim and long-tailed hawklike owls with small heads and often bulbous bright eyes.

This intensely thoughtful stare belongs to an Andean Pygmy-Owl—one of many forest-dwelling South American representatives of the genus Glaucidium.

Jens Linke

The smaller genera in Strigidae include some groups that are clearly closely allied to others (for example the fish-owls, Ketupa, closely resemble Bubo and are sometimes grouped with them). Those that have no obvious close relatives—the likes of Crested Owl, Maned Owl, and the charming Long-whiskered Owlet—are true oddities and are among the most fascinating owls of all.

Diversity and distribution

Owls occur on all continents except Antarctica, with the highest species diversity around the tropics. While most are woodland birds, some specialize in more open habitat types, from the Snowy Owl of the arctic tundra to the Burrowing Owl of Mexican deserts. The largest are the eagle-owls, seriously heavyweight predators that top the food chain in many ecosystems and can tackle formidable prey, such as young deer and foxes. At the other end of the scale, the Elf Owl is the size of a sparrow and feeds primarily on insects.

Most owls are sedentary, living in one relatively small territory for their whole lives, and building a deep familiarity with their patch. This means that there are numerous owl species that have a limited distribution. In island groups in the tropics, you will often find one species or subspecies of owl restricted to one individual island, with similar but subtly different forms on neighboring islands.

However, some of the most northerly owls are migrants, leaving their breeding areas in winter and moving south, while a few others are nomadic, making movements in any direction as required to find good feeding and breeding conditions—they rarely settle long in a regular territory. Their populations, therefore, can mix and interbreed over a wide area, meaning that distinct forms are less likely to evolve. A prime example of this is the migratory and nomadic Snowy Owl, which has a vast distribution but no subpopulations distinct enough to be considered subspecies.

Anatomy of a hunter

The attributes that make an owl look like an owl are adaptations to a challenging way of life. Catching and killing other animals, which don’t want to be caught and killed and will try to hide or escape from any attacker, or even fight back, is no mean feat. A high-level predator needs stealth, intelligence, concentration, speed, and power, and it needs to marshal those resources constantly if it is going to catch enough prey to feed itself and sustain a family.

The art of invisibility

Owls excel at stealth, both in their behavior and in the way their bodies are made. Being difficult to observe is essential when waiting for prey to wander along, and sit and wait is a common owl hunting strategy. Camouflage also helps protect the owl from other, larger predators when it is roosting, as well as from small birds, which often mob and harass roosting owls. All owls have camouflaged plumage, and because most species are woodland or forest birds, their plumage patterns and colors help them to blend in against a backdrop of shadowy tree bark and foliage. Many have a gray or brown base color marked with streaks that resemble the natural fine scars and cracks found on tree bark, and pale spotting to resemble dappled light shining through a leafy canopy. Like most animals, owls also exhibit counter-shading, whereby their underside is paler than their upperparts, to counteract the natural impression of solidity that all three-dimensional objects have when they are lit from above and shadowed below. A few owls deviate from the gray/brown template, because their habitat demands it. Most notable among these are the white-plumaged Snowy Owl of the Arctic tundra, and at the other end of the spectrum the Sooty Owl, whose dark, ashy gray plumage fits a dry forest habitat where fires that blacken the tree trunks are commonplace.

Some small owls, in particular, those of the genera Glaucidium and Athene, have an occipital face marking on the feathers of the nape—a pair of dark patches circled with white. This creates the illusion that the owl has eyes in the back of its head, and the stare of its false eyes may help protect it from attack from behind.

Occasionally, a wild owl will be born with a genetic pigmentation abnormality. Most common is leucism, where part or all of the plumage has reduced or no pigmentation, giving pale or white feathers (eye color is normal). Melanism (where excess melanin pigment means darker than usual plumage) is also known to occur. Such owls are at a grave disadvantage, because the lack of camouflage will seriously affect their survival chances. True albinism, where the eyes and other bare parts are also without pigment, is even more disastrous, because the bird will probably have eyesight deficiencies. This condition is extremely rare in wild birds.

Body shape, posture, and positioning are other ways that owls can disguise themselves. A perched owl can alter its shape by straightening up and sleeking its plumage, turning its outline from rounded to narrow and sticklike. The pointed ear tufts that adorn the heads of many owls enhance their resemblance to a broken branch. Owls also select spots where their surroundings help hide them—pressed up against a tree trunk, hiding in a crevice, or tucked deep in thick foliage. Owls that hunt in flight in the daytime often have pale bellies and underwings, and this helps make them less visible against a bright sky when viewed from directly below.

Camouflage is important to allow owls to hide from their prey, but it also helps small species, such as this Eastern Screech-Owl, avoid the attention of predators.

FLPA/Alan Murphy, BIA/Minden Pictures

Owl body plumage is dense and soft, making the bird look much bulkier than it really is. Many owls have downy feathers on their legs and sometimes also their toes—this is particularly prevalent in species that live in cold northern areas. The contour feathers that carry color and form the outer shell of the plumage each have a tuft of fluffy soft down at the base. The down layer traps heat and, by sleeking or fluffing up the contour feathers, the owl can hold in or release this warm air as required. Fluffed-up plumage also makes the bird look much larger—which is useful when trying to intimidate a rival or enemy.

The Northern Hawk Owl has thick, cushiony plumage and well-feathered legs and feet, allowing it to endure cold snowy winters.

iStock

Color changers

One of the peculiarities of owls is the tendency for the same species to exist in two or more distinct color morphs. Most commonly there are brown, rufous, and gray morphs, and often there are also intermediates between the morphs. In some cases, one morph is much commoner than the others, but in many polymorphic owls there is an even split. Different color morphs may survive better in different environments, with natural selection resulting in uneven distribution of the morphs across the species’ range. For example, Tawny Owls that live in pine forest in the north of their range are usually gray morphs, better matching the bark color of the trees, while those that live in deciduous forest farther south will probably be brown morphs. In mixed woodland types, a range of different morphs may be equally well camouflaged. Whether birds prefer to mate with a matching morph or not seems to vary between species—studies on Barn Owls indicate that they tend to prefer like-colored mates, while Tawnies and Eastern Screech-Owls show no preference.

Silent wings

Owls that live in more open country tend to have less strongly camouflaged plumage than forest owls and to be more active hunters, and if you are lucky enough to observe a hunting Barn Owl or Short-eared Owl at close range, you’ll notice that its wingbeats make no sound. For nearly all owls, not being heard while hunting is as important as not being seen, because even the sit-and-wait hunters have to fly down to take their prey. A silent approach means that the prey has no last-moment warning, and it also means that the owl can fully focus on any sounds the prey is making, without being distracted by the swishing of its own wings.

Eye color

The majority of owl species have yellow eyes—some bright lemon yellow, some pale, some tinted green, and some warm ocher. Of the rest, a number have brown eyes (often so dark as to appear black) and a few have reddish or orange eyes. Why the variation? It is sometimes said that nocturnal owls have dark eyes and more diurnal species have pale eyes, but this only fits for a few species—indeed, owls of the genus Aegolius are probably the most strictly nocturnal of all owls and they have bright yellow eyes. If there is any true functional significance to eye color, science has yet to identify it. In terms of how we relate to the owls we see, the difference is dramatic, because eye color has a big influence on the expression we perceive on the bird’s face. Yellow-eyed owls almost always look somewhat intense and, depending on other facial markings, can look startled, fierce, or furious. Dark-eyed owls, by contrast, look mellow, even kindly. This, of course, has no bearing on the owl’s actual temperament. The dark-eyed Ural Owl, for example, has a particularly gentle, almost avuncular look, but it defends its nest site with exceptional ferocity and can and will knock a human intruder to the ground with a well-aimed swoop and kick in the head.

Silencing a flight feather is not straightforward. The barbs that make up a normal flight feather attach to each other through tiny hooks, working like Velcro. This turns the feather into an air-resistant (though extremely lightweight) surface. In this way, it provides lift by pushing against the air when the wing is moved in a downstroke—but the action tends to make a sound. The flapping flight of large birds, such as swans, make quite a racket, and even the fluttering of small birds is audible. Gliding is silent, but it doesn’t offer the precision control that an owl needs when aiming for moving prey. Because owls have to use flapping flight when hunting, their flight feathers have a specialized structure to reduce sound to a minimum. The tips of the barbs on the leading edge of the feather do not zip together but stand separate, looking like the teeth of a comb. They disrupt airflow and deaden sound during wingbeats. The lower parts of the barb fix together as normal, making a solid shape to push against the air.

Those owl species that hunt on the wing over open countryside have much longer wings than their forest-dwelling cousins. A large wing surface area relative to bodyweight (low wing-loading) improves the energy efficiency of the slow, low, flapping flight that these owls use when actively searching for prey. They can save still more energy by utilizing the wind, flying into it for extra lift. If you are watching a hunting owl over a field, position yourself with the wind behind you and you will probably enjoy ever closer views. In still or windy conditions, this hunting style becomes much more difficult and the owls may switch to a sit-and-wait hunting method.

Night sight

In a typical nature documentary featuring cheetahs hunting gazelles on the plain, the camera switches between the faces of predator and prey as the tension builds—the eyes of the hidden cheetah fixed on its intended victim, and the eye (for only one is visible at a time) of the gazelle constantly scanning the entire vista. Those that are hunted tend to have eyes positioned on the sides of their heads, giving the widest possible field of view. They need to be able to see danger from all directions, even as they eat, drink, socialize, and generally go about their daily lives. The hunters, however, tend to have flatter faces with the eyes directed forward—meaning a narrower field of view, but the overlapping images from each eye provide better depth perception, and thus the ability to more accurately home in on their target. Owls have the most forward-facing eyes of all birds, and this helps them to direct their killing pounce at exactly the right spot.

Other adaptations peculiar to owl eyes relate to their nocturnal habits. Large eyes gather more light, and owl eyeballs are also tubular, meaning that the retina (the layer of light-detecting cells at the back of the eyeball) can be much larger than it would be in a normal spherical eyeball. The payoff is that the eyes are virtually immobile in their sockets—unlike us, an owl cannot glance around without moving its head. An exceptionally mobile neck helps to overcome this problem—owls can famously turn their heads almost 360 degrees, and tilt them so that the face is virtually upside down. The thick plumage obscures the length of the neck, but a look at an owl skeleton reveals this, as well as the bony tubes that contain the eyeballs. The eyeball shape also means that owls are farsighted—they cannot focus on objects that