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Avian Spooks Haunt the Night

By Dan Greaney on October 28, 2017 in BirdWords

Great Horned Owl

Who-h’hoo-hoo-hoo! Not a Halloween ghost, but an owl. Some owls are smaller than robins, others bigger than your poodle, but they live all around us, locally and worldwide, almost invisibly.

Most common in North America is the Great Horned Owl. It’s not really horned—just feather-tufted—but these owls have the hearing, eyesight, feathering, talons, and instincts that make them formidable nighttime spooks .

Being nocturnal, the owls must keep warm. Their thick blanket of soft feathers does the job. Their feathering is so plush that a child’s finger poked into it can disappear. The Great Horned Owl is about the size of a housecat, but weighs only half as much, maybe four pounds. The rest is feathers.

The softness of these feathers helps insulate the birds, but it also promotes their silence. You may have heard the stiff flapping of, say, a raven winging by in daylight hours. But the owl’s feathers, soft and fringed at the wings, slip silently through the air, so that an unsuspecting rat is given no warning of its doom.

“No warning” is important. Daytime raptors—hawks and eagles—generally catch their quarry only 20% of the time. Snatching prey in the night can only be more difficult.

But owls are up to the task. They have huge eyes; imagine tennis balls on our human faces. Their pupils can open wide to catch dim shades in the dark. Their retinas are rich in rod cells, the photoreceptors that see only black and white, but still see when color receptors have shut down with dusk. Their huge eyes leave no room for their pupils to slide left-right as ours do, but they compensate with 14 vertebrae in their neck, twice our number, allowing their famous three-quarter head swivel.

Owl hearing is exceptional. Their cheek feathers form two little dishes that funnel sound into their ears, one on each side of the head, one high and one low. That high/low offset helps the owl pinpoint the source of a sound, much as a dog will by cocking its head. Tests on barn owls have shown their ability to capture prey in total darkness, by sound alone.

Once its prey is located, a hunting Great Horned Owl will loft from its perch and wing forward like a shadow. Its talons—not the typical three toes forward, 1 toe back of songbirds, but rather angled two forward/two back—will encircle its prey. Scarily strong—reported to be able to pop a steel-belted tire—the talons will pierce the lungs or heart.

Great Horned Owls are not picky eaters. They may hop on the ground to snatch scorpions and other invertebrates; they may eat frogs, mice, rats, or rabbits; coots, ducks, or other birds; squirrels, cats, or, thanks to an absent sense of smell, skunks.

Their nocturnal versatility—night, after all, happens all over—permits Great Horned Owls to live in forests, fields, wetlands, and deserts. They hoot to establish a territory and to coax a mate. In spite of her larger size, she hoots the alto and he hoots the bass. All dueted up, they will nest in trees, in stick nests or cavities, or in old barns, or on rock ledges, where they will deliver shreds of the local vermin to their hungry chicks.

And at this Halloween time of year, you may hear their hoots, but also the hisses, shrieks, barks, whistles, and wavering cries with which owls haunt the darkened skies.

Plants for Birds

By Dan Greaney on October 9, 2017 in BirdWords

Cedar Waxwing on Toyon by Jay Thesken

After the long heat, the season for planting approaches. The local CNPS will hold its fall sale of native plants at the Shasta College Horticulture area on October 14, 8am-2pm. It may be an opportunity to dress up both your yard and the birds!

We only survive and flourish because of photosynthesis, the green-plant magic that turns solar energy into food energy. Without plants we would lack the wit to see a bird, as well as any birds to see. None would sing, or sprout a golden feather.

Praying Mantis

Fortunately, many plants survive our summer droughts and winter frosts. Trees, shrubs, forbs, and grasses provide a feast of seeds, nuts, berries, leaves, and nectar. Native plants support insects—caterpillars, leaf-hoppers, aphids, and more. Buckwheats, sages, coffeeberry, and toyon are among the many plants that support our pollinators—native bees, wasps, flies and beetles. The insects become food for so much of animate life, including our local fledglings who this month are fueling their first flights south.

Western Bluebird Fledglings Waiting to be Fed

Many birds are strongly associated with oaks. Besides making nesting sites, oaks make acorns, which are devoured by jays, magpies, crows, ravens, turkeys, and band-tailed pigeons. Acorn woodpeckers store the acorns in rotting branches for winter dining. Lewis’s woodpeckers do the same, but meticulously shell and split the acorns first!

Acorn Woodpecker Granary

And oaks pass storms of insect energy on to hungry birds! Woodpeckers, titmice, and nuthatches dine on the beetles, ants, and spiders of the woody branches, and on the wasp larvae in oak galls. A stunning 534 species of butterflies and moths are known to lay their eggs in oaks, and those caterpillars feed orioles, warblers, vireos, mockingbirds, and bushtits. Bluebirds and flycatchers hawk the insects that take wing, and robins, sparrows, and towhees pick dinner from the detritus under the trees. Oaks are the crowning gem of many a lively yard!

Oak Titmouse with Insect

Quail will roost in the oaks, but will gladly poke about at ground level in the thick protection of Ceanothus bushes, where foraging wrens and towhees may join them. Nearby lupines, after their bright show of blue flowers, will draw the quail out to dine on their nutritious seed pods.

California Quail Female with Chick

The fruits from Coffeeberry, Toyon, and Elderberry attract robins, bluebirds, mockingbirds, waxwings, and nuthatches. Currants will also draw these berry-loving birds.

Goldfinches flock to sunflowers and thistles. Milkweed supports not just monarchs but eleven other species of butterflies and moths, too. Colorful grosbeaks dine on their seeds, and hooded orioles use the plant fibers to weave their nests.

Swallowtail On Western Vervain

Four species of hummingbirds are regularly seen in our area, and many flowers sustain them—woolly blue curls, larkspurs, penstemons, monkeyflower, fuschia, currants, and salvia. Some of these plants bloom through the winter, sustaining the resident Anna’s hummingbirds.

Anna’s Hummingbird on Thistle

For the adventurous, poison oak provides fruit and cover for quail, thrushes, sparrows, goldfinches, flickers, juncos, kinglets, sapsuckers, wrens, titmice, and a host of other songbirds. Don’t get carried away with toxic adventures, though. Nandina, known as heavenly bamboo, is a colorful but dangerous invasive that poisons birds with its cyanide-laced berries.

Gardening for birds is best done with a dose of indolence. Leave those dead-heads on the plant; they’ll feed the finches. Leave the leaves on the ground. Towhees and sparrows will breakfast on the bugs that turn them into mulch. Native plants are generally a great bet. Together with the birds they form a beautiful gift to yards all over. Enjoy!

Birds Pull Out Their Winter Coats

By Larry Jordan on August 27, 2017 in BirdWords

Bald Eagle Juvenile photo courtesy David Bogener

What’s up with our backyard birds? Where are they?

You may have seen them over the last months busily carrying load after load of insects to feed their ravenous nestlings, then being raucously pursued by fledglings demanding yet more food – sometimes with two or even three batches of babies through the season. All this effort has taken a toll on the adult birds’ feathers and now, despite the daily care they have taken preening and cleaning them, the feathers are worn out. The birds are lying low during their molt – the annual or twice yearly loss and regrowth of feathers done by most songbirds. But don’t expect to catch a glimpse of bald birds – each worn feather becomes loosened in its socket and is pushed out by the growth of a new feather.

The process takes from 5 to 12 weeks for songbirds, after which some will appear in winter plumage quite different from the bold patterns some males sport in summer. For example, American Goldfinch males are bright canary yellow with bold black accents during the breeding season, but become a quieter butterscotch color, much like females and juveniles, in their winter garb. Similarly, you may see a male Western Tanager that has lost his gaudy orange head feathers and exchanged them to the muted gray of a female before starting the long, dangerous migration to Costa Rica for the winter.

Bald Eagle Sub-Adult photo courtesy David Bogener

Other groups of birds go about the molt differently. Ducks, geese and some other water birds go through a rapid “synchronous molt”. They change their feathers quickly in a period as short as two weeks which renders them flightless for that period. This seems like a risky business – but researchers have deduced that since these birds are heavy relative to their wing surfaces, losing a few feathers at a time would seriously hamper flying ability, so they get it over with as quickly as possible and minimize the length of time that they are especially vulnerable to predators.

Raptors (eagles, hawks, falcons and their kin) “make their living” on the wing and can’t afford to suffer periods of impaired flying abilities. These birds may take as long as two years to complete a molt. The loss of flight feathers must be symmetrical or flying would be skewed. A woman who raised an owl that could not be released into the wild observed this in action. She reported that her feathered friend pulled a loose wing feather out and gave it to her, then immediately removed the corresponding feather from the other wing.

Bald Eagle Adult photo courtesy David Bogener

To give young Turkey Vultures a good start, they don’t molt their flight feathers until they are two years old. The vultures soaring over minus a couple feathers are almost certainly adults.

In most birds, tail feather replacement is from the center of the tail toward the outer edge. Woodpeckers reverse this for a very good reason. Watch closely the next time you see one ratcheting up a tree and you will see that it braces itself firmly using its stiff tail feathers. The key for this is an inner pair of long feathers. Those are retained until the outer tail feathers have been replaced with fresh, strong vanes, keeping the woodpecker able to fully function searching for insects in the bark.

You may find a single feather in your yard – evidence that one of “your” birds has cast it off for a brand new set of feathers to get it through the winter or prepare it to head off to winter habitat in Mexico, Central America or South America. Enjoy the memento!

pH for Public Health, and Dinner, too

By Dan Greaney on August 8, 2017 in BirdWords

Turkey Vulture Juvenile

Most of us observe external adaptations—the vulture’s naked head, its sharp beak, its capacity to soar. But the MD’s among us develop a familiarity with internal adaptations. Redding’s own Dr. Lang Dayton has provided further details in response to last month’s article on turkey vultures.

He refers to pH, the chemists’ and pool-owners’ 0-14 scale. In this scale, seven is neutral, like pure water. The extremes, as they are in much of life, are toxic. High numbers are alkaline, also called basic: ammonia measures eleven, and bleach twelve. Low numbers are acidic—think lemon juice, which stings, or sulfuric acid, used in drain cleaners, or Iron Mountain runoff, which has been measured at sub-zero pH levels.

Dr. Dayton writes:

The main reason vultures can eat almost anything is that they have the lowest gastric pH in the animal kingdom. Stomach acid protects all animals because it digests bacteria and other living organisms along with other proteins. Human stomach acid has a pH of two. It kills 99% of bacteria in contact with it, but people still get sick and can die if they eat enough contaminated or rotten food.

Turkey vultures’ stomach acid has a pH slightly above zero, lower than car battery acid and 100 times as concentrated as human gastric juice. It can dissolve metal, e.g. shovels, as well as digest nearly all organisms, including those that cause botulism, anthrax, rabies, cholera, hepatitis, and polio, along with other proteins. Vultures can eat just about anything that is dead and rotten, including animals that died from infections that, in turn, would kill most people who ate them.

By consuming rotten and diseased meat they decontaminate it, which helps to prevent the spread of disease to both humans and other animals.

When India experienced a massive vulture die-off in the 1980s, feral dog populations exploded and, with them, the incidence of anthrax, rabies, and other communicable diseases. Unlike vultures, dogs do not so thoroughly disinfect what they eat. Feral pets that eat carrion can acquire and spread disease from their meals.

One of the things that I used to teach Interns and Residents in the Mercy Medical Center Family Practice Program was that stomach acid protects all animals as it digests swallowed organisms along with other proteins, and that it is a bad idea to take medicines that suppress gastric acid when going to 3rd world countries. People lacking stomach acid get sick on 1/100th the dose of ingested organisms as normal people. Vultures, on the other hand, could feed on botulinum toxin. Give them enough gastric acid suppressants, however, and they would likely die after their next putrid meal.

Turkey Vulture

So thanks again to vultures for their good work, which seems to take both soaring on wings and going low on pH, and to Dr. Dayton for teaching us about the vultures’ gastro-intestinal virtue.

Vultures Soar to do the Dirty Work

By Dan Greaney on July 3, 2017 in BirdWords

Turkey Vulture Adult and Juvenile

Summer is the season for soaring. Thermals, the warm air rising from the earth’s heated surface, can lift birds thousands of feet into the air with no more effort than spreading their wings. Larger birds, particularly raptors, for whom the quick flutter of small-bird wings would be physiologically impossible, are particularly famous for riding on thermals. The reigning champions of hot-air flight are, arguably, turkey vultures.

They’re ungainly, maybe disgusting. They can’t sing, only argue over food with a breathy hiss. They’re folklore symbols of doom and death. But supremacy in the air helps vultures prosper and decorate the sky through our sultry summer days. Some 90% of the soaring birds we see are apt to be not birds of prey but turkey vultures.

These vultures can be identified at a great distance. They hold their wings up in a V, a gift of their initial letter that hawks and eagles cannot replicate. The V shape, known in aviation as a dihedral, helps stabilize the birds in windy weather. When winter buffets the north state, the resident vultures ride the winds that replace the lazier-seeming currents of summer. Other turkey vultures will honor autumn tradition and head south—but they will still sail the winds, as they can ride as far down-continent as ever-blustery Tierra del Fuego.

Wherever they are, turkey vultures must soar to find their food with the most efficiency. Unlike most birds, they hunt with a keen sense of smell. Eagle-eyed predators can spot a salmon below the river’s ripple. Owls can hear a mouse squeak a football-field away. Vultures’ food, already dead, will not squeak or scurry for the ear or eye. Turkey vultures hunt mainly by smell. Their acute olfactory sense will not only find their carrion dinner, but will tell them whether it is too rotten to interest a civilized vulture. Indeed, while large owls, with their absent sense of smell, may gulp down a skunk, vultures will regularly discard at least the skunk’s scent gland.

But they really are not delicate diners. Vulture beaks are sharp and strong, but when particularly tough hides must be pierced, they may need to wait for early decay or a bigger predator to open the carcass. Since they will then be eating meals past their expiration date, and since they seem to prefer eating entrails from the anus up, vultures are heavily exposed to toxins. Fortunately, they are adapted to the dangers. Their naked heads not only keep feathers from being matted with contaminants, but also allow their skin bacteria, thicker and harsher than our own, to attack microbes in the meat, averting facial infection. The birds seem to be immune to effects from many biotoxins, and their own exceptionally virulent intestinal bacteria help them finish the job.

Their job is in fact a substantial service. Vultures find and scavenge about 90% of sizable dead animals in their range, reducing both disease and cleanup costs we would otherwise face.

Their condor cousins, with the rise of lead shot in carcasses and, longer term, no more mega-fauna to clean up, have been teetering on the edge of extinction for some time. Turkey vultures, on the other hand, perhaps responding to clearing of forests, an increase in roadkill, and a warming climate, have been extending both their breeding and wintering ranges northward.

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