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Bird Migration Fueled by Fall Bounty

By on September 28, 2016 in BirdWords
Yellow Warbler

Yellow Warblers surge down local riversides in September feeding on abundant insects from streamside vegetation

Salmon will be arriving soon, and the birds will know it. Turkey vultures know the smells, and will congregate in bare trees at fish-rich creeksites. Experienced eagles will displace the vultures at sand-spit carcasses. Mergansers and cormorants will swallow salmon fragments in the water. Herons and egrets will ply the shorelines where carcasses wash up. Sandpipers may join them. Insects will quickly colonize the dead fish, and their swarming hordes will feed the thrushes, warblers, and flycatchers who come to share in the salmon bounty.

The fall run of Chinook salmon to north state rivers and creeks delivers a huge, valuable load of Pacific Ocean protein and calories that benefit a wide range of wildlife—bears, foxes, otters, fishers, raccoons, skunks, coyotes, bobcats, and a variety of insects that in turn feed more mammals, reptiles, amphibians, and fish. For many birds, the salmon calories are especially important.

Birds that migrate long distances can as much as double their weight in preparation for the trip. In the weeks before flight, they go into hyperphagia, a profound over-eating binge that can see their weight increase as much as 10% per day. They store the energy as fat, which concentrates their necessary fuel in a form lighter than carbohydrates or muscle. The birds then burn this fuel in flight, arriving at their wintering grounds once again slim and hungry.

Of local birds that eat salmon, perhaps the most fish tonnage goes into turkey vultures. Some vultures spend winters in the north state, but most still migrate to Mexico or throughout South America, up to 6000 miles from Redding. Even soaring most of the way, as vultures do, the calorie requirement is high.

Smaller birds cannot soar their way south, but must flap almost nonstop. For numerous songbirds, riversides are highways full of calories. Right now they are hungrily devouring insects, from salmon, from oak trees, from cottonwoods; they are not particular. In addition to insects many songbirds devour the grapes, blackberries, and pokeberries scattered along autumn shorelines. Thrushes, waxwings, tanagers, orioles, vireos, and flycatchers all wolf down this wealth of food to enable their flights south.

Some of our most numerous gems flocking downriver right now are yellow warblers. Relying on insects, they are swarming through Shasta County streamside woodlands, bulking up their little third-of-an-ounce bodies for a flight of two to three thousand miles. They are on the move, and may appear just as flashes of yellow through the pale September foliage, but scores of them can sometimes be seen in a brief streamside stroll.

Fortunately our departing birds do not exhaust the food supplies. Many birds that summered in Canada’s prairies or forests, or in the high arctic will soon flock hungrily into Shasta County, and they should find plenty to eat. Ducks and gulls will feed on salmon that still wash to the riverbanks. Robins and hermit thrushes will eat grapes hanging high in cottonwood trees. Little bushtits, who nested here, will now stay the winter, finding sustenance in the insect larvae and eggs tucked into crevices of leaves and twigs. The bounty of autumn rivers keeps on giving.

Bird Vacation Season is Now

By on August 27, 2016 in BirdWords
Vermillion Flycatcher

Vermillion Flycatcher Photo By Larry Jordan – Click on photos for full sized images

Winter is not yet chasing birds southward, but it’s late summer, and the nesting season is pretty much done. This is slack time, a time to relax, to vacation. For empty-nesters and fledglings of many species, this is a time to go traveling.

Where do they go? Bird-watching field guides have long offered range maps, showing winter ranges and summer ranges in different colors. Now, with more data informing the range maps, a variety of colors and dotted lines try to illustrate normal migration routes.

But some birds just aren’t routine. They travel outside the lines.

In biology, these wanderers are known as vagrants. Because they fly, birds are particularly capable of vagrancy, and this can make for pleasant surprises in local parks and ponds.

Vagrants often are young birds who, having strayed from their species’ tried and true, may stay in a strange land for a long time. Black Scoters, for instance, are ocean ducks that nest along the north and west coasts of Alaska. In 2011-12 a young Black Scoter lived at Turtle Bay East and Kutras Lake for a full year.

Black Scoter Photo By Peter Massas

Black Scoter Photo By Peter Massas

Sometimes illness or injury can send a bird awry. In 1991, a Laysan Albatross, which normally soars far and wide over the Pacific Ocean and nests in Hawaii or the Philippines, turned up at Whiskeytown Lake. The bird had had some run-in with people, however. It had a dab of red paint on its forehead, and died days after arriving.

Laysan Albatross Photo By Peter Massas

Laysan Albatross Photo By Peter Massas

Storms may blow birds off course, or sometimes their magnetic sense of north seems to get reversed. Or some birds just seem to wander more than others. Indigo buntings—yes, they’re a deep purple-blue—nest in the eastern US and winter in Central America and Cuba, but we have had visits to Whiskeytown Lake and to the Clear Creek Water Treatment Plant. The Water Treatment Plant also hosted a 2013 September stop by a wayward Buff-breasted Sandpiper, which normally flies down the Mississippi River from its Arctic Ocean nest to its winter home in Argentina.

Buff-breasted Sandpiper

Buff-breasted Sandpiper Photo By Mario Suarez

Also in 2013 a Black-capped Chickadee, common all along the Canadian border and down to the mountains north and west of us, showed up at a Redding backyard feeder.

Black-capped Chickadee

Black-capped Chickadee Photo By Mdf

The flame-brilliant Vermilion Flycatcher lives in South America and up to as far north as Southern California, but this past winter one spent a few weeks at the Maxwell Cemetery, with his own bright plumage complementing the cut flowers there.

Vermillion Flycatcher

Vermillion Flycatcher Photo By Larry Jordan

Tufted ducks—paddlers with jazzy fifties-style ponytails–normally live in Japan and the Koreas, but one visited Redding in 2006. Another colorful traveler from east Asia, a Falcated Duck, has wintered at the Colusa Wildlife Refuge in four of the last six years, attracting a small horde of humans in its wake.

Falcated Duck

Falcated Duck Photo By Larry Jordan

Vagrancy in birds comes with both benefits and risks. Among the benefits, vagrants may help mix genes among separate populations, enriching the genetic health of the species. If they establish themselves in a new area, they expand their species’ range, supporting a new area’s vitality with a robust and stabilizing diversity.

On the negative side, vagrants may spread disease such as West Nile virus, or otherwise threaten existing species, as common ravens are certain to do by preying on nestlings as they expand into the Far North.

But for bird-watchers, vagrants are mostly a treat, a chance to witness the variety of life’s beauties here in our own neighborhood.

Jaybirds—Thieves and Oak-farmers

By on July 27, 2016 in BirdWords
Western Scrub-Jay

Western Scrub-Jay

Common as dirt and all around us, anyone who sets foot outdoors must have seen the Western Scrub Jay, boldly sitting atop the highest tree, scolding raucously, or flying with an acorn in its beak. Sometimes mistakenly called “Blue Jay”—that’s its cousin east of the Rocky Mountains who sports a perky blue crest—the Western Scrub Jay is a foot-long crestless jay with blue on head, wings and tail, a pale brownish-gray back, and a gray-white throat.

The male and female form a long-term pair bond and raise 3 to 6 young per year in a nest built of sticks. Rather than picking sticks up off the ground, I have seen them break sticks off a tree, often discarding any that don’t meet their standards.

Although the diet of the Western Scrub Jay includes fruit, seeds, insects, small animals (and it does rob nests), its mainstay is acorns which it often buries in the ground for consumption later, a practice called caching.

I watched a jay stick an acorn into the soft soil of the front of my vegetable garden. Immediately, another jay showed up and swiped the acorn and buried it in back in a tomato cage. Then jay number 3 flew in after the same acorn, but was chased off by the second jay.

Similar lunchtime observations of jays’ thieving by a research scientist at UC Davis led her to an investigation in the lab. She found that individuals that stole food from other jays’ caches spent much more time moving and reburying the same piece of food than non-thieves did. So, thieves suspect that everybody else is a thief, too.

Acorn Woodpeckers, who cooperatively make their own caches, or “granaries,” of acorns in holes in trees, are also on to the tendency of Western Scrub Jays to steal nuts. The woodpeckers always have a member of their group on guard and if a jay comes near, the woodpeckers go into noisy “red alert,” and several fly in to chase the potential raider away.

Another ramification of Western Scrub Jays’ and related species’ habit of caching acorns relates to their importance in the scrub oak woodlands.  Of course, the birds never find all the acorns that they’ve buried and many remain to sprout into oak seedlings.

Researchers recorded that the related Blue Jay cached significant numbers of acorns – 50 jays cached 150,000 acorns in 4 weeks, leading to speculations that the swift extension of oak forests as the ice retreated at the end of the last ice age was due to the activity of the jays.

A botanist looked at this more closely. He superimposed a map of the world-wide distribution of oaks upon a map of the occurrence of acorn-caching jays of various species and found that no oaks were found where there were no jays, although the jays survived in areas without oaks. His conclusion was that oak forests are entirely dependent upon jays for their reproductive survival. So, our local feathered rascal has an important job to do for our oak forests!

Western Scrub Jays are common in our neighborhoods and woodlands, so watching them in action takes little more than patience and curiosity.

Western Kingbirds on Field Patrol

By on June 25, 2016 in BirdWords

Western Kingbird

Most birds are more sensible. They gather their food from the ground, or leaves, or something solid, or at least liquid! But flycatchers make a living on the wing, plucking insects—not necessarily flies—right out of the air.

The flycatchers are a large group of birds that thrive in many habitats. Some are small, greenish, and tucked in close to riparian brush. Some hunt in woodlands or forest canopies. Some flash brightly along open fields.

But all of them share their hunting behavior. They scan from a perch, fly out in pursuit of an aerial insect, and, with any luck, snatch the bug with their beak and return to a perch to dine. If you see a bird fly out, squiggle in the air, and return to a post or prominent branch, you are almost certainly watching flycatching.

Our largest flycatcher, the western kingbird, is frequently seen on roadside fence-wires. The fences make perfect perches from which to hunt over the fields they prefer. A nearby oak or telephone pole will provide a nesting site, and the kingbirds are good to go!

Not shy at all, western kingbirds decorate their neighborhoods with bright flashes of color from their lemon-yellow bellies, and loud, rubber-ducky chattering. They will tolerate nearby nests of what they judge as gentler birds, such as robins and doves, but aggressively harass hawks, owls, and nest predators such as ravens, crows, and magpies. While defending their nesting territories, kingbirds may become aroused, causing their head feathers to stand erect and revealing the crimson crown that is normally completely hidden but earns the kingbird its name.

Like other flycatchers, kingbirds must be strong flyers. To support their aerobatics, they have a keeled breastbone—picture a fin of bone extending out from your breastbone. This structure allows the strong muscles that move the wings to anchor farther forward, giving them better leverage for power and agility. A less pronounced version of the keeled breastbone may be seen in your chicken dinner.

Unlike chickens, kingbirds migrate a long way. Most western kingbirds winter in Central America. In March and April they flap a couple thousand miles into the western US or Canada. There they build a nest of soft plant material, usually high in a tree or human construction, and incubate a handful of camo-blotched eggs. The number of eggs per clutch and the number of clutches attempted vary with the abundance of food.

The hatchlings emerge naked in about eighteen days, and set about gaping for food and growing their muscle, bone, and feathers—gray head and back, yellow belly, and black tail with fine white edgings. If all goes well and the nest predators are kept at bay, in just three more weeks a new generation of western kingbirds is ready to try its skill at hunting the bugs that buzz our fields.

Green Herons: Flying Footballs

By on May 30, 2016 in BirdWords

Green Heron

Green Heron (Butorides virescens) Hunting

Herons and egrets are some of our most elegant birds, standing regally or stepping slowly, with ballet precision and pointed intent. Indeed, it was the egrets’ showy white plumes that, hunted for use on fashionable ladies’ hats, helped spark the formation of the Audubon Society in 1905.

But the Green Heron is a scrappier member of the tribe. Low to the ground, darker, smaller, the bird is less striking than its cousins. But this time of year you may spot what looks like a football with wings flapping overhead as a green heron moves between riverbank and lakeside.

The birds are not so colorless as they likely appear to the unaided eye. A view with binoculars will reveal this little heron’s green umber back and crown, its rusty breast and cheeks, and frog-yellow legs and lores—the area between the eye and bill.

When looking for food, green herons typically huddle motionless at water’s edge, scanning for a minnow, snail, or other small animal that might make a meal. Their skulls hold their eyes with a downward slant, providing the binocular vision of hunters and directing their gaze where they want it, on the surface below.

Green Heron

Sometimes these little herons fish more actively: they use bait! Like just a few of their relatives, green herons have been observed repeatedly dropping insects, worms, or bread crumbs into the water and then snatching the small fish that are drawn in. Sometimes they even fish with their version of artificial lures—feathers or plant material. It is unknown whether this particular skill is genetically inherited, culturally learned, or individually discovered.

Each spring, following their optional migration, green herons court with wing-flapping and bill-clacking. The male chooses a nest site, either in a green heron neighborhood or in a more isolated spot, and either in a tree or on the ground. He coaxes his mate with various heron dance moves, including swaying back and forth with his bill pointed skyward. Then he typically frames their nest with a collection of thin sticks. He continues to bring sticks, but the female takes over their placement to meet her standards—which vary from flimsy to substantial.

Green Heron

Green Heron Nestlings Feeding

She lays about four pale green-bluish eggs, which both parents incubate for about three weeks. The helpless hatchlings rely completely on their parents, who feed them by regurgitation. After several weeks of such fare, the young begin to catch their own food.

Green herons live near quiet waters from the northern arc of South America up through Mexico and, in the summer, up into Vancouver. East of the Mississippi they nest throughout the States, but are declining there, probably due to loss of wetlands. The California population is thriving, and in the Redding area green herons are common during the breeding season and can be spotted occasionally even in the winter.