Neighborhood Naturalist Fall 2018

neighborhood naturalist CORVALLIS, OREGON — FALL 2018

Cooper’s Hawk

T

he high, panicked cries of chickadees, agitated barks of robins and raspy squawks of scrub-jays suddenly fall silent as a Cooper’s Hawk glides low across the yard. He perches on a branch and shakes his long, banded tail from side to side, knowing that the wave of alarm calls has betrayed his presence. He flies into a dense conifer, prepared to wait and watch until he’s been forgotten. A towhee’s moment of inattention is all he needs for a successful hunt.

Almost everyone who feeds birds knows the Cooper’s Hawk—whether they want to or not. They’re beautiful, fierce birds with incredible agility and stealth, but their relentless attacks on songbirds upset some bird lovers. As members of the genus Accipiter, they’re between the Sharpshinned Hawk and the Northern Goshawk in size. The confusingly similar Sharp-shinned Hawk is also a predator of backyard feeders, especially in the winter, while Northern Goshawks are usually confined to older montane forests.

Of all the accipiters, the Cooper’s Hawk has integrated its life cycle into suburban areas to the greatest degree, successfully breeding in neighborhood parks and urban stream corridors.

Historically, the Cooper’s Hawk population suffered from more human persecution than most other raptor species. Farmers shot them on sight because they were known as “chicken hawks,” and some states even paid a bounty for carcasses of both Cooper’s and Sharp-shinned Hawks. Tens of thousands of these hawks were slaughtered annually, and they became quite rare in parts of North America. But once shooting was outlawed, the population began to recover slowly, at first hampered by DDT-related eggshell thinning, until that, too, was banned. As their numbers increased, Cooper’s Hawks began to nest in close proximity to humans, even within major metropolitan areas. Their success story is a testament to their adaptability, and to the change in human tolerance and appreciation for raptors.

article and photography by Lisa Millbank, illustrations by Don Boucher

While Cooper’s Hawks do breed in expanses of wild forest, the density of nesting pairs in this type of habitat is low. Suburbs often have surprisingly robust bird populations, and the structurally complex, patchy habitat suits Cooper’s Hawks well. The popularity of bird feeders also concentrates prey, making them easier targets for hawks. Sharp-shinned Hawks also breed locally, but they

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stealth, explosive speed and agility, not endurance over long distances. As they hurtle fearlessly through small gaps in pursuit of fleeing birds, they tuck their wings to slip between branches and brake with their tails to quickly change direction. Cooper’s Hawks also take the occasional small mammal, and they’ll even chase rats or mice on foot.

They can run surprisingly well with their long legs.

During courtship, Cooper’s Hawks can be vocal, and they often flare out their white undertail coverts like a pair of loose, fluffy underpants. The size difference between the male and female is apparent here; the female is being followed by the male.

prefer to nest in relatively young, dense stands of conifers rather than in residential areas. We see an influx of Sharpshinned Hawks in the fall, most of them migrating from the boreal forests of Canada and Alaska. In contrast, many Cooper’s Hawks appear to be more sedentary, living in the same general area year-round.

All accipiters have short, broad wings that allow them to accelerate quickly, and long tails that let them maneuver through branches during high-speed chases. They rely on

They prefer to carry their prey into dense cover and eat it there, but large, heavy prey may be eaten where it was brought down. This one has pulled an almost-fledged House Sparrow out of its nest in a street lamp, and really doesn’t like having its picture taken!

A Cooper’s Hawk is well-equipped with keen hunting instincts, sharp senses and a body built for the job. But learning and hard-won experience are equally necessary to keep it alive. The hawk builds a mental map of its territory, learning where birds congregate, where it can hide, and ways to get around unnoticed. On most days, it spends part of its morning soaring high, a behavior that could help it find hunting spots, look for flocks of songbirds, or perhaps improve its ability to navigate the area. When hunting in a suburban neighborhood, a Cooper’s Hawk uses houses, hedges and fencelines to conceal its movements. To target a backyard feeder, it glides low to the ground behind houses or fences until it gets as close as possible to the feeder.

With a powerful burst of speed, it vaults over the obstacle, scattering the birds. The hawk selects a bird to pursue in a fraction of a second, and chases it for a short distance, even into dense brush. Each attack has only a small chance of succeeding, so it makes many attempts each day.

Individual Cooper’s Hawks develop unique hunting techniques. One day, Don came home with a story from his bike commute through downtown Corvallis. He watched a Cooper’s Hawk flying down the street in front of a city bus, just a few feet above the road surface. The hawk matched the speed of the bus and continued down the street until Don lost sight of it. Was the hawk actually using the bus as a distraction to allow it to move down the street unnoticed? We can’t be certain that it was, but Cooper’s Hawks are certainly capable of exploiting features of the human landscape while hunting. I’ve watched a few hawks who recognize nest boxes as potential food sources, reaching in to grab chicks while clinging to the roof with one foot.

I used to see a big female Cooper’s Hawk who seemed to specialize in killing the downtown Rock Pigeons. Pigeons aren’t easy prey; they’re strong, swift fliers, capable of speeds of at least 70 mph. The sudden clapping of the pigeons’ wings as they were startled into flight was my cue to watch for the Cooper’s Hawk inevitably in pursuit. I never saw her catch one, but the evidence of her success was easy to find.

Tufts of plucked feathers littered the grass, crusts of dried blood accumulated beneath her favorite perches, and gory bits of pigeon carcasses turned up here and there. A pigeon lay upside-down on the bike path with its wings spread, all of the flight muscles and organs in its chest and belly

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Adult female

Adult male

The sex of adults can sometimes be determined by factors other than size. In most males, the cheek area is gray, but females usually have a hint of rufous color on the cheek. Most males have bluish-gray backs, while females are more slate-colored. Females’ legs are thicker.

The female’s rusty breast barring is paler and has a slightly coarser pattern than a male’s barring. Dark red eyes often indicate a male.

For Cooper’s Hawks, the onset of nesting season means torn out and eaten. The size of the prey must have made all the failed chases worthwhile; I thought that she might that their hunting skills will be put to the ultimate test. cache a pigeon in a tree and eat at her leisure for a few days. Pairs spread out and defend large territories, giving loud kak-kak-kak calls. The male does most of the nest-building.

Most of the Cooper’s Hawks I see are the ones who hunt He makes a large cup from sticks, and lines it with flakes in our yard. We’ve tried to make the yard as bird-friendly of bark. The female lays 2-6 eggs, and she incubates for a as possible, but we also know that bird feeders concentrate little more than a month. During this time, the male brings birds and may expose them to more predation and disease all of her food, calling her to a perch where he transfers the than they’d face if they were foraging under more natural prey to her. Once the eggs hatch, the male has to step up conditions. The magnitude of the effect is hard to measure, prey delivery even more. The female tears off bits of prey to and it’s unknown whether the increased risk from predators feed the downy chicks, while the male continues to hunt. is outweighed by any positive effects of the supplemental Most Cooper’s Hawk eggs hatch in May or June, when food source. If a Cooper’s Hawk or other raptor seems to be monopolizing a feeding area, flocks of small birds songbird chicks are fledging. These fledglings are easier prey usually seek food elsewhere for a few days. Concerned feeder owners can also take their feeders down temporarily, to force the songbirds and the hawk to disperse. I feel that the hawks and songbirds in our neighborhood achieve a balance, and that the predation does have positive effects.

Cooper’s Hawks, like most predators, provide some benefits to the species upon which they prey. For example, Pine Siskins often suffer from salmonellosis, a deadly infection of the digestive tract. The disease is spread when infected droppings contaminate food sources, such as the accumulation of seeds and droppings beneath hanging feeders. Cooper’s Hawks snatch these lethargic birds right off the feeder, eliminating carriers of the disease, while also bringing a mercifully swift end to the siskins’ misery.

Cooper’s Hawks often kill injured birds, or birds with neurological or physical abnormalities, helping to ensure that only healthy birds go on to reproduce. As observers, we are privileged to witness the hawk’s speed, power and agility pitted against the alertness and evasive behaviors of its prey. A successful hunt is often over before I even recognize what’s happening; just a blur of wings, a swinging bird feeder and a few feathers hanging in the air. For me, This immature Cooper’s Hawk shows the teardrop-shaped streaks the event is thrilling and somber at the same time. on the breast and belly. Its upperparts are brown, with a banded tail.

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An adult Sharp-shinned Hawk shows its square tail tip, slightly paddle-shaped wings, and small head with a dark hood.

crows turned the tables on the young hawks by banding together to dive-bomb them.

This immature Cooper’s Hawk is enjoying itself by harassing some crows. It is still receiving food deliveries from its parents.

than adult birds, and it’s a good thing for the male Cooper’s Hawk, as he alone must feed himself, his mate and their young chicks. Females are about 30% larger than males, reflecting the general trend among raptors. The reason for the size difference is unknown, but it could allow the pair to exploit a broader range of prey sizes as they hunt together in the same territory. The lighter male is also more maneuverable in flight, which may confer an advantage.

As the chicks grow, the female stops brooding them and hunts along with her mate. The chicks take about a month from hatching to fledging.

Young Cooper’s Hawks are noisy, playful, curious and unwary, seemingly lacking the stealth of their parents.

Fledglings chase and spar with one another, their play mimicking the hunting techniques of adults. They even seem to tease one another; I watched one youngster tweak the tail of a sibling, provoking a loud squeal of protest before the chasing games continued. Some years ago, several newly-fledged Cooper’s Hawk siblings showed up at Sunset Park in Corvallis. The young hawks amused themselves by chasing the local crows around in a playful manner.

Although the crows seemed to realize that the hawks were inexperienced, the surprise attacks still frightened them.

When they’d endured more than enough harassment, the

They may act carefree and playful, but once their parents stop providing food, all young accipiters live on the edge of starvation. The majority of them die well before reaching adulthood. In a study done in Milwaukee, fewer than 10% of fledgling accipiters made it through their first winter.

Of course, mild Willamette Valley winters don’t compare to the frigid upper Midwest. Even so, probably no more than 25% of the youngsters here survive long enough to breed. Their lifestyle also exposes them to serious injury.

A study of Cooper’s Hawk skeletal remains showed that 23% had healed pectoral bone fractures, probably from collisions with branches or windows. Many simply starve after suffering such a fracture. Those Cooper’s Hawks who do reach maturity may live about 12 years, though one wild bird reached 20 years of age.

The Cooper’s Hawk’s story is ultimately an uplifting one, as thoughtless destruction was gradually supplanted by tolerance and admiration. Cooper’s Hawks and other backyard raptors help us understand nature’s ancient balance between predator and prey, up close through the kitchen window. Adaptable and resilient, they have carved out their niche in the human world, bringing a touch of wildness into suburban life. ó Watch a video and listen to the sounds of Cooper’s Hawks www.neighborhood-naturalist.com

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Cooper’s Hawk

The adult’s dark crown is somewhat flat on top with a shaggy, paler nape. The immature’s head has a buff wash between brown streaks and the white stripe over the eye is short. Adult eyes are orange to red, and an immature has pale yellow eyes.

Adult female

Sharp-shinned Hawk

The crown is round and smooth. A dark hood extends from the forehead to the nape and back. The immature’s head has light gray or white between brown streaks, and the white stripe over the eye usually extends to the back of the head. Adult eyes are orange to red and immature’s eyes are bright yellow. Compared to the Cooper’s, the eye is larger in proportion to the head.

Dark cap, pale nape

Adult male Dark hood

Squared head, “meaner” look from brow ridge

Small round head with prominent eye, lacks brow ridge

Immature Immature

Fluffy feathers often cover the thick legs

Thin legs usually not covered by belly fluff

White & fluffy under tail Squared tail tip with thin white terminal band

Tail proportionally shorter than Cooper’s

Rounded tail tip with prominent white terminal band

Size comparison

Female Female

Male

Male

Accipiters are challenging The continuum of eye color ranges from pale yellow to dark bloodred, gradually becoming redder as the bird ages. Adult males’ eyes ultimately become a darker red than most females’ eyes do. Maybe the darker red signals that a male would make a good mate. Older males are more experienced hunters, which could improve the survival of offspring.

Even expert birders can’t always tell the two species apart, especially with brief sightings. Individual variation and feather wear in both Cooper’s and Sharp-shinned Hawks mean that some of the classic field marks, such as tail shape, aren’t always reliable. Size is notoriously difficult to judge—a robust female Sharpie can be nearly as large as a smaller male Cooper’s. And while their calls are easily distinguished, both species are quiet during the non-breeding season.

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Blue Elderberry article by Don Boucher photography by Lisa Millbank

W

hen we moved to a new neighborhood, we were delighted that there was a tree-sized Blue Elderberry in a nearby park. Previously, obtaining the berries meant leaving our neighborhood.

The berries are tart and intensely flavorful, but they aren’t sweet enough eat in quantity fresh. They’re more often cooked with sugar or mixed with sweeter fruits. The berries and flowers have medicinal uses, but the rest of the plant is toxic (though not dangerous in small quantities).

It’s also a choice plant for native landscaping.

Elderberry is scarce. The plants bloom at different times, with the pyramidal clusters of Red Elderberry flowers and fruit appearing about a month earlier than the flat ones of Blue Elderberry. In early spring, before either species blooms, they aren’t so easy to tell apart.

The two species are in the genus Sambucus. We have one type of Blue Elderberry in our area, but the science isn’t settled on which species it is. The USDA regards our Blue Elderberry as S. nigra ssp. cerulea. Under this interpretation, it’s the same species as the Black Elderberry, S. nigra ssp. canadensis, which occurs east of the Rockies.

Blue Elderberry foliage stands out among nearby shrubs The Oregon Plant Atlas considers our Blue Elderberry to be and trees, due to the large, pinnately compound leaves S. mexicana ssp. cerulea, which would affiliate it with other that give the shrub a layered structure. It usually grows to Blue Elderberry subspecies found in northern Mexico, the 13-25 feet, occasionally taller, and has multiple stems at Southwest and other arid places in the west. And finally, ground level. The leaves come in pairs, on opposite sides other botanists elevate our variety to full species status; of the twigs. It blooms in late spring and early summer S. cerulea. The botany is more settled for Red Elderberry, with cream-colored, flat umbrella-like flower clusters. The S. racemosa. Most all Red Elderberries in our area are S. berries ripen in late summer or fall, depending on elevation. racemosa var. arborescens but an unusual variety is found Like blueberries, these fruits have a pale powdery coating, in the Cascades, S. racemosa var. melanocarpa, so named which is a kind of epicuticular wax produced by the plant. for its black fruits.

Blue Elderberry grows in moist locations west of the Rockies, from southern British Columbia to northern Baja California. Locally, it thrives in woodland clearings from the valley bottom to the mountains, commonly below 4,000 feet. Sometimes Blue Elderberry shares its habitat with Red Elderberry, all parts of which have some degree of toxicity to humans. Red Elderberry is more numerous at high elevations and along the Oregon coast, where Blue

Blue Elderberries provide a feast for wildlife, including Band-tailed Pigeons, Pileated Woodpeckers, Northern Flickers, Western Bluebirds, Swainson’s Thrushes, American Robins, Steller’s Jays, Cedar Waxwings, Douglas’s Squirrels, Townsend’s Chipmunks, and California Ground Squirrels.

Black bears will tear apart the shrubs, breaking branches to access out-of-reach berries. Red Elderberry fruits, too, are relished by birds.

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Some of the most commonly documented flower visitors are thrips, stink bugs, longhorn beetles, hoverflies, chalcid wasps, sweat bees, honey bees, bumble bees, moths, butterflies and their predators like lacewings, crab spiders and lady beetles. The foliage may be affected by aphids, but the Elderberry Borer, a beetle that damages stems, hasn’t made it west of the Rockies.

Blue Elderberry features in the history of the Corvallis area. A band of the Kalapuya who lived along the Marys River, near its confluence with the Willamette River, were called the Champinefu. This translates to “at the place of the Blue Elderberry.” Chepenefa Springs Park in Corvallis also refers to these people, but the spelling Champinefu represents more recent linguistic and historical research.

Tribes all over the Northwest used Blue Elderberries for food and medicine.

Elderberry fruit and flower extracts are widely known as a remedy for the flu and other viral infections, and elderberry products (usually Black Elderberry) are sold at drugstores. The scope of the health and efficacy claims are too broad to summarize here, but the science looks promising. Elderberry contains chemical compounds that seem to interfere with the ability of some viruses to bind to cells. Most studies have been done in vitro, and not enough research has been done on human subjects to clarify how effective elderberry is. I wouldn’t recommend using elderberry as a replacement for vaccines and other treatments prescribed by your doctor.

Blue Elderberry is a good choice for native landscaping and many local nurseries carry them. They do best in welldrained but moist soil in partial shade or even full sun.

New plants can be started from softwood cuttings. If you want to try it, you’ll want to look up detailed gardening articles on the subject, but here’s an overview. Take cuttings of soft, flexible branches about five inches long, and pinch off all but the top pair of leaves. Poke the cuttings into damp potting soil. You may have better results if you first dip the cut ends into rooting hormone powder. Cover with plastic and mist them daily, and a couple of months later you should have healthy roots that are ready for transplanting.

They don’t require cross-pollination, but it’s reported that you’ll get bigger berry clusters if you have multiple plants originating from different shrubs. You can prune them yearly to control their size in your garden.

Whether you grow your own, collect them in quantity, or just nibble on a few on your next hike, I hope you can enjoy the potent flavor of Blue Elderberry this fall. ó

That being said, the science is good enough for me to consider that elderberry may help. It’s inexpensive, safe, and delicious. We use it, both from the drugstore and from berries we’ve collected, but I always get my annual flu shot.

The berries are flavor bombs, and are great as an ingredient in jams, jellies, pies, syrup and more, when a tart, flavorful and colorful component is desired. They’re nutritious too, with lots of vitamins A and C, and the rich color is linked to flavonoids, which can have health benefits. I don’t want to hype them as a superfood, but they’re certainly good for you.

Before cooking, it’s best to separate the berries from the bitter stems. If you try this while they’re fresh, the berries rupture, as they tear from the stems, and it makes quite a mess. If you freeze them first, you can cleanly pop them off the stems while still frozen. The same principle works for dried berries. Dry them as clusters and then remove the berries. The dried berries have a different color and flavor, but they’re delicious anyway.

Most Blue Elderberry plants are less than 25 feet tall. This exceptional specimen grows in Village Green Park in Corvallis.

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Blue Elderberry

Red Elderberry

Compound leaves, opposite on the twigs, 5-8 inches long with 5-9 leaflets. Leaflets are hairless, 2-6 inches long each, with finely-toothed margins. Berry clusters are somewhat flat.

Long-stemmed compound leaves, opposite on the twigs, 4-11 inches long, 5-7 leaflets. Leaflets are hairless, 2-6 inches long each, with finely-toothed margins. Berry clusters are somewhat pyramid-shaped. For scale, notice the American Robin on the right side (who was eating the berries).

Berries are about ¼” dia. with a pale, powdery coating.

Berries are less than ¼” in diameter and are glossy.

Flower clusters are flat.

Flower clusters are pyramidshaped.

Blue Elderberry flower photo - https://bit.ly/2QNJr9y - by Dcrjsr (CC BY)

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