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Nature you can find in town and the nearby countryside Corvallis, Oregon Winter 2012-13 Great Blue Heron article, illustration & photography by Lisa Millbank S tanding nearly four feet tall, and boasting a wingspan of over six feet, the Great Blue Heron has become a symbol of wetlands—a well-loved but almost banal icon. But beyond the Great Blue Heron’s beautiful-yetconventional image, there’s a complex, intelligent and fascinating bird. Valley don’t need to migrate, since wetlands don’t freeze for long periods and there’s abundant food year-round. It’s likely that some herons from northern Canada and Alaska or the east side of the Cascade Range spend the winter in the valley with our resident birds. A Great Blue Heron has superb vision, and its retina Where winters are long and harsh, Great Blue Herons is packed with rod cells that help it detect motion in low migrate south. But herons breeding in the Willamette light. With five times the density of rods as a human retina, herons can hunt effectively around the clock. Although a heron spends most of its time catching fish and frogs, it’s an indiscriminate carnivore, willing to eat almost any unlucky creature that ventures into striking range. Insects, salamanders, crustaceans and snakes are all snapped up with aplomb. Even other birds, including ducklings, songbirds and small shorebirds are on the menu. A heron must swallow all of its prey whole, so whatever can fit down its expandable throat is fair game. When a heron catches a fish, it aligns the fish so it’ll go down headfirst—a necessity for fish like Yellow Perch, whose spiny dorsal fin rays could otherwise get lodged in its throat without such a precaution. During the winter, many Great Blue Herons leave their usual wetland haunts for open agricultural fields. Herons are skilled hunters of Gray-tailed Voles and other native rodents that can be abundant in ryegrass or fescue fields. Great Egrets (a close relative), Red-tailed Hawks, American Kestrels, Coyotes and Bobcats will often join in the rodent feast. In the winter, when rivers run high and wetlands overflow, fish are less concentrated and have more opportunities to hide in deeper water. Rodent-hunting in fields of short grasses may be easier for herons and egrets than catching fish this time of year. Neighborhood Naturalist, Winter 2012-13 v10 #3 • page 1 does manage to kill an adult heron, but in most cases it’s after an easier meal. By frightening the heron, the eagle hopes to force the heron into dropping or regurgitating its prey, similar to the way it harasses an Osprey carrying a fish. Herons won’t overlook an easy meal either; John James Audubon claimed to have witnessed piracy by a Great Blue Heron, as it overtook and lunged at an Osprey in flight, then glided down to swallow the Osprey’s dropped fish. Bald Eagles aren’t the only threat to Great Blue Herons. A Cornell Lab of Ornithology webcam observing a heron nest recorded a Great Horned Owl repeatedly attacking the female heron while she incubated. She appeared to be shaken but uninjured, but if there had been unattended heron nestlings there instead, the owl might have gotten a meal. It’s unclear whether owl attacks are common or not. A juvenile Great Blue Heron hunts for voles in a field. Red-tailed Hawks, American Crows, Common Ravens, Great Blue Herons are adaptable birds who can live gulls and raccoons will help themselves to unattended eggs more than twenty years, and they refine their hunting or nestlings. techniques over time. They can learn some remarkable Most nests escape predation, which is due in part to skills, including the use of tools. Like some Green Herons and Black-crowned Night-Herons, individual Great Blue the way Great Blue Herons nest. They prefer to nest in a Herons have been observed to pick up pieces of bread colony, often called a heron rookery or a heronry. In the that people have tossed for ducks. But the heron has no Willamette Valley, many heronries are in tall stands of Black plans to eat the bread. By placing the bread on the water’s Cottonwood along rivers or marshes. However, with the surface and waiting, the heron catches the fish that rise to increasing year-round presence of Bald Eagles in the valley, the bait. Tool use is very uncommon in Great Blue Herons, some herons have taken to using large conifers where their and appears to be learned on an individual basis, so most nests are more concealed. birds never practice bait-fishing. On several occasions, I’ve watched a Bald Eagle chase a terrified, squawking Great Blue Heron. Rarely, an eagle Ne i g h b o r h o o d Na t u r a l i s t promotes interest about nature in mid-Willamette Valley backyards, neighborhoods, and countryside. Subscribe 4 issues per year By mail: $12/year E-mail:free 5008 SW Technology Loop #9 Corvallis, OR 97333 printed on recycled paper 541-753-7689 [email protected] www.neighborhood-naturalist.com ©2013 Don Boucher and Lisa Millbank. Part of a large heronry is visible in a cottonwood grove along the Willamette River. Many nests are reused year after year, with new material added every breeding season. Neighborhood Naturalist, Winter 2012-13 v10 #3 • page 2 Mid-to-late winter marks the onset of breeding season in the Willamette Valley, and it’s the time that Great Blue Herons look their best. Herons begin breeding when they’re about two years old. Males and females are difficult to distinguish, with both sexes sporting long, black ornamental plumes on the head and long, tapering white and gray feathers along the neck and shoulders. Their bills become bright yellow and their lores (area between the eye and bill) turn bluish-green at the height of breeding activity. A typical heronry in a cottonwood grove may contain anywhere from a few to over 100 nests. In February, well before the trees unfurl new leaves, male herons start to arrive at the heronry to claim old nests or suitable sites for new nests. Research has shown that an individual Great Blue Heron may choose to nest in a different heronry from one year to the next. If a heron does return to the same heronry, it may not select the same nest that it used the year before. A male heron attempts to defend a nest site and begin displaying there before females begin to arrive at the heronry. While many birds pair for life, studies indicate that most Great Blue Herons pair up with a new partner each year. To show that he’s single and looking for a mate, a male sits at his nest site and performs a display in which This heron is hunting along the Willamette River in late summer. he extends his neck, points his bill upward and fluffs out After the breeding season is over, the bill turns a dull yellow and his long neck and head plumes. He gives a groaning call gray, and the plumage is gradually molted over a long period of time. while he retracts his neck. A female arriving at a heronry can inspect and choose among multiple displaying males, and she’s likely to favor males near the center of the heronry, where fewer nests are raided by predators. Once she’s made her decision, the pair will engage in more than a dozen different courtship displays to strengthen their bond before they start a family. If they’re using an old nest, the herons will repair and enlarge the nest, but herons often start new nests in the heronry. In either case, the male does most of the stickcollecting. Every time he brings a the stick to the nest site, the two perform a series of displays as he offers the stick to her. She is responsible for almost all nest construction, and once a soft lining of grasses is added, she’ll begin laying 3 to 7 eggs. Eventually, fragrant cottonwood leaves screen the heronry from view, but the sounds of begging chicks and the hoarse croaks of the adults give a hint of the activity happening within. Both parents take turns incubating for about four weeks, and begin feeding their babies regurgitated fish upon hatching. Over the next two months, In mid-winter, a heron has its full breeding plumage and its bill is the parents start leaving whole fish in the nest, and the little herons soon reach adult size. becoming a bright yellow-orange. Neighborhood Naturalist, Winter 2012-13 v10 #3 • page 3 A Great Blue Heron’s wingspan can be more than six feet, and this one is giving a loud squawk as it flies. Herons almost always fly with their necks folded into an S-shape, with their extended legs trailing behind them. Even before they fledge, Great Blue Herons devote a lot of time to caring for their plumage, maintaining its waterproofing and insulating qualities. Hidden under the contour feathers along the sides of a heron’s belly are two tracts of powder down. Powder down feathers are specialized, yellowish down feathers that grow continuously, and are only present in some types of birds. While preening itself, a heron nibbles at the powder down, which crumbles into a fine keratin dust, nearly as fine as talcum powder, although somewhat oily. The heron distributes the powder throughout its plumage, to which it adheres. The function of the powder is not fully understood, but it probably helps the heron clean mud, fish slime and other sticky debris off its plumage. Powder down contributes a soft “bloom” to the color of a Great Blue Heron’s plumage. A Great Blue Heron also has a specialized middle claw, called a feather comb or a pectinated claw. The edge of the claw has a row of tooth-like projections, and is probably important in feather care, but the exact function is unknown. Great Blue Herons are known for the impressive squirt of whitish droppings they void upon taking off. It makes sense for a heron to lighten its load during liftoff, but this habit earned them the humorously descriptive country name of “shite-poke” and a number of even more colorful names I won’t list here. Look for the telltale white splashes along riverbanks and wetland shores. One word of caution: If you ever find a sick or injured Great Blue Heron, avoid handling it and call a wildlife rehabilitator if possible. A frightened heron can inflict serious injuries if it tries to defend itself by striking out with its dagger-like bill, or it can hurt itself while struggling to escape a rescuer. Take the time to watch these stately birds this winter, whether they’re hunting voles or fishing, or better yet, look for an active colony as spring draws nearer. Great Blue Herons are abundant in the Willamette Valley, but they depend on continued protection of water quality, river and wetland habitats, and the surrounding bottomland forests. ó A juvenile Great Blue Heron lacks a white crown and white cheeks and the ornamental head, neck and shoulder plumes of the adults. Youngsters tend to have rusty highlights throughout their plumage. Watch a video of Great Blue Herons at www.neighborhood-naturalist.com Neighborhood Naturalist, Winter 2012-13 v10 #4 • page 4 Western Gray Squirrel article & illustrations by Don Boucher photography by Lisa Millbank I was introduced to the Western Gray Squirrel not long after I moved to the Willamette Valley. I set up bird feeders in the trees behind the apartment. Soon enough, I saw a chunky, cool-gray squirrel stuff herself into the wooden house-style bird feeder to eat sunflower seeds. It was a comical sight, with her head and front paws sticking out of one side, and her big fluffy tail hanging out the other. wherever there are conifers. The Western Gray is common in oak forests or mixed oak and conifer woods. They’re common in urban areas where there are plenty of trees. The habitats of the two species may overlap. Another squirrel that looks a bit similar in size, color and shape is the California Ground Squirrel. There are some easy visual cues that you can learn to help you recognize them (see back page). A ground squirrel has a very different lifestyle, Western Gray Squirrels can hardly go unnoticed, because but it can live in the same areas as a Western Gray. they’re the largest native squirrels in our area. When a twopound Western Gray leaps through the trees, large branches In some urban areas, people encounter additional species, sway noticeably. the introduced Eastern Gray and Eastern Fox Squirrels (see page 7). The Eastern Gray is most common in large cities, Western Grays are fairly quiet. It was about year or so but sparse in small cities like Albany and Corvallis. The after my first sighting that I heard one calling. I was walking Eastern Fox is primarily found in Portland, Salem and through the neighborhood and heard a raspy, cough-like Eugene, especially in nut orchards. But in wilder areas sound I had never heard before. I finally spotted a Western such as forested hills, oak woodlands and oak savannas, Gray with its head poking out of a tree cavity. They can the Western Gray is the only large tree squirrel you’ll see. also make a similar but sharper and higher-pitched sound that serves as an alarm call in the presence of a predator or other impending threat. Watch a video of Western Gray Squirrels at www.neighborhood-naturalist.com Their range is western Washington and Oregon and most of California. Most people in the Willamette Valley regularly see two tree squirrel species. There’s the little Douglas’ Squirrel (see back page), which is common Neighborhood Naturalist, Winter 2012-13 v10 #4 • page 5 a drey from materials at hand when preferred materials are scarce. Sometimes one species will modify an abandoned drey of another species. Western Gray Squirrels begin their courtship in late winter. One or more males chase a female around until she selects the best one for mating. All parenting is done by the female. Young are born between March and June, and the well-grown young usually emerge from their tree cavities in mid-summer. Thereafter, the young squirrels may make dreys to sleep inside, just like adults do. Competition from the Eastern Gray and Eastern Fox Squirrels is a threat to Western Gray Squirrel populations in parts of Washington and California. In western Oregon, wildlife agencies are monitoring the status of the Western Gray closely, but so far, both wild and urban populations are strong. In winter, it’s easy to notice clusters of leaves and twigs in the crowns of leafless trees. Most of these are bird nests, generally flat on top, with a open cup shape. But if you notice a spherical cluster, you’ve probably found a tree squirrel’s drey. Though there is a small entrance hole, it’s usually not visible. Tree squirrels (and flying squirrels) use dreys as sleeping chambers. Despite the drey’s resemblance to a bird’s nest, tree squirrels raise their young in tree cavities. During particularly cold and stormy weather, tree squirrels abandon their dreys and seek shelter in tree cavities. The size and composition of the drey depends on the species and location. Western Grays, Eastern Grays and Eastern Fox Squirrels typically use a lot of leaves. Douglas’ Squirrels use more twigs and conifer needles and Northern Flying Squirrels use a lot of shredded bark. A naturalist may guess the species just by looking at the drey, but it’s not possible to be certain until the inhabitant is spotted. A squirrel may belie the trend of its species and construct Above: A midden of acorn shells on a stump. Right: A Western Gray Squirrel has been eating these russula mushrooms. Western Grays eat and cache a lot of acorns, and you may find a pile of acorn shells, called a midden, wherever they live. They may live in areas with only a few oaks present, as long as other food is plentiful or, at least, competition for a few acorns is low. Western Grays who live around conifers happily include conifer seeds in their diet. Also, they’ll take nuts and fruit from any wild or domestic tree. Like other tree squirrels, mushrooms and truffles are a significant part of their diet. They’ll eat insects, and may occasionally raid bird nests. Of course, peanuts and corn from backyards are always appreciated. Forget about the backyard battle over bird feeders and marauding squirrels. Isn’t it more fruitful to enjoy their antics by providing feeders dedicated to squirrels? Consider yourself lucky to have Western Gray Squirrels as residents in your domain. For those who don’t A typical Western Gray Squirrel’s drey is about two feet in diameter. get to see them daily outside their window, all you have to The main structure is sticks with progressively smaller material do is travel to the nearest park or to the hills at the edge inward and a soft lining on the inside cavity. The gaps are stuffed of town. ó with dry leaves. Neighborhood Naturalist, Winter 2012-13 v10 #4 • page 6 Western Gray Squirrel Sciurus griseus Native Head and body are largely a uniform, cool-gray color. The thick, large tail is uniformly fluffy and tidy with white-tipped hairs. Tall ears White underside Dark gray feet Dark marginon flank Eastern Fox Squirrel Sciurus niger Introduced to urban areas Ears set low on the head Similar in size to the Western Gray, but some individuals are slightly larger. It has a gray back and crown with extensive buff or rusty-orange coloring on the ears and face. It has a long, somewhat flat, two-toned tail with a rusty-orange underside and buff-tipped hairs on top. Populations in its native range have other color patterns, but this is the variety you’ll see in our area. Buff or rustyorange underside Buff or rusty-orange feet Eastern Gray Squirrel Sciurus carolinensis Introduced to urban areas Small, but larger than the Douglas’ Squirrel. It’s mostly gray with brownish colors on the head and side. The tail is shaggy and mottled. White underside Pale gray feet Neighborhood Naturalist, Winter 2012-13 v10 #4 • page 7 Other Native Squirrels California Ground Squirrel Townsend’s Chipmunk Douglas’ Squirrel While our Townsend’s Chipmunks look distinctive, they are close relatives of the ground squirrels. All ground squirrels and chipmunks can climb in shrubs and trees, but they can’t take flying leaps between branches or climb down vertical tree trunks like tree squirrels do. They scamper and run while traveling on the ground. They have cheek pouches for carrying food, and use burrows for shelter. California Ground Squirrels hibernate and sometimes estivate (similar to hibernation) during hot and dry weather, and Townsend’s Chipmunks hibernate in colder climates. The Douglas’ Squirrel is closely related to the other tree squirrels on page 7. It’s quite small, with a black nose patch and orange underside. Tree squirrels either bound or walk slowly across the ground. They use dreys and tree cavities. Tree squirrels lack cheek pouches, so they carry food with their teeth. Tree squirrels remain active all year long. In this issue: Western Gray Squirrel Great Blue Heron Neighborhood Naturalist 5008 Technology Loop #9 Corvallis, OR 97333 photos by Lisa Millbank The California Ground Squirrel looks somewhat similar to the gray tree squirrels on page 7, but it has pale spots on its back, a silver shoulder patch and a tail that’s not quite as bushy as tree squirrels’ tails. EVENTS Naturalist Adventures Third Sunday of the Month, 9am-Noon Jan 20 Jackson-Frazier Wetland: Meet at the north end of NE Lancaster St., Corvallis Feb 17 Sunset & Starker Parks: Meet at the paved parking area at Sunset Park: 1650 SW 45th St., Corvallis March 17 Finley NWR, carpool from Corvallis: Meet at Avery Park Rose Garden Parking Area: 1310 SW Avery Park Dr, Corvallis April 21 Peavy Arboretum: Meet at the Woodland Trail Parking Area : 8392 NW Peavy Arboretum Rd., Corvallis Come learn or share your knowledge about nature in the Willamette Valley. We look at birds, flowers, animal tracks and all kinds of other things. Our nature walks are slow-paced and casually structured. Bring along a hat, rain gear and shoes that can get muddy. Please, no dogs. Activities are geared toward adults but children may enjoy them too. Rain or cold will not prevent us from going out and enjoying nature. Remember to dress for the rainy and/or cold weather. May be canceled without notice if road conditions are dangerous. For other events or more information: www.neighborhood-naturalist.com Don Boucher, 541-753-7689, [email protected] Consider a Gift Subscription 4 issues a year • seasonal 8-page • full color Printed copy (by mail)—$12 per year E-mail subscriptions are free e-mail them this link www.neighborhood-naturalist.com make checks payable to: Don Boucher Your name q check here if you’d like to remain anonymous name of subscriber (recipient) address address line 2 citystate zip phone (optional) E-mail pay securely and quickly online with PayPal www.neighborhood-naturalist.com make checks payable to: Don Boucher 5008 SW Technology Loop, Apt. 9 Corvallis, OR 97333