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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
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©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]
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