Early May Migration

National Weather Service radar showed a sizeable nocturnal flight of migrating birds early this morning.  Let’s go for a short stroll and see what’s around.

Radar returns from State College, Pennsylvania, display several bands of light rain and a massive flight of migrating birds.  (NOAA/National Weather Service image)
Birds of Conewago Falls in the Lower Susquehanna River Watershed: Gray Catbird
After coming in on an overnight flight, Gray Catbirds were numerous at dawn this morning.
Birds of Conewago Falls in the Lower Susquehanna River Watershed: Black-and-white Warbler
Masses of Neotropical migrants are just beginning to arrive.  This Black-and-white Warbler was found feeding on insects in a Green Ash tree that, so far, has survived Emerald Ash Borer (Agrilus planipennis) infestation.
Birds of Conewago Falls in the Lower Susquehanna River Watershed: Veery
The Veery is a Neotropical thrush that nests in understory vegetation on forested slopes in the Lower Susquehanna River Watershed.
Birds of Conewago Falls in the Lower Susquehanna River Watershed: Orchard Oriole
Orchard Orioles are here.
Birds of Conewago Falls in the Lower Susquehanna River Watershed: Baltimore Oriole
And Baltimore Orioles are here too.  Vibrant colors like these are what many observers find so wonderful about many of the Neotropical species.
Birds of Conewago Falls in the Lower Susquehanna River Watershed: Double-crested Cormorants
Not all migrants move at night.  While you’re out and about, keep an eye on the sky for diurnal fliers like these migrating Double-crested Cormorants, seen this morning a full ten miles east of the river.
Birds of Conewago Falls in the Lower Susquehanna River Watershed: Carolina Wren
While many birds are still working their way north to their breeding grounds, resident species like this Carolina Wren are already feeding young.  This one has collected a spider for its nestlings.

Photo of the Day

Birds of Conewago Falls in the Lower Susquehanna River Watershed: Winter Wren
Winter Wrens will soon be gone for the year.  For now, they can still be found creeping around like a tiny mouse among fallen timber in moist forests and in dense thickets of brush.  To sustain themselves through the coldest months of the year, they pick invertebrates from among the wood and bark along the undersides of decaying logs, where the process of decomposition creates enough warmth to keep their prey alive in all but the most severe of weather conditions.  Along the Susquehanna near Conewago Falls, look for them among the stonework of the abandoned Pennsylvania Canal.  Listen too for their uniquely mystic song, a long jumble of fluted and chattering notes that softly floats through quiet woodlands, sometimes raising the question: Is that a bird?

Five Best Values for Feeding Birds

Despite being located in an urbanized downtown setting, blustery weather in recent days has inspired a wonderful variety of small birds to visit the garden here at the susquehannawildlife.net headquarters to feed and refresh.  For those among you who may enjoy an opportunity to see an interesting variety of native birds living around your place, we’ve assembled a list of our five favorite foods for wild birds.

American Goldfinches in drab winter (basic) plumage visit the trickle of water entering the headquarters pond to bathe and drink.  In addition to offering the foods animals need to survive, a source of clean water is an excellent way to attract wildlife to your property.

The selections on our list are foods that provide supplemental nutrition and/or energy for indigenous species, mostly songbirds, without sustaining your neighborhood’s non-native European Starlings and House Sparrows, mooching Eastern Gray Squirrels, or flock of ecologically destructive hand-fed waterfowl.  We’ve included foods that aren’t necessarily the cheapest but are instead those that are the best value when offered properly.

Bread, “bargain” seed mixes, and cracked corn can attract and sustain large numbers of House Sparrows and European Starlings.  Both are non-native species that compete mercilessly with indigenous birds including bluebirds for food and nesting sites.  Though found favorable for feeding Northern Cardinals without attracting squirrels, the expensive safflower seed seen here is another favorite of these aggressive House Sparrows.  Ever wasteful, they “shovel” seed out of feeders while searching for the prime morsels from which they can easily remove the hulls.  Trying not to feed them is an ongoing challenge, so we don’t offer these aforementioned foods to our avian guests.

Number 5

Raw Beef Suet

In addition to rendered beef suet, manufactured suet cakes usually contain seeds, cracked corn, peanuts, and other ingredients that attract European Starlings, House Sparrows, and squirrels to the feeder, often excluding woodpeckers and other native species from the fare.  Instead, we provide raw beef suet.

Because it is unrendered and can turn rancid, raw beef suet is strictly a food to be offered in cold weather.   It is a favorite of woodpeckers, nuthatches, and many other species.  Ask for it at your local meat counter, where it is generally inexpensive.

Raw beef suet is fat removed from areas surrounding the kidneys on a beef steer.  To avoid spoiling, offer it only in the winter months, particularly if birds are slow to consume the amount placed for them.  If temperatures are above freezing, it’s important to replace uneaten food frequently.  The piece seen here on the left was stored in the freezer for almost a year while the rancid piece to the right was stored in a refrigerator at about 40 degrees Fahrenheit for just two months.  You can render raw beef suet and make your own cakes by melting it down and pouring it into a form such as cupcake tin.  But do it outdoors or you’ll be living alone for a while.
A female Downy Woodpecker feeds on raw beef suet stuffed into holes drilled into a vertically hanging log.  Because they can’t be cleaned, log feeders should be discarded after one season.  Wire cage feeders though, can usually be scrubbed, disinfected, dried, and reused.
Pesky European Starlings might visit a raw beef suet feeder but won’t usually linger unless other foods to their liking are available nearby.
This male Downy Woodpecker has no trouble feeding on raw beef suet packed into holes drilled into the underside of this horizontally hanging log.  Starlings don’t particularly care to feed this way.
Unusual visitors like a Brown Creeper are more likely to stop by at a suet feeder when it isn’t crowded by raucous starlings, House Sparrows, and squirrels.   This one surprised us just this morning.
Below the feeders, scraps of suet that fall to the ground are readily picked up, usually by ground-feeding birds.  In this instance, a male Eastern Bluebird saw a chunk break loose and pounced on it with haste.

Number 4

Niger (“Thistle”) Seed

Niger seed, also known as nyjer or nyger, is derived from the sunflower-like plant Guizotia abyssinica, a native of Ethiopia.  By the pound, niger seed is usually the most expensive of the bird seeds regularly sold in retail outlets.  Nevertheless, it is a good value when offered in a tube or wire mesh feeder that prevents House Sparrows and other species from quickly “shoveling” it to the ground.  European starlings and squirrels don’t bother with niger seed at all.

Niger seed must be kept dry.  Mold will quickly make niger seed inedible if it gets wet, so avoid using “thistle socks” as feeders.  A dome or other protective covering above a tube or wire mesh feeder reduces the frequency with which feeders must be cleaned and moist seed discarded.  Remember, keep it fresh and keep it dry!

Niger (“thistle”) seed is very small, so it is offered in specialized feeders to prevent seed from spilling out of oversize holes as waste.
An American Goldfinch in winter plumage feeding on niger seed from a wire mesh feeder.  By April, goldfinches are molting into spectacular breeding feathers.  Niger seed can be offered year-round to keep them visiting your garden while they are at maximum magnificence.
American Goldfinches in August.  This tube feeder is designed specifically for goldfinches, birds that have no difficulty hanging upside down to grab niger seed from small feeding ports.
During invasion years, visiting Pine Siskins favor niger seed at feeding stations.
Like goldfinches, Pine Siskins are quite comfortable feeding upside down on specialized tubes with perches positioned above the seed ports.  Seeds dropped to the ground are readily picked up by ground-feeding birds including Mourning Doves and Dark-eyed Juncos.  Periodically, uneaten niger seed should be swept up and discarded.

Number 3

Striped Sunflower Seed

Striped sunflower seed, also known as grey-striped sunflower seed, is harvested from a cultivar of the Common Sunflower (Helianthus annuus), the same tall garden plant with a massive bloom that you grew as a kid.  The Common Sunflower is indigenous to areas west of the Mississippi River and its seeds are readily eaten by many native species of birds including jays, finches, and grosbeaks.  The husks are harder to crack than those of black oil sunflower seed, so House Sparrows consume less, particularly when it is offered in a feeder that prevents “shoveling”.   For obvious reasons, a squirrel-proof or squirrel-resistant feeder should be used for striped sunflower seed.

Striped sunflower seed.
A male House Finch and a Carolina Chickadee pluck striped sunflower seeds from a squirrel-resistant powder-coated metal-mesh tube feeder.
An American Goldfinch in winter plumage finds striped sunflower seeds irresistible, even with niger seed being offered in an adjacent feeder.
A Tufted Titmouse visits a feeder stocked with striped sunflower seeds.
Northern Cardinals readily feed on striped sunflower seeds, especially those that fall from our metal-mesh tube feeders.
An Eastern Gray Squirrel (Sciurus carolinensis) has no choice but to be satisfied with striped sunflower seeds that spill from our wire-mesh tube feeders.

Number 2

Mealworms

Mealworms are the commercially produced larvae of the beetle Tenebrio molitor.  Dried or live mealworms are a marvelous supplement to the diets of numerous birds that might not otherwise visit your garden.  Woodpeckers, titmice, wrens, mockingbirds, warblers, and bluebirds are among the species savoring protein-rich mealworms.  The trick is to offer them without European Starlings noticing or having access to them because European Starlings you see, go crazy over a meal of mealworms.

Dried mealworms can be offered in a cup or on a tray feeder.  Live mealworms need to be contained in a steep-sided dish, so they don’t crawl away.  Unless you’re really lucky, you’ll probably have to place your serving vessel of mealworms inside some type of enclosure to exclude European Starlings.
A male Eastern Bluebird tossing and grabbing a dried mealworm.
A female Eastern Bluebird with a dried mealworm.
A pair of Eastern Bluebirds.  The value of mealworms is self-evident: you get to have bluebirds around.

 

To foil European Starlings, we assembled this homemade mealworm feeder from miscellaneous parts. The bluebirds took right to it.
It frustrates the starlings enough to discourage them from sticking around for long.
If you’re offering dried mealworms, a source of clean water must be available nearby so that the bluebirds and other guests at your feeder don’t become dehydrated.

Number 1

Food-producing Native Shrubs and Trees

The best value for feeding birds and other wildlife in your garden is to plant food-producing native plants, particularly shrubs and trees.  After an initial investment, they can provide food, cover, and roosting sites year after year.  In addition, you’ll have a more complete food chain on a property populated by native plants and all the associated life forms they support (insects, spiders, etc.).

In your garden, a Northern Mockingbird may defend a food supply like these Common Winterberry fruits as its sole means of sustenance for an entire winter season.  Having an abundance of plantings assures that in your cache there’s plenty to eat for this and other species.
The American Goldfinches currently spending the winter at our headquarters are visiting the feeders for niger and striped sunflower seeds, but the bulk of their diet consists of tiny seeds from the cones on our Eastern Hemlock trees.  At night, birds obtain shelter from the weather by roosting in this clump of evergreens.
While the Eastern Bluebirds visiting the susquehannawildlife.net headquarters are fond of mealworms, the bulk of their diet here consists of these Common Winterberry fruits and the berries on our American Holly trees.
Cedar Waxwings are readily attracted to red berries including Common Winterberry fruit.
Migrating American Robins visit the headquarters garden in late winter each year to devour berries before continuing their journey to the north.

Your local County Conservation District is having its annual spring tree sale soon.  They have a wide selection to choose from each year and the plants are inexpensive.  They offer everything from evergreens and oaks to grasses and flowers.  You can afford to scrap the lawn and revegetate your whole property at these prices—no kidding, we did it.  You need to preorder for pickup in the spring.  To order, check their websites now or give them a call.  These food-producing native shrubs and trees are by far the best bird feeding value that you’re likely to find, so don’t let this year’s sales pass you by!

A Visit to Waggoner’s Gap

Nothing beats spending a day at a hawk watch lookout—except of course spending a day at a hawk watch lookout when the birds are parading through nonstop for hours on end.

Check out Waggoner’s Gap, a hawk count site located on the border of Cumberland and Perry Counties atop Blue Mountain just north of Carlisle, Pennsylvania.  It is by far the Lower Susquehanna River Watershed’s best location for observing large numbers of migrating raptors during the October and November flights.

Waggoner’s Gap is located where Route 74 crosses Blue Mountain north of Carlisle.
The entrance to a parking area for hawk watch visitors is designated by this sign located along Route 74 several hundred yards north of the summit of Blue Mountain.
Since acquiring the site in 2000, Audubon Pennsylvania has added improvements to expand the function of Waggoner’s Gap Hawk Watch to include education for both formal students and the public at large.
The site is named in honor of the late conservationist Clifford L. Jones, a business leader, a former Chairman of the Pennsylvania Public Utilities Commission, a cabinet secretary for six Pennsylvania governors (both major parties), a director on the boards of numerous conservation organizations, and an active birder.
Orange falcon silhouettes function as blazes for the trails that lead from the parking area to the lookout.  The trail and the lookout consist entirely of boulders.  Some of these move when stepped upon.  Others may be slick.  Use caution at all times.
The lookout at Waggoner’s Gap is staffed by official counters from August through December each year.  They are tasked with enumerating every migratory raptor’s passage during that period.
Sure-footed observers climb into a comfortable position among the Tuscarora quartzite boulders and begin watching the flight.
The view from the lookout is spectacular.  To the east, downtown Harrisburg can be seen in the distance.
During a recent afternoon with breezes from the “southwesterlies”, a steady stream of  migrating Sharp-shinned Hawks, including this juvenile, passed by the lookout.
Sharp-shinned Hawks were ready subjects for photography as they sailed on updrafts along the south side of the ridge.
An adult Sharp-shinned Hawk.
A second-year Sharp-shinned Hawk.
A Sharp-shinned Hawk below eye level.  Over 400 Sharp-shinned Hawks migrated past Waggoner’s Gap Hawk Watch on this particular early October day.
The local Turkey Vultures at Waggoner’s Gap seem ubiquitous at times.  They’re on the radio towers, they’re flying overhead, and a few are cruising the slopes below the crest.  But on the day of our recent visit, their numbers were eclipsed by the more than 300 “T.V.s” that migrated down the ridge.
Black Vultures, both migrants and local birds, are seen from the lookout.
Northern Harriers are a hawk watch favorite.  Their long uptilted wings, long tail, and white rump make them easy to identify, even for beginners.  Their plummeting numbers make them a treasured sighting for everyone.
A Red-tailed Hawk on a close approach.
A distant Red-shouldered Hawk.  Numbers of these migrants peak later in the season.
A Peregrine Falcon darts past the lookout.  Note the white forehead, throat, and breast.  This bird is probably a “Tundra Peregrine” (Falco peregrinus tundrius).  In the lower Susquehanna valley, this subspecies is strictly migratory, a transient in spring and fall.  “Tundra Peregrines” breed in the arctic and winter as far south as South America.
An immature Bald Eagle.  Waggoner’s Gap is a superb place for sighting eagles, especially on a breezy day.
Hundreds of Blue Jays filtered through as their southbound exodus continues.  Other songbirds of interest included Blue-headed Vireos (Vireo solitarius), Winter Wrens, Red-breasted Nuthatches, Pine Siskins, and both Ruby-crowned and Golden-crowned Kinglets.

Waggoner’s Gap is a hardy birder’s paradise.  During the latter portion of the season, excellent flights often occur on days that follow the passage of a cold front and have strong northwest winds.  But be prepared, it can be brutal on those rocks during a gusty late-October or early-November day after the leaves fall—so dress appropriately.

To see the daily totals for the raptor count at Waggoner’s Gap Hawk Watch and other hawk watches in North America, and to learn more about each site, be sure to visit hawkcount.org

Loading Up For Winter

A very light fog lifted quickly at sunrise.  Afterward, there was a minor movement of migrants: forty-nine Ring-billed Gulls, a few Herring Gulls, a Red-shouldered Hawk following the river to the southeast, and small flocks totaling nine Cedar Waxwings and twenty-eight Red-winged Blackbirds.

A Belted Kingfisher in the morning fog.
A Ring-billed Gull calls as active migrants pass overhead on their way downriver.
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In the Riparian Woodland, small mixed flocks of winter resident and year-round resident birds were actively feeding.  They must build and maintain a layer of body fat to survive blustery cold nights and the possible lack of access to food during snowstorms.  There’s no time to waste; nasty weather could bring fatal hardship to these birds soon.

A Carolina Chickadee (Poecile carolinensis) feeds on the seeds of an Eastern Sycamore (Platanus occidentalis), also known as American Sycamore.  Chickadees are generalist feeders, eating invertebrates and suet at feeding stations in addition to the seeds of many plants.  Carolina Chickadees are year-round residents at Conewago Falls.
A fast-moving Golden-crowned Kinglet zips from limb to limb to grab tiny insects and other invertebrates.  During the winter, these petite birds will carefully probe the bark and crevices of trees to glean enough food to survive.  Golden-crowned Kinglets are winter residents at Conewago Falls.  In spring, they will depart to nest in coniferous forests.
A Downy Woodpecker (Picoides pubescens) searches an infected tree for insects.  They are year-round residents.
Carolina Wrens (Thryothorus ludovicianus) are considered year-round residents at Conewago Falls, though they may withdraw to the south during severe winters.  Carolina Wrens sing year-round.  Today, their loud melody echoed through the Riparian Woodland all morning.
The tiny bob-tailed Winter Wren is an elusive ground-dwelling winter resident at the falls.  You may hear their scolding chatter from rocky areas and tree logs where they climb around mouse-like in search of small invertebrates.  Their song is a fast jumble of dainty musical trills that can sometimes be heard echoing through the Riparian Woodland in winter.  In spring, they’ll depart to nest in damp coniferous forests.

Anthropoavians

Temperatures plummeted to well below freezing during the past two nights, but there was little sign of it in Conewago Falls this morning.  The fast current in the rapids and swirling waters in flooded Pothole Rocks did not freeze.  Ice coated the standing water in potholes only in those rocks lacking a favorable orientation to the sun for collecting solar heat during the day to conduct into the water during the cold nights.

On the shoreline, the cold snap has left its mark.  Ice covers the still waters of the wetlands.  Frost on exposed vegetation lasted until nearly noontime in shady areas.  Insect activity is now grounded and out of sight.  The leaves of the trees tumble and fall to cover the evidence of a lively summer.

The nocturnal bird flight is narrowing down to just a few species.  White-throated Sparrows, a Swamp Sparrow (Melospiza georgiana), and Song Sparrows are still on the move.  Though their numbers are not included in the migration count, hundreds of the latter are along the shoreline and in edge habitat around the falls right now.  Song Sparrows are present year-round, migrate at night, and are not seen far from cover in daylight, so migratory movements are difficult to detect.  It is certain that many, if not all of the Song Sparrows here today have migrated and arrived here recently.  The breeding population from spring and summer has probably moved further south.  And many of the birds here now may remain for the winter.  Defining the moment of this dynamic, yet discrete, population change and logging it in a count would certainly require different methods.

Song Sparrows are now abundant in the brushy edges of fields and woodlands.  They may even break into song on sunny days.

Diurnal migration was foiled today by winds from southerly directions and moderating temperatures.  The only highlight was an American Robin flight that extended into the morning for a couple of hours after daybreak and totaled over 800 birds.  This flight was peppered with an occasional flock of blackbirds.  Then too, there were the villains.

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They’re dastardly, devious, selfish, opportunistic, and abundant.  Today, they were the most numerous diurnal migrant.  Their numbers made this one of the biggest migration days of the season, but they are not recorded on the count sheet.  It’s no landmark day.  They excite no one.  For the most part, they are not recognized as migrants because of their nearly complete occupation of North America south of the taiga.  If people build on it or alter it, these birds will be there.  They’re everywhere people are.  If the rotten attributes of man were wrapped up into one bird, an “anthropoavian”, this would be it.

Meet the European Starling (Sturnus vulgaris).  Introduced into North America in 1890, the species has spread across the entire continent.  It nests in cavities in buildings and in trees.  Starlings are aggressive, particularly when nesting, and have had detrimental impacts on the populations of native cavity nesting birds, particularly Red-headed Woodpeckers, Purple Martins (Progne subis), and Eastern Bluebirds.  They commonly terrorize these and other native species to evict them from their nest sites.  European Starlings are one of the earlier of the scores of introduced plants and animals we have come to call invasive species.

Noisy flocks of European Starlings are right at home on man-made structures in city and country.

Today, thousands of European Starlings were on the move, working their way down the river shoreline and raiding berries from the vines and trees of the Riparian Woodlands.  My estimate is between three and five thousand migrated through during the morning.  But don’t worry, thousands more will be around for the winter.

European Starlings mob a Sharp-shinned Hawk from above, a common behavior.
An Eastern Bluebird feeds on the few berries left untouched by passing European Starlings.

Feathered Fallout

The NOAA National Weather Service radar images from last evening provided an indication that there may be a good fallout of birds at daybreak in the lower Susquehanna valley.  The moon was bright, nearly full, and there was a gentle breeze from the north to move the nocturnal migrants along.  The conditions were ideal.

Rising from daytime roosts in New York and Pennsylvania, then streaming south in moonlit skies, migrating birds are recorded as echoes on this post-sunset composite NEXRAD loop from last evening.  (NOAA/National Weather Service image)

The Riparian Woodlands at Conewago Falls were alive with migrants this morning.  American Robins and White-throated Sparrows were joined by new arrivals for the season: Brown Creeper (Certhia americana), Ruby-crowned Kinglets (Regulus calendula), Golden-crowned Kinglets (Regulus satrapa), Dark-eyed Junco (Junco hyemalis), and Yellow-rumped Warbler (Setophaga coronata).  These are the perching birds one would expect to have comprised the overnight flight.  While the individuals that will remain may not yet be among them, these are the species we will see wintering in the Mid-Atlantic states.  No trip to the tropics for these hardy passerines.

American Robins continued migratory flight into the first hour of daylight this morning.  Their calls are commonly heard at night as migrating individuals pass overhead.
White-throated Sparrows are nocturnal migrants, and are a familiar find on woodland edges and at suburban feeding stations through the winter.
Dark-eyed Juncos, also nocturnal migrants, are common winter residents in the Lower Susquehanna River Watershed, frequently visiting bird feeders.
Heavy rain earlier this week in the Susquehanna River drainage basin has flooded most of the Pothole Rocks; the rapids of Conewago Falls have returned.
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A Quick Getaway

It was a placid morning on Conewago Falls with blue skies dotted every now and then by a small flock of migrating robins or blackbirds.  The jumbled notes of a singing Winter Wren (Troglodytes hiemalis) in the Riparian Woodland softly mixed with the sounds of water spilling over the dam.  The season’s first Wood Ducks (Aix sponsa), Blue-winged Teal (Spatula discors), Herring Gull (Larus argentatus), Horned Larks (Eremophila alpestris), and White-throated Sparrows (Zonotrichia albicollis) were seen.

There was a small ruckus when one of the adult Bald Eagles from a local pair spotted an Osprey passing through carrying a fish.  This eagle’s effort to steal the Osprey’s catch was soon interrupted when an adult eagle from a second pair that has been lingering in the area joined the pursuit.  Two eagles are certainly better than one when it’s time to hustle a skinny little Osprey, don’t you think?

But you see, this just won’t do.  It’s a breach of eagle etiquette, don’t you know?  Soon both pairs of adult eagles were engaged in a noisy dogfight.  It was fussing and cackling and the four eagles going in every direction overhead.  Things calmed down after about five minutes, then a staring match commenced on the crest of the dam with the two pairs of eagles, the “home team” and the “visiting team”, perched about 100 feet from each other.  Soon the pair which seems to be visiting gave up and moved out of the falls for the remainder of the day.  The Osprey, in the meantime, was able to slip away.

In recent weeks, the “home team” pair of Bald Eagles, seen regularly defending territory at Conewago Falls, has been hanging sticks and branched tree limbs on the cross members of the power line tower where they often perch.  They seem only to collect and display these would-be nest materials when the “visiting team” pair is perched in the nearby tower just several hundred yards away…an attempt to intimidate by homesteading.  It appears that with winter and breeding time approaching, territorial behavior is on the increase.

The second migrating Osprey of the day ran the gauntlet of marauding eagles without incident.

In the afternoon, a fresh breeze from the south sent ripples across the waters among the Pothole Rocks.  The updraft on the south face of the diabase ridge on the east shore was like a highway for some migrating hawks, falcons, and vultures.  Black Vultures (Coragyps atratus) and Turkey Vultures streamed off to the south headlong into the wind after leaving the ridge and crossing the river.  A male and female Northern Harrier (Circus hudsonius), ten Red-tailed Hawks, two Red-shouldered Hawks (Buteo lineatus), six Sharp-shinned Hawks, and two Merlins crossed the river and continued along the diabase ridge on the west shore, accessing a strong updraft along its slope to propel their journey further to the southwest.  Four high-flying Bald Eagles migrated through, each following the east river shore downstream and making little use of the ridge except to gain a little altitude while passing by.

(Top and Middle) Turkey Vultures riding the fresh breeze and teetering to-and-fro on up-tilted wings.  This wing posture is known as a dihedral.  (Bottom) More than 100 migrating Black Vultures climbed high on the afternoon breeze to make an oblique crossing of the river and maintain a southbound course.

Late in the afternoon, the local Bald Eagles were again airborne and cackling up a storm.  This time they intercepted an eagle coming down the ridge toward the river and immediately forced the bird to climb if it intended to pass.  It turned out to be the best sighting of the day, and these “home team” eagles found it first.  It was a Golden Eagle (Aquila chrysaetos) in crisp juvenile plumage.  On its first southward voyage, it seemed to linger after climbing high enough for the Bald Eagles to loose concern, then finally selected the ridge route and crossed the river to head off to the southwest.

Ring-billed Gulls began feeding during the afternoon as clouds preceding stormy weather approached.
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Birds of a Feather-The Basics

When we look at birds, we are fascinated by the unique structure and appearance of their feathers.  They set birds apart from all other life forms on the planet.  Feathers enable most birds to achieve a feat long envied by humans…flight.  Birds on the wing awaken a curiosity in man.  They are generally the largest animals one will see in the air.  People want to know the name of a bird they see flying by, and want to know more about it.  The method and style of bird flight can aid an observer who attempts to determine which of the world’s 10,000 bird species he or she is studying.  Body shape and bird sounds often tell us a lot about the birds we encounter.  But most often, we rely on the unique colors, patterns, and shapes of the feathers, the plumage, to identify the bird we are seeing.

To birds, feathers are survival.  They are lightweight and strong to support the mechanics of flight.  Feathers are superb insulators against the elements, and provide additional buoyancy for birds spending time on the water.  For most birds, feathers provide a coloration and a texture similar to their surroundings, enabling them to hide from predators or to stalk prey.  In the case of some species, extravagant showy plumage is acquired, at least during the breeding season, and often only by males, as a way to attract a mate, intimidate rivals, defend a territory, or lure an intruder away from a nest site.  Because they become worn and damaged, all feathers are periodically molted and replaced by fresh plumage.

The feathers worn by a young bird leaving the nest are called the juvenile plumage.  Typically, this is followed by a molt into a basic (non-breeding) plumage.  The oft times extravagant breeding feathers are the result of a molt into an alternate (breeding) plumage.

While making field observations, the species, subspecies, gender, age, and other vital statistics of a bird can often by discerned easily by noting the plumage.  In the case of some other birds, diligence, experience, research, and an exceptionally good look and/or a photograph may be required to interpret these particulars.  In still other instances, a trained expert with a specimen in the hand is the only method of learning the bird’s identity and background.

This juvenile House Wren (Troglodytes aedon) left the nest wearing plumage very similar to that of its parents.  In lieu of bright colors, the male House Wren relies upon a vigorous bubbly song and a scrappy demeanor to defend its breeding territory.  This species nests in cavities on the edges of the Riparian Woodlands of Conewago Falls.  Males may have more than one mate.  House Wrens probably migrate at night and will winter in the southern border states and further south.

The age at which birds acquire adult breeding and non-breeding plumages varies by species.  Many juvenile birds resemble adults in basic (non-breeding) plumage as soon as they leave the nest.  For these birds, there is little difference between their juvenile plumage and the appearance of the feathers which follow the molt into their first basic (non-breeding) plumage.  Bird species which sexually mature within their first year may acquire their first basic (non-breeding) plumage before arrival of their first winter, followed by an alternate (breeding) plumage by their first spring.  This is particularly true for smaller short-lived birds.  Other species, normally larger long-lived ones, may experience a sequence of molts through multiple basic (non-breeding) plumages over a period of years prior to resembling an adult.  Some of these species, such as eagles, retain their juvenile plumage for as long as a year before extensive molting into a first basic (non-breeding) plumage begins.  Still others, including many gulls, attain a first-winter (formative) plumage prior to molting into their first basic (non-breeding) set of feathers.  Sexual maturity and initiation of an annual molt to alternate (breeding) plumage, if there is one, may take as long as three to five years for these bigger birds.

For nearly all species of birds, the molts which produce basic (non-breeding) plumage occur on at least an annual basis and include a total replacement of feathers.  This process renews worn and missing plumes including the flight feathers of the wings and tail.  Any molt to alternate (breeding) plumage often excludes the replacement of the feathers of the wings and tail.  There are many exceptions to these generalities.

A mid-summer nesting species, the American Goldfinch, Spinus tristis, male (left and right) molts into a glamorous alternate plumage for the breeding season.  The adult female’s alternate plumage (top) is a subdued green-yellow and black.  Her feathers resemble the foliage around the nest and offer protection from discovery during incubation.  Juvenile plumage (bottom) is similar to that of the female, but duller with a buffy tone.  By November each of these birds will have molted into a tan-buff basic (non-breeding) plumage, the male’s with a slight yellow hue.  During their first spring, juveniles attain sexual maturity and, like the adults from the previous year, molt into alternate (breeding) plumage.  The breeding birds seen here will probably winter in the southern United States, and birds that nested to our north will arrive to remain as winter residents.  Various stages of molt can be seen simultaneously during spring and autumn migrations as populations of goldfinches from multiple latitudes intermingle as they pass through the Susquehanna River watershed.
This juvenile Spotted Sandpiper (Actitis macularius), lacks the namesake dark markings on its white underside, thus it presently resembles an adult in basic (non-breeding) plumage.  Upon reaching sexual maturity, it will molt into a spotted alternate (breeding) plumage for the nesting season during each remaining year of its life.  Females of this species defend a territory and lay eggs in a nest located among cover near the shoreline.  A female may have as many as five mates.  Males alone incubate the eggs, usually four, for 20-24 days.  The young leave the nest upon hatching and are escorted by the male for about two to three additional weeks.  They are the only sandpiper to nest on the Susquehanna River shoreline.  Spotted Sandpipers migrate to the southern border states and further south for winter.  At Conewago Falls, they arrive in late April to nest, with birds, possibly migrants from further north, remaining until well into October.  In any plumage, you can easily recognize the Spotted Sandpiper by its habit of teetering its body at the hips to pump the tail up and down.
Bald Eagles go through a series of five molts before reaching adult plumage.  The first plumage, Juvenile, is nearly all dark brown with white linings along the forward underside of the wings.  The wing and tail feathers are a bit longer than in later plumages to aid the inexperienced birds during their clumsy first flights.  Due to the additional feather length, Juveniles look larger than older birds, but they are not as heavy as their seniors.  The bird seen here flying above Conewago Falls is probably in its second year.  This plumage, Basic I, also known as “White Belly I”, is characterized by a nearly full set of new flight feathers.  Note that some of the longer Juvenile feathers are still present, giving the wings a jagged sloppy look, particularly near the center of the trailing edge.  Third-year (Basic II) birds often have at least some white belly feathers and are sometimes known as “White Belly II” Bald Eagles.  Basic II birds typically possess a complete set of adult flight feathers, so the trailing edge of the wing has a neater and more uniform appearance.

The Bald Eagle in the two photographs above is in its first year.  This plumage, known as “Juvenile”, is characterized by dark flight feathers which appear uniformly long in length when the bird is airborne.  The eye is dark brown.  The iris of the eye will lighten in the second year (Basic I) and will become cream-colored by the third year (Basic II).  The bill, which is all dark gray when the bird is in the nest, has begun the slow progression to a yellow color that will be complete in the bird’s fifth year (Basic IV).  Third year (Basic II) birds molt to white crown and throat feathers, but have a dark set of feathers through the eye producing an “Osprey face” in most individuals.  In its fourth year (Basic III), this eagle will molt to a white tail with just a thin dark brown terminal band.  The head will become nearly all white except for a few dark spots through the eye, which will have a yellow iris.  A cleaner white head and tail will develop during the fifth year (Basic IV) and will persist through the familiar adult Bald Eagle plumages (Definitive Plumage) for the remainder of its life.

The Juvenile and non-breeding (basic) plumages of late-summer may seem drab and confusing, but learning them is a worthwhile endeavor.  Consider that most of the birds coming south during the migration will be adorned in this fashion.  The birds of North America are in their greatest numerical mass of the year right now, and nearly all are females, juveniles, other non-adults, or molting males.  There are few males in breeding plumage among the autumn waves of migrants.  In the coming months, there will be an abundance of opportunities to enjoy these marvels on wings, so getting to know the birds in non-breeding feathers is time well spent.  Make haste and get ready.  For our feathered friends, it’s autumn and they’re on their way south.

Here come the confusing fall migrants.  Twelve Semipalmated Sandpipers (Calidris pusilla) and sixteen unidentified “peep” sandpipers (Calidris species) were seen feeding in Conewago Falls on August 27.  This Semipalmated Sandpiper is either an adult in worn alternate (breeding) plumage or a Juvenile.  Adults of this species molt into basic plumage on the wintering grounds.  The Semipalmated Sandpiper breeds in the high arctic tundra and winters in the West Indies and northern South America.
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SOURCES

Dunne, Pete.  2006.  Pete Dunne’s Essential Field Guide Companion.  Houghton Mifflin Company.  New York.

Hayman, Peter; John Marchant, and Tony Prater.  1986.  Shorebirds, An Identification Guide to the Waders of the World.  Houghton Mifflin Company.  New York.

Kauman, Kenn.  1996.  Lives of North American Birds.  Houghton Mifflin Company.  New York.

McCullough, Mark A.  1989.  Molting Sequence and Aging Of Bald Eagles.  The Wilson Bulletin.  101:1-10.