A Natural History of Conewago Falls—The Waters of Three Mile Island
Hawkwatcher’s Helper: Identifying Bald Eagles and other Diurnal Raptors
HAWKWATCHER’S HELPER
A Photographic Identification Guide to the
Diurnal Raptors
of the Lower Susquehanna River Watershed
WHERE TO OBSERVE DIURNAL RAPTORS
One can study diurnal raptors almost anywhere in the Lower Susquehanna River Watershed. Vultures can be seen cruising the skies in search of roadkill and other carrion. Red-tailed Hawks and American Kestrels can be found in rodent-rich grasslands and pastures. As farm acreage decreases, the former has transitioned to suburban life and, in many cases, squirrel consumption. Cooper’s Hawks too, have, in recent years, adapted to life in and around city and town. Ospreys and Peregrine Falcons, lost entirely as a breeding species for much of the twentieth century, again nest at a few locations along the Susquehanna. And then there are the Bald Eagles, which again nest not only along the river, but in upland areas as well, often joining vultures and Red-tailed Hawks as carrion-eaters on agricultural lands, even where high-intensity farming is practiced. Beginning in November each year, a visit to the lower Susquehanna offers an opportunity to examine Bald Eagles, our national emblem, in abundance, particularly at Conowingo Dam where a hundred birds or more often gather during late fall and early winter. But without a doubt, the best time to learn diurnal raptor identification is during the spectacular autumn migrations when their numbers and variety are at their maximum. It is during this time that an observer has the opportunity to compare the familiar species with those that are uncommon or are not likely to be encountered during other times of the year.
Enthusiasts travel hundreds of miles to observe and photograph Bald Eagles at Conowingo Dam (where U.S. Route 1 crosses the Susquehanna River at Rising Sun, MD). Eagles are most numerous from mid-November through early winter. Another concentration in mid-spring may include both non-breeding eagles from the lower Susquehanna/upper Chesapeake region and post-breeding wanderers from nesting areas in southern states, particularly Florida.
To save energy while migrating, many raptors, particularly vultures and Broad-winged Hawks, seek out thermal updrafts (air rising above surfaces heated by the sun) to soar upon and gain altitude before gliding away. Birds using this tactic can be observed from almost any location with an unobstructed view of the sky. A hill or a rooftop situated along the birds’ flightpath will often suffice. If you keep a close eye on the skies of the Lower Susquehanna River Watershed during the month of September, you stand a pretty good chance of seeing at least one “kettle” of Broad-winged Hawks passing by—even from your own home!
Soaring Broad-winged Hawks circle in a thermal updraft to gain altitude on a September day. Solar heating of south-facing hillsides, parking lots, and other surfaces creates the columns of rising air that these birds are so adept at locating during their autumnal flights.After ascending, “Broad-wings” stream away from the top of the warm air column and continue off to the southwest, gliding slowly down to the lower reaches of yet another updraft to repeat the process. Broad-winged Hawks migrating from the northeast make a long trek toward the Houston, Texas, area, then turn due south along the Gulf of Mexico on their way to the tropics for winter.
More often though, migrating raptors seeking to save energy will utilize the updrafts created by winds striking the slopes of the region’s numerous ridges. These northeast-to-southwest-oriented ridge lines deflect skyward the horizontal flow of the northwest winds that often blow during the days that follow the passage of the cold fronts that motivate birds to move south in fall. This linear system of rising air creates a network of highway-like “microflyways” that just happen to facilitate travel in the direction many raptors want to go—southwest. To expedite their journey and expend less energy, opportunistic fliers follow these routes for at least a portion of their trip—entering and exiting at will. On an ideal day, the raptor traffic can be quite heavy along one or more of these “highways”, much to the delight of any observer fortunate enough to be positioned at a lookout atop a ridge in their path.
Eagles migrating in a southwest direction can save energy and travel great distances by gliding and soaring on the updrafts generated as northwest winds strike the slopes of the northeast-to southwest-oriented ridges of the Lower Susquehanna River Watershed.
Each raptor species, being a bird of prey, is at the top of its food chain and, as such, can be a good indicator of the health of the ecosystems supporting the links in that chain. It is therefore beneficial to monitor the population trends of raptors as indicators of environmental health. Hawk counting got its start at Hawk Mountain Sanctuary in 1935 when Maurice Broun began keeping daily records of the migrating raptors seen each autumn. Hawk Mountain’s data helped reveal the declines of the Osprey, Bald Eagle, and Peregrine Falcon during the 1950s and 1960s due, at least in part, to the effects of D.D.T. Today, there are sites all over North America where official hawk counts are conducted. To enumerate the birds migrating along the raptor “highways” of the Lower Susquehanna River Watershed and nearby areas of the Schuylkill River watershed (Hawk Mountain and Blue Mountain Route 183), observers have discovered many advantageous lookouts from which to see moving birds. Eight of the best are plotted on the map which follows, including four where official counts are currently conducted each autumn.
Locations in and near the Lower Susquehanna River Watershed for watching autumn flights of migrating vultures, ospreys, eagles, harriers, hawks, and falcons. (NASA Earth Observatory base image)
Excellent autumn flights, particularly on days with winds from the northwest. Fewer birds but closer looks on southerly winds. Golden Eagles from late October through November.
Good autumn flights with best numbers on southwest winds—possibly due in part to crossovers from Blue Mountain. The access road can be rough, but observers can park right next to the lookout—no hiking.
Second Mountain Hawk Watch offers viewing from alongside the parking area…… but you may need a rugged vehicle to get there.
Excellent autumn flights, particularly on days with winds from the northwest. Museum and interpretive programs offered. Official counters on duty throughout the fall season and sometimes during spring flights. Very crowded during peak autumn weekends. The hike to North Lookout atop Blue Mountain (often called Kittatinny Ridge at Hawk Mountain and at points to the east) is almost a mile. Admission fee.
Good autumn flights, particularly on northwest winds. Many of the birds counted at nearby Hawk Mountain continue following updrafts along Blue Mountain to also pass this location.
PIEDMONT PROVINCE (SITES 6-8)
#6—Governor Dick Fire Tower—Clarence Schock Memorial Park, Mount Gretna, Lebanon County, PA
“Furnace Hills” location just east of the former Cornwall Fire Tower Hawk Watch site. Observations of autumn and spring migrations through the Piedmont highlands can be made from the top of the sixty-six-foot-tall tower or from ground level in the forest clearing that surrounds it.
For those using binoculars, a cage installed on the Governor Dick Fire Tower to prevent rappelling can make scanning the skies for birds a challenge. Choosing a suitable location on the grounds surrounding the tower may offer better observing conditions.A view of the “Furnace Hills” looking east from Governor Dick Fire Tower. From 1975 to 1992, the Lancaster County Bird Club conducted an autumn hawk count at the former Cornwall Fire Tower location where the cluster of antennas can be seen.
#7—Conewago Falls—Susquehanna River at Collins Road, Falmouth, PA
Viewing from amid the “pothole rocks” in the narrow section of river downstream of Three Mile Island. This site is accessible only when the river stage at Harrisburg, PA, is below four feet. During spring and autumn, fair numbers of birds are seen either following the river or the diabase ridge that it intersects here. Nesting Ospreys, Bald Eagles, and Peregrine Falcons in spring and summer. Riverine birds year-round.
The diabase “pothole rocks” at Conewago Falls on the Susquehanna River. Hawkwatchers with a knack for fishing can multitask here.
A site in a powerline right-of-way with a viewing platform and interpretive displays. One of the few locations with good autumn flights on northeast winds.
Rocky Ridge County Park Hawk Watch observation platform. The cluster of masonry structures in the distance are the electrical generating stations at Brunner Island and Three Mile Island.
Further afield, these regional hawk watch sites are worth a visit:
Site overlooking the Susquehanna River valley from along the western edge of the Catskill Mountains. Autumn flights including Golden Eagles from late October through November.
Site atop a beachside World War II-era bunker in Cape Henlopen State Park. Excellent autumn raptor flights—plus sea watching for birds and cetaceans. Falcons from late September into October. Some birds arrive after coming south along the western shore of Delaware Bay; others make landfall after crossing the mouth of the bay from Cape May.
Cape Henlopen Hawk Watch viewing deck on a World War II-era defense bunker.
Site with a viewing platform adjacent to the lighthouse parking area in Cape May Point State Park. World-renowned autumn birding and hawk watching. Northwest winds bring the southbound raptors right down the beach. Falcons from late September into October. Birds of all kinds get stalled and “pile up” around Cape May before attempting to cross Delaware Bay. Something unusual always seems to show up.
Site on Chesapeake Bay near the southern tip of the Delmarva Penninsula. Phenomenal flights of raptors and other migratory birds in autumn. Rarities surprise observers with some regularity.
IN THE BLUE RIDGE MOUNTAINS (SOUTH MOUNTAIN) PROVINCE
Hawk watching from the top of a stone tower. Spring and fall flights.
*Locations staffed by official counters during the fall and/or spring season. Click the hawk watch name to access travel directions, site information, and the latest count data from the Hawk Migration Association of North America’s hawkcount.org website.
TOPOGRAPHY OF A DIURNAL RAPTOR IN FLIGHT
Order-Accipitriformes
(New World Vultures, Ospreys, Eagles, Kites, Harriers, and Hawks)
Family-Cathartidae
(New World Vultures)
BLACK VULTURE (Coragyps atratus)
A Black Vulture. (October)Black Vultures have silvery undersides on their primary feathers. Quick choppy wingbeats and a short tail are clues to help identify this species even at a considerable distance. (November)
BLACK VULTURE (Coragyps atratus) Adult
An adult Black Vulture. Note the yellow tip on the black bill. (November)A Black Vulture undergoing molt of the flight feathers during autumn is an adult bird. (September)
BLACK VULTURE (Coragyps atratus) Hatch-Year (Juvenile)
A hatch-year/juvenile Black Vulture. The all-dark bill is characteristic of a young bird. The white shafts and silvery undersides of the primary feathers are shared traits among all age classes. (September)Adult (left) and hatch-year/juvenile (right) Black Vultures. (November)
TURKEY VULTURE (Cathartes aura)
Soaring and gliding Turkey Vultures of all age classes are easily recognized by their up-tilted wing posture often referred to as a dihedral. As a means of adjusting and maintaining their flight trajectory, “T.V.s” are frequently observed rocking from side to side on outstretched wings.
TURKEY VULTURE (Cathartes aura) Adult
An adult Turkey Vulture is easily recognized by its red head and yellow-tipped bill. (January)An adult Turkey Vulture. Note the silvery underside of the entire set of flight feathers, a field mark shared with all age classes. (November)The angle of the sunlight illuminating the silvery undersides of a Turkey Vulture’s flight feathers can dramatically alter the bird’s appearance. (November)An adult Turkey Vulture. (December)
Hatch-year/juvenile Turkey Vultures have a gray/black head, a black bill, and a full set of fresh juvenile flight feathers. (September)A hatch-year/juvenile Turkey Vulture. Note the neat and clean appearance presented by the absence of molt in the flight feathers. (September)A hatch-year/juvenile Turkey Vulture. (September)
A second-year/immature Turkey Vulture showing traces of red coloration in the head, a paler bill color than a juvenile bird, and replacement of some of the juvenile flight feathers. (October)
Family-Pandionidae
(Osprey)
OSPREY (Pandion haliaetus)
Osprey are easily recognized by their long slim wings and dark carpal (wrist) patches. (August)While flapping, gliding, and soaring, an Osprey’s wings appear to be held up by the wrists, creating an M-shaped flight posture. (October)
OSPREY (Pandion haliaetus) Adult
An after-second-year/adult Osprey undergoing molt. Because first-year/juvenile Osprey retain their first set of flight feathers until well after their first autumn migration, then tend to remain on the wintering grounds and not migrate north during their second year, Osprey seen losing and replacing rectrices and remiges while in the Lower Susquehanna River Watershed are generally regarded as adult birds in at least their third year of life. (August)An after-second year/adult Osprey molting and replacing flight feathers. (September)
OSPREY (Pandion haliaetus) Hatch-Year (Juvenile)
During autumn migration, Osprey with unstreaked white breasts and no evidence of molt in the flight feathers are often hatch-year/juvenile birds. (September)Pale edges on the upperwing coverts indicate this is a hatch-year/juvenile Osprey, but note the presence of light streaking on the breast. (October)Neat and clean with no signs of molt in the flight feathers, a possible hatch-year/juvenile Osprey. (October)
Family-Accipitridae
(Eagles, Kites, Harriers, and Hawks)
BALD EAGLE (Haliaeetus leucocephalus) Adult (Definitive Plumage)
An adult Bald Eagle. (August)An adult Bald Eagle in definitive plumage undergoing an annual molt. (August)An adult Bald Eagle in definitive plumage. (September)An adult Bald Eagle in definitive plumage (top) and a Broad-winged Hawk (bottom). (September)Note the flat board-like flight posture of the wings displayed by these soaring Bald Eagles. (October)An adult Bald Eagle in definitive plumage. (October)An adult Bald Eagle in definitive plumage. (October)When observed as mated pairs, Bald Eagles, like other birds of prey, often reveal noticeable sexual dimorphism, the female (left) being larger than the male (right). (November)
BALD EAGLE (Haliaeetus leucocephalus) Hatch-Year (Juvenile)
A hatch-year/juvenile Bald Eagle. (August)A hatch-year/juvenile Bald Eagle. Note the neat and clean molt-free appearance of the flight feathers, the bright white axillaries (“wing pits”), and the dark belly; all are typical field marks of first-year birds. (September)A hatch-year/juvenile Bald Eagle prominently showing “windows” in the innermost primary flight feathers. At a distance, these markings may create the illusion that the bird is undergoing molt, indicating that the eagle is older than a first-year bird. Primary “windows” have prominent dark borders on older birds, those in their second and third years. (October)The same hatch-year/juvenile Bald Eagle as shown previously. Again, notice the “windows” on the innermost primaries. (October)A hatch-year/juvenile Bald Eagle. During the first three years life, Bald Eagles show extensive areas of white on the underside of their wings, densest on the linings toward the leading edge and in the “wing pits”. (November)Beware! A non-adult Bald Eagle can easily be mistaken for a Golden Eagle. This hatch-year/juvenile Bald Eagle gave the illusion of being a Golden Eagle while gliding by a hawk watch station (left)…until, moments later, it was seen soaring above the lookout (right). Note the extensive areas of white in the wing linings and in the “wing pits”, key field marks for identifying Bald Eagles during their first three years. (November)A hatch-year/juvenile Bald Eagle. (December)
BALD EAGLE (Haliaeetus leucocephalus) Second-Year (Immature Basic I)
A second-year/Basic I immature Bald Eagle in April of its second calendar year, probably about one full year after hatching. The innermost primaries on the right wing have been replaced with dark-bordered translucent feathers, those on the left wing are undergoing molt. This bird is beginning to acquire the white belly and back feathers that are typical of Bald Eagles in their second and third years. (April)A second-year/Basic I immature Bald Eagle. Birds at this age are also known as “White Belly I” Bald Eagles. (August)A second-year/Basic I immature Bald Eagle. Extensive molt of the flight feathers (replacement of long juvenile remiges with shorter primaries and secondaries) gives a bird at this age a messy, ragged appearance. (October)A second-year/Basic I immature Bald Eagle. Note the dark borders surrounding the “windows” on the innermost primaries. (October)A second-year/Basic I immature Bald Eagle (left) and an adult Bald Eagle in definitive plumage (right). (October)A second-year/Basic I immature Golden Eagle (left) and a second-year/Basic I immature Bald Eagle (right). Note how the shorter head projection of the Golden Eagle gives the bird a long-tailed appearance while the head and tail on the Bald Eagle seem equal in length. This is a prime differentiating field mark for the two species in all age classes. (November)A second-year/Basic I immature Bald Eagle. Note the retained juvenile secondaries (the longer flight feathers that give the trailing edge of the wings a jagged appearance). The “windows” on the innermost primaries have more extensive dark borders than those of hatch-year/juvenile Bald Eagles. (November)Two second-year/Basic I immature Bald Eagles. (November)A second-year/Basic I immature Bald Eagle photographed in light reflected by snow cover. (December)
BALD EAGLE (Haliaeetus leucocephalus) Third-Year (Immature Basic II)
A third-year/Basic II immature Bald Eagle. Birds at this age are also known as “White Belly II” or “Osprey Face” Bald Eagles. The bill, particularly the proximal half, begins to acquire more extensive yellow color at this age. Look carefully and you’ll see that this particular bird has retained a longer darker juvenile secondary in each wing. (October)A third-year/Basic II immature Bald Eagle. (November)A third-year/Basic II immature Bald Eagle. Birds at this age begin replacing white feathers in the wing linings, in the “wing pits”, and on the belly with brown plumage. Gradual replacement of the crown and throat feathers with white plumage gives many birds at this age an Osprey-like face pattern. (November)A third-year/Basic II immature Bald Eagle (bottom) with a second-year/Basic I immature Bald Eagle (top). (November)A third-year/Basic II immature Bald Eagle (top) with a second-year/Basic I immature Bald Eagle (bottom). As seen here, birds in both of these age classes typically have white back feathers. (November)Composite image of Bald Eagles as they typically appear during November in each of their first three years.
BALD EAGLE (Haliaeetus leucocephalus) Fourth-Year (Immature Basic III)
A fourth-year/Basic III immature Bald Eagle. A conspicuous dark tail band and white mottling in the wing linings are traits typical of a bird this age. (September)A fourth-year/Basic III immature Bald Eagle (right) and an adult Bald Eagle in definitive plumage (left). This particular fourth-year bird still has a thin dark line through the eye on an otherwise all-white head. Note the dark border surrounding the white tail and the abundance of retained white feathers in the wings and on the belly. (November)A fourth-year/Basic III immature Bald Eagle. The dark line through the eye and the yellow bill are typical of a bird this age. (November)
BALD EAGLE (Haliaeetus leucocephalus) Fifth-Year (“Sub-adult” Basic IV)
NOTE: The term sub-adult, here applied only to a fifth-year eagle, is sometimes applied to birds in their second through fifth years, and on occasion includes first-year/juvenile eagles as well.
A probable fifth-year/Basic IV “sub-adult” Bald Eagle. Note the dark tips on the nearly all-white rectrices (tail feathers) and the white head. Even among the most diligent of observers, the thin tail band will often escape notice on a passing bird. (October)A probable fifth-year/Basic IV “sub-adult” Bald Eagle. Note the retained white body feathers on this particular individual. (October)A probable fifth-year/Basic IV “sub-adult” Bald Eagle. The next to outermost rectrices on this bird have been replaced by all-white feathers. (October)The same fifth-year/Basic IV “sub-adult” Bald Eagle shown in the previous image, seen here being harassed by a Sharp-shinned Hawk. (October)A probable fifth-year/Basic IV “sub-adult” Bald Eagle. The majority of fifth-year Bald Eagles are territorial and sexually mature. (November)A fifth-year/Basic IV “sub-adult” Bald Eagle. In addition to dark tips on some or all of the rectrices, birds at this age may show signs of a dark line through or behind the eye. (November)A closer look at the spread tail of the fifth-year/Basic IV “sub-adult” Bald Eagle shown in the preceding image. Note the trace of dark color on the tips of the outer rectrices and remnants of a wider dark band on the innermost ones, field marks that could easily be overlooked. (November)Three views of the spread tail on a probable fifth-year/Basic IV “sub-adult” Bald Eagle. (December)
BALD EAGLE (Haliaeetus leucocephalus) Sixth-Year (Adult)
A bird that may be exactly five years old, a sixth-year/adult Bald Eagle nearing definitive plumage. Note the retention of at least one black-edged rectrix (tail feather). (March)By autumn of their sixth year, the majority of Bald Eagles are in adult definitive plumage. Traces of dark markings may remain on the otherwise all-white head and tail feathers of birds then and at any age thereafter. (October)
GOLDEN EAGLE (Aquila chrysaetos)
The gilded head plumage of a Golden Eagle is visible in all age classes.
GOLDEN EAGLE (Aquila chrysaetos) After-Third-Year
Click the “Golden Eagle Aging Chart” tab at the top of this page to learn more about the molt sequence of Golden Eagles.
An after-third-year Golden Eagle. (November)An after-third-year Golden Eagle. (November)
GOLDEN EAGLE (Aquila chrysaetos) Third -Year (Immature Basic II)
Click the “Golden Eagle Aging Chart” tab at the top of this page to learn more about the molt sequence of Golden Eagles.
A probable third-year/Basic II immature Golden Eagle. (November)A probable third-year/Basic II immature Golden Eagle. Note the retained juvenile secondaries (the longer flight feathers that create a ragged appearance along the trailing edge of the wings) on this molting bird. (November)
GOLDEN EAGLE (Aquila chrysaetos) Before-Third -Year
Click the “Golden Eagle Aging Chart” tab at the top of this page to learn more about the molt sequence of Golden Eagles.
A before-third-year Golden Eagle. (October)A before-third-year Golden Eagle (left) and a hatch-year/juvenile Bald Eagle (right). Note the Bald Eagle’s proportionately longer head projection when compared to the Golden Eagle. (November)Non-adult Golden Eagles including the before-third-year bird seen here (left) often have conspicuous white bases on the primary and/or secondary flight feathers, while Bald Eagles during their first three years of life (right) have varying amounts of white mottling concentrated mostly in the linings toward the leading edge of the wings. Note too the extensive white mottling on the belly of this third-year/Basic II immature Bald Eagle. (November)A before-third-year Golden Eagle. (November)A before-third-year Golden Eagle. (November)A before-third-year Golden Eagle. (November)
GOLDEN EAGLE (Aquila chrysaetos) Hatch-Year (Juvenile)
A hatch-year/juvenile Golden Eagle. (November)A hatch-year/juvenile Golden Eagle. (November)A hatch-year/juvenile Golden Eagle. (November)
Click the “Golden Eagle Aging Chart” tab at the top of this page to learn more about the molt sequence of Golden Eagles.
SWALLOW-TAILED KITE (Elanoides forficatus)
Swallow-tailed Kites are unmistakable when seen with anything close to favorable viewing conditions. These magnificent raptors nest in a greatly reduced breeding range that presently includes Florida, the Gulf States, and South Carolina. They are very rare late-spring visitors in the Lower Susquehanna River Watershed. This particular bird was found in poor health during the late winter on March 13, 2005, near Octoraro Creek in Lancaster County, Pennsylvania. It subsequently died. (Specimen in the Pennsylvania Game Commission collection at the Middle Creek Wildlife Management Area Visitor’s Center)
MISSISSIPPI KITE (Ictinia mississippiensis)
Mississippi Kites are recognized by their long, pointed wings and graceful flight. (June)
MISSISSIPPI KITE (Ictinia mississippiensis) Adult
An adult Mississippi Kite “feeding on the wing”. Dragonflies and other large flying insects are a favorite food. (May) (Vintage 35 mm image)
Second-year/immature Mississippi Kites. (June)A second-year/immature Mississippi Kite. A banded tail and gray underparts are typical of this age class. (June)A second-year/immature Mississippi Kite in the early stages of juvenile flight feather replacement showing loss of a tail feather (retrix). (June)A second-year/immature Mississippi Kite showing replacement of a juvenile tail feather with an all-dark adult retrix . (June)The second-year/immature Mississippi Kite from the previous image feeding on a periodical cicada. (June)A second-year/immature Mississippi Kite molting juvenile flight feathers. (June)Second-year/immature Mississippi Kites feeding on periodical cicadas. (June)
NORTHERN HARRIER (Circus hudsonius)
Silhouette of a Northern Harrier. The dihedral flight posture of the narrow wings, the long tail, and the short head projection often make the “marsh hawk” an easy bird to identify. (October)Long uptilted wings give the Northern Harrier a flight posture that is unique among the diurnal raptors of eastern North America.
NORTHERN HARRIER (Circus hudsonius) Adult
An adult male Northern Harrier. Even at a considerable distance, the white rump patch can clinch the identification of this species in all plumages. (October)An adult male Northern Harrier, dorsal view showing gray plumage. (October)An adult male Northern Harrier, ventral view. These birds are white below with dark wing tips and a dark trailing edge on the secondaries. (October)An adult male Northern Harrier, known colloquially as a “gray ghost”. (October)A second-year/adult female Northern Harrier. Note the streaked breast and the retained juvenile secondaries (the longer feathers in the wings). (October)An after-second-year/adult female Northern Harrier in spring. Note the buff-colored upperwing coverts and grayish cast to the brown flight feathers. (April)An adult female Northern Harrier. (October)An adult female Northern Harrier. Note the heavily streaked breast. (October)
A hatch-year/juvenile Northern Harrier. Note the cinnamon-rufous tint of the bird’s body plumage. (September)A hatch-year/juvenile Northern Harrier (lower right) soaring with an adult Broad-winged Hawk (upper left). (September)A hatch-year/juvenile Northern Harrier. When seen, the owl-like face and “headless hawk” flight posture are two good field marks. Normally a graceful flier, a Northern Harrier may appear clumsy while flapping because of its long wings. (October)A hatch-year/juvenile Northern Harrier. Note the pointed look of the wings while the bird is gliding. (October)A gliding hatch-year/juvenile Northern Harrier. (October)
SHARP-SHINNED HAWK (Accipiter striatus)
A Sharp-shinned Hawk (right), the smallest of the North American accipitrids, tangles with an American Kestrel (left).
SHARP-SHINNED HAWK (Accipiter striatus) Adult
A probable second-year/adult Sharp-shinned Hawk. “Sharpies” often glide with an arched posture, their tails raised above the plane of the forward portion of the body. (September)An adult Sharp-shinned Hawk. (October)An adult Sharp-shinned Hawk. A squared-off or notched tail is typical of all “Sharpies” in powered flight, as is a snappy set of wing beats between glides. (October)An adult male Sharp-shinned Hawk. When fully mature, all accipiters have red eyes like this bird. (November)
A hatch-year/juvenile Sharp-shinned Hawk showing short head projection and a squared-off tail with a notched appearance. (September)A hatch-year/juvenile Sharp-shinned Hawk. (September)A hatch-year/juvenile Sharp-shinned Hawk. Note how the head barely projects beyond the wrists on this gliding bird. (October)A hatch-year/juvenile Sharp-shinned Hawk. Note the yellow eyes, a field mark of “sharpies” in their first year of life.A hatch-year/juvenile Sharp-shinned Hawk. (October)
COOPER’S HAWK (Accipiter cooperii) Adult
An adult Cooper’s Hawk. The red eyes indicate that this bird is probably, at a minimum, beginning its fifth year. (January)An adult Cooper’s Hawk early in its second year (still less than one year of age). Reddish-brown markings are visible where juvenile feathers along the flanks and in the underwing coverts have been replaced. There is not yet any sign of molt in the flight feathers. Note that the well-worn juvenile rectrices (tail feathers) appear nearly equal in length on this particular individual. (February)An adult Cooper’s Hawk. Note the long, rounded tail. While in a glide, the head projects well forward of the wrists. (October)A soaring adult Cooper’s Hawk. Note the double-notched appearance of the tail’s trailing edge created by the shorter outer tail feathers, a shape often reminiscent, when a bird is seen at this angle, of the top of a keystone. (October)An adult Cooper’s Hawk. In a glide, the shorter outer tail feathers contribute to the rounded appearance of the compressed tail. (October)An adult Sharp-shinned Hawk with slightly rounded corners on the tail (left) compared to the adult Cooper’s Hawk from the preceding image (right). Note the heftier appearance of the protruding head and more tubular contour of the Cooper’s Hawk’s body and tail. (October)On an adult male Cooper’s Hawk, the gray cheek and nape adjoin a notably darker cap in the area behind the eye. At some angles, including the one seen here, this trait can give an observer the illusion of a white superciliary line (eyeline), suggesting a Northern Goshawk. If the bird in this image were a goshawk, the wings would be broader, particularly near their base, and usually more tapered near their tip. This slate-blue accipiter with long wings and dark tips on the primaries (hands) is most likely an adult male Cooper’s Hawk. Though similar in appearance, adult male goshawks have extensively dark primaries as well as secondaries, giving the wings a two-toned look when seen from above. Dorsally, adult female accipiters are generally uniform in color. (October)The orange eye and rich gray plumage indicates that this adult Cooper’s Hawk may be in its third or fourth year. (November)Note the slightly shorter outermost tail feathers on this adult Cooper’s Hawk. In flight, particularly while soaring or gliding, they will cause the corners of the tail to appear notched or rounded. (December)
A hatch-year/juvenile Cooper’s Hawk showing both a central notch and rounded corners on its tail. (September)A hatch-year/juvenile Cooper’s Hawk. Note the long wings and tail. (September)A hatch-year/juvenile Cooper’s Hawk. While soaring with wings fully extended, this species often gives the impression of a flying cross. (October)A hatch-year/juvenile Cooper’s Hawk. When soaring, the tail of this species appears especially large for the bird. (November)A hatch-year/juvenile Cooper’s Hawk. Yellow eyes are diagnostic of juvenile accipiters. (November)A hatch-year/juvenile Cooper’s Hawk in the early stages of molt showing some gray adult feathers on its back. (December)A hatch-year/juvenile Cooper’s Hawk. (December)
A hatch-year/juvenile Northern Goshawk. Note the hefty barrel-chested appearance of this accipiter. Goshawks at this age have a “dirty” appearance created by dense streaking on the breast that extends along the flanks into the undertail coverts. (November)A hatch-year/juvenile Northern Goshawk. (November)
RED-SHOULDERED HAWK (Buteo lineatus)
The translucent wing panels on Red-shouldered Hawks of all age classes appear as crescent-shaped “windows” at the base of the primary wing feathers.
RED-SHOULDERED HAWK (Buteo lineatus) Adult
A second-year/adult Red-shouldered Hawk beginning molt of juvenile rectrices and remiges. Of the ten primaries on each wing, the innermost four are being replaced by noticeably black and white adult feathers. This bird is approximately one year of age. (May)A second-year/adult Red-shouldered Hawk molting juvenile rectrices and remiges. (June)An adult Red-shouldered Hawk. (January)An adult Red-shouldered Hawk. (June)An adult Red-shouldered Hawk. (September)An adult Red-shouldered Hawk. (November)An adult Red-shouldered Hawk soaring. (November)An adult Red-shouldered Hawk in a glide. (November)An adult Red-shouldered Hawk in a glide. (November)An adult Red-shouldered Hawk in powered flight. (November)An adult Red-shouldered Hawk with a damaged rectrix. (November)
A hatch-year/juvenile Red-shouldered Hawk soaring. Note the translucent wing panels, crescent-shaped “windows” at the base of the primaries. (August)A hatch-year/juvenile Red-shouldered Hawk in a glide. (November)
BROAD-WINGED HAWK (Buteo platypterus)
Migrating Broad-winged Hawks “kettling” on a thermal updraft. (September)Broad-winged Hawks gliding away to the southwest after gaining altitude in a column of rising warm air. (September)
BROAD-WINGED HAWK (Buteo platypterus) Adult
A molting second-year/adult Broad-winged Hawk showing retained juvenile (longer) secondary flight feathers. (September)An adult Broad-winged Hawk. (September)An adult Broad-winged Hawk. Note the translucent wing panels, with light visible throughout the primaries. (September)An adult Broad-winged Hawk. (September)A backlit adult Broad-winged Hawk. Note the wing panels, translucence extending throughout the primaries. (September)An adult Broad-winged Hawk. (September)
A hatch-year/juvenile Broad-winged Hawk. (September)A hatch-year/juvenile Broad-winged Hawk. (September)A hatch-year/juvenile Broad-winged Hawk. Note the translucent wing panels, with light visible throughout the primaries. (September)A hatch-year/juvenile Broad-winged Hawk “feeding on the wing” to consume a captured dragonfly. (September)
SWAINSON’S HAWK (Buteo swainsoni)
An adult Swainson’s Hawk. (May) (Vintage 35mm image)
RED-TAILED HAWK (Buteo jamaicensis)
In eastern North America, Red-tailed Hawks in all age classes have a speckled belly band. Compared between individuals and populations, its density and width will vary. (April)An adult Red-shouldered Hawk (left) harassing an adult Red-tailed Hawk. (September)
RED-TAILED HAWK (Buteo jamaicensis) Adult
A second-year/adult Red-tailed Hawk beginning molt of the juvenile primaries. (June)A second-year/adult Red-tailed Hawk beginning molt of the juvenile rectrices (tail feathers). Note the growth of the first red replacement. (Early July)A second-year/adult Red-tailed Hawk completing molt. Note the retained juvenile rectrix (the longer tail feather) and the translucent wing panels, with light showing through the inner primaries. (October)An adult Red-tailed Hawk. At times, intense backlighting can make all flight feathers appear translucent. (March)An adult Red-tailed Hawk in annual mid-summer molt. (Late August)An adult Red-tailed Hawk nearing completion of annual summer molt. (September)An adult Red-tailed Hawk soaring. The dark patagial bar on the leading edge of the proximal portion of each wing is a key field mark for all age classes. (October)An adult Red-tailed Hawk in a glide. Note the carpal crescents formed by a row of dark primary underwing coverts, another key field mark for “Red-tails” in all age classes. The dark terminal band along the trailing edge of the remiges is a characteristic only of adult birds. (November)An adult Red-tailed Hawk. (November)An adult Red-tailed Hawk being harassed by an American Crow. This bird is an example of the faint banding that can be detected in the rufous tails of some adult birds. (November)An adult Red-tailed Hawk. (November)An adult Red-tailed Hawk in a glide displaying a dark patagial bar, carpal crescents created by a row of dark primary underwing coverts, and a dark terminal band on the trailing edge of the remiges. (December)
A hatch-year/juvenile Red-tailed Hawk. Note the dark patagial bar on the leading edge of each wing and the carpal crescents formed by a row of dark primary underwing coverts. (October)A hatch-year/juvenile Red-tailed Hawk. Translucent wing panels, with light showing readily through the inner primaries and not the overlapping outer primaries, are a field mark most readily seen on first-year birds like this. Compared to older “Red-tails”, first-year birds can appear whitish, a look created by the pale juvenile rectrices (tail feathers) and the absence of the dark terminal band found along the trailing edge of the remiges on adults. (October)A hatch-year/juvenile Red-tailed Hawk. Juvenile rectrices may have a faint rufous tint suggesting adult plumage, but fine banding is always present on the tails of first-year birds. Molt of the juvenile rectrices typically occurs during the bird’s second summer. (October)A hatch-year/juvenile Red-tailed Hawk. (November)A hatch-year/juvenile Red-tailed Hawk. (November)A hatch-year/juvenile Red-tailed Hawk. (November)
A hovering hatch-year/juvenile “light morph” Rough-legged Hawk. Nearly all of a “Rough-leg’s” primary underwing coverts are black, creating a readily visible dark carpal patch. While gliding and soaring, this buteo can be recognized by its long wings held in a dihedral posture. (December)
Order-Falconiformes
(Falcons)
Family-Falconidae
(Falcons)
AMERICAN KESTREL (Falco sparverius) Male
A male American Kestrel. (January)A hatch-year/juvenile male American Kestrel. (August)A hatch-year/juvenile male American Kestrel displaying the “string of pearls”, a row of translucent “windows” along the trailing edge of the wings. (September)A male American Kestrel. (September)A photo study of a male American Kestrel in flight. (September)A male American Kestrel reveals a “string of pearls” along the trailing edge of the wings. (September)A male American Kestrel stooping on a dragonfly. (September)
AMERICAN KESTREL (Falco sparverius) Female
A female American Kestrel. (February)A female American Kestrel. (August)A female American Kestrel. (August)A female American Kestrel. (November)A female American Kestrel. (December)
MERLIN (Falco columbarius)
The Merlin is a fast, dark falcon that quickly passes lookout stations. (September)Silhouette of a Merlin. (October)A Merlin gliding in a strong breeze. Heavy streaking on the breast and belly gives this species a darker appearance than the American Kestrel. (October)The Merlin from the preceding image compared to a Sharp-shinned Hawk. In gusty winds, the latter will often fold its primaries creating a pointed-wing appearance similar to a Merlin or other falcon. (October)
“TAIGA MERLIN” (Falco columbarius columbarius)
Adult Male
A probable adult male “Taiga Merlin”. (September)
“TAIGA MERLIN” (Falco columbarius columbarius)
Adult Female or Hatch-Year (Juvenile)
A probable adult female “Taiga Merlin”. (May)A probable adult female “Taiga Merlin”. (May)A probable adult female “Taiga Merlin”. (September)A probable hatch-year/juvenile “Taiga Merlin”. (September)A probable hatch-year/juvenile “Taiga Merlin” with a dragonfly. (September)An adult female or hatch-year/juvenile “Taiga Merlin”. (November)
PEREGRINE FALCON (Falco peregrinus)
Silhouette of a Peregrine Falcon in a glide. Note the broad pointed wings and tapering tail. (September)A soaring Peregrine Falcon. (October)A gliding Peregrine Falcon. In powered flight, note that the tail appears widest at the base, tapering to its narrowest at the tip. (October)
PEREGRINE FALCON (Falco peregrinus) Adult
An adult Peregrine Falcon. (November)An adult Peregrine Falcon in a stoop, a maneuver enabling these birds to reach speeds approaching 200 miles per hour, the fastest of any animal on earth. (November)
A hatch-year/juvenile “Tundra Peregrine”. The pale forehead and thin mustache (malar stripe) are key field marks. (October)The same hatch-year/juvenile “Tundra Peregrine” seen in the preceding image. Note how the white superciliary lines (eyebrows) on this bird extend to the back of the head and down to the nape, a field mark shared with some juvenile “Peale’s Peregrines” (F. p. pealei), a mostly non-migratory subspecies found along Pacific Ocean coastlines from Alaska south to California. (October)A hatch-year/juvenile “Tundra Peregrine” equipped with a tracking transmitter. (October)A hatch-year/juvenile “Tundra Peregrine” equipped with a tracking transmitter. (October)
GYRFALCON (Falco rusticolus)
Powerful and robust Gyrfalcons are exceptionally rare visitors anywhere south of Canada. During the winter of 1981-82, this dark-morph female and a white-morph male wintered in the Lower Susquehanna River Watershed in the vicinity of the D. M. Stoltzfus Quarry near Leola, Lancaster County, Pennsylvania. A third Gyrfalcon, a gray-morph bird, was seen there on numerous occasions as well. To the astonishment of birders throughout the region, this female and the white-morph male returned to the Stoltzfus Quarry for a second consecutive winter on December 31, 1982. Soon though, she appeared to be ailing. A recovery operation was planned and on January 13, 1983, experienced rescuer Thomas Amico rappelled down the walls of the quarry to retrieve the ill bird. He instead found that she was already deceased. An examination revealed she died of a duodenal lesion and an abscessed liver caused by an intestinal flatworm. (Specimen in the Pennsylvania Game Commission collection at the Middle Creek Wildlife Management Area Visitor’s Center)
The perceived visual appearance of raptors in flight can be altered significantly by many conditions including observation angle, distance, lighting, prevailing weather, and a bird’s behavior and flight posture. Furthermore, some birds do look different than “normal”. In addition to the variation among individuals regularly occurring in a region, strays from more distant populations possessing unfamiliar traits may wander into an observer’s area from time to time and provide an experience that’s somewhat confounding. Familiarity with molt cycles and the resulting seasonal changes in plumage can be an asset for identifying and determining the age of a diurnal raptor. But these changes are not set in stone. The timing of feather molt can be impacted by genetic variation, nutrition, stress, breeding/nesting activity, and other factors. Therefore, the information found on this page should be considered as a photographic reference and general overview of field marks presented to familiarize the observer with the basics of identifying and possibly determining the age of a diurnal raptor. But keep in mind, you will encounter individuals that don’t quite fit the mold.
WILL YOU BE ABLE TO ACCURATELY INDENTIFY AND AGE EVERY DIURNAL RAPTOR YOU SEE?
YEAH, WHEN PIGS FLY.
Is it a bird? Is it a plane? Is it a flying pig? No, wait, it is a bird. It’s a migrating Broad-winged Hawk diving into the forest to spend the night. Identifying diurnal raptors sure can be tricky at times.
SOURCES
Amico, Thomas M. 1991. “Gyrfalcons in Lancaster County”. A Guide to the Birds of Lancaster County, Pennsylvania. Lancaster County Bird Club. pp. 116-119.
Dunn, Pete, David Sibley, and Clay Sutton. 1988. Hawks in Flight. Houghton Mifflin Company. Boston, MA.
Dunn, Pete, and Kevin t. Karlson. 2016. Birds of Prey: Hawks, Eagles, Falcons, and Vultures of North America. Houghton Mifflin Harcourt. New York, NY.
Liguori, Jerry. 2005. Hawks from Every Angle: How to Identify Raptors in Flight. Princeton University Press. Princeton, NJ.
Liguori, Jerry. 2011. Hawks at a Distance: Identification of Migrant Raptors. Princeton University Press. Princeton, NJ.
McCullough, Mark A. 1989. “Molting Sequence and Aging of Bald Eagles”. The Wilson Bulletin. 101(1): pp.1-10.
