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Identification of Red-shouldered, Broad-winged,

Cooper's and NorthernGoshawks in Immature

Plumageby

Bruce W. Duncan

Introduction broad wings and short, wide tails)Adult Red-shouldered Hawks while Cooper's and Northern(Buteo lineatus), Broad-winged Goshawks are in the subfamilyHawks (B. platypterus), Cooper's Accipitrinae (hawks with shorter,Hawks (Accipiter cooperiz) and rounded wings and longer, narrowerNorthern Goshawks (A. gentilis) dif- tails). In immature plumage, all fourfer distinctively in plumage, while are generally brown above andimmatures are quite similar to one whitish below, have brown streaksanother. All four species can be on the breast and belly, and a regu-seen in Ontario during spring, sum- larly banded tail. As they fly by,mer and fall and all but the Broad- distinctive features can be noted.winged in winter. However the bestopportunities fof viewing them are Size and Shapecertainly during migration at one of Overall Featuresthe major hawk lookouts along the All species of hawks exhibit a dif-shorelines of Lakes Erie and ference in size between male andOntario. Beamer Conservation Area female, with females being larger.near Grimsby in the spring and Among the four species discussed inPoint Pelee, Holiday Beach, Hawk this article, this reversed sexual sizeCliff and Hamilton in the fall are all dimorphism is most pronounced inexcellent sites from which to see the Cooper's Hawk, less so in thethese and other hawk species which Northern Goshawk, and is hardlyoccur in Ontario. noticeable in Red-shouldered and

Although all four birds are mem- Broad-winged Hawks. Thus, thebers of the family Accipitridae (the length of a male Cooper's and atrue hawks), two the Red-shoul- male Northern Goshawk is compara-dered and the Broad-winged, are ble to that of a Red-shouldered.included in the subfamily Female Northern Goshawks areButeoninae (hawks with fairly long, larger than all the others.

Bruce W. Duncan, Box 512, Caledonia, Ontario NOA lAO

ONTARIO BIRDS DECEMBER 1987

These size distinctions are help­ful when the observer has somefamiliarity with the species or whenmore than one bird is in the sky atonce. Against a vacant sky howev­er, birds can expand or contractremarkably and their size depends tosome degree on the mind-set of theperson watching. It is also useful toremember that hawks appear small­er against a clear blue sky thanagainst white clouds.

Of the four species, the slimmestis certainly the Cooper's Hawk. Italso appears to have the shortestwings and the longest tail, and 'withits relatively large head, gives onethe impression of a flying cross orpheasant (Figure 1). At the otherextreme is the Broad-winged Hawk,with proportionally much longerwings and shorter tail and a verychunky look to the body (Figure 2).These two are difficult to confuse.

Northern Goshawks, on the otherhand, are the most buteonine of theAccipiters, while Red-shoulderedHawks are the most accipitrine ofthe Buteos. Ignoring flight style forthe moment (which, in my opinion,make Red-shouldereds andCooper's more difficult to separate),Northern Goshawks (Figure 3) areheavier-bodied than Red-shoul­dereds (Figure 4) and as they passby show their considerably longertails.

TailsIt is not just the length of the tailfeathers themselves but also the nar­rowness of the tail that emphasizetail length in Accipiters. Buteoninetails, even when folded on glidingbirds, are wider and shorter.

Cooper's Hawk is the only one ofthe four species with very pro-

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nounced, rounded tip to the tail(Figure 1). In fact, on many birdsthe tail appears to have a lump stick­ing back out the middle betweenshorter outer tail feathers. NorthernGoshawk tails may be somewhatwedge-shaped, while Broad­wingeds and Red-shouldereds havevery slightly rounded or squared tipswhen folded and smoothly roundedends when spread. Also, on soaringButeos the spread tails are widerand make larger arcs than do those

•of Accipiters. Although I haven'tmeasured them, I suspect that singletail feathers of Buteos are widerthan those of similarly sizedAccipiters.

WingsWings of both Broad-winged andRed-shouldered Hawks appearlonger than those of Cooper's andNorthern Goshawks, especially fullyoutstretched as the birds soar. It isthe section of wing from the body tothe "wrist" (the point where thewing bends back) that seems longerin the Buteos than in the Accipiters.When gliding from one thermal tothe next, Broad-wingeds tuck theirwings slightly and thus become avery "neat-winged" bird; the "hand"of the wing forms a triangle, thetrailing edge is quite straight(emphasized by a dark edge band)and there is almost no "fingering"(i.e., separated primaries) at thewing tip (Figure 2). None of theother species looks this way. Dunneet ale (1982) note that when soaring,Red-shouldereds angle their wingsslightly forward as if reaching outfor something, while Broad-wingedshold theirs virtually at right anglesto the body.

The shorter wings of Cooper's

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Figure 1: Immature Cooper'sHawk, Point Pelee, Essex. Photo byBarry Cherriere.

Hawks and Northern Goshawks arenot identical. Goshawks have pro­portionally longer wings andaccording to Clark (1984) they arealso more tapered (Figure 3), whilethe wings of Cooper's Hawks aremore rounded.

MarkingsDorsalAlthough these four species do notoften show their backs to us land­bound watchers, birds flying low inearly morning and late evening andthose banking as they circle some­times allow us to see their dorsalsurfa-ces. The height of the NiagaraEscarpment at Beamer ConservationArea allows one to look down onhawks passing by Grimsby.

All four species, although basi­cally brown above, show clear dif­ferences. Northern Goshawks arepalest and have an even paler head;Cooper's Hawks appear dark brownon the back and tawny- or rufous-

ONTARIO BIRDS DECEMBER 1987

headed (see Duncan (1983) for amore detailed discussion of this).The white eyeline of the NorthernGoshawk can be seen even at a dis­tance but many immature Broad­wingeds and Red-shouldereds sharethis mark (Clark 1984). On mostNorthern Goshawks, however, anarrow white wingbar crosses thesecondary coverts (Figure 3). Thisis a good field mark.

The Broad-winged Hawk's backand wings are a uniform dull, darkbrown, with a little white speckling(not always visible) and a palerbrown towards the front. The headis also slightly paler. Red-shoul­dered Hawks, however, while basi­cally dull brown, tend to have somerufous along the leading edge of thewing - hints of the rich, red"shoulders" of the adults. They alsoshow the lovely, translucent cres­cents (what used to be called "wingwindows") in the primaries adjacentto the black tips of the feathers(Figure 4). These crescents are visi­ble from above and below and areclassic field marks. Do not confuse

Figure 2: Immature Broad-wingedHawk, Point Pelee, Essex. Photo byBarry Cherriere.

these crescent, moon-shaped brightareas with pale, squarish-shapedareas in the primaries of many otherspecies (e.g., Sharp-shinned Hawk(A. striatus), Red-tailed Hawk (B.jamaicensis) and especially Broad­winged Hawk).

Ventral"Brown streaks on white" describesall four of the species' body mark­ings below. Both immatureNorthern Goshawks and Cooper'shawks are sparsely marked on theventral surface but the Cooper'sstreaking ends on the belly, whilethat of the Northern Goshawk's con­tinues onto the undertail coverts.The Northern Goshawk's continuesonto the undertail coverts. TheNorthern Goshawk's streaks arewider and thus make the bird appearmore heavily marked; the basecolour is also creamy rather thanwhite as in Cooper's. Red-shoul­dered and Broad-winged Hawkstreaking is generally confined tothe chest and belly and varies inamount. Broad-wingeds, however,often have an unmarked white patch

Figure 3: Immature NorthernGoshawk, Point Pelee, Essex.Photo by Barry Cherriere.

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Figure 4: Immature Red-shoulderedHawk, Beamer Conservation Area,Grimsby, Niagara. Photo by BarryCherriere.

on the chest with streaking allaround; not so in Red-shoulderedsor the two Accipiters.

The streaking extends onto thewings in Red-shouldereds, as it doesin Cooper's and NorthernGoshawks. The wings of the Broad­winged Hawk are very sparinglymarked and appear quite whitish,emphasized by an outline of blackfeather tips and a neat, black trailingedge. The flight feathers of theother three are barred and mottledbut the translucent wing crescents ofRed-shouldereds separate them fromCooper's and Northern Goshawks.

Tail markings will help separateeach of these species. In Red-shoul­dereds and Broad-wingeds, the tailis pale brown with narrow, black­brown bands - about half-a-dozenare visible, in whole or in part. Thedark band closest to the tip of theBroad-wir.iged's tail is double thewidth of the others; it is the samewidth on Red-shouldereds. Boththese birds have a pale, narrow barat the very tip of the tail. Cooper'sand Northern Goshawks, have widerdark bars on the tail and a distinctly

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whitish tip - in Cooper's it is 1 cmor wider, in Northern Goshawks, itis much narrower. This wide, whiteband of the Cooper's is anothergood field mark.

Although difficult to see, it isuseful to know that the banding ofNorthern Goshawk tails is wavy orzigzag and each dark band has anarrow (about 1-2 mm wide), buffyedge. This is the only species of thefouf with a tricoloured tail.

FlightAll of these species do someflapping and gliding as well as ther­mal soaring, depending upon weath­er conditions. Broad-wingeds try tosoar and glide with as little flappingas possible, while Red-shoulderedsquite frequently flap their wings asthey glide along. Consequently, thelatter are readily mistaken forAccipiters, particularly Cooper'sHawks. However, Cooper's seem toflap more rapidly and with some­what stiffer wings, while Red-shoul­dereds have a slower, looser flap.Another stiff-winged flapper but onewith a slow beat is the Broad­winged Hawk.

The flight of Northern Goshawksis most difficult to describe. It maybe intermediate in style between theCooper's and Red-shoulderedbecause I have mistaken NorthernGoshawks for both. Since it is theheaviest of the species under consid­eration and has the highest wingloading, the flight looks heavy, as ifthe bird definitely is working to stayin the air. Female Cooper's mostnearly approach this appearance ofhard work in flight.

Broad-winged Hawks are mostoften seen soaring in kettles, while

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Cooper's and Northern Goshawksare usually spotted flapping andgliding. Red-shouldered Hawkssoar and glide, but also spend con­siderable time flapping and gliding.Keep in mind, however, that theycan fly both ways - and do.

Timing of MigrationAs mentioned earlier, in southernOntario it is easiest to see all four ofthese species during the spring andfall migrations. Broad-wingedHawks are by far the commonest,appearing by the thousands in bothseasons, with Red-shouldereds sec­ond (an average of about 700 eachspring at Beamer and 550 each fallat Holiday Beach). Cooper'sHawks come third (160 in spring atBeamer and 350 during the fall atHoliday Beach) and NorthernGoshawks last (fewer than 50 arerecorded annually in spring and fall,although more occur every ten yearsduring "invasions").

Since all species do not migrateat the same time, it is useful to knowwhen to expect each. I do not haveinformation for areas north of thelower two Great Lakes (Erie andOntario) but can provide dates basedon data from the Hawk MigrationAssociation of North Americacounts at Beamer ConservationArea and Holiday Beach (1977­1985). The dates listed are based onthe period during which about 85­90% of the migrants are seen andcounted (see Table 1).

When one of these brown andwhite immature hawks comes along,watch it carefully as it approaches,flies over and recedes into the dis­tance. Observation at each stagemay reveal features disguised by

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Table 1: Dates of migration for four hawk species in southern Ontario.

SPECIES

Northern Goshawk

Cooper's Hawk

Red-shouldered Hawk

Broad-winged Hawk

SPRING

I March-2 Aprilno distinct peak15 March-2 Maypeak about 10 April10 March-5 Aprilpeak about 23 March17 April-5 Maypeak about 26 April

FALL

25 September-30 Novemberno distinct peak20 September-25 Octoberpeak about 4 October6 October-15 Novemberpeak about 19 October7 Septernber-26 Septemberpeak about 15 September

perspective, distance of lighting atother stages. A little analyticalobservation by methodically recall­ing the characteristics to look forwill pay dividends in polishing iden­tification skills. Finally, there arethings to examine which are not yetwell studied in North America. Theshape and proportions of the "arm"and "hand" parts of the wing duringflight and the use of these partswhile flapping are some. It is onething to say that a NorthernGoshawk has a heavy flap butanother - and much better - todescribe it in terms of movement ofeach portion of the wing. I recom­mend these areas of study to keenerobservers.

AcknowledgementsMy thanks to all of my Hawk Clifffriends who have shown me thesebeautiful birds so many times overthe years and to all the faithfulwatchers at Beamer who haveshared with me many identificationdetails.

Literature CitedClark, W.S. 1984. Field identification of

Accipiters in North America. Birding16:251-263.

Duncan, B.W. 1983. Identification ofAccipiters in Ontario. Ontario Birds1:43-49.

Dunne, P., D. Sibley, C. Sutton and F.Hamer. 1982. Field identification.Newsletter of the Hawk MigrationAssociation of North America 7 :8-9.

NotesCommunal Sheltering Under Snow by

American Tree SparrowsWhile birding at the "LighthouseCrescent" field station of the LongPoint Bird Observatory on Old CutBoulevard in Long Point, RegionalMunicipality of Haldimand-Norfolkon 14 February 1987, I noticed anapparent absence of American Tree

Sparrows (Spizella arborea) in thered osier dogwoods (Cornusstolonifera) they had been frequent­ing all winter. As overnight temper­atures had dipped to -18°C with awind chill factor of -32°C, and a bit­terly cold wind made the -7°C at

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