11

Blue Jays Mimic the Calls ofRed-shouldered and

Broad-winged Hawksby

Ross D. James

Blue Jays (Cyanocitta cristata) vival value to the birds.have long been known to mimic On 21 July 1987, about 10 kmthe calls of other birds. Some con- southeast of Dwight, Muskokasider that they are able to repro- District Municipality, Ontario, induce the calls of many different an area where I have heard Red-species (Baird et al. 1875; Terres shouldered Hawks for many years1980), although they are most (including 1987), I was recordingrenowned for vocal mimicry of Blue Jays and the associated scold-hawks, particularly the Red-shoul- ing by Least Flycatchersdered Hawk (Buteo lineatus) (Empidonax minimus) and Red-(Nicholson 1936; Bent 1946; eyed Vireos (Vireo olivaceus)Godfrey 1986). The Red-tailed when I realized that it was the jayHawk (B.jamaicensis) and the giving Red-shouldered Hawk-likeAmerican Kestrel (Falco screams, rather than a hawk itself.sparverius) have also been includ- To my ears the jay call was a veryed in 'the jay repertoire (Baird et good rendition of the hawk, exceptal. 1875), and I can add the Broad- that the jay gave only single, well-winged Hawk (B. platypterus). If spaced syllables, rather than thejays are as good a mimic of small- usual repetitive call of the hawk.er birds as they are with hawks, Spectographs (Figure la, Ib)the habit may often be overlooked. revealed that the syllables utteredThe mimicked sound heard by a by the jay (a) were similar to thosefield observer might be assumed to of a Red-shouldered Hawk. Theemanate from the appropriate dominant frequency is nearly iden-species, rather than from a jay that tical and the structure of the calls,might not even be seen. But why including hannonics, is similar. Inthey should mimic other birds, and the second half of the call, howev-particularly hawks, has not been er, the jay (a) has emphasized theadequately answered. The follow- lower of two simultaneous fre-ing observations, while not provid- quencies in the 2 to 3 kHz rangeing definitive answers, suggest that (that soon blend together), while inthe habit is not of significant sur- the hawk call (b), this lower band

Ross D. James, Dept of Ornithology, Royal Ontario Museum, 100 Queen'sPark, Toronto, Ontario MSS 2C6

VOLUME 6 NUMBER 1

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&a b

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TIME (SEC)

Figure 1: Sonograms (wide band) of:(a) a Red-shouldered Hawk-like call given by a Blue Jay on 21 July 1987 in Muskoka District

Municipality, Ontario (dominant frequency 2-3 kHz; durations .47 sec);(b) a syllable from a longer call given by a Red-shouldered Hawk. recorded earlier on 21 July

1987 in the same locality as (a) (dominant frequency 2-3 kHz; duration.51 sec);(c) a Broad-winged Hawk-like call given by a Blue Jay on 26 July 1987 in Muskoka District

Municipality, Ontario (dominant frequency 4.0-4.5 kHz; duration 1.1 sec);(d) an example of a Broad-winged Hawk call recorded 7 JlD1e 1983, in Hastings Coonty,

Ontario (dominant frequency 4.5-5 kHz; duration 1.45 sec).

has all but disappeared. The jaycall is slightly shorter and notice­ably less pure in tone, but giventhe complexity of the call, it is aremarkable resemblance.

Only five days later, as I stoodrecording a bird on the shore of asmall lake, in the very same area, I

heard what I thought was a Broad­winged Hawk calling on the otherside of the lake. I expected Broad­winged Hawks, as I have alsofound them nesting there, andbirds were present in 1987. Soon,I noticed a Blue Jay fly across thelake to land within 30 m of where

ONTARIO BIRDS APRIL 1988

I stood. Both as it flew, and afterlanding in the forest, it uttered aseries of calls that I would havecontinued to think were given by ahawk if I had not seen the jay.Sonograms (Figure lc, d) againrevealed a similar call. The jayversion (c) is shorter and fades outmore noticeably toward the end,but the frequency of the call isvery close to the Broad-wingedHawk example (d), and there islikely variation among hawks.When given by the jay, the open­ing syllable is prolonged some­what, there are small but inaudiblebreaks, and the call is less pure intone, but to human ears it soundsessentially identical except forduration.

As would be appropriate at theend of July, what appeared to befamily groups of jays, with younglong out of the nest, were seen inthis area on a number of occasionsduring the week these recordingswere made. But on both recordingoccasions, lasting about oneminute each, the jays giving thecalls appeared to be alone,although likely within hearing dis­tance of other jays.

There have been nwnerous the­ories put forward as to why birdsin general mimic other species (seeBayliss 1982) or why jays in par­ticular might do this (Goodwin1976). Unfortunately there is asyet no proven reason why BlueJays should want to mimic thesounds of hawks. The fact thatjays have been doing it for decadessuggests that it may happen more

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than just by chance. However, ajay uttering hawk calls while for­aging alone in the forest late in thebreeding season does not lend sup­port to theories of enhanced sexualselection during pairing, mateidentification within pairs, or ofterritorial defense during the mat­ing season. And since nests werenot involved in these examples,nor were the hawks present, theo­ries relating to their use in mob­bing or of enhancing threats toother birds that might be approach­ing nests are also not supported.The vireos and fl ycatchers wereseemingly unaffected by the mim­icked hawk calls, as they contin­ued to scold the jays.

Perhaps the hawk calls are ofvalue to jays at some particulartime during the year. The birdsthat I recorded may well have beenyoung, practicing their vocalrepertoire for the future. But whyshould they learn hawk calls in thefirst place? If such calls reallywere of advantage to jays in con­veying a more precise indicationof a threat to the birds themselvesor to their nest, a possible reasonsuggested by Goodwin (1976),why should they not mimicAccipiter species (Sharp-shinnedHawKs Accipiter striatus, werealso seen in these forests in 1987)rather than Bweos that are lessdangerous to small passerines.And if the hawk calls were ofvalue in such situations, whywould all jays not quickly acquirethe habit (assuming they do not,because it is not apparent to us that

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all jays have this habit)?At present, the hawk calls given

by Blue Jays have no more ade­quate explanation than that theymay be sounds that the jays couldeasily learn, and amount to noth­ing more than "copying mistakes"of no value to the jays. Goodwin(1976) indicates that mimickedsounds are often given by jays inhighly emotional situations, pre­sumably similar to those underwhich the jays first heard thesound. The hawk calls that Irecorded then, although not givenat a time of any apparent stress,may have been acquired during aperiod of emotional stress causedby the presence of hawks nearthem, at a time when they werelearning their own songs and sen­sitive to such sounds in their envi­ronment. Calling B weos couldeasily be near Blue Jay nests ornewly flying- young and could cre­ate such stress.

Perhaps the quieter nature ofAccipiters when hunting lessensthe possibility of jays acquiringAccipiter calls. Even more likelyto preclude this possibility, howev­er, is the fact that the Accipitersare going to be much more lethalto young jays. When learningcalls, the jays are likely to berather young, and better able tosurvive the presence of Buteos inclose proximity.

ONTARIO BIRDS APRll.. 1988

AcknowledgementsJ.C. Barlow and G.K. Peck provid­ed helpful comments on themanuscript. M. Goldsmith and C.Sweeney typed various versions ofthe manuscript. I am grateful tothem for their assistance.

Literature CitedBaird, SF., TM. Br~w~rand R. RU:lg~way.

1875. A History of North AmericanBirds. Vol. ll. Little, Brown and Co.,Boston.

Bayliss,J.R. 1982. Avian vocal mimicry:it! function and evolution. pp. 51-83 inKroodsma, D.E. and E.H. Miller.Acoustic Cooununication in Birds.Vol. II. Academic, New York.

BenJ, A.C. 1946. Life Histories of NorthAmerican Jays, Crows and TItmice.U.S. Nat!. Mus., Bull. 191.

Godfrey, WE. 1986. The Birds of Canada.Revised Edition. National Musemns ofCanada, Ottawa.

Goodwin, D. 1976. Crows of the World.British Musemn, London.

Nicholson, DJ. 1936. Observations on theFlorida Blue Jay. Wilson Bulletin 48:26-33.

T~rus,JX. 1980. The Audubon SocietyEncyclopedia of North American Birds.A.A. Knopf, New York.