RANGE EXTENSION
WESTERN
OF THE BLUE JAY INTO
NORTH
BY KIMBERLY
AMERICA
G. SMITH
The Blue Jay (Cyanocitta
cristata)is a commonpermanent residentor
migratory summer resident in the eastern half of North America (reviewedby Wenger, 1975). Few extralimital winter recordsof Blue Jays
existedin westernNorth America prior to 1972. Sincethen, western
sightingshave been increasingannuallywith over 220 recordsin the
winter of 1976-77. BecauseBlue Jays are usuallyconspicuous,
easily
identified, and often remain in localized urban areas for several weeks,
thesereports reflect a genuine increaseand suggestthat the Blue Jay
is rapidly expandingits winteringrange. Recentrecordsalsoindicatea
westwardexpansionof the breeding range. This report reviewsthe recent changesin the Blue Jay'sdistributionand offers explanationsfor
two important questionsconcerningthis expansion:(1) what factorsare
influencingthiswestwardexpansion,and (2) where is the origin of these
pioneering individuals?
DISTRIBUTIONAL
CHANGES
Expansionof theBreedingRavage
The BlueJay breedingrange (Fig. 1) hasexpandedconsiderably
since
the publication of the most recent Check-list of North American Birds
(American Ornithologists'Union, 1957). Blue Jays now breed as far
westasthe foothillsof the RockyMountains,from Cheyenne,Wyoming,
to Pueblo, Colorado, generallyin the larger cities(H. Kingery, pers.
comm.). They are firmly establishedin both the Black Hills of South
Dakota (Pettingill and Whitney, 1965) and in western North Dakota
(Stewart,1976),and isolatedcolonieshaveexistedin Sheridan,Wyoming (H. Kingery,pers.comm.)and Portales,New Mexico(J. Hubbard,
pers.comm.)sincethe summerof 1975.AlsoBlueJaysapparentlyhave
bred in Garter and Powder River Go. in southeastern Montana (P. D.
Skaar, pers. comm., 1975). Long-rangevagrantsmay alsobe attracted
by urban situationsthat providesuitablebreedinghabitat:a pair of Blue
Jaysthat had winteredin Union, Oregon, raisedthree young in June
1977 (Van Horn and Toweill, in press).
Short-rangedispersalprobablyhasaccountedfor the "city-hopping"
expansionof the Blue Jay'sbreedingrange. Using Audubon Christmas
Count data, Bock and Lepthien (1976) concludedthat the winter distributionalpattern of Blue Jayshad changedbetween1962 and 1971
and that their numbershad increasedover 25% alongthe entire western
edgeof their range.The authorssuggested
that an increasein dispersal
from southernand central populationsaccountedfor this increasein
iratubersand for "colonizationof rather marginal habitatson the western plains." ttowever, the marginality of the habitat is debatable.For
example, the Blue Jaysin Portales,New Mexico, breed in the city park,
208
Vol.49,No.•
BlueJay
Range
Extension
[209
o
$
$
b
$
b
b
b
o
b
o
o
s
S
0
0
S
b
b
b
o
o o
F•aURE1. Expansionof the Blue Jay into western North America since 1957. Crosshatchedarea = approximaterange basedon lastA.O.U. Check-list(1957); b = confirmed breeding localities;o = occurrenceof one or two individuals(ma? represent
sightingsover several}'ears);s = areaswhere nearlyannualoccurrences
and/or winter
concentrationshave been reported since1970.
not in the semi-arid desert vegetation.Recent studies(e.g., Guthrie,
1974; Luniak, 1974; M•ller,
1976; Vale and Vale, 1976; Huhtalo and
J•irvinen, 1977; and referencestherein) have shown that distinct avian
communitiesare associatedwith urban areas,especiallythosewith mature (usuallyexotic and ornamental)vegetation.This may be due to
210]
K. G. Smith
Bird-Banding
Summer
1978
specificvegetationalcharacteristics(Hooper et al., 1975) or to urban
characteristics
suchasthe numberof gardens,bird housesand feeders,
catsand dogs(for discussion
seeThomas et al., 1977). Also city parks
mayoffer uniquenestingopportunitiesdependingon their sizeand the
landscaping
practicesemployed(Gavareski,1976). BecauseBlueJays
need only a few large treesto breed successfully
in an urban (Geis,1974,
1976) or rural (Guth, 1976) environment,they thereforemight be expectedto occur in westerncitiesas vegetationalcommunitiesmature.
Conceivablyornamentalplantingand landscapinghaveresultedin certain westerncitiescontainingdeciduousand mixed-forestislandsof favorablehabitatmuch like the oak woodlands(Pettingilland Whitney,
1965) and shade-treeurbanized areas (Godfrey, 1966) preferred by
Blue Jays elsewhere.
Expansionof theWinteringRange
Most westernwinter sightingsin recent years have been from Montana, Idaho, and Washingtonand thesestatesmay now be regular wintering areas (Table 1). The increase in winter sightingsin Wyoming
TABLE
1.
Occurrencesof Blue Jaysin westernNorth America from 1970 to 1976, with pre-1970
records tallied where possible.Based upon AudubonField Notes(1970), AmericanBirds
(1971-76), and personalcommunicationsto the author.
State
Win-
Win-
Win-
Win-
Win-
Win-
Pre-
ter,
ter,
ter,
ter,
ter,
ter,
ter,
1970
Records
197071
197172
197273
197374
197475
197576
197677
Montana
23 •
1
1
1
12
Win-
12
8
48
Wyoming
>
1
2
2
8
5
20
48
Idaho
22
0
0
8
2
0
6
50+
Utah
3$
0
0
0
0
0
0
7
Arizona
04
0
0
0
0
0
0
2
Nevada
0s
0
0
0
0
0
0
0
3 (?)
British Columbia
Washington
Oregon
California
0
0
3
3
0
1
11
Few6
08
2
0
2
0
1
0
1
1
8
0
8
0
467
8
3u
0
0
0
1
0
0
0
4
5
15
28
25
43
Total/Winter
P. D. Skaar, pers. comm.
Arvey, 1944; Burleigh, 1972.
Behle and Perry, 1975.
Phillipset al., 1964; K. Kaufman, pers. comm.
N. K. Johnson,pers. comm.; R. C. Banks,pers. comm.
Mattocks et al., 1976.
Weber, in press.
Gashwiler and Gashwiler, 1974.
McCaskie,1970; M.D. Arvey, pers. comm.
220+
Vol.
49,No.•
BlueJay
Range
Extensio•
[2 11
reflects establishmentof permanent resident populations.Unusually
large numberswinteredin Utah, Oregon,and BritishColumbiaduring
1976-77, and the samewinter producedtwo recordsfor Arizona (K.
Kaufman,pers.comm.).Mostof theseextralimitalrecordsare in urban
or riparian situations,suggesting
that suchareasattractor concentrate
winteringBlueJays("s"in Fig. 1). Nevadaisthe onlystatein the western
region without a report of a Blue Jay.
The increasingnumbers of wintering Blue Jays in western North
America might also be due to increasedpopulationsin the Midwest.
For example, the Blue Jay was accidentalin Midland, Texas 20 years
ago,but hasbecomean abundantwintervisitorfollowingthe maturation
of live oaks planted around residences.The native pecan trees along
streamcoursesdid not attract BlueJays(F. Williams,pers.comm.),thus
adding support to the idea that maturing urban vegetationis contributing to the Blue Jay expansion.Although most of the breeding range
expansionof the BlueJay is along the entire westernedge of its United
Statesrange, mostof the wintering expansionis restrictedto the northwesternstates.This pattern suggestsmore than one sourcearea for the
pioneeringindividuals.
An analysisof North Americanbandingdata showsa strongnorthsouthcomponentin BlueJay movements(Middleton,1974),primarily
amongpopulationsnorth of 35ølatitude(Wenger, 1975)and especially
west of the 100th meridian (K. G. Smith, unpubl. data). This suggests
that most winter migrants are originating in Canadian populations
whichextend westwardinto centralAlberta (Godfrey, 1966). Reportsof
BlueJaysappearingin southernAlberta (Godfrey, 1966)lend credence
to this hypothesis.Furthermore, Blue Jayshave been regular fall and
winter visitorsin southeastern
Washingtoneveryyearsince1968(Weber
and Larrison, 1977), but have only recently been seenwith any regularity in Idaho (Table 1). BlueJaybreedingpopulationsin westernCanada are only 500 km from winter concentrationareasin Washington
and Idaho (Fig. 1). Bandingrecoverieswestof the 100thmeridianreveal
that Blue Jaysare capableof migratory movementsin excessof 1,300
km (K. G. Smith, unpubl. data). A similar dispersalroute has recently
been shownfor the Barred Owl (Strixvaria), another expanding eastern
species(Taylor and Forsman, 1976).
DISCUSSION
The increaseof the Blue Jay in westernNorth Americais apparently
the resultof two different phenomena.Short-rangedispersalis responsiblefor the progressionof the breedingrange westward,whereaslongrange dispersal(and possiblymigration)is responsiblefor the rapidly
increasing number of western winter sightings. Interestingly, both
movementsare happening for the same reason:changesconcomitant
with urbanizationare creatingfavorablehabitatfor BlueJays.This does
not apply solelyto vegetation,but alsoincludesproper food supplies.
Although it seemsunlikely that Blue Jaysare food-limited(Bent, 1946),
212]
K. G. Smith
Bird-Banding
1978
Summer
the examplefrom Midland, Texas mentionedabovesuggests
that Blue
Jaysare at leastinfluencedby the foodbaseavailable.Bockand Lepthien
(1976) suggested
that bird feedershaveplayeda majorrole in changing
BlueJay winteringdynamics,and manyof the westernwintersightings
are at feederswhere a bird might be seenfor many weeks.Blue Jays
also seem to be able to survive on fruits
and berries
found
in exotic
ornamentalvegetation(Geis,1974).Thus, urbanizationnot only furnishesthe propernichegestalt(sensu
James,1971),butalsousablefood
resources.
Two other importantquestionsariseconcerningBlueJay expansion:
(1) whatare the ageclasses
of the migrating/dispersing
individuals,and
(2) will other corvidsaffect the BlueJay expansion?Althoughanswers
to thesequestionswill require further research,somespeculationcan
be made basedupon information now available.
BecauseyoungBlueJaysare knownto disperseor migrate(Hardy,
1961),manywesternsightingsmaybe of first-yearbirds.However,adult
BlueJaysare alsoknownto migrate(Laskey,1958;Middleton,1974).
Wenger (1975) analyzedall North AmericanBlue Jay bandingrecoveries before 1971 and found no correlation between age classesand
migratorybehavior.He estimated< 10% of the total populationto be
truly migratoryand suggesteda geneticbasisfor the migratorybehavior. Birds homozygous
for the migratorytrait wouldmigrateeveryyear
and birds homozygousfor the non-migratorytrait would be sedentary.
Heterozygousindividualswould usuallybe sedentary,but couldmigrate
when conditions,suchasseverewinter weatheror populationpressures,
triggered such behavior. Thus, individualsof all age classesmay be
involved in the expansion.BecauseBlue Jays can be aged easily by
plumagecharacteristics
(Pitelka,1946),age distributionscouldbe readily investigatedby westernbird-bandersand bird watchers.
By usingurban and/or riparian situations,the BlueJay is exploiting
habitatsgenerallyunusedby westerncorvids.AlthoughBlueJay x Steller's Jay (Qya•ocittastelleri)hybrids have been reported (Williams and
Wheat, 1971), Steller'sJays are usually rare in urban environments,
more often found in montane coniferousfbrests.The ScrubJay (Aphelocomacoerulescens)
is adapted to more southerly arid woodlandsand
shouldnot affect the Blue Jay expansionin the Northwest.The larger
Black-billed Magpie (Picapica) may represent a direct competitor althoughit tendsto be found in moreopen situations.The Northwestern
Crow (Corvuscaurinus)is a common urban resident in the extreme
Northwestand may be a potential competitorin that area. Blue Jays
may gain someadvantageover the other corvidsmentionedbecause
BlueJaysusebird feedersto a greaterextentduring the winter.
SUMMARY
AND
CONCLUSIONS
Within the last 10 years,the breeding range of the Blue Jay has expanded into easternMontana, Wyoming, and New Mexico, and the
wintering range apparently has expanded into the Northwest.Short-
Vol.49,No.3
BlueJayRangeExtension
[2 13
range dispersal from the Midwest is suggestedfor the increase in the
breeding range, whereaslong-rangedispersal(or migration) is suggested for the latter. The major reasonfor both of theseexpansionsappears
to be vegetationalchangesassociated
with urbanizationin westerncities.
BecauseBlue Jaysapparently are using habitatsthat other corvidsneglect,encounteringnew breedinghabitatsthrough ornamentalplanting,
and finding food sourcesin exoticvegetationand at bird feeders,there
is every reasonto believetheir expansionwill continuein westernNorth
America.
ACKNOWLEDGMENTS
This studycould not have been completedwithout the help of many
people, especiallyD. James, K. Kaufman, H. Kingery, T. Rogers, E.
Serr, D. Skaar, D. Van Horn, and J. Weber. To these and those not
mentioned,I offer my sincerethanks.John Tautin and KathyKlimkiewicz were helpful in obtainingbanding recordsfrom the Bird Banding
Laboratory.D. Andersen,T. Sordahl,and S. Vander Wall madehelpful
commentson an earlydraft, whereasK. L. Dixon commentedon several
drafts and was helpful and encouragingthroughout the study. This
researchwas supported by NSF grant DEB 75-13966 to James A.
MacMahon.
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Logan,UT
84322. Received17 January 1978, accepted15 February 1978.