AGE DETERMINATION OF BLUE JAYS
BY WARRENA. LAMB, ALICE H. KELLEY,AND STEVENM. COHEN
Dater(1970)reportedsuccessive
changes
in colorandbarringof dorsalwingcoverts
in theBlueJay(Cyanocitta
cristata).
Our plumagerecords
of recaptured,known-age
jays indicatethat enoughexceptions
to the
generalpattern of changerequire the useof additionalcharacterswhen
attemptingto age BlueJays.
METHODS
In the courseof bandingabout3,000 BlueJaysin Michiganwe recordedthe followinginformationabouttheir plumageand pigmentation: the presenceor absenceof bright blue color and blackbarson
secondary
feathers8, 9, and 10,on thegreatersecondary
coverts,alulars
and greaterprimarycoverts;the extentof blackpigmentation(usinga
scaleof 0-5) on the inner surfacesof the bill, on the tongue,and on the
interior portionsof the moutharoundthe glottis.
Our recordsof 92 individuals
aresuitablefor determiningwhetherthese
characteristics
are indicativeof specificages.First- and second-winter
plumage data were taken from 61 birds which we banded when their
postjuvenal
molt wasstillincomplete,and sowereof knownagewhen
banded and again when recaptured.The data for third-winter and all
subsequent
plumages,whichwe lumpedas "adult plumage,"are from
birds of unknownage when banded,but known to be in at leasttheir
third-winterplumagewhen recaptured.
Becausechangesin pigmentationmight be associatedwith seasonal
differences
in hormonelevels,weuseddataonlyfromrecaptures
in the
spring or summer.
RESULTS
Feather Colors
The leadingvanesof secondaryfeather 10 and of the greatersecondarycovertsweredull blueinjuvenalplumage(41 of 46 birds).During thepostjuvenal
moltbrightbluefeathersreplacethem,but notevery
bird completesthis molt (Pitelka, 1945, 1946, 1961). Of the birds we
examinedwhichwere in their first-winterplumage,6 of 47 still had
somedull blue greatersecondary
covertsor secondary
feather10.
The onlyjayswithbrightbluealularsor greaterprimarycovertswere
thosein the second-winter
or adult plumages.But since24 of 69 birds
in theseplumages
did not havebrightbluealularsor greaterprimary
coverts,the characteris of valuefor agingjays only whenit is present.
Black Bars
The blackbarsonjay wing feathersvary in appearance.
Somewere
darkandbroad;otherswerefaint,narrow,or spotty.Barringappeared
on all the greatersecondary
covertsand secondary
feathersin all plumagesafter completionof the postjuvenal
molt. The alularsof jhys in
215
216]
w. A. Lamb,A. H. Kelley,
andS. M. Cohen
Bird-Banding
1978
Summer
second-winterand adult plumageswere usuallybarred (50 of 65 birds)
as were their greaterprimary coverts(38 of 69 birds).But somebirds
in juvenal and first-winterplumagealreadyhad barred alulars(21 of
92 birds)or barredgreaterprimarycoverts(5 of 47 birds).Thus barred
alularsor greaterprimary covertsare not, in themselves,
reliableaging
criteria.
Mouthand TonguePigmentation
Nichols(1955) and Laskey(1958) reportedthat the colorof the inside
of a youngjay'sbill changesfrom mostlywhiteto almostall blackby its
firstspring.We observedthischangein 37juveniles.We alsonotedthat
juvenileshad pink tongueswhereasmostfirst- and second-winter
birds
had moderatelyblackor all blacktongues.But 17 of 43 adult birdshad
tonguesscored3 (i.e. more than half black)or less;one had a dramatic
reductionin tonguepigmentationfrom a scoreof 5 (i.e. all black)to a
scoreof 2 (i.e. lessthan half black). Two other jays had tonguesthat
were consistently
scored3 or lessover a four-year period. The extent
of pigmentationon the fleshyareaaroundthe glottisalsovaried.Three
of 46 adultshad very little pigmentationin that area.
Age Key
Our observations
confirm,in a generalway,the patternof changein
BlueJay plumagewhichDater reported.But applyingthe Dater aging
criteriato our sampleof 172 plumagerecordsof known-agejays yielded
the correctage only 62% of the time. We have constructeda key for
agingBlueJays(Table 1) whichrelegatesbirdswith ambiguousplumage
patternsto the "unknownage"category.When appliedto our records,
27% of the birds fell into this category.Only 2% of the birds were
incorrectlyaged; in eachcasethe bird incorrectlyaged wasin its firstwinter plumage,but had bars on its greater primary wing coverts.
TABLE
1
A key for aging the Blue Jay
la.
Inside
surfaces of the bill less than half black
................................
2
lb. Inside surfacesof the bill mostlyblack .......................................
2a. All the greater secondarycovertsand secondaryfeather 10 dull blue and not
barred
..................................................................
:3
HY
2b. At leastsomebright blue and barred ........................................
:3
3a. Blackbarsand bright blue color on only the proximal greater secondarycoverts
and/or secondaryfeathersexceptfor 10 .........................
Aug-Dec: HY
................................................................
Jan-July: SY
3b. All greatersecondary
covertsand secondaryfeatherswith blackbarsand bright
blue color .................................................................
4a. At leastone of the greaterprimarycovertswith blackbars .................
4
AHY
4b. None with black bars ......................................................
5
5a. At least one of the alulars and/or one of the greater primary covertsis bright
blue ...................................................................
5b. All are dull blue ...........................................................
AHY
6a. Jan-July ...............................................................
6b. Aug-Dec .................................................................
AHY
U
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Vol.
49,Noß
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Blue
JayAgeDetermination
[217
DISCUSSION
Althoughour plumageand pigmentationrecordswereextensive,they
suffered in that each of us was making qualitativejudgments of the
color of the feathers,the presenceof black bars on the feathers,and
the extentof blackpigmentationon severalareas.Our mostinconsistent
reporting probablyinvolvedthe presenceor absenceof blackbars in
thosecaseswhere the barswere very faint, or appearedonly on a few
of the feathers in an area. We estimatethat as many as 10% of the
birds we examined might have been judged inconsistentlyin this
regard. On the other hand, our mostreliablejudgment probablywasin
distinguishingbetweendull blue and bright blue feathers.Here again,
however,someinconsistency
in our reporting might haveoccurredbecause a variety of shadesof blue occurs and some might have been
calleddull blue becauseof poor light.
Our data from known-agejays show that Wood's reliance (1969) on
barring of the alulars and greater primary covertsis not satisfactory
because
this characteristic
is so variable.
Our
data
also show that
the
U.S. Fishand Wildlife Service's(Anonymous,1976) prohibitionof using
barring on "post-juvenalcovertsand alula"is too broad. We found that
the lack of bars on somegreater secondarycovertsis a reliable characteristicfor identifying HY birds and someSY birds.
SUMMARY
The recordsof 92 Blue Jays of known age were analyzedfor agerelated patternsin wing feathersand mouth pigmentation.Basedon
thoserecordsa key for aging the Blue Jay is presented.
ACKNOWLEDGMENTS
We wishto thank Brian Sharp and RobertPaynefor their constructive
criticismsof an earlier manuscript.
LITERATURE
CITED
ANONYMOUS.1976. North American Bird Banding Manual. U.S. Fish and Wildlife Service.
DATER,E. 1970. Dorsalwing covertsof Blue Jay (Cyatwcitta
cristata).Guide to age.EBBA
News, 33(3): 125-129.
LAS•:E•',A. R. 1958ß Blue Jays at Nashville, Tennessee: movements,nesting, age. BirdBa•dit•g, 26:211-218.
NICHOLS,
J. q'. 1955. A criterionfor )oung-of-the-yearin BlueJay.Bird-Ba*•dit•g,
26: 27.
PITELKA,F.A. 1945. Pterylograph), molt and age determinationof Americanjays of the
genusAphelocoma.
Co*•dor,47: 229-261.
1946ßAge in relation to migrationin the Blue Jay. Auk, 63: 82-84.
ß 1961. A curtailedpostjuvenalmoh in the StellerJay.Auk, 78: 634-636.
WooI•, M. 1969. A Bird-bander'sguide to determinationof age and sex of selected
species.University Park, PA, PennsylvaniaState Univ.
5069 24thAvenue,PortHuron,M148060; 3681 ForestHill Drive,Bloomfield
Hills, MI 48013; Museumof Zoology,
University
of Michigan,A• Arbor,MI
48109. Received15 August 1973, accepted3 April 1978.