Ornithological Monographs 29

THE

AND

MOLT

OF SCRUB

BLUE

JAYS

JAYS

IN FLORIDA

BY

G. THOMAS

BANCROFT
AND

GLEN

E. WOOLFENDEN

Departmentof Biology, University of South Florida,
Tampa, Florida 33620

ORNITHOLOGICAL

MONOGRAPHS

PUBLISHED

THE

AMERICAN

BY

ORNITHOLOGISTS'

WASHINGTON,
1982

NO.

D.C.

UNION

29


THE

AND

MOLT

BLUE

OF SCRUB

JAYS

IN

JAYS

FLORIDA


ORNITHOLOGICAL

MONOGRAPHS

This series,publishedby the AmericanOrnithologists'Union, has been establishedfor major paperstoo long for inclusionin the Union's journal, The Auk.
Publicationhas been made possiblethroughthe generosityof the late Mrs. Carll
Tucker and the Marcia Brady Tucker Foundation, Inc.

Correspondence
concerningmanuscriptsfor publicationin the seriesshould
be addressedto the Editor, Dr. Mercedes S. Foster, USFWS, National Museum
of Natural History, Washington, D.C. 20560.

Copies of OrnithologicalMonographs may be ordered from the Assistant to
the Treasurerof the AOU, Glen E. Woolfenden,Department of Biology, University of SouthFlorida, Tampa, Florida 33620.(See price list on back and inside back cover.)

OrnithologicalMonographs,No. 29, viii + 51 pp.
Editor of AOU Monographs, Mercedes S. Foster

Special Reviewers for this issue, Victor R. Dolnik, Biological Station
of Rybachy, Zoological Institute, USSR, Academy of Sciences,
Leningrad,USSR; Martin L. Morton, Departmentof Biology, Occidental College, Los Angeles, California; and Kenneth C. Parkes,
Life Sciences Department, Carnegie Museum of Natural History,
Pittsburgh, Pennsylvania
Authors, G. Thomas Bancroft and Glen E. Woolfenden, Department of
Biology, University of South Florida, Tampa, Florida 33620
First received, 22 December 1980; accepted, 7 April 1981; final revision
completed, 16 July 1981
Issued January 14, 1982

Price $8.00 prepaid($6.50 to AOU members)
Library of CongressCatalogueCard Number 81-86487
Printed by the Allen Press, Inc., Lawrence, Kansas 66044
Copyright ¸ by the American Ornithologists' Union, 1982


THE
AND

MOLT
BLUE

OF SCRUB
JAYS

JAYS

IN FLORIDA

BY

G. THOMAS

BANCROFT
AND

GLEN

E. WOOLFENDEN

Departmentof Biology, University of South Florida,
Tampa, Florida 33620

ORNITHOLOGICAL

MONOGRAPHS
PUBLISHED

THE

AMERICAN

BY

ORNITHOLOGISTS'

WASHINGTON,
1982

NO.

D.C.

UNION

29



TABLE
INTRODUCTION
MATERIALS
METHODS

OF CONTENTS

....................................................................................

1

..........................................................................................

1

..............................................................................................

2

SCRUB JAY MOLTS
..............................................................................
FIRST PREBASIC MOLT ........................................................................
DEFINITIVE PREBASIC MOLT ..............................................................

4
4
7

BLUE JAY MOLTS
................................................................................
FIRST PREBASIC MOLT ........................................................................
DEFINITIVE PREBASIC MOLT ..............................................................

23
23
25

COST

35

CURVES

FOR MOLT

BY JAYS

IN FLORIDA

............................

DISCUSSION
..........................................................................................
THE SCORING SYSTEM ........................................................................
FIRST PREBASIC MOLT

DEFINITIVE

LITERATURE

...................................

........................................................................

..............................................................................................
CITED

39

..............................................................

OF MOLT AND BREEDING

ACKNOWLEDGMENTS
SUMMARY

........................................................................

PREBASIC MOLT

INTERACTIONS

37
37

............................................................................

41
d........

43

46
46
48


LIST

OF FIGURES

Figure 1. Intensityof the first prebasicbody molt in juvenile Florida Scrub
Jaysexaminedin successivehalf-months..................................
2. Intensity of the first prebasicmolt in juvenile Florida ScrubJays
of different ages ......................................................................
3. Intensity of body molt in adult Florida Scrub Jays during different remex stagesof the definitive prebasicmolt ........................
4. Remex scoresof individual Florida Scrub Jay breedersexamined

two or more times during one definitive prebasicmolt ..............
5. Remex scoresof individual Florida Scrub Jay helpersexamined
two or more times during one definitive prebasicmolt ..............
6. Remex scoresfor adult Florida Scrub Jays examined during the
definitive prebasicmolt ............................................................
7. The timing of breedingand the definitiveprebasicmolt in Florida
Scrub Jays ..............................................................................
8. Remex scoresfor late-nestingFlorida ScrubJay breedersrelative
to day in their nest cycles ........................................................
9. Remex scoresfor four breedingmale Florida Scrub Jays examined four to six times during one definitiveprebasicmolt ..........
10. Intensity of the first prebasicbody molt of juvenile Florida Blue
Jays examinedin successivehalf-months..................................
11. Intensityof body molt for adult Florida Blue Jaysexaminedduring differentremex stagesof the definitiveprebasicmolt ..........
12. Remex scores for 20 adult Florida Blue Jays examined two or
more times during one definitive prebasicmolt ..........................
13. Remex scoresfor adult Florida Blue Jays examined during the
definitive prebasicmolt ............................................................
14. The timingof breedingand the definitiveprebasicmolt in Florida
Blue Jays ................................................................................
15. Molt cost curves for Scrub Jays and Blue Jays in Florida ..........

vi

6
9
12
13
14
18
20

21
22
24

29
30
32
34
36


LIST
Table

OF TABLES

1.

Percentageof juvenile Florida Scrub Jays examinedin successive
half-months molting feathers in various regions during the first
prebasic molt ............................................................................
5
2. Percentage of juvenile Florida Scrub Jays of different ages
molting feathers in various regions during the first prebasic
molt ..........................................................................................

8

3. Percentage of adult Florida Scrub Jays in each remex stage of

the definitive prebasic molt replacing primaries and secondaries

........................................................................................

10

4. Percentageof adult Florida Scrub Jays in each remex stageof the
definitive prebasic molt replacing rectrices ................................
10
5. Percentage of adult Florida Scrub Jays in each remex stage of
the definitive prebasic molt replacing body feathers, alulae, and
coverts .....................................................................................

11

6. Mean rate of the definitive prebasic molt in Florida Scrub Jays,
basedon recapturedata and regressionanalysis ........................ 15
7.

Variation

in the rate of molt

for

10 individual

Florida

Scrub

Jays ..........................................................................................
8. Percentageof adult Florida Scrub Jays examined in successive
half-monthsmolting feathers in various regionsduring the definitive prebasic molt ......................................................................
9. Percentageof adult Florida Scrub Jays examined in successive
half-months that had started the definitive prebasic molt ............
10. Percentageof male and female Florida Scrub Jay breedersin successivehalf-monthsthat had startedthe definitiveprebasicmolt ....
11. Percentage of juvenile Florida Blue Jays examined in successive
half-months molting feathers in various regions during the first
prebasic molt ............................................................................
12. Percentageof adult Florida Blue Jays in each remex stageof the
definitive prebasicmolt replacingprimaries and secondaries......
13. Percentageof adult Florida Blue Jays in each remex stageof the
definitive prebasicmolt replacingrectrices ................................
14. Percentage of adult Florida Blue Jays in each remex stage of the
definitive prebasic molt replacing body feathers, alulae, and coverts

.......................................................................................

16

17
19

20

23
26
27

28

15. Percentage of adult Florida Blue Jays examined in successive
half-monthsmolting feathers in various regionsduring the definitive prebasic molt ......................................................................
31
16. Percentage of adult Florida Blue Jays examined in successive
half-monthsthat had started the definitive prebasic molt ...........
33

vii


INTRODUCTION

Molt and breeding usually have separate schedulesin the annual cycles of
birds. The mostcommonexplanationgiven is that by staggeringthesetwo events
birds are subjectto less energy stress(Kendeigh 1949; Farner 1964). Reported
exceptionsincludesomebirds living in tropical climates,where presumablyfood
availabilityfluctuatesless seasonally,and somebirds from high latitudes,where
apparentlyfor a shorttime duringthe year sufficientfoodexistsfor the completion
of both molt and breeding(Payne 1972).
Missingfrom most reportson molt-breedingoverlap are molt data for individuals whose exact breedingstatus is known. Becausethe breedingschedulesof
populations,and especiallypopulationsliving in warm climates,can extend far
beyond that of an individual in that population, the information on true moltbreedingoverlap is far more limited than the literature suggests.Furthermore,if
molt beginsgradually,then the mere fact that molt overlapswith breedingcontributeslittle informationusefulto the studyof the schedulingof major activities
in the annualcycle of birds.
Characteristicsof the annualcycles of the two jay speciesthat breed in Florida
suggestedthat detailed knowledge of their molt regimesmight contribute to the
overall understandingof molt in birds. ScrubJays (Aphelocomacoerulescens)in
Florida have a relativelyshortnestingseason,March throughJune, and usually

attempt to produce only one brood of fledglingsper year (Woolfenden 1974). In
contrast, Blue Jays (Cyanocitta cristata) in Florida regularly nest into August,
and probably regularly attempt to producetwo broodsof fledglingsper year
(Woolfendenand Rohwer 1969).In addition,Florida ScrubJaysare cooperative
breeders,and manypairsare assistedby non-breedinghelpers(Woolfenden1974,
1975).Therefore, the populationincludessomeadult individualsthat have yet to
breed. Finally, these two closely related speciesexist in populationsthat breed
sympatricallyin a subtropicalclimate where, presumably,food is less scarcein
winter than in moretemperateregions.
Pitelka's(1945)carefulstudyof pterylography
andmoltin ScrubJaysprovides
a firm foundationfor our work. Further studyof molt in ScrubJayswasjustified,
however, becausefew Florida birds were available to Pitelka, and because neither

the breedingchronologyof that population,nor the fact that it exhibits cooperative breedingwith non-breedinghelperswas documentedat the time. Because
of the existence of a banded population, we describe molt for numerous Scrub
Jays of known age, sex, and exact breedingstatus. Our age and breedinginformation on Blue Jays is less detailed. Remarkably, however, despite extensive
bandingat many localities,no study of molt for the specieshas been published
previously.
MATERIALS

Detailed molt data were collectedon live Scrub Jaysand Blue Jaysat Archbold
Biological Station, HighlandsCounty, Florida (lat. 27ø10%where both species
are commonpermanentresidents(Woolfenden 1969). A populationof ScrubJays
has been studiedintensivelythere since 1969 (Woolfenden 1974, 1975), and all
Scrub Jays examinedfor molt already were banded, and most were of known
age, sex, and breedingstatus.In 1976and 1977,63 juveniles were examinedone


2

ORNITHOLOGICAL

MONOGRAPHS

NO. 29

to five times for a total sampleof 112juvenile Scrub Jay observations.During
these sametwo years, 94 Scrub Jays, agesone year or older, were examinedone
to eight times for a total sampleof 180 observations.
Blue Jays have not been studiedin detail at Archbold BiologicalStation, and
most of the individualscapturedhad not been marked. All previouslyunbanded
Blue Jays were banded upon capture. In 1976 and 1977, 73 juveniles were examined one to five times for a total sampleof 139juvenile observations,and 143
yeafling or older individualswere examinedone to six times for a total sample
of 195observations.In 1976,of the 105Blue Jayswe examined,only 12 had been
bandedpreviously.One of these 12 was a yearling, and 11 were older. In 1977,
of the 54 we examined25 hadbeenbandedpreviously;six of thesewere yearlings.
Remex and rectrix molt data taken by Woolfendenfrom 56 marked ScrubJays
captured76 timesduringthe years 1971through1975are usedin certainanalyses.
Of these 56 individuals,21 were capturedagain during 1976and 1977. In order
to acquire data from the spring months prior to concentrated field work, we
examined34 ScrubJay specimenscollectedbetweenJanuaryand April near the
Archbold BiologicalStation. Seven Blue Jays collectedin November and December near Whitfield, Santa Rosa County, Florida, were examinedto provide information from late fall when Blue Jays were difficult to catch at the station.
These specimensare located in the University of South Florida and Carnegie

Museumof NaturalHistorycollections,
respectively.
Thebreeding
dataonScrub
Jaysthat we use spanthe time of our molt work (Woolfenden1974,unpubl.field

notes).The few data on breedingby Blue Jaysobtainedat the stationin 1976also
are used.

METHODS

Florida ScrubJaysoften breedin family groupsin whichnon-breeding
young
from previousyears help to rear later broods(Woolfenden1974, 1975). When
analyzingmolt data, we separatedScrubJaysinto sevenclasses:juveniles,male
breeders,femalebreeders,oldermalehelpers,olderfemalehelpers,yearlingmale
helpers,and yearlingfemale helpers.All breedersand all older helpersexamined
were at least two years old.

Pitelka (1946) describedmethodsfor distinguishingyearlingsfrom older Blue
Jaysby plumage.The uppergreatersecondarycovertsare unbarredin thejuvenal
plumage,but barred in the definitiveplumage.Young Blue Jaysthat retain these
coverts during the first prebasicmolt can be recognizedas yearlings.However,
we found that most Blue Jays in Florida molt all the upper greater secondary
coverts during the first prebasic molt. This made use of these coverts alone
unreliablefor ageingFloridabirds. The alulaeand uppergreaterprimarycoverts
of the juvenal plumagealso are unbarredand grayer on the tip than in the definitive plumage, and thesefeathers are not changedduring the first prebasicmolt
of Florida Blue Jays. However, after nine months of wear, we found that we
were unable to use these features for ageingin the field.
With existinginformation,only the sex of female Blue Jayscan be determined
from externalcharacteristics,and then only when the femaleshave a broodpatch.
Therefore, for this studywe distinguishonly three classesof Blue Jays,juveniles,
breedingfemales, and yearling and older unsexed birds of unknown breeding


MOLT

OF SCRUB

JAYS AND

BLUE

JAYS

3

status.The six known yearlingsand 19 known older individualscapturedin 1977
permittedcomparisonof the onset of molt betweenthese age classes.
We follow the terminologyof Humphrey and Parkes (1959) when describing
the molts and plumagesof Scrub Jays and Blue Jays. The sequenceof events is
as follows. Feather replacement starts when individuals are about 2.5 months
old. This molt, the first prebasic[= post-juvenalof Dwight, in Humphrey and
Parkes, 1959] is incomplete.About a year later, and then annually thereafter,
these jays undergoa complete molt, the definitive prebasic[= post-nuptialof
Dwight] molt. The primaries are numberedone through ten from proximal to
distal; the secondariesare numberedone through ten from distal to proximal
(Van Tyne and Berger 1975).
A numerical systemsimilar to that of Ashmole (1962) and Newton (1966) was
used to score each remex and rectrix from 0 to 5 (e.g., 0 = not dropped, 5 -completelyregrown).A remex scorewas obtainedfor each bird by summingthe
individualscoresfor all 20 primariesand for both the left and right sixth secondary. Ligon and White (1974) used a similar system based on all 20 primaries and
both the fifth and sixth secondaries.For ScrubJaysand Blue Jays,excludingthe
fifth secondariesresultsin scoresmore linearly related to date, which is important
if recapture data and regressionanalysisare used to estimate the duration of
molt. A remex scoreof zero indicatesthat remigialmolt has not started, and an
overall score of 110 indicatesremigial molt is completed. Based on the remex

score, each bird was assignedto a remex stage of 1 through 11, or 11+ (1 =
remex score 1-10; 2--remex score 11-20; ...
11 = remex score 101-109;
11+ = remex score 110, all remigesnew). In our analysesmolt of other feathers
is comparedwith remex stage.
Molt for the six body tracts was scored from 0 to 3 (0 = no molt, 1 -- 1 to 3
feathers growing, 2 = every fourth feather growing, 3 = most of the tract with
feathersgrowing)following Ainley et al. (1976). For the first prebasicmolt separate scoreswere kept for severalregionsof three body tracts:
Spinal: pelvic, dorsal, interscapular, and cervical;
Capital: forehead, crown, nape, lores, auricular, and malar;
Ventral: submalar,cervical, sternal, and abdominal.

Using these numbers,a body intensity score was calculatedfor each bird by
summingthe scoresfor the six body tracts. Maximum scoresof 51 for the first
prebasicmolt and 18 for the definitiveprebasicmolt are possible.The difference
between maximumscoresreflectsthe different numberof regionsscored.Mean
body intensityscorewas comparedto remex stagefor the definitivemolt to show
whenthe greatestintensityof body molt occurred.For the first prebasicmolt the
body intensity scorewas comparedto date and age from hatchingto determine
the timing and intensityof the replacementof juvenal plumage.
Molt of the alulae and the wing and tail covertswas scoredonly as presentor
absent. For both the first and definitive prebasicmolts data were recordedfor
the alulae,uppergreaterprimary coverts,uppergreatersecondarycoverts,upper
middle secondarycoverts,lower primary coverts,lower secondarycoverts,marginal coverts,and upperand lower tail coverts.For the first prebasicmolt only,
the upper middle primary covertswere scoredalso, and the lower greaterand
lesserprimary covertswere scoredseparately.


4

ORNITHOLOGICAL MONOGRAPHS NO. 29

During the definitive prebasic molt, all but a few body feathers are replaced
within the time requiredto replacethe remiges.Therefore, estimatingthe duration
of remex molt givesan accurateestimateof the time requiredto replacevirtually
all feathers. Duration of the definitive prebasic molt was estimatedon the basis
of rate of remex molt in individual jays captured more than once, and by subjecting remex scoresfor all jays in active remigialmolt to linear regressionanalysis.
The duration of remex molt was estimatedindirectly usingmoltingjays captured two or more times at least 5 days apart. The difference in remex scores
between capturesdivided by the number of days between capturesis the rate of
molt and is given as points per day.
The timing of molt of each feather group is shownby tabulatingthe data as the
percentageof birds moltingthosefeathersduring the first half (early) and last half
(late) of each month. The timing of molt relative to the breedingseasonis shown
by plotting the percentageof birds moltingprimaries, secondaries,rectrices, and
body feathers againstdate on the samegraph as a histogramof the number of
active nests per week. The progressionof the first prebasic molt is shown by
plottingthe mean body m01tscoresfor half-monthperiods.The progressionof
the definitive prebasicmolt is shownby plotting remex scoresagainstdate.
SCRUB

JAY

MOLTS

FIRST PREBASIC MOLT

The first prebasicmolt of Florida Scrub Jays is a partial molt that includesall
body feathers, most of the alar and caudal tract coverts, a variable number of

secondaries8 through10, and a variable numberof rectrices(Table 1). No juvenile Scrub Jayswere examinedthat molted primaries or upper greater primary

coverts, and only three replacedeither the lower greater primary covertsor alula
feathers. New feathersin theseregionswere consideredreplacementsfor feathers
lost accidentally.
The onset of the first prebasic molt was marked by loss of some marginal
coverts and was followed quickly by molt of some feathers in the interscapular
region of the spinal tract and the sternal region of the ventral tract. The timing
and pattern of this molt in Florida Scrub Jays are shown in Table 1. The single
individual examinedin the first half of June had just startedto molt in the spinal
and ventral tracts, and in the marginal coverts. Of sevenjuveniles examined in
the second half of June, one had not started to molt, five had just started molt in
several body tracts, and one had feathers growing in all six body tracts. During
late June, 12 additional Scrub Jays, though not handled, were scrutinized from
a few centimetersdistance,and two appearednot to have startedmolt. The others
were molting in at least a few body tracts. Although there was some variation,
most Florida ScrubJaysbeganthe first prebasicmolt in June. ScrubJaysfledging
in late May or June probably began molt in July as shown by an individual
examined on 20 July that had not started molt. Unfortunately the exact age of
this individual was not known. All 16 individualsexaminedin August were molting. Scrub Jaysfinishedreplacingthe upper wing covertsduringlate Augustand
early September.All 55 juveniles examinedafter 15 August had replacedall the
upper secondarycoverts. By early Septembersome individualshad dropped all


MOLT

z
o

o

OF SCRUB

JAYS AND

BLUE

JAYS

5


6

ORNITHOLOGICAL

JUN

JUL

AUG

SEP

MONOGRAPHS

NO. 29

OCT

Fig. 1. Intensity of the first prebasicbody molt in juvenile Florida ScrubJays examinedin successivehalf-months.Intensity is describedby the mean body score(horizontalline), range(vertical
line),andonestandarddeviationoneithersideof themean(rectangle).Numbersaboverangesare sample sizes.

juvenal body plumage, and some had completedgrowth of new feathers on the
capital, humeral, and crural tracts. Others still hadjuvenal feathersin the capital
tract in late September.All l0 jays examined in late October had somefeathers
growing, but different individuals had completed growth in different feather regions. Five of the l0 late Octoberjays had only a few feathers still growing. The
threejays examinedin late November still were growinga few feathersin some
body tracts. Thus, growth of the last few feathers seemsto be drawn out over a
month or more.

The mean body molt intensity scorepeaked in Augustand decreasedthrough
October (Fig. 1). The singlevalue for the first half of Octoberwas for a jay from
a late brood. Thisjay was in an earlier stageof molt than mostjays at that time.
Molt of the proximal secondariesoccurred during August, September, and
October. Some Scrub Jays completedgrowth of molted secondariesby early
September. Of 42 juveniles examined after I September, 41 had molted secondaries 9 and 10, 11 also had molted secondary8, and one had molted only secondary 10. With the one exception excluded, secondary9 was molted before 10,
and secondary8 was molted either before 9 or after 10. Secondaries1-7 are not
replaced.
Normal rectrix molt was first recordedin early July when two of 25 ScrubJays
examined had droppedthe central pair of rectrices. Of 48 jays with seemingly
normal tail molt examined after 15 August, seven also had molted the pair of
rectrices immediately lateral to the central two. One jay captured in early September had molted no tail feathers. However, this was an individual from a late

brood, and by late October it had replaced the central pair. Thus, all 43 juveniles


MOLT

OF SCRUB

JAYS AND

BLUE

JAYS

7

examinedafter 1 Septemberhad replacedat least the central pair of rectrices.
Somejuveniles completedgrowth of molted rectricesby early September.The
outerfour pairsof rectriceswere not includedin the first prebasicmolt, although
sixjays had replacedsomeor all of thesefeathersafter their accidentalloss.
As most of the juveniles examinedwere bandedas nestlings,it was possible
.to comparethe timingof molt of eachfeathergroupto agefrom hatching(Table
2). Molt apparentlybeginsno earlier than two monthsafter hatching.The two
individualscaughtwhen 61 to 75 days old hadjust startedmarginalcovert molt,
and one had started molt in the interscapularregion of the spinal tract. Of 10
individualscapturedin the 76 to 90 day age bracket, two had not startedmolt,
three had startedmolt in somebody tracts, and one had startedmolt in all six
bodytracts.All 19jaysexaminedwhen91 to 105daysold hadstartedmolt. Thus,
most ScrubJays startedthe first prebasicmolt between60 and 90 days after
hatching.The intensity of body molt increasedto a peak from 121 to 135 days
after hatching and then decreased (Fig. 2). The most intense replacement of
juvenal plumageoccurredin a 75-dayperiodbetween90 and 166daysafter hatching. Molt of the proximalsecondariesoccurredbetween 105and 166days of age.
The last juvenal body feathersto be molted were in the auricular region of the
capital tract and were droppedbetween 120 and 15! days after hatching.Some
individualscompletedgrowthof new feathersin the capital,humera!,and crural
tracts when between 135and 166 days old. Althoughninejays between 180and
211 days of age still had somefeathersgrowing, all had completedgrowth of the
first basic plumagein some feather regions.All four jays capturedwhen 196 to
210 daysold had a few feathersstill growing,as did bothjays capturedwhen226

to 240 days old. Thus, it appearsthat the first prebasicmolt requiresfrom 140to
170 days from start to completion.
The central tail featherswere lost as early as 91 days post-hatchingand were
fully grownas early as 136days post-hatching.
Someyoungjays were growing
the central pair when 15! to 165days old. The few individualsthat replacedthe
secondpair droppedthem between 120 and 166 days of age.
DEFINITIVE

PREBASIC MOLT

PRIMARIES AND SECONDARIES

Remigial molt, which is highly symmetrical,startedwith the loss of primary 1
in Scrub Jays. The primarieswere molted in sequence,with from one to three
growingsimultaneouslyin each wing. Individualsbeganremigialmolt between
late April and late June and continuedinto August or September(Table 3). Secondary molt usually startedabout the time primary 4 was dropped. As many as
four secondariesper wing grew simultaneously.Generally, secondary8 was the
first secondaryto be dropped, but occasionallysecondary1 was droppedfirst.
Secondary9 was droppedsoon after 8, and sometimesbefore 1. After 9, secondaries7, 2, and 10 were droppedquickly in that order. Following 10, secondaries 3 through6 were droppedin order. Secondary6 was the last remex to be
replaced.
The mean number of primariesgrowing per wing increasedquickly to 3.1 at
remex stage3, decreasedslightly when the secondariesstartedmolting, and returned to 2.8 by stage9, after which it decreasedrapidly (Table 3). The mean


8

ORNITHOLOGICAL

MONOGRAPHS

NO. 29


MOLT

OF SCRUB

JAYS

AND

BLUE

JAYS

14

5O

9

16
2O

45
4O

•,

I0
19

35

0

•

$0
I0

0
•-

2

15

0

61 75

7690

91105

106120

DAYS

I•'1135

FROM

1•6150

151165

166180

[81195

196210

HATCHING

Fig. 2. Intensityof thefirstprebasic
moltinjuvenileFloridaScrubJaysof differentages.Intensity
is described
by themeanbodyscore(horizontalline),range(verticalline),andonestandarddeviation
on either sideof the mean (rectangle).Numbersaboverangesare samplesizes.

number of secondariesgrowingper wing increasedto a peak of 3.6 by remex
stage 7 and then decreased.
RECTRICES

Molt of the rectricesbeganbetween remex stages3 and 5 (Table 4). Two of
eight birds examinedwith primary 4 but not primary 5 growinghad molted at
leastthe centralpair of rectrices,andsevenof eightbirdsexaminedwith primary

5 but not 6 growinghad beguntail molt. Tail molt was centrifugal,and finished
with pair 6 aboutthe sametime as the remigesfinishedgrowing.Frequently,tail
featherswerelostaccidentally.We consideredall tail moltrecordedduringremex
stages1, 2, and 11+, and molt of the outer rectricesin remex stages3-5 to be
adventitious.

As many as 10 rectricesmay grow simultaneously.The meannumber increased
to 7.4 by remex stage7 and then decreasedafter remex stage9 (Table 4). The
peak number of growingrectricescoincidedwith the maximum mean number of
growingremiges(6.1 per wing).
BODY FEATHERS,ALULAE, AND COVERTS

Table 5 givesthe percentageof adult ScrubJaysin eachremex stagethat had
feathersgrowingin eachof the areasexamined.The uppergreaterprimarycoverts were moltedwith their corresponding
primaries.Individualsbeganmolting
upper secondaryand marginalcoverts about the sametime that the first secondaries were dropped,but upper covert molt finishedfirst. No individualshad any

body molt beforeprimary3 dropped.Four of eightbirdshandledwhenprimary
4 was growing had begun body molt, and all eight individualshandledwhen


10

ORNITHOLOGICAL

TABLE

MONOGRAPHS

NO. 29

3

PERCENTAGEOF ADULT FLORIDA SCRUB JAYS IN EACH REMEX STAGE OF THE
DEFINITIVE PREBASICMOLT REPLACING PRIMARIES AND SECONDARIES
Remex stagel
I

No. jays (42)

Primary

3

4

5

6

7

8

9

l0

(20)

04)

07)

(16)

(19)

(16)

(17)

(12)

(10)

II

ll+

(15)

(17)

I

100

90

64

0

0

0

0

0

0

0

0

0

2
3

62
2

100
70

86

100

0
59

0
0

0
0

0
0

0
0

0
0

0
0

0
0

0
0

4

5
6

0
0
0
0
0
0
0

0
0
0
0
0
0
0

57
0
0

100
35
0

0
0
6

76
100
47
6

0
0
8

0
0
0

0
0
0
0

0
58
100
42
0
0
0

0
0
88

0
0
0
0

63
100
69
0
0
0
0

8
92
100
67

0
30
90
90

0
0
0
0
0
13
13

0
0
0
0
0
0
0

7
8
9
10

Secondary

2

100
63
0
0

I

0

0

0

29

100

68

19

6

0

0

0

0

2
3
4
5
6

0
0
0
0
0

0
0
0
0
0

0
0
0
0
0

0
0
0
0
0

31
0
0
0
0

74
0
0
0
0

88
56
13
0
0

65
76
35
0
0

8
83
100
0
0

0
10
70
90
50

0
0
0
90
100

0
0
0
0
0

7

0

0

0

0

13

26

88

59

33

0

0

0

8
9
10

0
0
0

5
0
0

21
7
0

71
41
0

81
81
0

47
74
5

6
25
69

6
0
71

0
17
58

0
0
0

0
0
0

0
0
0

Mean no. growing
Primaries
Secondaries

1.6

0.0

2.6
0.0

3.1
0.3

1.9
1.4

2.3
3.1

2.0
2.9

2.5
3.6

2.4
3.2

2.8
3.0

2.1
2.2

0.3

1.5

0.0
0.0

• Remexstages
basedongroupings
of remexscores
(i.e., 1 = RemexScores1-10,2 = RemexScores11-20,. . . , 11= Remex
Scores 101-109, II+ = Remex Score 110).

TABLE

4

PERCENTAGE OF ADULT FLORIDA SCRUB JAYS IN EACH REMEX STAGE OF THE
DEFINITIVE PREBASlC MOLT REPLACING RECTRICES
Remex stage•
I

2

3

4

5

6

7

8

9

10

I1

11+

(33)

(17)

(10)

(14)

(16)

(19)

(14)

(16)

(ll)

(8)

(15)

(17)

6
5
4
3
2

3
0
0
3
0

0
0
0
0
0

0
7
0
7
14

6
0
0
19
75

5
5
21
95
95

21
50
86
79
93

44
75
75
81
50

100
100
100
64
0

100
100
38
13
0

67
20
0
0
0

I

3

0

0
10
0
0
0
10

50

100

89

36

0

0

0

0

0
0
6
0
0
0

No. jays

Rectrix

Left

Right

!

9

0

30

57

88

89

21

0

0

0

0

0

2
3
4

0
0
0

6
0
0

0
10
0

14
7
7

88
13
6

95
84
37

100
93
86

50
75
81

18
64

82

0
13
38

0
0
7

5
6

3
3

6
12

10
10

0
0

0
0

11
0

50
29

75
38

91
91

100
100

20
73

0
0
0
0
6

0.2

0.2

0.8

1.6

3.9

6.3

7.4

6.4

7.1

5.0

1.9

0.1

Mean no. growing

Determined as described in footnote, Table 3.


MOLT

OF SCRUB

JAYS AND

BLUE

JAYS

11


12

ORNITHOLOGICAL

MONOGRAPHS

NO. 29

9
18

I8I$

16

12

10

8

>-

II

o

m

6

4

10

o
0

I

I

2

3

4

I

I

I

I

I

I

$

6

7

$

9

I0

REMEX

I

II

STAGE

Fig. 3. Intensity of body molt in adult Florida Scrub Jays during different remex stagesof the
definitiveprebasicmolt. Intensity is describedby the meanbody score(horizontalline), range(vertical
line), and one standarddeviationon either side of the mean (rectangle).Numbersaboverangesare
samplesizes.

primary 5 was growinghad begunbody molt. Molt in the capitaltract and alulae
started between the loss of primaries 6 and 9. Regrowth of the body tracts extended beyond completionof remex growth. Tail covert molt began soon after

the onsetof tail molt duringremex stage4. The intensityof body 'molt increased
from remex stage4 to a peak at stages8 and 9 and decreasedthrough stage 11
(Fig. 3). Body molt reached maximum intensity during the same three remex
stagesin whichthe maximumnumberof remigesand rectriceswere growing(Fig.
3, Table 5).
DURATION

OF MOLT

We plottedremex scoreagainstdate for individualScrubJaysfrom five classes,
based on birds caughtmore than once, and then connectedremex scoresfor the


MOLT OF SCRUB JAYS AND BLUE JAYS

13

lOO
M

80

n-

o

60

x

'•

40

20

I

I

I

I

F

8O

o

6O

x

40

20•

N.11

0

MAY

JUN

JUL

AUG

SEP

Fig. 4. Remex scoresof individualFlorida ScrubJay breedersexaminedtwo or more timesduring
one definitive prebasicmolt (M = male breeders;F = female breeders).

sameindividual on successivecapture dates (Figs. 4, 5). Changesin the slopeof
a line reflect changesin rate of remex molt. Unfortunately, no older female helpers were caught more than once in the same molt cycle.
A mean rate of molt in points per day was determined for each of the five
classesof ScrubJays(Table 6). Only rates calculatedfrom jays capturedin active
molt were used, and only one rate was calculated for each individual based on


14

ORNITHOLOGICAL

MONOGRAPHS

NO. 29

lOO

OM
8o

6o

4o

2o

o

lOO

8o

o• •o
•

40

n-'

20
•

N•8

0

lOO

8o

6o

4o

2o

y
MAY

N•6
JUN

JUL

AUG

SEP

Fig. 5. Remexscoresof individualFloridaScrubJayhelpersexamined
two or moretimesduring
onedefinitiveprebasicmolt(OMH, oldermalehelpers;YMH, yearlingmalehelpers;YFH, yearling
female helpers).


MOLT

OF SCRUB JAYS AND BLUE

JAYS

TABLE

15

6

MEAN RATE OF THE DEFINITIVE PREBASICMOLT IN FLORIDA SCRUB JAYS,
BASED ON RECAPTURE DATA AND REGRESSION ANALYSIS
Recapture
Class

Male breeders

n

rate •

Regression
s.d.

n

rate

s.d.

10

1.064

0.086

49

0.99

0.00021

Female breeders

4

1.020

0.284

25

1.104

0.00074

Older male helpers
Yearling male helpers
Yearling female helpers

2
8
6

0.893
0.996
1.054

0.089
0.138
0.137

11
25
21

0.852
0.918
1.040

0.00033
0.00036
0.00038

1.03

0.145

Combined

30

Changein remex scoreper day.

the changein remex scorebetweenfirst and last capture.A comparisonof these
rates using a test for means with unequal variances (Sokal and Rohlf 1969:372),
was not significant(F = 1.29; d.f. = 4, 5.76; P > 0.05). Thus, jays in all five
classesapparently replace their primaries at the same rate. Therefore, a mean
remex molt rate of 1.03 pointsper day (s.d. = 0.145, range = 0.71-1.44, n = 30)
was calculated for all five classes combined. At this rate remex molt would be

completedin 107 days. If a Scrub Jay were to maintain either of the extreme
rates, remex molt would be completedin 76 or 155days. A late-breedingfemale
with nestlingsexhibited the slowest rate, 0.71 points per day. However, this
calculationis basedon observationsmadeonly 7 days apart. Two breedingmales
had slow rates duringthe early part of remex molt but increasedtheir rateslater.
One male changedonly 18 points in 23 days (0.78 p/d) and 13 points in the next
16 days (0.81 p/d). The other male changedonly 8 points in 12 days (0.67 p/d).
These slow ratesfor all three birds occurredwhile they were tendingactivenests.
The two malesincreasedtheir rates to 67 points in 58 days (1.16 p/d) and 47
points in 40 days (1.18 p/d) following nesting. The increasein rate following
nesting suggeststhat breeding males may protract molt if molt and breeding
overlap and then increasethe rate of molt after breedingis finished. Breeding
femalesthat protractedmolt while nestingprobablyalsoincreasedtheir molt rate
following nesting.An older male helper Scrub Jay also had a slow rate of 0.74
points per day (32 p/43 days), but his rate increasedto 41 points in the next 45
days (0.91 p/d). This older male helper averaged0.84 pointsper day over the 88
days betweenfirst and last capture.
Remex molt was most rapid for a breeding female who fledged young on the

late date of 2 June. She had not started molt on 30 May, yet had a remex score
of 45 by I July, indicatinga remex molt rate of at least 1.44 points per day.
Another breedingfemalechanged39 pointsin 28 days (1.39 p/d) between21 July
and 18 August, followingsuccessfulbreeding.Three individuals,a breedingmale,
a yearlingmale helper, and a yearlingfemale helper, that were capturedmore
than 30 daysaparthad increasedtheir remex scoresbetween1.24and 1.27points
per day. If thesefast rateswere maintainedthroughremexmolt, theprocesswould
be completedin lessthan 90 days. A yearlingfemale helper increasedher remex
score35 pointsin 24 days (1.45 p/d) duringthe early part of her remex molt, but


16

ORNITHOLOGICAL

TABLE

VARIATION

NO. 29

7

IN THE RATE OF MOLT FOR 10 INDIVIDUAL

Class

MONOGRAPHS

FLORIDA

SCRUB JAYS

Ratex betweensuccessive
captures

Male breeder
Male breeder
Male breeder
Male breeder
Older male helper

1.00
1.06
0.78
0.67
0.74

(12)2
(49)
(23)
(12)
(43)

1.14
1.33
0.81
1.18
1.00

(29)
(15)
(16)
(40)
(5)

Yearlingmalehelper

0.93 (56)

1.04 (26)

Yearling male helper
Yearling female helper
Yearling female helper
Yearling female helper

1.12 (56)
0.94 (48)
1.46 (24)
t .26 (35)

0.90 (20)
1.03 (32)
1.02 (57)
1.27 (23)

1.00 (59)
0.81 (27)
1.08 (26)

1.11 (32)

0.90 (40)

Pointsper day.
Number in parentheses= days between successivecaptures.

then slowedto 58 pointsin the next 57 days (1.02 p/d). Overall her averagerate
was 1.15 pointsper day, which indicatesremex molt would take about 96 days.
Remex molt rates based on Scrub Jays captured both early and late in their
molt cycles are nearly identical to those calculatedfrom the total sample.Nine
birds that were caughtfrom two to six times, whoseremex scoreshad increased
more than 80 points, averaged 1.06 points per day (s.d. = 0.06, range = 0.961.15 p/d). The sampleincludedfour breedingmales, one breedingfemale, one
older male helper,one yearlingmale helper, and two yearlingfemalehelpers.
Fluctuations in the rate of molt were examined for 10 Scrub Jays captured
three or more times (Table 7). Two breedingmales showedthe greatestfluctuations, their fastest rates being 1.8 and 1.4 times their slowest. The rates were
slow duringnestingand increasedafterward. The fastestrate for an individual
was 2.2 times the slowestrate of a different individual. Several Scrub Jays maintained relatively constantrates of molt betweencaptures.
Remex scoresfor all birds capturedin active molt were plotted againstdate,
and the plots subjectedto linear regressionanalysis(Table 6). Analysisof covariance showsthat the rates of molt for the five classesdid not differ statistically
(F = 1.485; d.f. = 4, 122; P > 0.05, Snedecorand Cochran 1967). A mean rate
basedon the total samplewas not calculatedbecauseof the spreadin the start
of molt within the population.The onsetof molt must by synchronizedin order
for regressionanalysisto estimatethe durationof molt accurately,or the duration
is overestimated(Newton 1966; Pimm 1976). The rates of molt based on the
regressionanalysisare similarto thosecalculatedfrom recapturedata.
Basedon thesecalculations,most ScrubJaysprobablycompleteremigialmolt
in 95 to 115 days. The rapid molt exhibitedby a few ScrubJays suggeststhat
someindividualsmay replacetheir remigesin lessthan 90 days;the slowrate of

an older male helper suggeststhat a few jays may take more than 130 days.
CHRONOLOGY OF MOLT

SomeScrubJaysbeganmoltingin late April, and all birdswere moltingby the
last half of June (Table 8). None of 34 Scrub Jays collectedin central Florida
between 1 Januaryand 30 April was molting.The earliestrecordof normalmolt


MOLT

OF SCRUB

JAYS

AND

BLUE

JAYS

17