Ornithological Monographs 35

(ISBN: 0-943610-44-5)

ECOGEOGRAPHICAL
IN

SIZE

VARIATION

AND

PROPORTIONS

OF SONG

SPARROWS

(MELOSPIZA

MELODIA)

BY

JOHN

W. ALDRICH

Department of Vertebrate Zoology
National Museum of Natural History, Smithsonian Institution
Washington, D.C.

ORNITHOLOGICAL

MONOGRAPHS
PUBLISHED

THE

AMERICAN

BY

ORNITHOLOGISTS'

WASHINGTON,
1984

NO.

D.C.

UNION

35


ECOGEOGRAPHICAL
VARIATION
IN SIZE AND PROPORTIONS
OF SONG SPARROWS

(MELOSPIZA MELODIA)


ORNITHOLOGICAL

MONOGRAPHS

This series,publishedby the American Ornithologists'Union, has been established for major paperstoo long for inclusionin the Union's journal, The Auk.
Publication has been made possiblethrough the generosityof the late Mrs. Carll
Tucker and the Marcia Brady Tucker Foundation, Inc.

Correspondence
concerningmanuscriptsfor publicationin the seriesshouldbe
addressedto the Editor, Dr. David W. Johnston,Department of Biology, George
Mason University, Fairfax, VA 22030.
Copies of OrnithologicalMonographs may be ordered from the Assistantto

theTreasurer
o•'theAOU;FrhnkR. Moore,
Department
ofBiology,
University
of SouthernMississippi,.SouthernStation Box 5018, Hattiesburg,Mississippi
39406. (See price list on backhandinside b•ick covers.)

Ornithological
Monographs,
No.'35,'x+ 134pp.
Editors of AOU Monographs, Mercedes S. Foster and David W. Johnston

SpecialReviewers for this issue,Richard F. Johnston, Museum of Natural

,History,
University
OfKansas,
Lawrence,
Kansas;
DennisM. Power,
Santa Barbara Museum of Natural History, Santa Barbara, California
Author, John W. Aldrich, Department of Vertebrate Zoology, National

Museum of Natural History, SmithsonianInstitution, Washington,
D.C.

20560

First-received, 13 August 1982; accepted 10 February 1983; final revision
completed, 15 June 1984
Issued December 24, 1984

Price $10.5'0 prepaid ($8.50 to AOU members).
Library of CongressCatalogue Card Number 84-73324

Printed by the Allen Press,Inc., Lawrence, Kansas 66044
Copyright ¸ by the American Ornithologists'Union, 1984
ISBN:

0-943610-44-5

ECOGEOGRAPHICAL
IN SIZE AND

VARIATION
PROPORTIONS

OF SONG

SPARROWS

(MELOSPIZA

MELODIA)

BY

JOHN W. ALDRICH
Department of Vertebrate Zoology
National Museum of Natural History, Smithsonian Institution
Washington, D.C.

ORNITHOLOGICAL

MONOGRAPHS
PUBLISHED

THE

AMERICAN

BY

ORNITHOLOGISTS'

WASHINGTON,
1984

iii

NO.

D.C.

UNION

35


iv


TABLE

LIST OF FIGURES

.........................................................................................................................................
viii

LIST OF APPENDICES
LIST

OF TABLES

INTRODUCTION
METHODS

OF CONTENTS

.................................................................................................................................
ix

.....................................................................................................................................................
x

...................................................................................................................................................
1

..................................................................................................................................................................
4

WING MEASUREMENTS
...............................................................................................................................
6
TOTAL WING LENGTH ..................................................................................................................................
6
Sex Differences ..........................................................................................................................................
6

Differencesby Life Area ...................................................................................................
6

Differencesby Ecoregion Province .................................................................................
8
Differencesby EcoregionSection/Life Area ...............................................................
9
Discussion

...................................................................................................................................................
14

WING-TIP LENGTH .............................................................................................................................................
15
Sex Differences ..........................................................................................................................................
15

Differencesby Life Area ...................................................................................................
15
Differencesby Ecoregion Province .................................................................................
16
Differencesby EcoregionSection/Life Area ...............................................................
17

Discussion ...................................................................................................................................................
21
RATIO OF WING-TIP TO WING LENGTH ............................................................................................
21
Sex Differences ..........................................................................................................................................
21

Differencesby Life Area ...................................................................................................
22

Differencesby Ecoregion Province .................................................................................
23
Differencesby EcoregionSection/Life Area ...............................................................
24
Discussion

..............................................................................................................................................
28

DISCUSSION OF ALL WING MEASUREMENTS ................................................................................
28
BILL

MEASUREMENTS

......................................................................................................................................
30

TOTAL CULMEN LENGTH .................................................................................................................................
30
Sex Differences

..........................................................................................................................................
30

Differencesby Life Area ...................................................................................................
30
Differencesby Ecoregion Province .................................................................................
31
Differencesby Ecoregion Section/Life Area ...............................................................

32

Discussion ..............................................................................................................................................
36
HEIGHT OF MAXILLA ........................................................................................................................................
36
Sex Differences

..........................................................................................................................................
36

Differencesby Life Area ...................................................................................................
36
Differences by Ecoregion Province ...................................................................................
37
Differencesby Ecoregion Section/Life Area ...............................................................
38
Discussion

...................................................................................................................................................
43

RATIO OF HEIGHT OF MAXILLA TO CULMEN LENGTH ....................................................
43
Sex Differences ..........................................................................................................................................
43

Differencesby Life Area ...................................................................................................
43

Differencesby Ecoregi0nPr9vince .............................................................................
44
Differences by Ecoregion Section/Life Area ...............................................................
45
Discussion
WIDTH

..............................................................................................................................................
49

OF MAXILLA

Sex Differences

.........................................................................................................................................
49
......................................................................................................................................
49

Differencesby Life Area ...................................................................................................
49
Differences by Ecoregion Province ...................................................................................
50
Differencesby Ecoregion Section/Life Area ...............................................................
51
Discussion

..............................................................................................................................................
.•.

............ 80
OF MAXILLA TO CULMEN LENGTH ......................................................
80
Sex Differences ..................................................................................................................................
80

RATIO OF WIDTH

Differencesby Life Area .........................................................................
:.............................................
81
Differencesby EcoregionProvince ...............................................................................
82
Differencesby EcoregionSection/Life Area ...............................................................
83

Discussion ..............................................................................................................................................
84
DISCUSSION OF ALL BILL MEASUREMENTS ...................
:................................................................
85

TARSUS MEASUREMENTS

.............................................................................................
•....................................
86

TARSUS LENGTH .................................................................................................................................................
86

Sex Differences

......................................................................................................................................
86

Differencesby Life Area ............
•...........................................................................................
86
Differencesby Ecoregion Province .................................................................................
87
Differencesby Ecoregion Section/Life Area ...............................................................
88
Discussion

....................................................................
•...........................................................................................
91

RATIO OF TARSUS LENGTH TO WING LENGTH .......................................................................
92
Sex Differences ......................................................................................................................................
92

Differencesby Life Area ...................................................................................................
92
Differencesby EcoregionProvince ...............................................................................
94
Differencesby Ecoregion Section/Life Area ..............................................................
95

Discussion

..............................................................................................................................................
99

DISCUSSIONOF ALL TARSUSMEASUREMENTS...........................................................................
99
TAIL

MEASUREMENTS
.....................................................................................................................................
101
TAIL LENGTH ...................................................................................................................................................
101
Sex Differences ......................................................................................................................................
101

Differencesby Life Area ............................................................................................
101
Differencesby EcoregionProvince ................................................................................
102
Diff6rencesby EcoregionSection/LifeArea .............................................................
103
Discussion

...............................................................................................................................................
106

RATIO OF TAIL LENGTH TO WING LENGTH .................................................................................
107

Sex Differences ..................................................................................................................................
107

Differencesby EcoregionProvince ..............................................................................
107

Discussion ...................................................................................................................................................
108
DISCUSSION OF ALL TAIL MEASUREMENTS ....................................................................................
108
MIDDLE

TOE

LENGTH

Sex Differences

......................................................................................................................................
109

..........................................................................................................................................
109

Differencesby Life Area ...................................................................................................
109
Differencesby EcoregionProvince ................................................................................
109
vi

Differencesby EcoregionSection/Life Area ...............................................................
110
Discussion

...................................................................................................................................................
114

GENERAL DISCUSSION OF ECOGEOGRAPHICAL VARIATION .........114
SEXUAL DIMORPHISM

........................................................................................................................................
115

OVERALL ECOGEOGRAPHICVARIATION ..............................................................................................
1 16
ACKNOWLEDGMENTS
SUMMARY

..................................................................................................................................
118

.................................................................................................................................................................
119

LITERATURE CITED ..............................................................................................................
:...... 120

vii

LIST
Figure 1.
2.
3.

Life Areas of North America

....................................................................................................
2

Ecoregionsof North America .......................................................................................
3
Map of North-South Transects Connecting Ecoregion Section/
Life Area Units

4.

OF FIGURES

.................................................................................................................................
6

Map of East-West Tmnsects Connecting Ecoregion Section/Life
Area Units

..............................................................................................................................................
8

5. Relative Wing Lengths of Males in Different Ecoregion Sections 11
6. North-South Transects of Mean Wing Lengths ...................................................
12
7. East-West Transects of Mean Wing Lengths ..........................................................
13
8. Relative Wing-tip Lengths of Males in Different Ecoregion

Sections ............................................................................................................................................
18

9. North-South Transectsof Mean Wing-tip Lengths ........................................
19
10. East-West Transectsof Mean Wing-tip Lengths ................................................
21
11. Relative Ratios of Wing-tip to Wing Length of Males in Different
Ecoregion Sections ...........................................................................................................
25
12. North-South Transectsof Mean Wing-tip to Wing Length Ratios 26
13. East-West Transectsof Mean Wing-tip to Wing Length Ratios _ 27
14. Relative Total Culmen Lengths of Males in Different Ecoregion

Sections ................................................................................................................................................
33

15. North-South Transects of Mean Total Culmen Lengths .........................
34
16. East-West Transects of Mean Total Culmen Lengths .................................
35
17. Relative Heights of Maxillae of Males in Different Ecoregion

Sections ................................................................................................................................................
40

18. North-South Transects of Mean Heights of Maxillae .................................
41
19. East-West Transectsof Mean Heights of Maxillae .........................................
42
20. Relative Ratios of Height of Maxilla to Total Culmen of Males
in Different Ecoregion Sections ....................................................................................
46
21. North-South Transects of Mean Height of Maxilla to Culmen
Ratios

........................................................................................................................................................
47

22.

East-West Transects of Mean Height of Maxilla to Culmen

23.
24.
25.
26.

Relative Tarsus Lengthsof Males in Different EcoregionSections 89
North-South Transects of Mean Tarsus Lengths ...............................................
90
East-West Tmnsects of Mean Tarsus Lengths ......................................................
92

Relative Ratios of Tarsus Length to Wing Length of Males in
Different EcoregionSections......................................................................................
96
North-South Transects of Mean Tarsus to Wing Ratios ........................
97
East-West Transects of Mean Tarsus to Wing Ratios ................................
98
Relative Tail Lengthsof Males in Different EcoregionSections.. 104
North-South Transects of Mean Tail Lengths ......................................................
105
East-West Transects of Mean Tail Lengths ..............................................................
106
Relative Middle Toe Lengths of Males in Different Ecoregion

Ratios

27.
28.
29.
30.
31.
32.

........................................................................................................................................................
48

Sections ................................................................................................................................................
111

viii

33.
34.

North-South Transectsof Mean Middle Toe Lengths ...............................
112
East-West Transects of Mean Middle Toe Lengths .......................................
113

LIST
I.
II.
III.
IV.
V.

OF APPENDICES

Song Sparrow Breeding Habitats ......................................................................................
124
SongSparrow Migration .................................................................................................
128
Recoveriesof Winter-banded (January-February)SongSparrows 131
Food of Song Sparrows .....................................................................................................
133
Differences in Proportions of Animal Food of Song Sparrows
during Breeding and Winter Seasons................................................................................
134

ix


LIST
Table

1.

OF TABLES

Mean Linear Measurements of Male Song Sparrows by Life

Area ........................................................................................................................................................
52
2.

Mean Linear Measurements of Female Song Sparrowsby Life

Area ........................................................................................................................................................
53
3.

Mean Linear Measurementsof Male SongSparrowsby Ecoregion
Province

.....................................................
:.............................................................................................................
54

5.

Mean Linear Measurements of Female Song Sparrowsby Ecoregion Province ............................................................................................................
56
Mean Linear Measurements of Male SongSparrowsby Ecoregion

6.

Mean Linear Measurements of Female Song Sparrows by Ecore-

7.

gion Section/Life Area .................................................................................................
64
Mean Ratios of Song Sparrow Linear Measurementsby Life Area 70
Mean Ratios of SongSparrow Linear Measurementsby Ecoregion

4.

Section/Life

8.

Province
9.

Area ...........................................................................................................................
58

................................................................................................................................................
71

Mean Ratios of SongSparrowLinear Measurementsby Ecoregion
Section/Life

Area ...............................................................................................................................
73


INTRODUCTION

The correlation of morphologicalvariation of plants and animals with environmental variableshas interestedbiologistsfor many years. Small, genetically
controlled variations for which environmental factorsact as selectiveagentsare
generallybelieved to be the building blocksof evolution. Intraspecificdifferences
that may lead to speciation are frequently coincident with variations in the environment within the species'range.
I studiedvariation in the wide rangingand morphologicallyhighly variable
North American SongSparrow,Melospiza melodia,in relation to the totality of
environmental factors representedby specificmajor biotic communities as recognizedand describedby ecologists.My purposewas to determine if particular
morphological differences in the birds coincided with the distribution of biotic
communities,thus indicating their morphologicaladaptation to the samefactors
that control the composition and distribution of those biotic communities. I
believedthat information on the nature and extentof morphologicalvariation in
SongSparrowsand its relation to factorsknown to control the compositionand
distribution of biotic communities would be significant in understandingthe
reasonsfor the marked intraspecific variation in animals and would provide a
rewarding approach to this phase of evolutionary biology.

In the presentstudyI have correlatedmeasurements
and proportionsof Song
Sparrowswith Life Areas(Aldrich 1963, 1966),EcoregionProvinces,Ecoregion
Sections(Bailey 1976), and combinationsof Life Areasand EcoregionSections,

in an attemptto determinethe probableadaptivevalue of the morphological
variation.Plumagecoloration,whichis knownto vary greatlygeographically,
was
not considered.My rationalefor usingLife Areasand Ecoregionswasthat both
are basedprimarily on climax vegetation,which impartsa specificidentifying
aspectto them, and that both are virtually visible expressionsof the environmental

factorsthat delimit them. AlthoughSongSparrowsdo not useclimaxvegetation
extensively,at leastduringthe breedingseason,in any part of their geographical
range (Appendix I), climax vegetation is an indicator of combined climatic and
physiographicfactors,as well as of the typesof habitatsof both climax and seral
communities,which do impinge directly on SongSparrows,and to which the
birdsmustbe adaptedin orderto survive.The significance
of the dominantclimax
vegetationasan indicatorof thetotalenvironmentof a geographical
areaistreated
at lengthby WeaverandClements(1938:89-90),Carpenter(1939),Clementsand

Shelford(1939),Pitelka(1941),Dice(1943),Odum(1953),andKendeigh(1954).
Manypreviousstudies(summarized
in Mayr 1951;Power1970;Selander1971)
havedealtwith the effectsof singleenvironmentalfactors,suchastemperature,
rainfall,or soils,on sizeproportions
or colorof birds.A fewworkers,however,
have studiedthe relationsbetweenvariation in morphologicalfeaturesand all
environmental
factorsthatcharacterize
ecogeographical
units.For example,Marshalland Behle(1942) described
two racesof SongSparrowsliving in adjacent

ecologically
distinctzonesin Utah. AldrichandFriedmann(1943)described
the
association
of morphological
variationin RuffedGrouse(Bonasaumbellus)
with
ecogeographic
unitsthroughoutthe entirespeciesrange.Aldrich (1963) showed
that geographical
racesof Americangrousespeciestend to be correlatedwith the


2

ORNITHOLOGICAL

;•"

•::•'"

•':•:•

•/•/•

'.

MONOGRAPHS

NO. 35

•

7 PacifIc
RainFoilIt

•

lO

•

1ß Mexican
FineandPlnl-Oik

FIG. 1. Life Areas of North America. Basedon Aldrich (1966).

ecologicalclimax areas in which they live, and suchecogeographicalunits, called
"Life Areas," were mapped. Rea (1973) correlated variations in Scaled Quail
(Ca!!ipepla squamata) with desert scrub and short-grassprairie ranges.Aldrich
and Weske (1978) related color and size variations in House Finches(Carpodacus
mexicanus)to the Biotic Provincesof Dice (1931. 1943) and Ecoregionsof Bailey
(1976).

The Life Areas of North America (Fig. l) were first mapped, describedand
discussedin relation to the distributionof subspecies
of North American grouse
(Aldrich 1963). Life Areas are basedon climatic climax dominant vegetationof

VARIATION

IN SONG

SPARROWS

3

FIG. 2. Ecoregionsof North America. Modified from Bailey(1976), and expandedbasedon Dice
(1943), Leopold(1950), Rowe (1959), Aldrich (1966), and Crowley (1967).

specific physiognomic types and thus resemble the Formations of Weaver and
Clements(1938) or Biomes of Clements and Shelford(1939). In contrast,however,
they include a few distinct and extensiveecotonesbetweenFormations or Biomes,
such as Northern Hardwood-Conifer, Oak-Savannah, and Aspen Parkland, and
alsoextensivefire-maintained subclimaxessuchas SoutheastEvergreenand Chaparral-Oak Woodland. Some boundaries of Life Areas based on Ktichler (1964)
were revisedby Aldrich (1966) after the first Life Area map was published.These
changesare chiefly in the distribution of the Grasslandsand Oak-Savannah Life
Areas. In the present study the Open and Closed Boreal Life Areas of Aldrich
(1966) are combined into a single"Boreal Life Area" (Fig. 1).
The Ecoregions(Fig. 2) are based primarily on Bailey (1976) for the United


4

ORNITHOLOGICAL

MONOGRAPHS

NO. 35

States,but modifiedto includeCanadaandMexicobasedonDice (1943),Leopold
(1950), Rowe (1959), Aldrich (1966), and Crowley (1967). Ecoregionsare continuousgeographicalareas,like the Biotic Provincesof Dice (1943). In this respect
they differ from Life Areas,which are as discontinuous
as the climax vegetation
types on which they are based. Ecoregionsare characterizedby the occurrenceof
one or more important ecologicalassociationsthat differ, at least in proportional
area covered, from associationsof adjacent regions. In general, Ecoregionsare
characterizedalso by a distinctive flora, fauna, climate, landform, soil, 'and ecological climax. They are divided into hierarchical levels including Domain, Division, Province, and Section in decreasingorder of inclusiveness.Provinces and
Sections are further divided into lowland and highland types. A Province is a
subdivisionthat correspondsto a broad vegetation region having a uniform regional climate and characteristictypes of zonal soils. Generally, each Province is
characterizedby a single chmax association,but two or more climaxes may be
representedwithin a single Province. The Ecoregi0n Provinces of Bailey (1976)
are similar to the Biotic Provincesof Dice (1943) but are more detailed and more
exactly ecologically oriented. An Ecoregion Section is based on local climatic
variation and characterizedby a singleclimax associationas defined by Kiichler
(1964), exceptin mountainous areaswhere zones of more than one climax type
occur.

METHODS

In the presentstudy I have employed the Life Area (Fig. 1), and the Ecoregion
Province and Section(Fig. 2), and combinationsthereof as data groupingunits
for comparingmean measurementsof SongSparrowS.I have further divided the
EcoregionSectionsinto their component zones (called "Life Belts") which are
equivalent to the Life Areas appearingas elevational belts in Figure 1. In mountainous regionsthese are the elevationalzonesrecognized,but not mapped, by
Bailey (1976). Compositionof the EcoregionSection/LifeArea units appearing
in Tables 5, 6, and 9 (Tables 1-9 arefound on pp. 52-78) are indicated by a prefix
number that identifies the Life Area (Fig. 1; Tables 1, 2), and a secondnumber
(following the dash), that identifies the Ecoregion Section (Fig. 2; Tables 5, 6).

The letters M, P, and A identify the Ecoregion as mountainous, plateau, or altiplano, respectively. The portions of Life Areas segregatedin Ecoregion Sections
and form4ngthe Section'sLife Belts are of a single climax community and are
equivalent to the "Life Are'as" of Aldrich's (1966) figure 1.
Specimensof Song Sparrows used in the present study were taken from areas
representingmost of the breedingrangeof that species
'and are chieflyfrom the
collections of the National Museum of Natural History, Washington, D.C., and

the Museum Of Vertebrate Zoology; UnivErsity of California •at Berkeley. No
specimensfrom California offshoreislands were included. Only specimenstaker/
from May througli August were used to avoid the inclusion of migrants. This

restrictedperiodof collectionalsoinsuredthat the specimens
wouldbe more
comparable from the standpoint of seasonalplumage wear.
Measurements used were the chord of the folded wing, length of the wing-tip

frome•d oflongest
secondary
t6 tip oflongest
primary,taillengthfrominsertion
of two middle tail feathersto the tip of the longestfeather, total culmen length
from depressionin forehead separatingculmen from cranium to tip of culmen,


VARIATION

IN SONG

SPARROWS

5

tarsuslengthfrom the posteriorproximal end of the tarsometatarsusto the anterior
distal end of the most distal tarsal scute, middle toe length from the end of the
most distal tarsal scuteto the distal end of the toe at its junction with the claw,
height of maxilla from edgeof the tomial notch to the oppositepoint on the dorsal
surface of the maxilla, and width of maxilla at its widest point. In addition, ratios
were determined for length of wing-tip to total wing length, height of maxilla to
lengthof total culmen, width of maxilla to lengthof total culmen, length of tarsus
to length of wing, and length of tail to length of wing. All measurementswere
made to 0.1 mm with a dial caliper equipped with needle points.
I groupedthe 828 male and 406 female specimensby sexinto the ecogeographic
unit which they representand determined the means and standard deviations of
the measurementsand their ratios for each group. The sampleswere arranged in
descendingorder of magnitude of the means of each measurement and ratio to
permit grosscomparison of the relationship of populations representingthe different ecogeographicalunits. I grouped the mean measurementsand ratios for
most male charactersin three size categoriesand indicated the categorieson maps
which appear as figuresin the appropriate character sections.The size categories
were derived by dividing the total range(for males) of means of eachmeasurement
and ratio for EcoregionSectionsinto three equal parts. The larger one-third of
means is designatedas "larger," "longer," or "higher," the middle one-third as
"medium," and the smaller one-third as "smaller," "shorter," or "lower," dependingon the nature of the charactermeasured.If meansare exceptionallylarge
or small, so that they distort the division of values into three equal parts of the
total, they are so indicated and were not included in computing the three size
categories.
Means Of measurementsand their ratios of birds from adjoining Life Area,

EcofegionProvince,and EcoregionSection/LifeArea,unitswerecomparedwith
the Student's t-test to determine if differenceswere significant;P values of 0.05

or lesswere consideredsignificant.The Student's t-test was used with these variables because it has been shown to be robust in the face of minor

violations

of

assumptionsfound in this type of data (Boneau 1960; Lee-Ann Hayek, pers.
comm.).

Finally, I arrangedmeans of measurementsand ratios representingEcoreglon
Section/Life Area units along eight north to south transectsand three east to west
transects(Figs. 3, 4) and comparedthem by Student'st-test to determine signif-

icant characterdifferencesthat might demonstrateprogressivetrends or sharp
morphological changesrelated to ecogeographicaldifferences. I compared the
resultsof all of theseanalysesin an attempt to elucidate patterns of variation in
SongSparrowsin relation to the ecogeographicalunits.
Means of each characterfor each sex for each of the 49 EcoregionSection/Life
Area units were comparedby the Student's t-test to determine sexualdimorphism
in those characters.Correlation of the variations in male and f6male characters
and, in a few cases, correlation of variations in two different characters in the

samesex,weredetermined.
Correlation
coefficients,
r, is wellasP values,were
determined by standard programs of the Howlett•Packard 67 Oalculator. (
Measurements of all specimens.used"in this study are available for further

analysis

in the-"species
files"of theU.S.FishandWildlifeService
offices,
Bird
Division, National Museum of Natural History, Washington;D.C. 20560.


6

ORNITHOLOGICAL

MONOGRAPHS

NO. 3 5

Pacific Coa•
ntral

Forests

Alask•
•stern

Sierra Nevada

Forests
•,tlantic
Marshes

A5

ns
4

Interior Basin,,

i

H

---.

'

Fro. 3. Map of north-south transectsconnectingEcoregionSection/Life Area units. A. Pacific
Coast:1--Alaska Range(Aleutians);2--Alaska Pacific;3 -- SitIraSpruce-Cedar-Hemlock;
4--Redwood
Forest; 5--California Chaparral. B. Alaska Pacific-Cascades-SierraNevada: 1--Alaska Pacific; 2--

Columbia Forest(montane);3--Silver Fir-Douglas-fir(Cascades);4--Sierran Forest (montane);5-California Grassland (valley); 6--California Chaparral. C. Interior Basins: l--Central Boreal; 2-PalouseGrassland;3--Sagebrush-Wheatgrass;
4--Lahontan Saltbush-Greasewood;
5--Mojave Desert;
6--Sonoran Desert.D. RockyMountains: 1-- CentralBoreal;2--Columbia Forest(moist);3--Northem RockyMountains(montane);4--Upper Gila MountainsForest;5--Mexican ShrubSteppe(north).
E. Central Plains: 1--Central Boreal;2--Aspen Parklands(east);3 --Short-grassPrairie east.F. Central
Forests: l--Central Boreal; 2--Spruce-Fir (Minnesota); 3--Northern Hardwoods (New York-Wisconsin);4--Oak-Hickory-Bluestem Parkland; 5--Oak-Hickory Forest. G. Eastern Forests:1--NewfoundlandBoreal; 2--Northern Hardwood-Spruce(maritime); 3--Northern Hardwood-Spruce(New
England);4--Northern Hardwoods(New York-Wisconsin);5--Appalachian Oak (deciduous);6-SoutheasternMixed Forest. H. Atlantic Coastal Marshes: 1--Ariantic Coastal Marsh (north); 2-Ariantic CoastalMarsh (south).

WING
TOTAL WING

MEASUREMENTS

LENGTH

Sex differences.--Males have longer wings than females in all 49 Ecoregion
Section/Life Area samples of more than one specimen of each sex. Male wings
are significantly longer in 41 populations (all except 3-1320, 3-1320A, 4-2111,
7-M2413, 9-3111, 6-M3111, 11-3112 and 13-3140).

Differencesby Life Area (Fig. 1; Tables 1, 2).--Means of total wing lengths
arranged in order of decreasingsize for males are:


VARIATION

IN SONG

SPARROWS

7

Mean
1
11

• N

Mean

Arctic-Alpine (Aleutian)

59

81.43

38

78.27

Northern

96

68.56

40

64.64

50

68.19

30

64.14

Desert

Scrub

14

Pition-Juniper-Oak

lO

Oak-Savannah

17

Mexican

Pine-Oak

9

Grasslands

7

Pacific Rain Forest

6

Montane

5

Aspen Parkland

3

Boreal

2

67.90

0

--

18

67.79

3

63.87

49

67.72

31

64.18

107

67.62

71

63.83

26

67.53

16

63.85

Woodland-Brush

6

67.32

3

64.67

22

66.30

6

63.85

6

61.95

13

Mesquite-Grassland

14

66.06

12

Southern

Desert

25

65.97

12

62.32

4

Northern

Hardwood-Conifer

112

65.96

40

62.92

8

Eastern Deciduous

115

65.45

46

62.36

62.47

12

58.55

15

Scrub

Forest

Chaparral-Oak Woodland

31

The correlation between male and female wing lengths is high (r = 0.99, P <
0.001).
Significant differences between mean wing lengths of adjacent Life Areas are:
Arctic-Alpine > Boreal (& •); Northern Hardwood-Conifer > Eastern Deciduous
Forest ½); Grasslands) EasternDeciduous Forest (& •); Northern Desert Scrub )

Southern Desert Scrub (& •); Mexican Pine-Oak ) Mesquite-Grassland(& •);
Grasslands) Mesquite Grassland(& •).
In addition to differences in mean wing lengths of birds from different Life
Areas, mean wing lengthsof birds from different EcoregionSectionswithin Life
Areas differ significantlyas follows:
Boreal

3-1320B Central Boreal > 3-1320a Newfoundland Boreal ½)

Northern Hardwood-Conifer
4-2111 Spruce-Fir (N. Minnesota) ) 4-2113 N. Hardwoods (New York-Wisconsin) (•)

Pacific Rain Forest

7-M2416 Alaska PacificForest ) 7-2410 Willamette-PugetForest (•)
7-M2416
½, •)

Alaska

Pacific Forest )7-M2411

Sitka

Spruce-Cedar-Hemlock

7-M2411 Sitka Spruce-Cedar-Hemlock > 7-M2412 Redwood Forest (& •)
7-M2413 Pacific Forest (inland) > 7-M2412 Redwood Forest (& •)
7-M2411 Sitka Spruce-Cedar-Hemlock ) 7-M2415 CascadesForest (•)
Eastern

Deciduous

Forest

8-2214 Appalachian Oak (deciduous)> 8-2320 SoutheasternMixed Forest (•)


8

ORNITHOLOGICAL

MONOGRAPHS NO. 35

Northern

i

i
i

Median

e I0!
lB

IC

Southern

CI3

i

FIo.4. Mapof east-west
Wansects
connecting
Ecoregion
Section/Life
Areaunits.A. Northern:1-Newfoundland
Boreal;2--Spruce-Fir
(Minnesota);
3--AspenParklands

(east);4--CentralBoreal;5AlaskaPacific;
6--AlaskaRange(Aleutians).
B. Median:1--NorthernHardwoods-Spruce
(Maritime);
2--NorthernHardwoods-Spruce
(New England);3--Northern Hardwoods(New York-Wisconsin);

4--Tall-grass
Prairie(west);
5--Short-grass
Prairie(east);
6--Short-grass
Prairie(west);
7--Northern
RockyMountains
(montane);
8--Columbia
Forest
(moist);
9--SilverFir-Douglas-fir
(Cascades);
10SitkaSpruce-Cedar-Hemlock.
C. Southern:
1--At]anticCoastalMarshes(south);2--Southeastern
MixedForest;
3--MixedMesophytic
Forest;
4--Oak-HickoryForest;
5--Oak-Hickory-Bluestem
Park-

land;6--Tall-grass
Prairie(west);
7--Short-grass
Prairie(east);
8--Northern
RockyMountains
(montane);9--Sagebrush-Wheatgrass;
10--Labantan
Saltbush-Greasewood;
11--Sierran
Forest
(montane);
12--CaliforniaGrassland(valley);13--CaliforniaChaparral.

Northern Desert Scrub

11-3131 N. Desert Scrub (sagebrush)> 11-3132 N. Desert Scrub (Lahontan
Greasewood) (5)
Mexican

Pine-Oak

17- Mexican Pine-Oak(S. Mexico) > 17-M2620 CaliforniaChaparral(Pine-Oak
in Baja California) (5)

Differences
by EcoregionProvince(Fig. 2; Tables3, 4).--Means of total wing
lengthsarrangedin order of decreasingsize for malesare:

VARIATION

IN SONG

SPARROWS

9

Mean
M1310

Mean

59
9
47
108

81.43
69.43
68.62
68.55

38
1
19
56

78.27

68.50
64.76
64.56

Mexican Pine-Oak
Pacific Forest
Prairie Parkland

15
93

15
60

2

68.25
67.97
67.90

0

63.87
65.08
--

Short-grassPrairie
Tall-grass Prairie

7

13

67.71
67.37

11
6

64.46
64.47

3120

California Grassland
Palouse Grassland

3
21

67.10
67.08

4
9

6 !.80
64.14

2410

Willamette-Puget Forest

16

66.69

10

62.35

2110

Laurentian

47

66.39

20

62.90

1320

Boreal Forest
Columbia Forest
Colorado Plateau

22
13

0

66.30
66.23
--

6
5
2

63.85
63.46
63.10

Mexican Shrub Steppe

14

66.09

6

61.95

8
25
149

66.05
65.97

65.73

5
12
52

62.90
62.32
62.33

6

65.42

5

62.62

A3140
M3110

3130
17

M2410
2510
3110
2530

2610

M2110
P3130

3140
M2610
3220

2210
M3120
2320

M2620

Alaska Range (Aleutians)
Wyoming Basin
Rocky Mountains Forest
Intermountain Sagebrush

$N

Forest

Sierran Forest
American Desert
Eastern Deciduous

Forest

Upper Gila Mountains Forest

Southeastern

Mixed

California Chaparral

Forest

84

65.29

44

62.13

57

61.37

25

56.39

Male and femalewing lengthsare highly correlated(r = 0.97, P < 0.001).
Significantdifferences
betweenmeanwinglengthsin adjoiningEcoregionProvinces are: Alaska Range (Aleutian Islands)> Boreal Forest (6, $); LaurentJan
Forest > EasternDeciduousForest(6); Alaska Range(Aleutian Islands) > Pacific
Forest(6, •); PacificForest > Willamette PugetForest(•); California Grassland>
CaliforniaChaparral(6, $);RockyMountainsForest> ColumbiaForest(6);Mexican Pine-Oak(S) > Mexican HighlandsShrubSteppe(S) (6, $); Intermountain

Sagebrush> American Desert (6, $); Tall-grassPrairie > EasternDeciduousForest (6, $); Rocky Mountains Forest > PalouseGrassland(6).
Differences
byEcoregionSection/LifeArea(Fig.2; Tables5, 6).--When average
wing lengthsof populationsin adjacentEcoregion/LifeArea unitsare compared,
significantdifferences
are: l-M1310 Aleutians> 7-M2416 AlaskaPacific(6, $);
7-M2416 AlaskaPacific> 7-M2411 SitkaSpruce-Cedar-Hemlock
(6, $);7-M2411
Sitka Spruce-Cedar-Hemlock> 7-M2412 Redwoods(6, $); 7-M2413 PacificForest(inland) > 9-M2412 Redwoods(6, $);6-M2610 SierranMontane > 15-M2620
CaliforniaChaparral(6, $); 6-M3112 N. Rocky Mts. Montane > 14-M3111 OregonMontane (Pition-Juniper)(6); 11-3131 N. Desert Scrub(Sagebrush)
> 113132 N. Desert Scrub(LahontanSaltbush)(6); 11-3131 N. Desert Scrub(Sagebrush) > 9-3120 Palouse Grassland (6); 6-M3112 N. Rocky Mts. Montane >


10

ORNITHOLOGICAL

MONOGRAPHS

NO. 35

7-M2112 Columbia Forest (moist) (8); 3-1320B Central Boreal > 3-1320A Newfoundland Boreal (8); 4-2114A Northern Hardwoods (Maritime)> 3-1320A
Newfoundland Boreal (8); 8-2214 AppalachianOak (deciduous)> 8-2320 Southeastern Mixed Forest (8); 10-2511 Oak Savannah > 8-2215 Oak-Hickory Forest
(•); 9-2610 California Grassland > 15-M2620 California Chaparral (•, e).
In somecases,Life Belts (Life Areas)within the sameEcoregionSectiondiffer
significantly:15-M2620 California Chaparral (chaparral) > 9-M2620 California
Chaparral (grass) (8); 17-M2620 California Chaparral (Pine-Oak) > 15-M2620
California Chaparral (chaparral) (8); 9-M3111 Oregon Montane (grass)> 14M3111 Oregon Montane (Pition) (•); 15-M2620 California Chaparral (chaparral) > 9-M2620B California Chaparral (San FranciscoBay Marsh South) (8, e);
14-3132 Lahontan Saltbush (Pition) > 11-3132 Lahontan Saltbush (N. Desert)
(8); 15-M2620 California Chaparral (chaparral) > 9-M2620A California Chaparral (San Francisco Bay Marsh North) (e).

Relative lengthsof wingsof males in different EcoregionSectionsare shownin
Figure 5.

North-south transects.A north to south transect along the Pacific coast (Figs.
3, 6, transect A) shows a cline of significant progressivedecreasesin male and
female wing lengthsin succeedingpopulationsfrom the Aleutian Islands tundra
to the California redwoods,then a nonsignificantincreaseto the California Chaparral-Oak. The general trend along the coast is a marked north-south cline of
decreasingwing length.
A more interior transectfrom coastalAlaska southeastwardalong the Cascades
and Sierrasto the California Chaparral (Figs. 3, 6, transect B) showsa significant
decreasein male wing length to the Columbia Montane of northern Washington
and in female wing length to the Cascades,then no change in either sex from
there to the Sierra Forest, and finally, a significant decreasein wing lengths of
both sexespassingfrom the Sierra Forest to the California Chaparral. The general
trend is a lessprecipitousnorth to south cline of decreasingwing length than in
the coastal transect.

A transect from the Central Boreal south through the interior basins to the
Sonoran Desert of southernArizona (Figs. 3, 6, transect C) showsa significant
increase in male but not female wing lengths between the Palouse Grassland of
eastern Washington and the Sagebrush-Wheatgrassof the Northern Great Basin
of southernOregon and Idaho, a decreasein wing length significantin males and
insignificantin femalesfrom thereto the LahontanSaltbush-Greasewood
Section
in the central western Great Basin, then little changefrom there to the Sonoran
Desert of southern Arizona. No continuous cline is evident along the interior
basins transect. Rather increasesand decreasesbetween ecological units fluctuate.
Male wing lengthis maximal in the Sagebrush-Wheatgrass,
and femalewing length
greatestin the Central Boreal.

A transect from the Central Boreal down the Rocky Mountains (Figs. 3, 6,
transectD) showsa nonsignificantdecreasein wing lengthsof both sexesas far
as the moist Columbia Forest of northern Idaho and northwestern Montana, then
a significantincreasein male wing lengthto the northern Rocky Mountains Forest
of western Wyoming and Montana, followed by a significantdecreasein wing
lengthsof both sexesfrom there to the Upper Gila Mountains Forest of middle


VARIATION

IN SONG SPARROWS

11

FXG.5. Relativewinglengthsof malesin differentEcoregion
Sections.
L = Longer;S = shorter;
M = middle one-thirdof means;VL = very long;VS = very short.

ArizonaandNew Mexico.Apparentlywinglengthalongthe RockyMountains
transect does not show a north-south cline but rather increasesand decreasesin

relationto local ecological
factors.Maximum wing lengthsfor both malesand
femalesare foundin the northernRockies,minimummalewinglengthin the
UpperGila MountainsForest,andminimumfemalewinglengthin the Mexican
Shrub Steppe of Arizona.
Along a transectfrom the Central Boreal Sectionsouthwardin the Great Plains

grasslands

(Figs.3, 6, transectE), winglengthinitiallydecreases
veryslightlyto
the AspenParklandBelt, then very slightlyincreasesfrom there to the Short-

grass
Prairieofwestern
NorthDakotaandeastern
Montana.Maximummalewing


12

ORNITHOLOGICAL

WING:

•

BOo.

North-South

PACIFIC

MONOGRAPHS

NO. 3 5

Tronsect

B. ALASKA-

COAST

CASCADES- SIERRA NEVABA

o.ool

D. ROCKY

60

o.1

0.4

0.2

SOj

MOUNTAINS

o.2
F. CENTRAL

60
] 0.4o 0.9
o
G. EASTERN

FORESTS

ß

o.o2 ---•)•--_o

FORESTS

60

0.2

H. ATLANTIC

COAS7AL MARSHES

Tø
1•

so .... •T• ....

FIG. 6. North-south transectsof mean wing lengths.Figureson vertical axis are mean measurements. Figureson horizontalaxis refer to EcoregionSections(Fig. 3). Numbersbetweensections
indicate probabilitiesof difference.Solid line male, dashedline female.

length is found in birds of the Short-grassPrairie, and for females in the Central
Boreal. Minimum wing length is found in males in the Aspen Parkland and in
females of the Short-grassPrairie. Thus, no trend is shown in this Great Plains
transect.

On the transect from the Central Boreal Section southward through the Central

Forests(Figs. 3, 6, transect F), wing length decreasessignificantlyin females, but
not males, from the Spruce-Fir of northern Minnesota to the Northern Hardwood
of Wisconsin, and decreasessignificantly in males from the Prairie Parkland of
Illinois to the Oak-Hickory Forest of western Kentucky. Maximum male wing
lengthsare found in birds of the Prairie Parkland and maximum female wing
lengthsin birds of the Central Boreal. Minimum wing lengthsfor both sexesoccur
in birds of the Oak-Hickory Forest.
Along a transect from the Newfoundland Boreal southward through eastern
forest areas (Figs. 3, 6, transect G), wing length increasessignificantlyin males,
but not females,to the Maritime Northern Hardwoods-Spruce,thencelittle change
in either sex southwardto the Appalachian Oak Section (deciduousforest belt)
of Pennsylvania and southernNew England, then a significantdecreasein males,
but not females, from the Appalachian Oak into the SoutheasternMixed Forest
of eastern Maryland and eastern Virginia. Maximum wing lengths of both sexes
are in the Maritime Northern Hardwoods-Spruce and minima of both sexes,in
the SoutheasternMixed Forest. After an initial increase from Newfoundland, the
trend in the eastern forest transect is a north-south decreasein wing length.
Birds along a transect in the Atlantic Coastal Marshes (Figs. 3, 6, transect H)
show little changein wing length from the marshesof New York and New Jersey
to those of Maryland and Virginia.


VARIATION

IN SONG

WING:
A.

SPARROWS

East-West

13

Transects

NORTHERN

SO
70

o.ool,•?

o.os

60

B.

MEDIAN

70
1 0409oos
0.9
0.9
o.•_..•l
0.•0.4
.

6o .....•---- •-•.•-•- •- o%.•-o•
C.

SOUTHERN

.....
<....
<___
o-•_•_•4
70•.
0.90•
_0.0•05
0.4
0.•1
- 0.9.
- 0.9.
- 0.9
0.•
60

o.•

o.•

o•-

-

o.•

ß

E]G. 7, •st-wcst •aas•ts O•mc• •aS ]caS•s, EJSur• oa •c•J•
Fishes oa ho•oaa] axis mfcr to
probabi•fi• of di•crca•. Solid •ac male, dashed]iac female.

ß

axis •c mcaa mcas•cmcats.

Although in all eight north-south transectsthe total decreases(both significant
and nonsignifican0in wing length outnumberthe increases,the differenttransects
differ considerablyin this respect. Whereas decreasesconsiderablyoutnumber
increasesin the Pacific Coast, Alaska-Cascades-Sierra Nevada, and Central Forest
transects, the numbers of increases and decreasesare more even in the Interior

Basins, Rocky Mountains, Central Plains and Eastern Forest transects.
Contrary to the usual trends in progressingfrom north to south, significant
increasesin wing length occur between the more northern Palouse Grassland and
more southern Northern Desert Scrub (8), between more northern Columbia
Forest (moist) and more southernNorthern Rockies (Montane) (8, e), and between
the more northern

Newfoundland

Boreal and more southern Northern

Hardwood-

Spruce(Maritime) (8). In these casesit appearsthat some factor, such as higher

elevation producinga colder climate, or more open habitat resultingfrom a dryer
climate, may offset the effect of generally increasingtemperature resulting from
the southward progression.
East-westtransects.In the northernmost transect (Figs. 4, 7, transect A) average
wing length increasessignificantlyin males and nonsignificantlyin females from
Newfoundland Boreal to the Spruce-Fir (near Boreal) of northern Minnesota and
southwesternOntario; little change occurs from there to the Central Boreal of
Northern Alberta, but then a significantincreaseoccursin males but not females
from there to coastal Alaska, then a significant increase in both sexes to the
Aleutian Tundra. The general trend in this most northern transectis a consistent
increasein average wing length from east to west.
In a median east to west transect(Figs. 4, 7, transectB) no significantchange
occurs from the Maritime Northern Hardwoods-Spruce to the Northern Hardwood of Wisconsin, then a significantincreasein wing length is found in males,


14

ORNITHOLOGICAL

MONOGRAPHS

NO. 35

but not females,from there to the Tall-grassPrairie of easternNorth Dakota, and
the montane Woodlands of the northern Rockies, then a significantdecreasein
males and nonsignificantdecreasein females from there to the moist Columbia
Forest, then little changeto the Cascades,then a significantincreasein females
but not males from there to t ae wet Sitka Spruce-Cedar-Hemlock Forest of the
Pacific Coast. The general tre••d of this median transect is an increase from the
Northern

Hardwood-Conifer
Forests to the Grasslands and continuing to the
northern Rockies, then a dec :easefrom there to the Cascades,followed by an
increase to the Pacific coastal forests.Thus, the longestwings are in birds of the
Pacific coastal,Rocky Mounta [ns,and Great PlainsGrasslandunits,with greatest
values for both sexes in the ••orthern

Rockies Montane

Woodland.

Minimum

wing length is found in males of the New England Northern Hardwoods-Spruce
and in females of the Cascade s.

In the southernmosteast to west transect (Figs. 4, 7, transect C) wing length
does not change significantly between the Atlantic coastal marshes of Maryland
and Virginia and the Oak-Hickory Forest of western Kentucky, then increases
significantly in males from there to the Oak-Savannah of Illinois, then shows a

series
of nonsignificant
decregses
andincreases
fromthereto themiddleRocky
Mountains,
thenlittleif any•hangefromthereto theSagebrush-Wheatgrass
of
thenorthern

GreatBasin,
thega significant
decrease
in males
andnonsignificant

decrease
in females
fromther•totheLahontan
Saltbush-Greasewood
ofwestern
Nevada, then no significantcl!angefrom there to the California Valley Grassland,
but a significant decrease in both sexes from there to the western California
Chaparral. The general trends in this transect are a pronounced increasein wing
length from the Eastern Deciduous Forests and coastal marshesto the interior
grasslands,then a slight increase in females but not males from there to the
Northern Rocky Mountains./• marked decreasein male wing lengthoccurswithin
the Northern Desert Scrub ofl he Great Basin from the southernIdaho SagebrushWheatgrassto the westernNe vada Lahontan Saltbush-Greasewood,followed by
a slight increase to the Calif• mia Central Valley Grassland, then a pronounced
decreaseto the Chaparral of coastalCalifornia. Maxima for wing lengthsof both
sexes are in the Middle Roclc es Montane Woodland; minima for both sexes are
in the California Chaparral.
In general the east-westtraJtsectsindicate an increasein wing length from east
to west in the boreal forest, rel atively long wingsin the grasslandsnorthern Rocky

Mountains and northern des{:rtscrub, and relatively short wings in easterndeciduous forests and California Chaparral.

Discussion.
--In allpopulations
wings

ofmales
average
longer
thanthose
of
females.
Thereis goodagree•nent
between
sexes
in winglengthin LifeAreas.
There is some differencebelween males and femalesin order of wing length
betweenEcoregionProvinces'.particularly: Pacific Forest, California Grassland,
Willamette-Puget Forest, and Mexican Shrub Steppe.
Taking all data together fr, ,m comparison of mean wing lengths classifiedby
Life Area, Ecoregions,and c,>mbinationsof the two, there is a general trend of
decreasingwing length from r .orthto south which is modified locally by elevation
and densityof vegetation.Wi• tglengthsare greaterat higherelevationsin montane
forests and more open plant associationssuch as tundra, grasslands,savannas,
and deserts at the same latitu

les. Thus, wings are longest,by far, in the Aleutian