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MANKVAKWD

UNIVERSITY

Postilla

PEABODY MUSEUM OF NATURAL HISTORY

YALE UNIVERSITY
NEW HAVEN, CONNECTICUT, U.S.A.

Number 105 February 6, 1967

VARIATION IN THE STERNAL NOTCHES OF
SUBOSCINE PASSERIFORM BIRDS

Mary A. HEIMERDINGER
CARNEGIE MUSEUM, PITTSBURGH, PENNSYLVANIA

PETER L. AMES
MUSEUM OF VERTEBRATE ZOOLOGY, UNIVERSITY OF CALIFORNIA, BERKELEY

ABSTRACT

The present study was undertaken to record the variations of the pos-
terior border of the sternum of the New World suboscines, in an attempt
to determine the reliability of this area of the sternum as a taxonomic
character. The conclusions drawn from this survey (of 993 specimens) are
that, within a broad range of variants, two basic kinds of sternal configura-
tion are found: two-notched (Types 2-3-4, as defined), and four-notched
(Types 5-6). The four-notched sternum is not confined to genera in the
Rhinocryptidae and Conopophaga, as previously believed. Variations within
the two- and four-notched sterna may not be considered taxonomically
significant unless they can be shown to be consistent in a large series of
specimens. In no case should a single specimen of a species be assumed to
show the only sternal configuration of the species. The possible adaptive
significance of the observed range of variation is briefly discussed, but no
conclusions may be drawn until a functional analysis of the passerine ster-
num can be made.

INTRODUCTION

The shape of the posterior border of the sternum has long
deen accepted as a useful character in the classification of birds.
Within the Passeriformes it has been employed particularly to

NO

Postilla Yale Peabody Museum No. 105

distinguish between several of the families of the superfamily
Furnarioidea. It was once believed that the only passerines possess-
ing four (rather than two) notches in the posterior border of the
sternum were the tapaculos (Rhinocryptidae) and the tendency
of taxonomists was to include any “four-notcher” passerine within
that family. Sclater (1874, p. 191) stated: “The only other known
Passerine form in which two emarginations are present on each
side |[i.e. a total of four notches| of the posterior margin of the
sternum is the Australian genus Atrichia |—Atrichornis|. Whether
this form certainly belongs to the Pteroptochidae {—Rhinocryp-
tidae|, cannot be positively ascertained until the structure of its
larynx is known; but I have little doubt that such is the case.”
In diagnosing the family Atrichiidae (—Atrichornithidae) Sharpe
(1890, p. 659) remarked: “Dr. Sclater... refers to the double-
notched sternum of Atrichia rufescens, but Garrod [1876] figures
the sternum of A. rufescens with only a single indentation. . .,
and only one notch exists in the sternum of A. clamosa in the
Museum of the Royal College of Surgeons.” Sharpe must have
considered Sclater to be in error, for his diagnosis for Atrichiidae
in the Catalogue reads (loc. cit.): “sternum with a single deep
lateral indentation on its hinder margin;...”

In 1881 Forbes noted that the antpipits (Conopophaga) also
possessed two pairs of notches, and he used this and other evidence
to erect the family Conopophagidae for the genera Conopophaga
and Corythopis, although the sternum of Corythopis had not been
examined.

The tendency has remained, however, to place in the family
Rhinocryptidae any passerine found to have a four-notched ster-
num. For example, Shufeldt (1913) described Hebe schucherti
as a new genus and species of passerine from the Lower Eocene,
Green River Formation, Wyoming; he tentatively placed the form
in the Rhinocryptidae on the basis of its four-notched sternum,
and Brodkorb (1965) has concurred, at the same time substitut-
ing the new generic name Neanis for Hebe, preoccupied. W. D.
Miller and A. Wetmore (in Wetmore, 1926, p. 292) moved
Melanopareia from the Formicariidae to the Rhinocryptidae after
it was found to have four sternal notches. Plotnick (1958) placed
the antwren Psilorhamphus in the Rhinocryptidae primarily on the
basis of its tracheal syrinx and four-notched sternum. All of these

1967 Sternal Notches of Passeriform Birds 3

actions imply a heavy reliance upon sternal notches as a taxo-
nomic character in this group of passerines.

The configuration of the posterior border of the sternum has
also appeared in most of the technical diagnoses of passerine famil-
ies. It should be mentioned here that the key to mesomyodian pas-
serines in Cory and Hellmayr (1924, p. 1) contains at least two
errors. The Formicariidae are incorrectly characterized by: “‘Ster-
num with two pairs of posterior notches; nares schizorhinal” in
contrast to the Conopophagidae and Pteroptochidae (—Rhinocryp-
tidae) with: “Sternum with one pair of posterior notches; nares
holorhinal.” This key was adapted from Ridgway (1907, pp. 331-
332) who correctly lists the two-notched sternum for the Formi-
cariidae and the four-notched for the Conopophagidae and Rhino-
cryptidae. Both keys are in error in stating that the Formicariidae
have schizorhinal nares; in passerines schizorhinal nares are found
only in the Furnariidae (Garrod, 1877).

PROCEDURES

In the course of an anatomical study of the Conopophagidae
we examined the sterna of several species of Conopophaga and
Corythopis. We were surprised to find two-notched sterna in the
first spec:mens studied, not four-notched as Forbes’ work had led
us to expect. We therefore undertook a survey of the sterna of a
large number of suboscines in an attempt to determine the range
of variation in this structure, and its consequent reliability as a
taxonomic character. We were able to examine at least the major-
ity of the skeletons of the Furnarioidea available in this country.
In addition, we studied a sample of other suboscine families, con-
centrating on the New World forms, and we also included a few
oscines and non-passerines for comparison. In most cases we were
working with skeletons that had been prepared by maceration,
dermestid beetles, or both. In a very few instances, genera of par-
ticular interest were not available as skeletons, so their sterna were
examined in specimens preserved in alcohol. In the alcoholic speci-
mens, the notches of the sternum were noted from the inner
(dorsal) surface, in order to minimize damage to the thoracic area.

In all, we examined 993 specimens representing 276 species and
146 genera of suboscines; we were unable to obtain a specimen of
Atrichornis, but otherwise at least one genus of each of the sub-

4 Postilla Yale Peabody Museum No: “105

oscine families was seen. (An unsuccessful search was made for
the British specimens of Atrichornis mentioned in the Introduction;
apparently they have been lost or destroyed during wartime.) The
full list of specimens examined is presented in Table I.

NOMENCLATURE

Fortunately the nomenclature of sternal anatomy is not quite
so confused as it is in most anatomical fields of study. The ster-
num is almost universally agreed to consist, at least topographi-
cally, of two areas: the “costal sternum” which refers to the
anterior half, associated with the ribs; and the ‘“metasternum”
which refers to the posterior half, caudal to the ribs. In this paper
we are dealing solely with the metasternal area. The metasternum
usually shows a variably thin process, directed posteriorly, on the
lateral edge: the “posterior lateral process” (see fig. 1, on Type 6).
Although admittedly this process is part of the metasternal area,
the word “metasternum” as traditionally used in descriptions
excludes the process. Conforming to this traditional usage, “meta-
sternum” in the remainder of this paper will refer only to the cen-
tral bony plate of the posterior sternum (see fig. 1, Type 2).
A few species have an additional process between the posterior
lateral process and the medial metasternum: the “lateral metaster-
nal process” (see fig. 1, Type 6). We have coined this new term
for the structure because we feel that the others (“internal lateral
process,” “intermediate lateral process,” ‘internal lateral xiphoid
process,” etc.) which have been used, are unsatisfactory. Our
work and several embryological studies indicate that this process
is derived from the metasternum, not from adventitious growth
or from subdivision of the posterior lateral process. Forbes used
“internal xiphoid process” but Lindsay (1885), who did the basic
embryological study on the structure, used ‘“xiphoid” to refer
just to the ends of both processes. We believe, therefore, that
“lateral metasternal process” is less confusing, more descriptive,
and that it reflects the metasternal origin of the structure.

ACKNOWLEDGEMENTS

We should like to thank the authorities in charge of collections
at the following institutions for generous permission to study the
anatomical material in their care: the American Museum of Nat-

1967 Sternal Notches of Passeriform Birds 5

ural History; British Museum (Natural History); Field Museum
of Natural History; Museum of Natural History, University of
Kansas; Museum of Natural Science, Louisiana State University;
Museum of Zoology, University of Michigan; Museum of Com-
parative Zoology, Harvard University; and the United States
National Museum. We also examined specimens at Peabody Mu-
seum, Yale University, while we were students at that institution,
and at Carnegie Museum and the Museum of Vertebrate Zoology,
University of California. We should also like to thank Pierce
Brodkorb, Graham S. Cowles, William G. George, Philip S.
Humphrey, Thomas E. Lovejoy III, Eleanor H. Stickney, and
Stuart L. Warter who particularly helped us to obtain specimens.
Eugene Eisenmann discovered the inconsistencies between the keys
in Ridgway, and Cory and Hellmayr, and was kind enough to
bring them to our attention. Finally, we should like to express our
gratitude to N. Philip Ashmole for his interest in and advice on
the study, and to Kenneth C. Parkes for his stimulating discussions
on the subject with the senior author and for invaluable help with
the manuscript. The manuscript was also read by Philip S. Hump-
hrey, Alexander Wetmore, and Richard L. Zusi, to whom we wish
to extend thanks.

RESULTS

The 993 specimens of suboscines examined represent a struc-
tural continuum from an unperforated sternum to one with two
processes and two notches on each side. In order to evaluate the
distribution of the various configurations, the following categories
were set up (see fig: 1):

Type 1. Sternum entire: no notches or perforations.

Type 2. Sternum with a lateral fenestra on each side: the
posterior lateral process bears a wide terminal flange
which either touches or is continuous with the
metasternum, enclosing a fenestra or window.

Type 3. Sternum with a lateral notch on each side (the “two-
notched” sternum): the flange of the posterior lateral
process, if present, does not touch the metasternum.
The opening (notch) may be wide or very narrow.

6 Postilla Yale Peabody Museum No. 105

Type 4. Sternum with a lateral notch and small medial fenes-
tra or fenestrae on each side: this condition is the
same as Type 3 except that the metasternum is per-
forated by at least one small hole, whose diameter
is not larger than one-fifth the width of its side of
the metasternum.

Type 5. Sternum with a lateral notch and a large medial
fenestra on each side: this condition is like Type 4
except that the fenestra is wider than one-fifth the
width of its side of the metasternum. (Experience
later showed that this fenestra is always wider than
one-half the width of its side of the metasternum. )

Type 6. Sternum with a lateral and a medial notch on each
side (the “four-notched” sternum): the flange on the
lateral metasternal process, if present, does not touch
the medial metasternum.

Although the categories were established in advance simply as a
means of recording the variations in the sternum, we found that
nearly all of the specimens fell clearly into one of the six categories.
We anticipated difficulties in distinguishing between Types 4 and
5 because they were based on arbitrary size differences of the
fenestrae. We found, however, that the fenestrae occurred in two
distinct size classes. Type 4 characteristically had many small
fenestrae, asymmetrically placed; Type 5 had a single pair of
large, more or less symmetrical, fenestrae. Some individuals of
some species were bilaterally asymmetrical in the entire metaster-
num, but with only four exceptions, the two sides fell into cate-
gories consecutive on the above list. The system of sternal types
established for this study, therefore, seems to represent a natural
rather than an artificial morphological sequence.

Artifacts

Some of the “fenestrae” observed in the sterna were clearly
either artifacts resulting from collection or preparation, or the
products of the physiological state of the bird when it died; these
were discounted in the classification into sternal types. Natural
fenestrae have a smooth, finished-looking rim, usually with a

1967 Sternal Notches of Passeriform Birds 4 |

slight thickening or lip; artificial holes (such as those caused
by shot or by dermestids) are jagged and/or thin-edged.

A serious problem occurs, however, in young or incompletely
ossified specimens in which the cartilage or cartilage-bone inter-
face has been lost in preparation. Klima (1964) and others have
shown that during embryological development and post-hatching
maturation of passerines, ossification of the sternum begins in the
costal sternum and gradually extends posteriorly. The last area to
ossify is the posterior edge of the metasternum and the posterior
lateral processes. It is important, therefore, to know the age of a
specimen in order to be sure it has completed its bone deposition.
Unfortunately very few of the available specimens had age data.
The extent of the skull ossification was recorded for many individ-
uals to indicate probable age, but this is not an entirely reliable
character as some suboscines, notably the Rhinocryptidae, never
complete skull ossification. Being aware of this general age effect
on skeletal material, we have attempted to take possible incom-
plete sternal ossification into consideration in the analysis of our
data. It is likely, however, that some individuals classified as having
open notches would actually have had closed notches (fenestrae )
if the bridges of cartilage had had time to ossify. Nevertheless,
for consistency we have recorded only the condition of the bone,
not the cartilage. Artifacts in bone can be seen clearly, but cartil-
age varies too greatly to be dependable. Much of the cartilage
undoubtedly has been removed by dermestids or maceration, but
on some poorly cleaned specimens it is still present and often
impossible to distinguish from other dried soft tissue, particularly
at the ends of the processes.

The effects of the general physiological condition of adult birds
on sternal morphology are also difficult to assess. To our knowl-
edge, studies have never been made on the impact of such proc-
esses as egg formation, molt, etc., upon the general skeletal ossifi-
cation of adult passerines. (For a discussion of these effects on
some non-passerines, see Hanson, 1962.) The observations made
in this study have led us to believe that, at least in some species,
there are periods in adult life during which the bone loses and
later regains some of its substance. Unfortunately most of the
specimens lack sufficient data on breeding condition, molt, cause
of death, etc., for us to be able to pursue this line of investigation.

8 Postilla Yale Peabody Museum No. 105

Experience with many hundreds of sterna, however, gradually led
us to believe that a metasternum riddled with many tiny holes is
the result of a general lack of ossification, and is of no phylogenetic
significance. These “‘pinholes” were not included in the final clas-
sification of specimens into sternal types.

No attempt has been made to distinguish between the various
shapes observed in the metasternum and processes. Several genera
or groups of genera appear to be distinguishable by the shape of
the sternum itself, as well as the shape of the flanges on the ster-
num and processes, the depth of the notches, relative differences in
length between the sternum and processes, etc. It is probable that
these variations have phylogenetic significance in some groups,
but this is difficult to determine with the available material. Arti-
facts of preparation, especially the warping that results from
maceration or bleaching, render it almost impossible to obtain an
accurate outline of the sternum in some specimens. Sterna suitable
for study of general shape would rep:esent only a small fraction
of the sample we examined for notching.

Age, Sex, and Population Effects

In a few genera it was possible to obtain enough material with
data to determine the possible effects of age, sex, and geographical
population upon sternal notching. Comparison of 61 specimens of
Tyrannus tyrannus showed almost no variation in sternal type, and
none that could be attributed to a peculiarity within a small gene
pool or a particular sex or age class (other than the extent of ossi-
fication mentioned above). A sample of 60 specimens of Xipho-
rhynchus spp., on the other hand, showed wide va..ac.on (see
Table I) but again no correlation within age, sex, or population
groups. Of this genus, the best sample from a single locality was
a series of six X. triangularis collected at El Sauce, Cartago
Province, Costa Rica, in less than a month, and including both
males and females with fully ossified skulls. Of these, five (3 6 2,
2? 2) had Type 3 sterna and one (sex unknown) had a Type 2
sternum. In the latter the sternum was asymmetrical, with the
left posterior lateral process fused to the metasternum with a wide
bridge of bone, and the right with a broad flange touching (not
fused with) the equally broad flange extending from the meta-
sternum. Two other specimens of X. triangularis, one from another

1967 Sternal Notches of Passeriform Birds 9

province in Costa Rica, and one from Colombia, had Type 3
sterna. Similar variation was seen in smaller samples of other
species of Xiphorhynchus, but never in this or any other genus
was the type of any one s2x, age, or population seen to be con-
sistently different from the type of any other. We believe, therefore,
that (allowing for possible error caused by scoring incompletely
ossified specimens) the range of variation observed in the sterna
represents that of the species itself, unaffected by age, sex, or
population.

Variation within Taxa

Table I lists the series of specimens examined and the sternal
types found in each. The Table is arranged in the taxonomic order
followed by Peters (1951) for the Eurylaimidae through the
Rhinocryptidae, and by Hellmayr (1929) and Cory and Hellmayr
(1927) for the remainder of the New World families. The speci-
mens are recorded by sternal types, in columns, each “x” repre-
senting one specimen.

Dendrocolaptidae: 173 specimens of 29 species in 9 genera
were examined. It was found that the woodcreepers varied widely
in sternal type. The only passerine (aside from Menura) in the
entire study that had a solid sternum, without notches or fenestrae
(Type 1), was one specimen of Xiphocolaptes promeropirhynchus;
two additional specimens of the species, however, had Type 2
sterna, and two others had Type 3. Many other genera and species
of woodcreepers also showed wide variability. For instance, in
Xiphorhynchus flavigaster three specimens had Type 2 sterna, two
had Type 2 on one side and Type 3 on the other (Type 2-3 asym-
metry), fifteen had Type 3 on both sides, two had Type 3-4
asymmetry, and two had Type 4 sterna. Within the family as a
whole, the Type 3 sternum was the most common (128 of the 173
specimens examined), Type 2 occurred fairly often (20 speci-
mens), Type 4 less so (7), and Type | only once. Of asymmetrical
sterna, five specimens were of Type 2-3 and nine of Type 3-4.
The only individuals in the entire study (again, aside from Men-
urc:) that showed non-consecutive sternal types were two Dendro-
colaptes certhia and one Xiphorhynchus lachrymosus which had
small (Type 4) medial fenestrae in Type 2 sterna; other speci-
mens of these species had Type 3, Type 4 or Type 3-4 sterna.

10 Postilla Yale Peabody Museum No. 105

Furnariidae: 199 specimens of 71 species in 33 genera were
examined. Considerably more consistency was seen in this family
than in the woodcreepers; every ovenbird studied had a single pair
of notches in the sternum, and some individuals had additional
medial fenestrae. The great majority of the specimens (166) had
Type 3 sterna, 18 had Type 4, and 5 had Type 5. There was also a
limited amount of asymmetry, with nine Type 3-4 and one of
Type 4-5. Some intraspecific variation was seen, for example, in
Cinclodes fuscus, with three specimens of Type 3, one of Type 3-4,
two of Type 4 and one of Type 4-5. The genera usually placed at
the end of the family (Xenops, Pygarrhichas and Sclerurus) were
the only ones examined that had large symmetrical medial fenes-
trae (Type 5).

Formicariidae: 194 specimens of 54 species in 32 genera were
examined. Although wide variation in sternal types was observed
in this series of antbirds, there appears to be less intraspecific and
more interspecific and intergeneric variation than in the previous
families. The only species found to have more than two types was
Dysithamnus mentalis, a specimen of which was the only antbird
examined that had a Type 2 sternum. Of a series of 15 individuals
1 had Type 2, 12 had Type 3, | had Type 3-4, and 1 had Type 4.
In the family as a whole, 171 specimens had Type 3 sterna, 1 had
Type 2, 9 had Type 4, 2 had Type 5 and 7 had Type 6. Very little
asymmetry was seen, with only four individuals having Type 3-4
asymmetry.

The great majority of antbirds were found to have two-notched
sterna, and a few had small medial fenestrae. One group of genera
(Pittasoma, Grallaricula and Grallaria), however, was markedly
different from the rest of the family. A single specimen of Pit-
tasoma michleri had a Type 6 sternum and one of Grallaricula
nana had a Type 5. The species of Grallaria separated into two
distinct groups: G. guatimalensis (2 specimens), varia (3), hap-
lonota (1), quitensis (1), ruficapilla (1) and rufula (1) had Type
3 sterna; G. fulviventris (1 specimen), perspicillata (5), and
ochroleuca (1) had Type 6 sterna, except for one specimen of
perspicillata in which the lateral metasternal process was fused to
the metasternum, forming a Type 5 configuration. [Ridgway
(1909, p. 71) erected Hylopezus for Grallaria perspicillata and
later (1911) added G. (fulviventris) dives and macularius to the

1967 Sternal Notches of Passeriform Birds et

new genus; he did not have G. ochroleuca available for study.
Hylopezus was separated from Grallaria by differences in the nasal
fossae, nostrils, bill, etc., and by the lack of rictal bristles.] In view
of their sternal disparity with the rest of the Formicariidae, it will
be important to reexamine the taxonomic status of Pittasoma, Gral-
laricula, and Grallaria, and particularly to review the relationships
of the species currently placed in the latter genus. Available ana-
tomical material (9 out of 27 species) is not sufficient for a
thorough study of the genus Grallaria, but these preliminary find-
ings suggest that its division into two genera may well be justified.

Conopophagidae: 28 specimens of this family were examined,
20 in 4 species of gnateaters (Conopophaga) and 8 in the 2 species
of antpipits (Corythopis). The two genera were found to differ
strongly and consistently. Nineteen specimens of Conopophaga had
Type 5 sterna, the remaining individual being Type 5-6. All 8
specimens of Corythopis had Type 3 sterna. These and other ana-
tomical findings have led us to believe that this is an artificial
family, and that Conopophaga should be placed in the Formi-
cariidae and Corythopis in the Tyrannidae.

Rhinocryptidae: 25 specimens of 9 species in 5 genera were
examined. The tapaculos were found to be quite consistent in
sternal type; all but one specimen had the Type 6 sternum. In the
exception, one of two individuals of Pteroptochos tarnii examined,
only the left side of the sternum was Type 6; on the right, the
medial notch was replaced by two large fenestrae, side by side.

Cotingidae: 79 specimens of 22 species in 15 genera were
examined. A certain amount of variation was found in the cotingas,
but only four genera showed individuals with sterna other than
Type 3. Some specimens of Lipaugus, Procnias, and Rupicola
had Type 2 sterna, but others had Type 3; one specimen of Tityra
semifasciata had Type 3-4 asymmetry, but thirteen others had
symmetrical Type 3. The family totals were: 6 specimens with
Type 2; 1 with Type 2-3; 71 with Type 3; and 1 with Type 3-4.

Pipridae: 42 specimens of 10 species in 6 genera were exam-
ined. Almost no variation was observed in the manakins; two
specimens (one Pipra coronata and one Manacus manacus) had

2 Postilla Yale Peabody Museum No. 105

Type 2-3 asymmetry, but at least four other specimens of each
species, and all of the rest of the family were found to have Type
3 sterna.

Tyrannidae: 220 specimens of 55 species in 33 genera were
examined. Within this sample of tyrant flycatchers, 203 individuals
had Type 3 sterna, 5 had Type 2, 4 had Type 2-3, 5 had Type
3-4, and 3 had Type 4. Alll but three of the individuals that were
not Type 3 were of species which also included Type 3 specimens
in their series; the three exceptions were species of which only
single specimens were examined (Myiobius barbatus and M. sul-
phureipygius, Type 2, and Capsiempis flaveola, Type 4).

Oxyruncidae and Phytotomidae: 1 specimen of Oxyruncus
cristatus, 4 specimens of Phytotoma rara and 2 of P. rutila were
examined. The sharpbill and the plantcutters all showed Type 3
sterna.

Eurylaimidae, Pittidae, Philepittidae, and Acanthisittidae: In
these Old World families, the following limited series was exam-
ined: 8 specimens of 5 species in 4 genera of broadbills; 11 speci-
mens of 8 species in the single genus of pittas; 1 specimen of the
asity, Philepitta castanea; and | specimen of each of the two genera
of New Zealand Wrens. All were found to have Type 3 sterna,
except for one individual of Pitta moluccensis, which had Type 4.

Menuridae: The four specimens of lyrebirds (Menura superba)
examined were consistent in having a basic sternal shape different
from that of any other passerine examined. The sternum was
unusually long and narrow, and the bone was comparatively thick
and solid. In the two Type 3 individuals the notches were very
shallow and narrow. In the Type 1-4 asymmetrical individual, the
notch, which was on the left side, was covered by a thin sheet of
cartilage and there were two small fenestrae in the metasternum,
close to the keel. On the right side a shallow notch was indicated
by thinner bone where the cartilage had evidently ossified, leaving
the filled “notch” plainly visible. The fourth individual was com-
pletely Type 1, showing no suggestion of notches. Because of the
unusual nature of its whole sternum, Menura will be largely
omitted from the following discussion of the suboscine sternum.

1967 Sternal Notches of Passeriform Birds 13)

DISCUSSION

The posterior border of the sternum of suboscines has been
found to be much more variable than had been previously sus-
pected. Most passerine anatomical features that have been exam-
ined for variability (e.g. pterylosis |Heimerdinger, M.A. 1964.
A study of morphological variation in the dorsal and ventral
pterylae of Passeriformes. Ph.D. Diss., Yale Univ. 241 p.],
syrinx [Ames, P.L. 1965. The morphology of the syrinx in pas-
serine birds: its application to the classification of the order
Passeriformes, Ph.D. Diss., Yale Univ. 315 p.], etc.) exhibit only
a very limited amount of individual variation and in studying these
features the anatomist can fairly safely depend on a single speci-
men of a species to be typical of that species. This is not true of
the sternum. The present study has shown that, aside from possible
ossification effects, there is probably no variation correlated with
sex, age, or infraspecific populations; on the other hand, wide
individual variation may exist in sternal types, in the size of
notches and fenestrae, and in bilateral symmetry. Of the 150 New
World suboscine species represented in this study by two or more
specimens, 24 per cent (36 species) contained individuals of two
or more sternal types, and an additional 26 species contained
asymmetrical specimens. Some families were more variable than
others. Ten species of woodcreepers were represented by series of
five or more specimens. Of these species, six had specimens of
two sternal types, and two had specimens of three types. Com-
parable figures for the tyrant flycatchers were much lower: two
out of twelve species contained two types and none was found to
contain three.

In addition to the simple presence or absence of notches and
fenestrae recorded in this study, many other variations were ob-
served. For example, the following characters were seen to vary
within a genus or species, or even from side to side of a single
sternum: the size and shape of notches, fenestrae, metasterna, and
processes; the width of the bridge of bone connecting the lateral
processes to the metasternum in Types 2 and 5; and the number,
size, and position of the small fenestrae in Type 4. In the case of
the small fenestrae, asymmetry was more common than symmetry.

Analysis of the variations in type, however, shows two funda-
mental kinds of sternal condition. Types 2, 3, and 4 all contain

14 Postilla Yale Peabody Museum No. “105

an essentially solid metasternum with a pair of posterior lateral
processes. The observed intraspecific variations make it difficult
at this time to see any taxonomic significance in whether the end of
the posterior lateral process is free from (Type 3) or touches or
fuses with (Type 2) the metasternum, or in the presence of small
asymmetrical fenestrae in the metasternum (Type 4). This general
connection between Types 2-3-4 is clearly shown by the large num-
ber of instances of occurrence of more than one of these configura-
tions within a single species, or on the two sides of a single
specimen. Even the apparent significance of the difference between
solid and perforated sterna in suboscines is weakened by the find-
ing of a specimen with a Type | sternum in a genus (Xiphocolap-
tes) of which all others seen were Type 2 or Type 3. This, of
course, is not meant to imply that a solid versus a perforated ster-
num (or any other sternal variation) may not have taxonomic
siginificance in any group of birds, but differences must be shown
to be consistent, and not just to be two or three out of a wide range
of individual variations.

Type 5 and Type 6 also demonstrated a fundamental similarity
to each other, both in morphology and in occurrence. From the
specimens examined, it appears that the bridge between the lateral
metasternal process and the metasternum is almost as “easily”
formed or lost as that between the posterior lateral process and the
metasternum in Types 2-3-4. The sample of sterna of Types 5 and
6 was small, as taxa which possess these types are unfortunately
rather rare in anatomical collections. Nevertheless, single individ-
uals of two unrelated species, Conopophaga lineata and Pterop-
tochos tarnii, were bilaterally asymmetrical Type 5-6, and Grallaria
perspicillata showed both Type 5 and Type 6 specimens.

Examination of Table I will show a strong tendency of subos-
cines to vary only within one of the two fundamental kinds of
sterna; this tendency suggests some type of basic separation
between them. In no instance was a species found to vary between
the two-notched (Types 2-3-4) and the full, four-notched, Type 6
sternum. The only intermediates found were between Types 3 and
5, or Types 4 and 5. These exceptions were in three genera of
ovenbirds: one specimen of Cinclodes fuscus, Type 4-5 (compared
to six others of the species which were Types 3, 3-4, or 4), and

1967 Sternal Notches of Passeriform Birds 15

several specimens of Xenops and Pygarrhichas, which showed
Type 5 (with additional specimens of Type 3 or 4).

The evolutionary significance of this segregation into Types
2-3-4 or Types 5-6 is not understood. Logically the intermediate
morphological steps between two and four notches should be, first,
a formation of one or more small fenestrae, which may then
enlarge and/or merge to form a single large fenestra, which in
turn may lose its posterior border and open to form a notch. The
process can, of course, be reversed, in that the notch closes, and
the fenestra ossifies to form a solid metasternum. A remarkably
small number of the examined specimens appeared to be inter-
mediate in these respects. Most of the Type 4 specimens had
small, irregularly and asymmetrically placed fenestrae; in none
was it clear that several small fenestrae had merged to form a
larger, irregularly shaped fenestra, approximately symmetrical with
one on the opposite side of the sternum. An occasional Type 4
specimen had a symmetrical pair of small fenestrae in the pos-
terolateral corners of the metasternum; these fenestrae showed
some variation in size, but none reached the size originally desig-
nated as the dividing line between Types 4 and 5. The only
specimen in the study that showed some indication of a mor-
phological progression between the two- and four-notched sternum
was the single individual of Cinclodes fuscus, in which there was a
large fenestra on one side opposite a small fenestra on the other.
This individual seems to indicate that the progression between
Type 4 and Type 5 is possible, but the fact that it was the only
one out of 993 specimens that bridged the two- and four-notched
sterna, argues for a fairly strong barrier between them.

Other rare conditions found in the study were four instances
of small metasternal fenestrae in association with Type | or 2
sterna. Two specimens of Dendrocolaptes certhia and one ot
Xiphorhynchus lachrymosus had these Type 4 fenestrae in other-
wise Type 2 sterna, and one specimen of Menura superba had an
asymmetrical Type 1-4 sternum. Although all three genera showed
generally wide variability (Types 2, 2-3, 3, 3-4, and 4 in the two
woodhewers, and Types | and 3 in the lyrebird) these specimens
also serve to demonstrate that the postulated sequence of phy-
logenetic development of the two Type 4 characters (lateral
notches and small medial fenestrae ) might occasionally be reversed.

16 Postilla Yale Peabody Museum No: i@s

The functional and adaptive significance of the observed varia-
tions in the sternum is not evident from the material that we have
examined. Previous studies by others indicate that strength of
flight and the consequent development of the pectoral and abdom-
inal muscles influence the shape and heaviness of the sternum.
In a basic embryological study of the non-passerine sternum,
Lindsay (1885, p. 707) stated: ‘“...since the posterior border
of the sternum affords attachment to two opposite sets of muscles,
(a) the pectoral, (b) the abdominal, the resultant of their forces
must be to some extent expressed in its shape, for in general the
outline of a bone tends to express the direction and strength of the
mechanical forces acting on it. In other words, we should expect
to find the posterior border of the sternum varying with the habits
of the bird, whether it is a good flyer, and uses its pectoral muscles
most, or is accustomed to run or hop, and thus makes a greater
proportional use of its abdominal muscles.” Lindsay found that in
non-passerines, birds with strong flight (e.g. gulls) had long, broad
and solid sterna with short processes, but ground-living species
(e.g. tinamous and galliforms) had short sterna with long thin
processes for the attachment of the enlarged abdominal muscles.

This generalization seems reasonable, and it appears to be
largely (but not invariably) true for passerines as well as for more
primitive birds. The taxa examined in the present study in which
the sternum is relatively short with long thin processes (Types 5
and 6: Rhinocryptidae, Grallaria spp., Conopophaga, etc.) are
generally ground-dwelling, weak-flying birds. Those with relatively
longer and heavier sterna with fewer and shorter processes (Types
i through 4: the majority of suboscines and all known oscines) are
largely arboreal and have good powers of flight. Many exceptions
to this generalization, however, may be found: for example,
Cinclodes (of which one specimen was Type 4-5) is an unusually
strong flyer for its family, yet the majority of the ovenbirds are
Type 3; and a great many basically terrestrial forms (e.g. Geo-
sitta, Formicarius, Chamaeza, Pitta, etc.) have Type 3 or 4 sterna.
Perhaps the greatest contradiction to this “rule of thumb” for an
interrelationship between sternal shape and power of flight is
Menura superba. The lyrebird, a markedly aberrant passerine in
almost all aspects of its morphology, has a uniquely long and
heavy sternum, with very short if any processes, yet it might be

1967 Sternal Notches of Passeriform Birds 1EY/

considered to be the most terrestrial of all passerines. It may be,
of course, that this solid sternum is a specialization for terrestrial
life, but in an entirely different way from the rest of the passerines.

Oscines which have a specialized form of locomotion such as
creeping on vertical surfaces (Certhia, Sitta), or which are partially
terrestrial (Eremophila, Cinclus), have exactly the same sternal
characters as the more typical oscines. It is also true, however,
that many of these specialized species are migratory; the impor-
tance of certain regular, but short-time, activities during the life
span may override a tendency toward adaptation for the daily
type of locomotion. Unfortunately, the behavior and life histories
of most of the sternally exceptional suboscines are poorly known.

An alternative explanation for why certain forms do not
possess the sternal type “expected” for the mode of life involved,
is that some groups, such as oscines, have not had the time or the
genetic latitude to produce sternal variation. This seems unlikely
because the marked variation in some of the relatively closely
related suboscines shows that the genetic potential is present in
the order, and that it can be extremely active in some families.

The final answer as to why the New World suboscines show a
high degree of variability cannot be given until a thorough func-
tional analysis can be made of the sternum, its processes, and
attached muscles. Once the function of this complex is known, then
the adaptive significance of the various configurations can be stud-
ied and understood as well.

Previous investigators who have studied the posterior border
of the sternum have all concluded that it is an extraordinarily
plastic structure. Klima (1962, p. 151) summarized his and earlier
embryological studies on passerine and non-passerine sterna by
stating: “The results obtained suggest that the avian sternum is a
very young, still considerably plastic, element which, during phy-
logenesis, has undergone progressive evolution.” The results of the
present study, derived from the adult sternum, confirm the con-
clusions drawn from embryological material.

Garred (1877) was probably the first to suggest that the
ancestral passerines possessed a two-notched sternum. Forbes
(1881, p. 438) apparently agreed with this, for in his discussion
of the four-notched sternum of Conopophaga and the Rhinocryp-

18 Postilla Yale Peabody Museum No. 105

tidae, he stated: *...I am not inclined to consider it in any way a
primitive character, but rather as an instance of a simple modi-
fication having been independently acquired in different groups of
birds. ...” The present study has shown that the great majority of
modern passerines have basically two-notched sterna (Types
2-3-4). All the variants observed may be morphologically achieved
through a structural progression from Type 3: Types | and 2 by
fusion and ossification between the posterior lateral process and the
metasternum, and Types 4, 5, and 6 by fenestration and separa-
tion of the lateral metasternal process from the metasternum. Be-
cause the entire variation can be arranged sequentially (Types 1
through 6), however, it is impossible to state definitely which is
the basic structural type, and which are the derivations. Unfor-
tunately, there are no clues to the basic type, either from the fossil
record or from related modern taxa. Many of the Piciformes,
believed to be the order most closely related to the Passeriformes,
have a very specialized form of pedal locomotion. The wood-
peckers and toucans examined for comparison in this study had
Type 6 sterna, but the processes were relatively much shorter and
broader than those in the passerine Type 6 sternum; four genera
of barbets and one jacamar had longer thinner processes, more like
the passerine type, but all four processes had very wide posterior
flanges which were rarely found in the Type 6 suboscines. If any of
the above theorizing on function affecting the shape of the sternum
is correct, then we cannot expect evolutionary indicators in this
case from such a highly specialized group as the Piciformes.

CONCLUSIONS

The main conclusion of this study is that the suboscine ster-
num is an exceptionally variable anatomical structure. We recom-
mend caution, therefore, in the taxonomic use of sternal configura-
tions until their range of variation has been determined, and their
functional and adaptive significance can be understood. The pres-
ent investigation was designed only to sample the range of varia-
tion, and although the evolutionary significance of this variation
is not yet known, we hope our purely observational results can
have some immediate utility for the taxonomist.

In order to use the posterior border of the sternum as a taxo-
nomic character, reasonably large series must be examined and
differences must be shown to be consistent before they can be

1967 Sternal Notches of Passeriform Birds 19

considered significant. If, however, only a few specimens are
available and they all show either Types 2-3-4 or Types 5-6, then
we feel it is relatively safe to conclude that the species is basically
either two- or four-notched. Basing one’s conclusions on these
sternal criteria (rather than on Types) in small series also avoids
most of the errors possible with incompletely ossified specimens,
particularly in confusing Type 2 with 3 and Type 5 with 6. As an
example, if only single specimens of Species A and Species B were
available, and one had a Type 2 sternum and the other a Type 3,
then these would not be considered significantly different. If, on
the other hand, Species C were found to have a Type 3 sternum
and Species D a Type 6, then this could be considered important
as the separation between the two- and four-notched sterna has
been shown to be quite consistent.

The present study has also indicated that certain families or
groups of genera have general types of sternal characters which
may be useful in taxonomic decisions. The woodcreepers (Den-
drocolaptidae) show a tendency toward Type 2 sterna, and they
also possess a striking sternal diversity which is interesting in
view of the rather strong ecological and behavioral homogeneity
of the family. In contrast, the ovenbirds (Furnariidae) show con-
siderable homogeneity in the sternum, but a broad range of eco-
logical and behavioral diversity. Certain sternally aberrant ovenbird
genera (Cinclodes, Xenops, etc.) may warrant additional ana-
tomical study. The majority of the antbirds (Formicariidae) have
two-notched sterna, but certain genera possess four-notched sterna
(Pittasoma, Grallaricula, and Grallaria). It will be important to
study further this subdivision of the family, and also to investigate
Grallaria in which the presence of both two- and four-notched
sterna strongly suggests that the genus as presently defined is a
composite. The Conopophagidae, as shown elsewhere (Ames,
P. L., M.A. Heimerdinger, and S. L. Warter, unpublished. The
anatomy and systematic position of the antpipits Conopophaga
and Corythopis.), are an artificial family; we advocate returning
the gnateaters (Conopophaga: four-notched) to the Formicariidae,
and including the antpipits (Corythopis: two-notched) in the
Tyrannidae. The tapaculos (Rhinocryptidae) are characterized
by having a four-notched sternum, but contrary to previous belief,
the four-notched sternum is not unique to the rhinocryptids and
Conopophaga.

20 Postilla Yale Peabody Museum No. 105

The New World Tyrannoidea (Cotingidae, Pipridae, Tyran-
nidae, Oxyruncidae, and Phytotomidae) and the Old World subo-
scines, with the exception of Menura, all show a consistent two-
notched sternum, with only limited variation away from the Type 3
configuration. The sternum of Menura is unique among all other
passerines studied.

LITERATURE CITED

Brodkorb, P., 1965. New taxa of fossil birds. Fla. Acad. Sci., Quart. Jour.
28: 197-198.

Cory, C. B. and C. E. Hellmayr, 1924. Catalogue of birds of the Americas
and the adjacent islands. Field Mus. Nat. Hist. Pub. 223, Zool. Ser.
13(3). 369 pp.

, 1927. Catalogue of birds of the Americas and the adjacent
islands. Field Mus. Nat. Hist. Pub. 242, Zool. Ser. 13(5). 517 pp.
Forbes, W. A., 1881. Contributions to the anatomy of passerine birds. Part
IV. On some points in the anatomy of the genus Conopophaga, and its

systematic position. Zool. Soc. London 1881, Proc.: 435-438.

Garrod, A. H., 1876. On some anatomical characters which bear upon the
major divisions of the passerine birds. Pt. 1. Zool. Soc. London 1876,
Proc. 506-519.

, 1877. Notes on the anatomy of passerine birds. Pt. 2. Zool.
Soc. London, 1887, Proc. 447-452.

Hanson, H. C., 1962. The dynamics of condition factors in Canada geese
and their relation to seasonal stresses. Arctic Inst. No. Am. Tech.
Paper No. 12. 68 pp.

Hellmayr, C. E., 1929. Catalogue of birds of the Americas and the adjacent
islands. Field Mus. Nat. Hist. Pub. 266, Zool. Ser. 13(6). 258 pp.

Klima, M., 1962. The morphogenesis of the avian sternum. Acta Acad. sc.
Cechosloy. bas. Brunensis 34: 151-194.

, 1964. Die Entstehung und Formung der Crista sterni bei
Vogeln. Zool. Anzeiger 172: 395-402.

Lindsay, B., 1885. On the avian sternum. Zool Soc. London 1885, Proc.:
684-716.

Peters, J. L., 1951. Check-list of birds of the world. 7. Mus. Comp. Zool.,
Cambridge. 318 pp.

Plotnick, R., 1958. Posicién sistematica del género ‘“Psilorhamphus”
(Rhinocryptidae, Passeriforme): Physis, Buenos Aires 21: 130-136.

Ridgway, R. 1907. The birds of North and Middle America. U. S. Natl.
Mus. Bull. 50(4). 973 pp.

, 1909. New genera, species and subspecies of Formicariidae,
Furnariidae and Dendrocolaptidae. Biol. Soc. Wash. Proc. 22: 69-74.

———————.,, 1911. The birds of North and Middle America. U.S. Natl.
Mus. Bull. 50(5). 859 pp.

Sclater, P. H., 1874. On the neotropical species of the family Pteroptochidae
Ibis 1874: 189-206.

Sharpe, R. B., 1890. Catalogue of the birds in the British Museum. 13.
London. 701 pp.

Shufeldt, R. W., 1913. Fossil feathers and some heretofore undescribed fossil
birds. Jour. Geol. 21: 628-652.

Wetmore, A., 1926. Observations on the birds of Argentina, Paraguay,
Uruguay, and Chile. U.S. Natl. Mus. Bull. 133. 448 pp.

1967 Sternal Notches of Passeriform Birds Dal

costal
sternum

Ue

Va metasternum

lateral fenestra

metasternum

——posterior lateral Process
lateral metasternal Process

medial notch

lateral notch

Fig. 1. Passerine sternal types.
from specific specimens. Type 3 sho

Generalized representations, not drawn
wn in place on the trunk skeleton.

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DAIDUOIAID

DIDpNDI
ppiydowKiqg

p{na
Dass
DAOAIINUAO J

sisuaxinb
spidoysoso1y

SNIDUIGADLUYNA
SNUYIO]ISdA1d HY

AOJOINSIYIS
STAD] JIXD
S1JUAAIAN{
SISUIWUIDULANS
DINAIYJOULLA AV

saisadg

105

No.

Postilla Yale Peabody Museum

32

xx

sodA, YOON [eUulI1S

XXXXX

XXXXXXXXXXXXX

XXXX

Xxxx

SUuosf1q]D
SAYJIg

puosiuvdwups
pzapuipy

syjpuv
SNLDIIULAO

XDAOYIOAD
xppAydousd py

pauisnisaf
pnsxa
DIIDIWAKPN

suosfyfna
DIOJSOUILIg

DiAaDu
DIAIIDIIS

sdajipnu
pyyII0UuU ay

godky, 9-G adky cs odky S-poedhy poddky p-¢ odhy ¢ adh

€-T adh, 7 dL

sa1seds

‘sautiassed auldsoqns oy} ur sodA} [eusa}s JO UOTNIySIG

(pjuos) |] aTavy

33

Sternal Notches of Passeriform Birds

1967

XXXx x

mK mK

XxX

ie

XXXXX

ponajo4yoo
pjp}191dssad
SLyuaalapnt
ppn{n4
pyidvoifi4
sisuajinb
pjouojdpny
DIIDA
sisua]DUyons
DIAD]JDAD

pupu
DINI1AD]]DAD)

14a] YOIUt
DULOSDIN1d

DID]NIDWUOAT1U
sisdosajyd

SaplolAapu
xpjxydoja Yq

sidspona]
pynsyna
scysidouway

godky 9-gadky cs adky ¢-padky podky p-¢ odhL
sodA, YON [eusas

¢ odA TL

€-7T adAy, TAAL

so1seds

105

No.

Postilla Yale Peabody Museum

34

pjndaqna

EN Ee
SNPIYILOJIIS

snipodpsau

NuUAD]
soyr0j doa} d

‘B1oUaz ¢ ‘SudUIdads ¢Z
soepndArsouryy Apiwme;

pyonbsoq
Ipuv]vjap
sidoysAsoy

sdoupjau
puplAniad
1Alagod

ppaul]
vévydodouo)

‘Bisues 7 ‘SUDUTIDAds BZ

:oepiseydodouo, Ajime,y

XXXX
Xxx
XXXXX
Xxx
XXXXX
x
x
Xxx
Mo XSROKENORON.
XXXXXXXX
godkjy 9-¢adkAyT CG adAL S-F adAy poddAy p-¢ odAL ¢ odAL €-~ adA], 7 adkL

sodA], YON [PUBS

sa1sedg

‘souiiassed aulssoqns 9y} ul sodA} [eusa}s JO UONNGINSIG

a (pquos) | ATaVy

35

Sternal Notches of Passeriform Birds

1967

XXXX snaaipods
DIY
XX 14a ffald
[siuso] yong, = | vjoaidig
XXXX siuuad jaw]
puajoyd1y
XX 1ADMSP14
DSUNOD
x snjpydavounjau
[uoyadu p = | siusodiny
“elouas C] ‘SUSUIDEds 6/
soepisunoyg Arey
Xx pxoppivd
pj]joAsngy
XXXXX SnIIUD]JasDUL
XXX SUOA{IUISAD
x 40]091uN
sndopvjK4og
x SHIIUOUDADUL
piaipdouvj ap
godAj g-¢adAy codky ¢-podAy poadky p-¢ addky ¢ odAy €-7 odAT, ZT OdAL sarsedg

sodA], YJON [eUII1S

105

No.

Postilla Yale Peabody Museum

36

godkt 9-¢ adAy ¢ adh 6-p OdAL

XXXX

x
XXXXXXXXXXXXX

XXXX

xx

podky p-¢ odAL
sodA], YDJON [eUusa}S

¢ odAL

SnJoUusoO
snsajdojpyday

pyoandind
pjn4Aano

doqisinbui
pIpIISv{1iuas
DAKJLT

aviv] sv
siupsd av] d

4olpu
snisajdoyrkjod
snydwpiKyovd

sn{naun
SLID]Dqns
snénvdiy]

DAYJAAIJOY
pusajdyayy

py4iXkdodxy
DADIOIUDT

€-7 aA] 7 AdAL

sorsedg

‘soulLiossed guissoqns oy} ul sodA} [eUusa}s JO UOTINGIYSIG

(pjuos) | ATav

Si)

Sternal Notches of Passeriform Birds

1967

godky 9-G adkp ¢ adAy ¢-p addy podky p-¢ adAL

sodA, YON [eUIIIS

XXXXXXXX 1apuvdo
XXXXXXX xX snopuput
snovudpw
XXX DOYALOINI]
odidpioy
XXX pjoaavd
x: sipauly
piydixosy,
xX mMuUDUz]01S
SAINIUUDAK [
XXXXX pjoydas01ysasa
XXXXXXX SYDJUIU
XXXX xX DIDUOLOI
vidid
“B19Uas 9g ‘SUdWIOSdS Tp
soeplidig A[IWwey
XXXXX x puplAniad
XXXXXXXXX xX pjooidna
pjooidny
XX DID]NIUNADIIAY
x OUDAIIAD
XXXXXXXXXX XXXX Syjooipnu
x pq]D
SDIUIOL
¢ odAL €-7T dA ZT OdAL saisedg

105

XXXX

No.

xx

XXXXXXXXK

snuigna
snpoydaI01K

paid
DIOIIAN]

aqaoyd
SIULOADS,

pD{na
DIUOSSIT

suosfig]D
pjp4jsidvo
DJOIIXDS1IISN PW

adoskd
smujox

‘elauasd ¢¢ ‘sUdLUIDads ()7Z
roepruueisds | A[Iuey

Postilla Yale Peabody Museum

SNUIPAN]
SIUAOL1YIS

godky 9-¢odAy ¢ odAy ¢-podAy podhy p-¢ adh ¢ odA TL,
sodA J, YON [eussis

€-~ edA], Z add 1.

sarsads

‘souliassed gurdsoqns oy} ul sodA} [eUId}s JO UONNGIYsSIG

(pju0s) | ATV

38

59

Sternal Notches of Passeriform Birds

1967

XXXXXXX snjvinydjns
SNSUDJIg
XxX SISUIPDUDAS
XXXXX Suis
SAJaJaZOlIKBW
XXXX x pnsuvjid
SNYIUKIDS AW
x snjojnopu
XXX §14JUIAIAJN]
Saispucpoik Ay
x SMIADA
snuouopidwuy
XXXXXXXXXX SIsuaDIUIUOp
XXXXXXXXXXX SNINOYIUD]AU
XXXX SIDIYAIA
XX SUDAIJIIOA
XXXXXXXXXXXX
XXXXXXXXXXXXXXX
XXXXXXXXXXXXXXX
XX XXXXXXXXXXXXXXX xx SHUUDAA]
SNUUDAK
x XXXXX vpysof
DAOAIISN
godkj 9-¢adAy ¢odAy ¢-podA, podky p-¢ adAL ¢ odAT €-7 odAT, 7 AdAL sarsadg

sodA] YdJON [RUINS

105

No.

Postilla Yale Peabody Museum

40

xx

~ KK KM MK

x XXXX

xx
x xx
XXXXXXXXXX
x XXXXXXXXXXX

snis Kdiaanydjns
SnjDqAvq
SHIGOIAJN

snodaz20avyd
sauvydaAply

1JYSlUM
SmUuqUiUt
ATO
SUIISAAIA
SLJUIAIAD]
xpuopidwq

[snona]osaul = | s1]pa40q
SIULO[DIINN

4afno4aqny
xOs1af
SN|NUUDAKY
SUIISDAIUII

SNJMIAD
SNYIADIA JAY

gg adh], g-cadky cg odky ¢s-podky podAL p-¢ adh ¢ odAL €-Z dA, ZT AdAL
sodA], YOON [eUuss}1S

sa1sedg

‘soutiassed auidsoqns oy} ul sadA} [eusa}s JO WORNQINSIG

(pjuos) | aATaVy

41

Sternal Notches of Passeriform Birds

19G7

gadkf 9-¢ adAT,

cg adky, ¢-podAy poddAy p-¢ adAy

sadA J] YSION [BUIIS

¢ odAT,

xx

Xx

sdaydoona]
SN]NIABIOIIW

pjoaany
siduaisdv)

snjvapid
SNIIAOYdOT

IADING1AAIUII
DULOJSOIUQ

LUnNIJD]NIDU
LUNIAIUID
WNAJSOAIPO T

STJSOMAIAG
snpaxroyoucyy

suadsainyd]ns
spiaulow]o I

SNUIMMOALIUDI
snaovIscu
SNYIULAKID] I

SNJDUOLOI
snyoucysoyoauc

snyp1ospf
snqoydolk W

€-Z adAy, 7 3dAL

saisedsg

105

No.

Postilla Yale Peabody Museum

42

xX

XXxX

XXXX

XXXXXX

gadkt, 9-¢ adh, ¢adky, ¢-padky, poddy p-¢ adAy € odd

sadA[, YJION [BUIIS

SNIDISIAD
SNIUNAKXE

‘snues | ‘uowIdods |
:QeplounIAXO Awe}

paulsvajo
pydsowoidig

4020
SNUINSS1]1A
SNISIUUDAK J,

uinjajOsqo
piuojsojduiny

DULINUL
SDIAWUOADY

DIDIIPIAIA
MpADULIDS
sdao1q]D
dajspsoan]f

piuav]q

€-7 edAT, 7 OdAL sa1sedg

‘souliassed sulssoqns 9y} url sodA} [euIa}s JO UONNGIIYsIG

(pjuos) | aAlavy,

43

Sternal Notches of Passeriform Birds

1967

DIUDISDI
yd ay

‘snuas | ‘uawtdeds |
soepnudopiyd Aju

XxX

AOJOIISAIA
DpIpsos
IMOUIYIIAA
SISUIIINJOUL
puvipns
AIJSVBOAYINAD
GAME)
DANKYIDAG

DUN

‘snuas | ‘suausads | |
sepa Apu

XXXX

DpMNA
DADA
DIUOJOJAYd

‘snuos | ‘suowiseds 9
soeprumojoyAYy A[Iwey

goedky], g-¢adky, ¢odAy, ¢-podsy, pods], p-¢ adAL

sodA], YDJON [eUusays

¢ odAT,

€-T adAJ, 7 add, saisadg

‘Z] ‘d ‘9x0} Gas fp-] adA ‘19y10 oy} ] adAT ‘uowdeds 9uQC;
‘TT ‘d ‘}x0} 996;

‘OPIS 9UO UO BI}JSOUDJ [[BUIS B YA:

‘6 ‘d 3x9} 908 {| adA] ‘uowIoads [eUOTIPpYy;

No. 105

XOX pXX pqsadns
DANUIW

‘snues | ‘susuideds p
:oeplLinusyy Ape 4

x sadisuo]
snomaxX

x S140] YI
DILISIYJUDI PY

“elouas J ‘SudtUIdeds 7
roepHisiqjueoy Ayime 4

Postilla Yale Peabody Museum

godky 9-¢ odAL ¢ adky, s-podkAy podkyL p-¢ adh | ¢ odAL, €-Z odAZ, 7T9dAL sa1sedg

sodA, YION [BUIAS

‘soulsassed ourdsoqns oy) url sodAy yeutays Jo YORNISIG

(pjuos) | ATaV

44

Fn ae
eRe eS
aa Siero

PIT FS

2 ghet|
oerarer

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