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Phylogeny of the Waxwings
and Allied Birds
BY
M. DALE ARVEY
University of Kansas Publications
Museum of Natural History
Volume 3, No. 3, pp. 473-530, 49 figures in text, 13 tables
October 10, 1951
UNIVERSITY OF KANSAS
LAWRENCE
1951
UNIVERSITY OF KANSAS PUBLICATIONS, MUSEUM OF NATURAL HISTORY
Editors: E. Raymond Hall, Chairman, Edward H. Taylor,
A. Byron Leonard, Robert W. Wilson
Volume 3, No. 3, pp. 473-530, 49 figures in text, 13 tables
Published October 10, 1951
University of Kansas
Lawrence, Kansas
PRINTED BY
FERD VOILAND, JR., STATE PRINTER
TOPEKA, KANSAS
1950
[Illustration: union label]
23-1019
Phylogeny of the Waxwings
and Allied Birds
by
M. DALE ARVEY
CONTENTS
PAGE
Introduction 476
Acknowledgments 476
Nomenclatural History 477
Materials 478
Diagnoses 478
Coloration 485
Courtship 489
Nest Building 491
Food 493
Skeleton 494
Skull 494
Humerus 499
Pygostyle 502
Sternum 505
Relative Lengths of Bones 505
Leg-trunk Percentages 509
Arm-trunk Percentages 511
Musculature 514
Caudal Muscles 514
Pectoral Muscles 517
Hind Limb Musculature 517
Digestive Tract 517
Origin of the Species 519
Conclusions 521
Summary 524
Bibliography 525
INTRODUCTION
A small family of passerine birds, the Bombycillidae, has been
selected for analysis in the present paper. By comparative study of
coloration, nesting, food habits, skeleton and soft parts, an attempt
is made to determine which of the differences and similarities between
species are the result of habits within relatively recent geological
time, and which differences are the result of inheritance from ancient
ancestral stocks, which were in the distant past morphologically
different. On the basis of this information, an attempt is made to
ascertain the natural relationships of these birds. Previous workers
have assigned waxwings alone to the family Bombycillidae, and a
question to be determined in the present study is whether or not
additional kinds of birds should be included in the family.
It has generally been assumed that the nomadic waxwings originated
under boreal conditions, in their present breeding range, and that
they did not undergo much adaptive radiation but remained genetically
homogeneous. Also it is assumed that the species were wide ranging and
thus did not become isolated geographically to the extent that, say,
the Fringillidae did. The assumption that waxwings originated in the
northern part of North America or Eurasia may be correct, but it is
more probable that the origin was more southerly, perhaps, in northern
Mexico, of North America (see p. 519.) Subsequent to the
differentiation of this stock in the south, there was a northerly
movement, while certain populations remained behind and underwent an
evolution different from the northern group. Since the fossil record
does not permit us to say when in geological time the family
originated, we must rely on anatomical evidence and the distributional
evidence of present-day species to estimate when the family stock had
diverged from some unknown group sufficiently to merit the status of a
separate family.
ACKNOWLEDGMENTS
It is with pleasure that I acknowledge the guidance received in this
study from Professor E. Raymond Hall of the University of Kansas. I am
indebted also to Dr. Herbert Friedmann of the United States National
Museum for the loan of certain skins, skeletons, and alcoholic
material; to Mr. Alexander Skutch, for notes on certain Central
American birds; and to Dr. Henry W. Setzer, Mr. George H. Lowery, Jr.,
Mr. Victor E. Jones, Mr. Victor Housholder, Mr. Alvaro Wille-Trejos,
and Mr. Morton F. Davis, for gifts of specimens that have been used in
this work. Suggestions and critical comments from Professors Worthie
H. Horr, Charles G. Sibley and Edward H. Taylor are gratefully
acknowledged. I wish also to thank Mrs. Virginia Unruh for the
preparation of the drawings used in this work.
NOMENCLATURAL HISTORY
The oldest name available for any species of the waxwings is _Lanius
garrulus_ Linnaeus (1758). _Lanius garrulus_ and _Lanius garrulus_
variety B _carolinensis_ were described as conspecific. The
description has been associated with the first of the two names. The
latter name is a _nomen nudum_ since it was not accompanied by a
separate description. The generic name _Lanius_ was originally applied
to both shrikes and waxwings by Linnaeus. Since that name is applied
to the shrikes only, the next available generic name that may be
applied to the generically different waxwings must be used. This is
_Bombycilla_, a name originally proposed by Brisson (1760) for the
Cedar Waxwing. In the 12th Edition of the Systemae Naturae (1766)
Gmelin proposed the generic name _Ampelis_ for the Bohemian Waxwing,
and combined it with the specific name _garrulus_, the Cedar Waxwing
being termed variety B. Vieillot (1807) proposed the generic name
_Bombycilla_ and combined it with a new specific name, _cedrorum_, for
the Cedar Waxwing. Vieillot has been cited as the author of
_Bombycilla_ since that time, although Brisson used _Bombycilla_ 33
years before. Oberholser (1917) did not cite Brisson's work in his
discussion of the proper generic name for the waxwings, and
_Bombycilla_ should be ascribed to Brisson and not Vieillot, since
Opinion 37, rendered by the International Zoological Committee on
Nomenclature, states that generic names used by Brisson (1760) are
valid under the Code. In consequence, the specific name available for
the Cedar Waxwing, since Brisson is ruled not to be a binomialist, is
_Bombycilla cedrorum_ Vieillot (1807).
Most workers prior to 1900 utilized the family name Ampelidae to
include waxwings, silky flycatchers, and palm-chats. Ridgway
(1904:113) elevated the silky flycatchers to family rank under the
name Ptilogonatidae, and assigned the palm-chats to a separate family,
the Dulidae.
MATERIALS
The following specimens, numbering 238, and representing each
currently recognized species and subspecies, were used in the study,
and were supplemented by observation in 1947 on specimens in the
United States National Museum.
====================================================================
Species or Subspecies | Skin | Skeleton| Alcoholic
----------------------------------------+------+---------+----------
_Phainoptila melanoxantha melanoxantha_ | 8 | 1 | 2
_Phainoptila melanoxantha minor_ | 2 | |
_Ptilogonys cinereus cinereus_ | 13 | 3 | 4
_Ptilogonys cinereus molybdophanes_ | 6 | |
_Ptilogonys caudatus_ | 16 | 3 | 4
_Phainopepla nitens nitens_ | | 1 | 5
_Phainopepla nitens lepida_ | 12 | 5 | 4
_Bombycilla cedrorum_ | 53 | 27 | 8
_Bombycilla garrula garrula_ | 4 | 3 |
_Bombycilla garrula centralasiae_ | 9 | 2 |
_Bombycilla garrula pallidiceps_ | 7 | 3 | 2
_Bombycilla japonica_ | 10 | |
_Dulus dominicus dominicus_ | 9 | 5 | 2
_Dulus dominicus oviedo_ | 4 | 1 |
|---------------------------
Totals | 153 | 54 | 31
--------------------------------------------------------------------
DIAGNOSES
Family Bombycillidae
_Diagnosis._--Bill short, flat, somewhat obtuse, minutely notched near
tip of each maxilla, flared at base; gape wide and deeply cleft;
culmen convex; nasal fossa broad, exposed, or filled with short, erect
or antrorse, close-set velvety feathers; nostril narrowly elliptical;
rictal vibrissae long, short, or absent; lacrimal bone free,
articulating at two points; wings long and pointed, or short and
rounded; primaries ten, tenth reduced in some species; tail short,
narrow, even, two thirds or less length of wing, or much longer and
forked or rounded; feet weak (except in _Dulus_ and _Phainoptila_);
tarsus generally shorter than middle toe and claw, distinctly
scutellate with five or six divisions, the lateral plate subdivided
(except in _Phainoptila_); lateral toes of nearly equal length; hallux
approximately as long as inner lateral toe, or shorter; basal phalanx
of middle toe more or less united to that of outer and inner toes;
body stout; head generally conspicuously crested; plumage soft, smooth
and silky (except in _Dulus_); eggs spotted; nest in trees; three
subfamilies, five genera, eight species.
Subfamily Ptilogonatinae
_Diagnosis._--Rictus with conspicuous bristles; nasal fossa almost
entirely exposed; tail long and rounded, graduated, or square; caudal
muscles and pygostyle well developed; wings rounded and short, first
primary a half to a third as long as second; second primary shorter
than third; humerus long, with small external condyle; plumage soft
and silky, less so in _Phainoptila_; sexes dissimilar, young like
adult female; three genera, four species.
Genus =Phainoptila= Salvin
_Phainoptila_ Salvin, Proc. Zool. Soc. London, 1877:367, April 17,
1877. Type _Phainoptila melanoxantha_ Salvin.
_Diagnosis._--Without crest; tarsus longer than middle toe and claw,
and booted or very slightly reticulate; tail shorter than wing,
rounded; nostril exposed, ovate; rictal bristles distinct; first
primary well developed; plumage normal, bill flared slightly at base.
_Range._--Costa Rica and Panama.
=Phainoptila melanoxantha melanoxantha= Salvin
Phainoptila
_Phainoptila melanoxantha melanoxantha_ Salvin, Proc. Zool. Soc.
London, 1877:367; April 17, 1877.
_Diagnosis._--Coloration of adult males: Pileum, hindneck, back,
scapulars, and upper tail coverts Black (capitalized color terms after
Ridgway, Color Standards and Color Nomenclature, Washington, D. C.,
1912), with Bluish Gray-Green gloss; rump Lemon Yellow tinged with
Olive; lower breast and abdomen Gull Gray or Slate Gray; sides and
flanks clear Lemon Yellow; lower chest, upper breast, and under tail
coverts Yellowish Olive-Green, extending to patch on sides and flanks
of same color; bill and feet Black or Blackish Brown. Coloration of
adult females: Most of upper parts Olive-Green, with Yellowish Olive
on rump; thighs Olive-Gray, as are sides of head; rest of coloration
as in male. Coloration of young: As in adult female, but duller
throughout.
_Measurements._--Wing 99.0, tail 88.5, culmen 15.2, tarsus 28.4.
_Range._--Highlands of Costa Rica and extreme western Panama (Volcan
de Chiriqui).
=Phainoptila melanoxantha minor= Griscom
Phainoptila
_Phainoptila melanoxantha minor_ Griscom, Amer. Mus. Novitates,
141:7, 1924.
_Diagnosis._--Coloration as in _P. m. melanoxantha_, but female with
hindneck more extensively gray and of slightly darker shade; rump,
upper tail coverts, and edgings to tail feathers slightly greener,
less yellow; average size smaller than in _P. m. melanoxantha_.
_Range._--Highlands of westeran Panama (Cerro Flores and eastern
Chiriqui).
Genus =Ptilogonys= Swainson
_Ptilogonys_ Swainson, Cat. Bullock's Mex. Mus., App. 4, 1824.
Type _Ptilogonys cinereus_ Swainson.
_Diagnosis._--Tail much longer than wing, even or graduated; head with
bushy crest; nostril large, rounded and fully exposed, bordered by
membrane; rictal bristles well developed; tarsus shorter than middle
toe with claw; plumage soft, blended.
_Range._--Southwestern United States to Costa Rica.
=Ptilogonys cinereus cinereus= Swainson
Ashy Ptilogonys
_Ptilogonys cinereus cinereus_ Swainson, Cat. Bullock's Mex. Mus.,
App. 4, 1824.
_Diagnosis._--Coloration of adult male: Frontals, supralorals, malars,
and chin White; orbital ring White; auriculars and nape grayish brown;
rest of head smoke gray; back, scapulars, wing coverts, rump, and
upper tail coverts plain Bluish Black; rectrices (except middle pair)
with large patch of White midway between base and tip, rest plain
Bluish Black; chest, breast, and anterior parts of sides plain Bluish
Gray-Green, much lighter than back, and fading into paler Gray on
throat; abdomen and thighs White; flanks and posterior part of sides
Olive-Yellow or Yellowish Olive; under tail coverts Lemon Yellow;
bill, legs and feet Black. Coloration of adult females: Head plain
Smoke Gray, passing into White on frontals, malars, and chin; back,
scapulars, wing coverts, and rump Hair Brown; upper tail coverts Dark
Gull Gray; remiges and rectrices Black with faint Dusky Green gloss,
edged with Gull Gray; chest Dark Grayish Brown lightening to Wood
Brown on sides and flanks; abdomen White; under tail coverts Yellow
Ocher. Coloration of young: As in adult female, but paler throughout.
_Measurements._--In adult male, wing 94.0, and tail 104.2; in adult
female, wing 93.3, and tail 94.8; both sexes, culmen 11.1, and tarsus
18.7.
_Range._--Mountainous districts of central and southern Mexico, in
states of Durango, Zacatecas, Hidalgo, Mexico, Oaxaca, Colima,
Morelos, Veracruz, San Luis Potosi, Guerrero and Michoacan.
=Ptilogonys cinereus molybdophanes= Ridgway
Ashy Ptilogonys
_Ptilogonys cinereus molybdophanes_ Ridgway, Man. N. American Birds,
464 (footnote), 1887.
_Diagnosis._--Coloration of adult male: Upper parts darker bluish than
in _P. c. cinereus_; venter paler; flanks Olive-Green rather than
Olive as in _P. c. cinereus_. Coloration of adult female: Like female
of _P. c. cinereus_ but colors darker throughout; dorsum more
olivaceous.
_Measurements._--In adult male, wing 89.4, and tail 97.1; in adult
female, wing 89.4, and tail 93.3; both sexes, culmen 11.7, and tarsus
17.3.
_Range._--Western Guatemala, in subtropical and temperate zones.
=Ptilogonys caudatus= Cabanis
Costa Rican Ptilogonys
_Ptilogonys caudatus_ Cabanis, Jour. fuer Orn., 1866:402, Nov. 1866.
_Diagnosis._--Coloration of adult male: Forehead and crown Pale
Grayish Blue, slightly paler anteriorly; orbital ring Lemon Yellow;
rest of head and neck, including crest, Olive-Yellow; throat paler and
tinged with Light Gull Gray; back, scapulars, rump, upper tail coverts
and wing coverts uniform Bluish Slate-Black; chest and breast similar
but paler; sides and flanks Yellowish Olive-Green; thighs, lower
abdomen, and under tail coverts Lemon Yellow; remiges, primary coverts,
and tail Black, glossed with Bluish Black and edged with Gull Gray;
inner webs of rectrices (except two middle pair) with large middle
patch of White; bill, legs, and feet Black. Coloration of adult
female: Forehead and crown Pale Gull Gray, becoming paler anteriorly;
rest of head, together with neck, back, scapulars, rump, and wing
coverts plain Yellowish Olive Green; chest and breast similar but more
grayish; lower abdomen and flanks White tinged with Yellowish Olive;
under tail coverts Olive-Gray; remiges, primary coverts, and rectrices
Black with Gull Gray edges. Coloration of young: Dorsum plain Light
Grayish Olive; upper tail coverts Brownish Olive; underparts Grayish
Olive anteriorly, becoming more Yellowish Olive on abdomen; under tail
coverts pale Yellowish Olive with Grayish Olive base; bill and feet
Brownish Drab.
_Measurements_--In adult male, wing 96.2, and tail 135.7; in adult
female, wing 93.9, and tail 113.7; both sexes, culmen 12.6, and tarsus
19.1.
_Range._--Highlands of Costa Rica and extreme western Panama.
Genus =Phainopepla= Sclater
_Phainopepla_ Sclater, Proc. Zool. Soc. London, 26:543, 1858. Type
_Phainopepla nitens_ (Swainson).
_Diagnosis._--Tail almost as long as wing; head with pointed crest of
narrow, separated feathers; rectrices without white; bill narrow,
compressed terminally; conspicuous white patch under wing; nostril
small, exposed; rictal bristles distinct; tail slightly rounded.
=Phainopepla nitens nitens= (Swainson)
Phainopepla
_Phainopepla nitens nitens_ (Swainson), Anim. in Menag., 1838:285,
Dec. 31, 1837.
_Diagnosis._--Coloration of adult male: Uniform glossy Bluish Black;
inner webs of primaries except innermost pair with middle portion
White; bill, legs, and feet Black. Coloration of adult female: Plain
Olivaceous Black, longer feathers of crest Black, edged with Gull
Gray; remiges and rectrices Dusky Drab to Black; rectrices and coverts
margined by White; bill and feet Brownish Drab to Dusky Brown.
Coloration of young: Like adult female but more Brownish Drab.
_Measurements._--No specimens examined; larger than _P. n. lepida_
(Van Tyne, 1925).
_Range._--Central and southern Mexico, in states of Coahuila, San Luis
Potosi, Durango, Guanajuato, Mexico, Puebla, and Veracruz.
=Phainopepla nitens lepida= Van Tyne
Phainopepla
_Phainopepla nitens lepida_ Van Tyne, Occ. Pap. Bost. Soc. Nat.
Hist., 5:149, 1925.
_Diagnosis._--Coloration same as _P. n. nitens_; separated by smaller
size.
_Measurements._--Wing 91.0, tail 90.3, culmen 11.5, tarsus 17.6.
_Range._--Southwestern United States, from central California,
southern Utah, and central western Texas southward to Cape San Lucas
in Baja California, and into northwestern Mexico (Sonora and
Chihuahua).
Subfamily =Bombycillinae=
_Diagnosis._--Wings long and pointed, reaching almost to tip of tail;
first primary spurious; second primary longest; tail short and even;
rictal vibrissae few and short; secondaries generally, and sometimes
also rectrices, tipped with red, corneous appendages; nasal fossa
partly filled with short, antrorse, close-set velvety feathers;
plumage soft, silky; tail tipped with yellow band (red in _B.
japonica_); sexes alike; humerus short with large external condyle;
caudal muscles and pygostyle not well developed; bill flared widely at
base; one genus, three species.
_Range of subfamily._--Holarctic breeding area; wanders nomadically
south in winter to Central America and West Indies, southern Europe
and Asia.
Genus =Bombycilla= Brisson
_Bombycilla_ Brisson, Orn. ii, 1760:337. Type _Bombycilla garrula_
(Linnaeus).
_Diagnosis._--As described for the subfamily.
=Bombycilla cedrorum= Vieillot
Cedar Waxwing
_Bombycilla cedrorum_ Vieillot, Hist. Nat. Amer., 1:88, Sept. 1, 1807
_Diagnosis._--Coloration of adults: Shading from Saccardo's Umber on
dorsum to Bister on top of head; upper tail coverts and proximal
rectrices Gull Gray; underparts shade through pale Lemon Yellow wash
on belly into White on under tail coverts; forehead, lores, and
eye-stripe Black; chin same, soon shading into Blackish Mouse Gray and
into color of breast; side of under jaw with sharp White line; narrow
line bordering forehead, and lores, White; lower eyelid White; quills
of remiges Dark Mouse Gray, darkening at tips; inner quills tipped
with red horny wax appendages; tail feathers like primaries, but
tipped with Lemon Yellow, and occasionally showing also red horny wax
appendages; bill and feet Black. Coloration of young: Dorsum as in
adult, but lightly streaked with White; head concolor with dorsum;
forehead White; lores Black; eye stripe Black anterior to eye and
White posterior to eye; throat Light Buff; belly with alternate
streaks of Dresden Brown and light Ochraceous Buff but posteriorly
White; tail tipped with Lemon Yellow bar; bill black at tip, shading
to Sepia at base.
_Measurements._--Wing 92.9, tail 55.5, culmen 10.9, tarsus 16.8.
_Range._--Breeds from central British Columbia, central Alberta and
Manitoba, northern Ontario, southern Quebec and Cape Breton Island
south to northwestern California, northern New Mexico, Kansas,
northern Arkansas, North Carolina, and northern Georgia. Winters south
to Louisiana, Mississippi, Texas, Arizona, Colorado, Florida,
Honduras, Costa Rica, Jamaica, Little Cayman Island, Haiti, and
Panama.
=Bombycilla garrula= (Linnaeus)
Bohemian Waxwing
_Bombycilla garrula_ (Linnaeus), Syst. Nat., 10th Ed., 1758:55.
_Diagnosis._--Coloration of adults: General color Olive-Brown, shading
insensibly from clear Smoke Gray of upper tail coverts and rump to
Cinnamon-Drab anteriorly, heightening on head and forehead to Hazel;
narrow frontal line, lores, broader mask through eye, chin, and upper
throat, Sooty Black; under tail-coverts Cinnamon-Brown; tail Smoke
Gray, deepening to Blackish Mouse Gray distally, and tipped with Lemon
Yellow; wings Blackish Mouse Gray; primaries tipped with sharp spaces
of Lemon Yellow or White, or both; secondaries with White spaces at
ends of outer web, shafts usually ending with enlarged, horny red
appendages; primary coverts tipped with White; bill Blackish Slate and
paler at base; feet Black. Coloration of young: Much like adult, but
general color duller; some streaking on venter and back; chin, throat,
and malar region dull White. Three subspecies.
=Bombycilla garrula garrula= (Linnaeus)
Bohemian Waxwing
_Bombycilla garrula garrula_ (Linnaeus), Syst. Nat., 10th Ed.,
1758:55.
_Diagnosis._--Coloration: As described for the species, but darkest of
the three subspecies; tending to be more Vinaceous dorsally than
either _pallidiceps_ or _centralasiae_.
_Measurements._--Wing 113.5, tail 63.1, culmen 12.5, tarsus 20.7.
_Range._--Europe; breeds north to northern Russia and Norway, south to
about 65 deg. N latitude; winters south to England and Ireland, southern
France, northern Italy, and Turkey.
=Bombycilla garrula centralasiae= Poljakov
Bohemian Waxwing
_Bombycilla garrula centralasiae_ Poljakov, Mess. Orn. vi:137, 1915.
_Diagnosis._--Coloration: As described for the subspecies _garrula_,
but less Vinaceous dorsally, and more Cinnamon; venter lighter gray
than _garrula_, and much paler than _pallidiceps_.
_Measurements._--Wing 114.7, tail 63.0, culmen 12.2, tarsus 21.0.
_Range._--Asia; breeds northern Siberia south to Vladivostok; winters
to Turkestan and central eastern China and Japan.
=Bombycilla garrula pallidiceps= Reichenow
Bohemian Waxwing
_Bombycilla garrula pallidiceps_ Reichenow, Orn. Monats. 16:191, 1908.
_Diagnosis._--Coloration: As described for the species, but more
grayish above and below than _B. g. garrula_; darker gray than in
_centralasiae_.
_Measurements._--Wing 115.1, tail 71.7, culmen 12.6, tarsus 21.1.
_Range._--Breeds from western Alaska to northern Mackenzie and
northwestern Manitoba south to southern British Columbia, southern
Alberta, northern Idaho, and possibly Colorado (Bergtold 1924) and
Montana (Burleigh 1929); winters east to Nova Scotia and irregularly
over much of Canada, and south irregularly to Pennsylvania, Ohio,
Michigan, Indiana, Kansas, Colorado, California, Arizona, and Texas.
=Bombycilla japonica= (Siebold)
Japanese Waxwing
_Bombycilla japonica_ (Siebold), Nat. Hist. Jap., St. No. 2:87, 1824.
_Diagnosis._--Coloration: Dorsum generally Brownish Drab shading to
Light Brownish Drab on lower back, rump, and upper tail coverts;
secondary and tertiary coverts Pale Brownish Drab, washed on outer web
with Carmine; primary coverts Blackish Slate, with White edging; tail
feathers Slate-Gray, broadly tipped with Carmine, bordered anteriorly
by subterminal Black bar; head crested, forehead Chestnut; lores,
frontals, and stripe extending around eye and nape, Black; throat
Black, narrowing on lower throat; breast, sides of flanks Light Drab;
venter pale Sulphur Yellow; thighs Brownish Drab; under tail coverts
Carmine; bill, legs, and feet Black.
_Measurements._--Wing 108.3, tail 53.6, culmen 11.2, tarsus 19.4.
_Range._--Breeds eastern Siberia, northern China; winters south in
China, and to Japan (Hokkaido, Kyushu), Taiwan, and Korea.
Subfamily _Dulinae_
_Diagnosis._--Bill deep and compressed, culmen strongly depressed;
nostrils circular, wholly exposed; tail even, and shorter than wing;
tenth primary less than half length of ninth; under parts streaked;
plumage hard and harsh; rictal bristles minute; wing rounded; humerus
long and with small external condyle; pygostyle and caudal muscles not
well developed; one genus, one species.
_Range of subfamily._--Islands of Haiti and Gonave, Greater Antilles.
Genus _Dulus_ Vieillot
_Dulus_ Vieillot, Analyse, 1816:42.
_Diagnosis._--Like the subfamily.
=Dulus dominicus dominicus= (Linnaeus)
Palm-chat
_Dulus dominicus dominicus_ (Linnaeus), Syst. Nat., 12th Ed.,
1766:316.
_Diagnosis._--Coloration: Dorsum Olive, back, scapulars, and wing
coverts more Brownish Olive; lower rump and upper tail coverts
Olive-Green; pileum and hindneck with indistinct streaks of Brownish
Olive; tail Brownish Drab, edged with Light Olive Gray; lores,
suborbital region, and auricular regions Dusky Brown; malars Dusky
Brown and streaked with Sooty Black, streaks narrower on abdomen,
broader and paler on under tail coverts, bill Light Brownish Drab;
legs and feet Brownish Drab.
_Measurements._--Wing 85.0, tail 68.8, culmen 15.0, tarsus 24.7.
_Range._--Island of Haiti, Greater Antilles.
=Dulus dominicus oviedo= Wetmore
Palm-chat
_Dulus dominicus oviedo_ Wetmore, Proc. Biol. Soc. Wash., 42:117,
1929.
_Diagnosis._--Coloration: Like _D. d. dominicus_, but averaging more
Grayish Olive; rump and tail coverts with less greenish wash.
_Measurements._--Wing 90.1, tail 71.3, culmen 16.2, tarsus 25.1.
_Range._--Gonave Island, off Haiti, Greater Antilles.
COLORATION
The general coloration of waxwings is cryptic, that is to say,
concealing or blending. The lighter color of the venter, especially of
the belly, contrasts with the duller, darker vinaceous color of the
dorsum. Several ruptive marks tend to obliterate the outline of the
body. The crest of the head, when elevated, tends to elongate the
body, making the outline less like that of a normal bird. The facial
mask effectively breaks up the outline of the head, and conceals the
bright eye, which would otherwise be strikingly distinct. The white
spots on the distal ends of the secondaries of _B. garrula_ and the
yellow color on the distal ends of the rectrices (red in _B.
japonica_) are also ruptive. These ruptive marks on an otherwise
blending type of plumage might be important to waxwings, and probably
are more effective when the birds remain motionless in either a
well-lighted area or in one that is partly in shadow, rather than in
one that is wholly in shadow.
The red wax tips on the secondaries of the flight feathers, and
sometimes found on the ends of the rectrices in _Bombycilla_, are
puzzling and no wholly convincing reason has been suggested for their
occurrence. Two instances are known of yellow instead of red-colored
wax tips in _B. cedrorum_ (Farley, 1924). It is well known that many
individuals, especially of _B. cedrorum_, do not possess these tips;
they are absent in a smaller proportion of individuals of _B.
garrula_. Of the 53 skins of _B. cedrorum_ available in the University
of Kansas Museum of Natural History, which might be taken as a
sampling at random of the general population of this species, only 17
possess wax tips. A few specimens are unilateral, and the tips are of
varying sizes in different individuals. Of these 17 birds, 6 are
female and 7 male, the others being unsexed at the time of skinning.
This proportion is, roughly, half and half. Of the seven skins of _B.
garrula pallidiceps_ in the same Museum, five possess the tips, and
two that are females have no trace of the red tips at all. Of the five
which do have the tips, two are males, two are females, and one is
unsexed. In a series of 13 specimens of the three subspecies of _B.
garrula_, loaned by the United States National Museum, all but two
individuals possess the tips on the secondaries, and, in addition,
four specimens, equally divided between the two sexes, have color on
the rachis of some rectrices, and small appendages of pigment extend
beyond the feathers. Stevenson (1882) found that among 144 specimens
of _B. garrula garrula_ killed by storms in England in the winter of
1866-67, 69 individuals had wax tips. Of these, 41 were males and 27
were females; the remaining one was of uncertain sex. Among 38
definitely sexed _B. garrula pallidiceps_ in the California Museum of
Vertebrate Zoology, Swarth (1922:276) lists tips in 22 males and 16
females. These data indicate that the proportion of birds with the wax
tips is higher in _B. garrula_ than in _B. cedrorum_. The potentiality
for wax tips is possibly inherited according to Mendelian ratio.
_Bombycilla japonica_ is of interest in that the adults, at least,
seldom have the waxy appendages. Nevertheless, in the specimens
observed, the entire distal ends of the feathers normally possessing
the tips in other species are suffused with red color. This may be the
original condition of all waxwings, or perhaps, instead, this species
is in a transitional stage in the development of the tips. Swarth
(1922:277) says concerning the probable derivation of the wax tips in
_B. garrula_ (and in _B. cedrorum_): "the ornamentation, in fact, may
well have begun with the coloring of the shaft, spreading later over
adjoining feather barbs. The last stage would have been the coalescing
of the barbs, forming the waxlike scale as is now seen. Various steps
of this hypothetical development are supplied in the wing and tail
feathers of different birds of this series." _Bombycilla japonica_
thus may be close to the ancestral condition in the waxwing stock in
the development of the waxy appendage.
The rectrices of all three species of waxwings seldom possess the wax
tips, unless the secondaries have the maximum number of tips. In these
individuals, the pigment seems to "spill over" onto the tail feathers.
Eight is the maximum number of tips found on the secondaries.
Rectrices with wax tips are more frequently found in _B. garrula_, and
only occasionally in _B. cedrorum_. The pigment in the tip of the tail
of _B. japonica_ is red rather than yellow as it is in the other two
species, and some individuals of the Japanese Waxwing show a slight
amount of coalescence of wax in the tail feathers as well as in the
secondaries.
If the tips were present in all members of the two species, it could
be postulated, in line with recent investigational work by Tinbergen
(1947), that the tips are in the nature of species "releasers,"
facilitating species recognition. Such recognition is now regarded as
of prime importance in the formation of species. It is improbable that
sex recognition may be aided, as there is no evidence to indicate that
the tips are found predominantly in either sex.
The wax tips are not limited to the adult birds in the species _B.
garrula_. Swarth (_op. cit._) mentions the capture of several young
Bohemian Waxwings, and describes them as "possessing all the
distinctive markings of the most highly developed adult." This
includes wax appendages, and several citations are given (Wolley 1857,
Gould 1862) to indicate that this is the rule rather than the
exception, not only for the American subspecies _pallidiceps_, but at
least for the European subspecies _garrula_ as well. On the other
hand, the young of _B. cedrorum_ lack the wax tips, at least as far as
available data show.
Some characteristics of living animals are of the "relict" type; that
is to say, they were developed in ancient times when some unknown
ecological factor was operative which is no longer demonstrable, and
the characteristic is now neutral or at least not detrimental,
although of no positive value to the organism. Possibly the wax tips
of waxwings are thus to be explained. I am more inclined to the
opinion that the wax tips are adaptations to present-day ecological
conditions for the birds.
The wax tips are ruptive in effect, since the birds, especially in
winter, are habitues of bushes and trees that have berries, and the
tips, on the otherwise dull body, suggest berries. The red tips tend
further to disrupt the body outline at the midline, or slightly
posterior to this. Perhaps the wax tips on the rectrices emphasize the
end of the tail, the region of the body that is the least vital and
that may be expendable in times of pursuit by an enemy.
Any characteristic is of survival value to an organism if in any way
the characteristic enhances the chances of survival up to the time
when the organism can successfully raise even a few young to maturity.
If that character, as for example, the red wax tips on the
secondaries, helps to maintain the individual until it can raise to
independence a greater number than merely a few young, such a
character can be said to be of greater survival value. The character
may be effective for a brief period of time and may be uncommon; it
might be effective for a split second in time, and only at a
particular stage in the life history.
The winter period probably is the most hazardous for waxwings, in that
they then depend at times upon long flights to find food. The food is
vegetable, and thus is comparatively low in food value; the birds must
ingest large quantities of berries or dried fruits to maintain
themselves. In winter, in northern latitudes at least, predators are
more apt to prey upon those species which, like waxwings, do not
migrate south. The winter months are those in which waxwings frequent
berry bushes, and it may well be that in these months, the wax tips
that appear like berries, are especially valuable to the birds, and
operate selectively.
It is suggested, therefore, that the wax tips are of positive value to
waxwings, rather than being relict characters. Coalescence of pigment
has taken place in the formation of the wax tips. _B. japonica_ is
closer to the ancestral stock insofar as wax tips are concerned, and
generally lacks the tips. _B. cedrorum_ has the tips in approximately
half of the adults, and not at all in the young. _B. garrula_ has the
tips in almost all the adults, and in a like proportion of the young,
and probably has evolved further in the development and retention of
the wax tips than has either of the other two species.
The streaked plumage of _Dulus_ is decidedly generalized, and is
probably more nearly like the color of the ancestral stock. In this
connection it is notable that young Cedar Waxwings are streaked, and
young Bohemian Waxwings are streaked to a lesser degree. This
streaking is apparently a recapitulation of the feather color of the
stock. Perhaps the color of _Dulus_ has not changed, as the streaking
would not be a disadvantage to the birds in their environment of light
and shadow. In joining together in groups and in the construction of
large communal nests, _Dulus_ has evidently gained sufficient
protection against predators; other birds solve this problem by
modifying their coloration.
_Ptilogonys_ is ruptively colored, but in a different fashion than
_Bombycilla_. The tail markings, the distinct yellow on the under tail
coverts, the sharply marked pileum, are all examples of ruptive
coloration. The generally lighter venter (especially under tail
coverts), the crest that may be elevated, and the generally drab
bluish dorsum, are cryptic and serve to hide the animal insofar as is
possible considering its habits. The very conspicuous coloration of
the male, in contrast to the more drab color of the female, however,
would lead one to believe that in _Ptilogonys_, following the pattern
of many passerine birds, the male leads a predator from the nest,
leaving the drab female to incubate the eggs, and thus preserve the
young.
It is difficult to suggest reasons for the brilliant coloration of the
male _Phainopepla_, unless it is for decoying predators away from the
nest. Possibly some birds survive not because of, but in spite of,
their coloration, and _Phainopepla_ may be a case of this sort. Anyone
who has observed _Phainopepla_ in life will agree, certainly, that the
male makes no attempt at concealment, and flaunts his color to all
comers.
The coloration of _Phainoptila_, in contrast to _Phainopepla_, is much
more plain, and is suited to its habits of brush dwelling; in a brush
habitat the drab coloration is difficult to detect. The Yellowish
Olive under tail-coverts and the Olivaceous dorsum are all evidences
of cryptic coloration, and undoubtedly, this bird depends upon hiding
for escape from its enemies, since it is a bird of the dense forest
cover.
Coloration, which varies relatively rapidly in response to differing
ecological conditions, has become more different in the species of
Bombycillidae than is true in many other families of passerine birds.
The explanation lies in early geographical isolation of the three
subfamilies, with consequent radiation in three directions. Waxwings
have become adapted by possessing a thick protective layer of feathers
and drab coloration broken by ruptive marks. They still retain the
streaked plumage, which is probably ancestral, in the juveniles; this
is lost at the first molt in the fall. In its evolution, _Dulus_ has
developed large feet, heavy decurved beak, and the large communal nest
that affords protection from enemies; as a consequence, perhaps
_Dulus_ did not need a plumage different from the primitive and
streaked one. The survival of _Dulus_ may not have depended on either
ruptive marks or on brilliant and outstanding plumage. The large feet
and large bill seem to be responses to particular ecological
requirements, as will be shown later.
The Ptilogonatinae, with habits paralleling those of the flycatchers,
probably are considerably modified from the ancestral stock; the
coloration probably is more brilliant and conspicuous. Perhaps this
type of coloration and the habit of capturing insects from a perch are
correlated. Some amount of territoriality is characteristic of this
subfamily and dimorphism in color--the plumage of the male is
outstandingly conspicuous--possibly is of selective value to the race.
In a tropical forest community, a duller pattern possibly would be
more visible and thus would be selectively disadvantageous.
COURTSHIP
Waxwings are gregarious birds and individuals establish no
well-defined territories as do many birds. The nest itself is the only
defended territory, and as Crouch (1936) has shown, the Cedar Waxwing
will nest in close proximity to others of the same species. Swarth
(1932:275) mentions that the Bohemian Waxwing is tolerant of the nests
of other pairs near by. The extreme condition is that found in
_Dulus_, in which the territory is not limited even to the nest, but
to the individual compartment of the community nest. _Phainopepla_, a
less gregarious bird than _Dulus_ and waxwings, has a much more
definite territory, although individuals of _Phainopepla_ are tolerant
of others of the same species; no feeding territory is established,
and small flocks of birds feed together at any time of the year.
In birds whose territories lack well-defined boundaries, it would be
expected that elaborate song would not have evolved, and that most of
the recognition of kind and sex would be dependent upon the behavior
of the birds. This is the fact; song, as such, is lacking in the three
subfamilies Bombycillinae, Ptilogonatinae, and Dulinae. Waxwings utter
(1) notes that serve to keep the flock together, (2) calls used by the
young in begging for food, and (3) some low notes that Crouch (_op.
cit._:2) considered as possibly concerned with courtship.
_Phainopepla_ has various call notes, and in addition, a succession of
notes which are run together. _Ptilogonys_ utters a note which Skutch
(MS) characterizes as a loud, not unmusical "tu-whip" that is used as
the birds "fly in straggling parties which keep in contact by their
constant chatter." _Dulus_ is described by Wetmore and Swales
(1931:349) as having only a variety of rather harsh chattering notes
in chorus.
The most notable behavior pattern associated with courtship in
Waxwings, in the absence of song, is the so-called "mating dance"
described by Crouch (1936), and observed by me in Lawrence, Kansas, in
the spring of 1948. This consists of one bird of a pair (presumably
the male) hopping along a branch toward the other bird (the female),
then away again, repeating the procedure for some little time. The
female remains motionless until, as the male approaches, mutual
fondling of the head and neck feathers takes place, or the birds may
peck at each other's bill. A berry may be passed from bill to bill,
although generally the berry is not utilized for food, and this can be
interpreted as a nervous reaction of the birds. It may be an instance
of "false feeding" as is seen in many birds, in which the female begs
for food, as a nestling would beg, as a preliminary to the sexual act.
I am of the opinion that these reactions are in the nature of
behavioristic patterns that bring the birds into the emotional balance
for copulation, as copulation follows the "dance." Sometimes, however,
copulation is preceded by a "nuptial flight" around the nesting area,
at which time the birds utter loud calls. Armstrong (1924:183) is of
the same opinion, citing numerous instances in which nuptial flights
and elaborate displays have evolved for just this purpose. The birds
are then in the proper physiological balance to initiate the
complicated sequence of copulation, nesting, incubation, feeding, and
brooding of the young.
It would be valuable to know more concerning the life histories of the
other birds considered in this paper, since behavior is inherent, and
probably can be cited as evidence of close relationship or the
opposite. All that I have been able to learn is that _Phainopepla_ has
a nuptial flight in which the male chases the female, and that _Dulus_
(Wetmore and Swales, 1931:347) seeks the company of others of its kind
at all times, and that two birds, presumably paired, will sidle up to
one another when they are perched.
NEST BUILDING
There are numerous papers concerning the nesting of waxwings. _B.
garrula_, owing to its nesting in the far north, where observers are
few, has received less attention than _B. cedrorum_. There is, on the
other hand, no literature that deals with the nesting habits of the
majority of the Ptilogonatines, with the exception of _Phainopepla_,
on which there is considerable literature (Merriam, 1896; Myers, 1907,
1908). No detailed study of the nesting of _Dulus_ has been reported,
although Wetmore and Swales (1931) have described carefully the large
communal nest of this genus.
In _Bombycilla_, both members of a pair apparently aid in the
construction of the nest (Crouch, 1936; Swarth, 1932). Although the
sexes are alike in plumage and general appearance, most students of
the nesting of waxwings agree that one bird, assumed to be the female,
does most of the arranging of the material, and does the shaping of
the nest, whereas both birds carry materials to the nest site. As is
characteristic of many passerine birds, both members of the pair
gather materials and fly back to the nest site, where the female takes
the more active part in the construction of the nest itself.
Both species of American waxwings build bulky nests, with the base or
platform composed of a large amount of twigs and sticks, from which
there often trails a mass of sticks and moss or string. Softer
materials such as moss, plant fibers, and string, are placed inside
the platform; moss is readily available to, and preferred by, _B.
garrula_ according to Swarth (_op. cit._:271), and various plant
fibers and string are used by _B. cedrorum_. The inner lining consists
of soft plant fibers or down, dry grasses, and feathers. The nest is
usually unconcealed in a tree either adjacent to a trunk or on a main
side branch, but sometimes in a fork. Nest building by both Cedar and
Bohemian waxwings is rapid, taking from three to five days, and is
followed immediately by egg laying.
Nesting by waxwings is late in the season; June is the month in which
the nest is usually started. This is readily explainable in Bohemian
Waxwings, since adverse weather would prohibit earlier nesting in the
area in which they spend the summer. Crouch (_op. cit._:1) remarks
that _B. cedrorum_ possibly evolved in the far north where it was
impossible for it to start nesting earlier, and that the habit has
been retained. Perhaps, on the other hand, nesting is delayed until
the berry crop is ripe, to insure sufficient food for the young.
Desertion of the nest is not uncommon in waxwings, despite the
tolerance to other animals that is shown by the birds. A new nest may
suddenly be begun before the first one is finished, and all the
materials from the first nest may be removed, or the nest may be
abandoned before it is completed. The eggs may be left at any time up
to hatching, and the young may be deserted, especially in the earlier
stages of development.
The very large and bulky communal nest of _Dulus_ is not radically
different from the nest of waxwings. In the absence of sufficient
nesting sites, a pair of gregarious birds such as _Dulus_ could
combine their nest with those of other pairs, retaining for their own
territory only the nest cavity, and in this way communal nests might
have evolved. The nest of _Dulus_ is communal probably because of the
lack of suitable trees for nesting sites, and only incidentally does
this type of nest afford better protection from natural marauders.
Large numbers of Palm-chats work together in the construction of the
nest platform, and both sexes probably take part in the work.
In _Phainopepla_ the nest is built mostly by the male (Merriam, 1896;
Myers, 1908), although the female does some of the work, especially in
the shaping and lining of the nest. In this genus, the nest is usually
a compact structure, but exceptional nests are of considerable bulk.
The nest is commonly placed in a fork near the main trunk of a tree,
in a conspicuous location, and generally is 10 to 20 feet from the
ground. In shape and location, the nest closely corresponds to that of
_Bombycilla_, but the materials used for a base are stems of annual
plants, whereas _Bombycilla_ uses more woody twigs. The finer
materials used by _Phainopepla_ are more readily obtainable in the
ecological association inhabited by _Phainopepla_ than would be
heavier twigs such as _Bombycilla_ uses.
FOOD
Waxwings are typically frugivorous; berries are the staple food. The
birds are known to catch insects, especially in the spring and summer,
and their insect gathering technique has been likened to that of
Tyrannid flycatchers. Nice (1941) experimented with a young captive
Cedar Waxwing and found that it had a decided preference for red or
blue berries, and that meal worms were utilized as food only when the
birds became educated by other captive birds of other species as to
the food value of the worms. Post (1916) indicates that the food given
to the nestlings of Cedar Waxwings is entirely animal for the first
three days, and that a mixed diet of berries and insects is
subsequently offered.
In feeding of the young, regurgitation of partly digested food does
not take place, according to Wheelock (1905). Rather, the adults
"store" food in the form of berries in the expanded esophagus or crop,
feeding them whole to the young. Digestion is an unusually rapid
process, involving merely minutes for the passage of berries and
cherries. This is correlated with a short intestinal tract, which is
unusual for a frugivorous bird. Nice's (1940) experiments with Cedar
Waxwings revealed that cherries would pass through the digestive tract
in 20 minutes, blueberries in 28 minutes, and chokecherries in 40
minutes. Heinroth (1924) states that berries pass through the
digestive tract of Bohemian Waxwings in the space of a "few minutes."
This rapid digestion is obviously adaptive, since the value of the
food is slight and therefore large quantities of it must be ingested;
the large seeds would hamper further ingestion until they were
eliminated, since they seem not to be regurgitated.