Phylogeny of the Waxwings and Allied Birds.

by M. Dale Arvey.

INTRODUCTION

A small family of pa.s.serine birds, the Bombycillidae, has been selected for a.n.a.lysis 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 a.s.signed 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 a.s.sumed 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 h.o.m.ogeneous. Also it is a.s.sumed that the species were wide ranging and thus did not become isolated geographically to the extent that, say, the Fringillidae did. The a.s.sumption 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 a.s.sociated 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 a.s.signed the palm-chats to a separate family, the Dulidae.

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_; s.e.xes 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, pa.s.sing 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 s.e.xes, culmen 11.1, and tarsus 18.7.