OE of the most attractive birds of Mexican forests is the tawny little crested pewee, Mitrephanes phaeocercus, commonly called the Tufted Flycatcher. When I gathered material for a study of variation in the Mexican forms, I also compared all additional specimens of the genus I could borrow. Altogether I assembled 728 specimens, including all the proposed forms and series from every country and Mexican state the bird has been reported from except Ecuador. The genus name Mitrephanes was a substitute by Coues (1882) for Mitrephorus Sclater, 1859, preoccupied. Apparently no one has questioned the validity or limits of the genus, for the small, weak feet and tarsi, pycnaspidean (Ridgway, 1907:346 calls it quasi-pycnaspidean or quasi- holospidean) tarsal envelopes, and pointed crest make a unique combina- tion. Ridgway (1907) recognized five species, although he was able to examine only two. Hellmayr (1927) lumped the entire genus in a single species, as did Zimmer (1930; 1938a) in the most thorough revision thus far. Griscom (1932) restated the specificity of M. berlepschi, and Sutton and Burleigh (1940), while they did not discuss the South American forms, distinguished M. aurantiiventris (of southern Central America) as a species separate from M. phaeocercus. It should be noted that Zimmer had only 76 specimens altogether and Sutton and Burleigh only 38 from north of the Isthmus of Tehuantepec. H^BXTS ^) H^BXT^T My own field experience with Mitrephanes has been confined to Mxico. There M. phaeocercus inhabits the more humid parts of the pine-oak forest and cloud (subtropical) forest. In winter it lives in tropical de- ciduous forest, tropical evergreen forest, and tropical thorn forest as well as in lower-elevation pine forest and cloud forest; it deserts higher- elevation pine forest. All that I encountered in pine or pine-oak forests were foraging out from exposed perches at the rims of barrancas or moun- tain ridges. In cloud forest they were foraging out over openings or low trees and returning to perches 20 to 100 feet above the ground, in the manner of a pewee (Contopus). Skutch (1960) states that from Guatemala to western Panamir the Tufted Flycatcher is a permanent resident of subtropical forest and of temperate pine-oak forest. He describes the behavior briefly, including evidence of a close relationship with' the pewees. All localities in central and eastern Panam reported in the literature and on specimen labels (M.p. viridus and M.p. eminulus) are from elevations of 2,000 feet or more, apparently in the subtropical zone. But the few localities in which M.p. berlepschi has been found, in western Colombia and northwestern Ecuador, are near sea level in the humid tropical zone! On the other hand, M. olivaceus in Peru and Bolivia occurs in upper humid tropical and subtropical forests at elevations from 4,000 to 8,000 feet (Zimmer, 1938a). The literature makes no mention of migration in Mitrephanes except within Mxico, nor have I uncovered any evidence of such' movement. In Mxico a marked altitudinal migration occurs, first noted by Van Rossem (1945), from the high mountains to the tropical lowlands. It seems most marked in northwestern Mxico, where the breeding range is in the pine and pine-oak forests of the Sierra Madre Occidental and outliers (at elevations of 5,200-10,000 feet) but the wintering range is from lower pine-oak forests (Babizos and Rancho Batel, Sinaloa; moun- tains west of Tepic, Nayarit; 6,400-3,400 feet) to sea level in thorn forest (CuliacAn, Quelite, and Cacalotan, Sinaloa). In northeastern Mdxico Miller et al. (1957: 96) recorded a similar movement from cloud forest in spring down to tropical deciduous forest in winter, near G6mez Farias, Tamaulipas. Farther south I have examined winter specimens from near Valle Nacional, northern Oaxaca, 1,900 feet, tropical evergreen forest, and Jamaica Junction, southern Oaxaca, 3,000 feet, tropical deciduous forest. One specimen apparently represents a definite migration from one breeding area to a wintering area chiefly populated by a different race. I collected CAS 618550, adult male, 6 October 1955, 6 miles west of Tepic, Nayarit, in mixed woodland at 3,600 feet. Unlike 12 other fall and winter specimens from Nayarit, it is referable to the race burleighi rather than tenuirostris. This bird must have flown at least 75 miles west from its interior breeding range, unless it represents an unusual dark variation of tenuirostris. SPECIFIC LIMITS All the forms of Mitrcphan1/2s are allopatric. When Zimmer (1930) described the juvenal plumage of Peruvian M. olivaccus as more similar to that of the Central American forms than is the adult plumage, he argued that this showed their essential conspecificity. As shown in the section on variation below, present evidence shows distinct discontinuities in variation. The most abrupt break occurs in Ecuador, between the coastal forest of western Colombia and northwestern Ecuador on the one hand and the eastern slope of the Andes in Peru on the other. Lesser breaks occur in Central America--one between Nicaragua and Costa Rica, and another between central and extreme eastern PanamA. A moderate course between the extreme points of view, which recognize four species or one, seems best to express the phylogeny of the genus. I would recognize two species--M. pha1/2occrcus and M. olivaceus: phaeocercus olivaceus Northern M6xico to northwestern Eastern Peru and Bolivia Range: Habitat Size: Color: Ecuador Temperate pine and pine-oak forest, subtropical forest, and humid tropical forest Larger to smaller Brown to yellowish green If an intermediate population exists, central Andes of Colombia. Subtropical forest and upper humid tropical forest Larger than adjacent forms Green--contrast marked with phaeocerus ventrally, but moder- ate dorsally it may probably be found in the GENERIC RELATIONSHIPS Different authors have placed Mitrcphan1/2s with various other genera of flycatchers as the nearest relatives. Hellmayr (1927) put it in the subfamily Myiarchinae between Cnemotriccus and Terenotriccus. I com- pared skins of all 20 genera and most of the species included by Hellmayr in this subfamily except Aphanotriccus and Pracdo (now usually lumped in the single genus Aphanotriccus), plus Xcnotriccus Dwight and Griscom, 1927, and A1/2chmolophus Zimmer, 1938b, described subsequent to Hell- mayr's work. Mitrephanes is apparently a rather distinct genus, with closest relation- ships to Pyrrhomyias and Contopus, perhaps A1/2chmolophus and Xcno- triccus next. I suggest the linear order Nuttallornis, Contopus, Mitre- phan1/2s, Pyrrhonyias, Xcnotriccus, Empidonax. Table 1 compares all the genera of Myiarchinae that have any sort of a crest, even in one species. I have doubtless oversimplified some characteristics, for instance cate- gorizing rictal bristles as short, moderate, or long. As noted above, Skutch (1960) described the behavior of Mitrcphanes as rather similar to Contopus; but widely different from Terenotriccus and Onychorhynchus. Most recent authors merge Blacicus with Contopus, as I do here. The genus A1/2chmolophus cannot be maintained; it should be lumped with Xenotriccus. The transfer is accordingly made: Xenotriccus mexi- canus (Zimmer, 1938b) new combination. I studied 10 specimens of X. mexicanus and 3 of X. callizonus, all collected since Zimmer's work. These show that the differences between the two species in the shape of the crest and the shape of the tail are individual or seasonal. Valid dif- 290 J. D^T WEBSTER [Auk, Vol. 85 ferences are of the same type and magnitude as those between the various species of Empidonax. MOLTS AND PLUMAGES Material is adequate from Mxico for confident statements on molt in the races phaeocercus, burleighi, and tenuirostris. Adults have but one molt a year, a complete prebasic molt mainly in August. Evidence of some body molt was found as early as 4 July (a few fresh feathers in breast) and as late as 28 October (Allan Phillips specimen, label note "trace of molt on nape"). Only a few July adults show any molt, and most mid-September specimens appear to have completed their molt. A specimen I skinned 25 September showed no trace of molt. Th'e order of molt beginnings is approximately: body feathers, inner primaries, rec- trices, small wing feathers, tertials (about three-fourths of body plumage fresh by now), outer secondaries, crest. Judging from specimens and my own observations, most Mexican birds are hatched in June, with lesser numbers in May and July. The first pre- basic molt extends from as early as 14 July (some fresh plumage in back) to 28 October (not discernible in skin, but Allan Phillips label note "light molt on head, neck, belly, and flanks"). In most cases the main change occurs in August. The extent of the first prebasic molt varies; in most cases it includes all feathers except th'e primaries, secondaries, and rectrices. In about one- third of the specimens two or three juvenal (white-tipped) upper tail coverts are retained, and in fewer cases one or more tertials. Regarding the crest and the wing bars (secondary coverts), I am in doubt. The feathers of the crest are of such lax structure that I cannot tell whether slight white tips mark juvenal feathers or first basic plumage; these are present on two to six feathers in a few first year birds, November to February. The aspect of the wing bars in first year birds, October to January, varies from dull dark brown (as in adult basic plumage) to pale buffy, and no molt is evident after October. In several instances of pale wing bars, the feathers are freshly acquired first basic, and probably, though not certainly, these coverts are always replaced. As implied above, the juvenal plumage differs from the adult basic in that the feathers are generally barred or tipped with buff, which fades to white. In addition, the juvenal plumage is rustier or tawnier than the adult plumage in the brown races and more or less brown, rather than green, in the green races. The aspect of first year birds in fall and winter is identical with that of adults at the same seasons except that the rec- trices and primaries are tipped slightly with white. Also some of the upper tail coverts and crest feathers are sometimes tipped, and the edgings of the tertials and the wing bars are sometimes paler than in adult feathers. The last tipping to wear off is usually that on the rectrices, which persists even as late as March (one specimen). I am unable to detect any sign of prealternate molt at any age or season. The material at hand is inadequate in seasonal distribution and in label information to allow decisive statements about molts in the Central and South American forms, but apparently the prebasic molt occurs in olivaceus in July and August and in aurantiiventris and eminulus in August and September. GEoGR.PC VARATO Wing length.--Bergman's Rule is operative in both directions from the equator, but most changes are not abrupt. Table 2 shows a sharp break between Colombia and Peru with a nonoverlap gap of 4 mm (over twice th'e standard deviation), and lesser breaks (with slight overlap) between Colombia and eastern Panama and between central and western Panama. TABLE 2 SLIiVEiVEAR3/4 O1 1/2 MALE WING MEASURE2ViEIq'TS IN MILLIiVEETERS, Mitrephanes Coefficient Sample Standard of Taxon Population size Range Mean deviation variation tenuirostris burleighi phaeocercus nicaraguae aurantiiventris vividus eminulus berIepschi olivaceus Sonora, Chihuahua 29 70-77 73.28 1.86 2.53 Sinaloa 39 69-77 72.15 1.82 2.53 Durango 19 69-75 72.95 1.61 2.21 Nayarit 13 68-74 71.31 1.82 2.55 Zacatecas, Jalisco 11 69-75 72.09 1.83 2.54 Michoac/n, Morelos, Est. M6xico 35 68-75 71.86 1.96 2.73 Guerrero 14 69-76 72.71 1.95 2.68 Southern Oaxaca 7 72-75 73.71 -- -- Hidalgo, Puebla, Tamaulipas, San Luis Potosi 20 68-75 70.90 1.76 2.49 Veracruz, Northern Oaxaca 21 64-74 70.00 2.37 3.39 Chiapas, Guatemala 17 67-75 70.53 1.88 2.67 Honduras, E1 Salvador 30 65-73 68.77 2.16 3.13 Nicaragua 9 62-70 65.33 -- -- Costa Rica 30 61-70 64.47 2.56 3.96 Western Panam/ 37 60-69 64.38 2.01 3.11 Central Panama 9 58-64 61.00 -- -- Eastern Panama 11 59-65 61.73 1.82 2.95 Colombia 3 56-60 57.67 -- -- Peru, Bolivia 11 64-71 67.00 1.76 2.63 TABLE 3 SLwMXVrAR3/4 OF MALE TAIL LEIqGTI{ IN MILLIMETERS, Mitrephanes 293 C oe/ficient Sample Standard Taxon Population size Range Mean deviation variation phaeocercus tenuirostris Sonora, Chihuahua 29 58-65 60.96 1.63 . Sinaloa, Durango 58 56-63 59.64 1.65 . Nayarit 14 56-62 58.18 1.69 burIeighi Zacatecas, Jalisco, Michoacan, Morelos, Est. Mdxico 44 55-63 59.61 Guerrero, Southern Oaxaca 19 56-63 59.84 Hidalgo, Puebla, Tamaulipas, San Luis Potosl 20 57-65 59.60 1.83 ,, Veracruz, Northern Oaxaca 20 55-61 58.20 1.72 nlcaraguae Guatemala, Chiapas 18 54-63 59.39 2.30 , Honduras, E1 Salvador 26 51-59 54.23 2.07 ,, Nicaragua 9 50-56 53.22 -- aurantiiventris Costa Rica, Western Panama 63 47-55 51.63 1.91 vlvidus Central Panamft 9 48-56 50.89 -- erainuIus Eastern Panama 11 48-53 49.91 1.60 berIepschi Colombia 3 49-55 51.67 -- oIivaceus Peru, Bolivia 11 53-58 55.55 1.50 2.67 2.76 2.91 1.71 2.87 1.96 3.27 3.07 2.96 3.88 3.81 3.71 3.22 2.71 A smooth cline extends from western ?anam/t north through Chiapas to northeastern Mfixico and from eastern Mxico westward and thence north- ward as well as southward to Sonora and southern Oaxaca. Measurements of female wings average 2 to 4 mm less than those of males and show the same trends. Tail length.--The shortest-tailed population is in eastern Panam/t, and tail length increases in both directions from there. The sharpest break, or step, is between Honduras-El Salvador and Guatemala as shown in Table 3. Bill length.--Length of bill was measured from the feathers. It actually doesn't vary much geographically (Table 4), but note that the shortest- billed population is also one of the longest-winged, and that the shortest- winged population is also one of the longest-billed. Thus the wing length/' bill length ratio in northern burleighi is 8.4, in equatorial berlepschi 6.3. Bill width. The bill width was measured with a caliper at the center of the nostril. Unfortunately, differences in technique of the various preparators in closing the bill in this soft-billed flycatcher have badly obscured natural variation (note high coefficients of variation in Table 5). TABLE 4 SUMMARY O1' MALE BLL LrNcr > MILLIlVIETERS, Mitrephanes Coefficient Sample Standard of Taxon Population size Range Mean deviation variation tenulrostrs Sonora, Chihuahua 31 8.1-9.6 8.79 .363 4.13 , Sinaloa, Durango, Nayarit 74 8.0-9.7 8.78 .377 4.29 burleighi Zacatecas, Jalisco, Michoac/m, Morelos, Est. Mxico 50 7.8-9.6 8.55 .408 4.77 ,, Guerrero, Southern Oaxaca 21 7.9-9.4 8.71 .394 4.52 phaeocercus Tamaulipas, San Luis Potosl, Hidalgo, Puebla, Veracruz, Northern Oaxaca 48 7.8-9.4 8.62 .402 4.67 nicaraguae Chiapas, Guatemala 21 7.7-9.1 8.62 .379 4.41 , Honduras, E1 Salvador, Nicaragua 36 7.8-9.9 8.84 .452 5.12 aurantiiventris Costa Rica 30 8.0-9.6 8.82 .401 4.54 ,, Western Panam,5 39 8.2-10.0 9.13 .465 5.09 vlvldus Central Panam/ 9 7.9-9.7 8.63 -- -- eminulus Eastern Panam/ 11 8.4-9.5 8.98 .347 3.86 berlepschi Colombia 3 8.8-9.4 9.13 -- -- olivaceus Peru, Bolivia 11 8.3-9.5 9.09 .428 4.72 In an attempt to circumvent this problem, I separately calculated two samples collected only by Chester C. Lamb, one on the west coast of Mxico and the other on the east coast (marked with an asterisk in Table 5). Apparently the difference in bill width between the populations of eastern and western Mxico has been exaggerated in the past. The two smallest (shortest-winged) subspecies, vividus and berlepschi, have the broadest bills. Color of underparts.--In this and following sections, "fresh-plumaged" birds are arbitrarily defined as those taken from the acquisition of mostly fresh body plumage in August through February. "Recent specimens" are arbitrarily defined as those taken since 1930. Statements on plumage color refer only to fresh, recent specimens, except in the few cases where noted otherwise.* Capitalized color names are those from Palmer and Reilly (1956), with whose color standard comparisons were made at all stages. Five classes, with separation 100% from 100%, make simple, obvious divisions: (1) pale tawny--tenuirostris, burleighi, and phaeocercus; (2) * In this and succeeding sections specimens marked with an asterisk are either too old (before 1931) or worn (after February) for truly valid color comparison; a few were used because no recent, fresh material from certain states exists. TABLE 5 SUMMARY OF MALE BILL VIDTiI IN MILLIMETERS, Mitrephanes 295 Coefficient Sample Standard of Taxon Population size Range Mean deviation variation tenuirostris Sonora, Chihuahua 30 4.0-5.1 4.71 .252 5.35 ,, Sinaloa, Durango 58 3.3-5.2 4.67 .289 6.20 ,, Nayarit 16 3.8-5.2 4.76 .330 6.94 burleighi Zacatecas, Jalisco, Michoactn, Est. Mxico 45 4.2-5.4 4.72 .226 4.79 ,, Guerrero, Southern Oaxaca 20 3.8-5.2 4.52 .400. 8.87 phaeocercus Tamaulipas, San Luis Potosl, Hidalgo, Puebla 20 4.6-5.6 5.02 .300 5.98 ,, Veracruz, Northern Oaxaca 24 4.2-5.4 4.91 .401 8.17 nicaraguae Chiapas, Guatemala 21 4.0-5.2 4.70 .291 6.21 ,, Honduras, E1 Salvador, Nicaragua 39 3.2-5.4 4.46 .557 12.47 aurantiiventris Costa Rica, Western Panamir 68 4.3-5.8 4.92 .300 6.09 vivldus Central Panamir 9 4.5-6.0 5.02 -- -- eminulus Eastern Panamir 11 4.7-5.4 4.99 .178 3.57 berlepschi Colombia 3 4.9-5.2 5.10 -- -- olivaceus Peru, Bolovia 10 4.2-5.1 4.64 2.38 5.13 tenuirostris *Lamb collected, Sinaloa 35 4.0-5.2 4.69 .244 5.22 phaeocercus *Lamb collected, Puebla Vera Cruz 9 4.6-5.4 4.90 .231 4.72 Special groups see text. dark tawny--nicaraguae; (3) buffy yellow--aurantiiventris and vividus; (4) yellow--eminulus and berlepschi; (5) lime--o.livaceus. In addition to color, the contrast between anterior underparts (throat and breast) and posterior underparts (belly, crissum, and under tail coverts) is mod- erate and the transition gradual in classes 1, 2, and 5, but prominent and sharp in classes 3 and 4. Within each class, the specimens may be analyzed thus: (1) A gradual northwest to southeast cline of increasing darkness plotted in this order: 12 Sonora  --> 42 Sinaloa, 1 Chihuahua, 10 Durango, 12 Nayarit, 1 Jalisco, 13 Michoacn, 15 Guerrero --> 1 Nayarit, 2 Zacatecas, 2 Jalisco, 19 Est. Mxico --> 11 southern Oaxaca, 3 Tamau- lipas --> 5 Puebla, 13 Vera Cruz --> 6 northern Oaxaca. Separation on Arrows separate series that may readily be distinguished by eye, but commas have ,no significance; numbers are the actual specimens in the compared series. this character is 100% from 100% between the extremes (Sonora and northern Oaxaca) and about 90% from 90% between Sonora and Est. Mdxico or between Michoacfin and Vera Cruz. Anterior underparts are medium, yellowish Tawny; posterior underparts are light, brownish Buffy Yellow in this class. A few worn (March) specimens* suggest that San Luis Potosi and Hidalgo belong near Est. Mxico and Tamaulipas in the above series. (2) I see very little internal geographic variation. The contrast with the darkest group (northern Oaxaca) above is relatively slight, although all individuals of (2) are clearly darker and most are yellower posteriorly. Anterior underparts are dark, yellow-brownish Tawny; posterior under- parts are light, brownish Buffy Yellow in this class. Three old (February 1909) specimens* from Nicaragua are slightly paler and yellower than the 47 more recent ones from Chiapas, Guatemala, Honduras, and E1 Salvador. (3) I see no geographic variation within the 39 specimens from Costa Rica and western Panamfi, and the gap from class (2) is considerable. Anterior underparts are medium, between Buffy Brown and Buffy Yellow; posterior underparts are light Buffy Yellow. Six old (January 1926)* and seven worn (March 1951 and 1962) specimens* from central Panamfi are duller and less buffy anteriorly and paler, less buffy, more purely yellow posteriorly. (4) Two specimens from Cerro Tacarcuna, eastern Panamfi, are warmer, more orangish' on both areas than two. specimens from southern Colombia. In this class the anterior underparts are medium, brownish Buffy Yellow; the posterior are pale Yellow. Seven worn old (March-June, 1912 and 1928) specimens* from Cana, eastern Panamfi, show a distinct variance; they are colder, less buffy than those from Cerro Tacarcuna, although paler, less greenish anteriorly and less purely yellow posteriorly than specimens from Colombia, either northern* or southern. (5) I can see no geographic variation within Peru (four specimens), not even when an old specimen* from Bolivia is added. This class is distinctly darker posteriorly and greener throughout than all the preced- ing. The anterior underparts are dark, olivaceous Yellow Lime; the pos- terior are light, grayish olivaceous Yellow Lime. Color oJ upperparts.--Specimens compared were the same as those used for the ventral surface, above. Three major classes differ radically and obviously, segregation being 100% from 100%. (1) Varying from pale to dark Olive and pale to dark Brownish' Olive --Mxico and Central America south to E1 Salvador. (2) Approximately dark, yellow-limish Olive--Costa Rica and western Panamfi. (3) Varying from medium to dark olivaceous Yellow-Lime--eastern Panam& and South America. The general trends of dorsal color are: (a) A prominent north to south cline of increasing greenness runs from northwestern Mxico to Peru. In Mxico north of Tehuantepec the trend is from the Pacific slope to the Atlantic slope, but in Central America no Pacific versus Atlantic slope differences are apparent. (b) A two-way cline of darkness decreases from maximum in Chiapas northwest and southeast to minimum, or pallor, in northwestern Mxico and Peru. This seems to follow Gloger's Rule north from Chiapas, but to proceed almost inversely to, Glo.ger's Rule from Chiapas southward. (Portig, 1965, gives Central American rainfalls; the climates involved are poorly known in South' America.) (3) A slight cline of differing warmth (redness) in Mxico grades from warmest in central western Mxico to colder in eastern Mxico and coldest in northwestern and southern Mxico. Within each of the major classes these variations can be seen: (1) In northwestern Mxico grayness and pallor are extreme, and as far south as Nayarit and coastal Jalisco only slight warming appears. The color is yellowish Brownish Olive. In interior central Mxico (Zacatecas, interior Jalisco, Michoacgn, Est. Mxico) and south to. the Pacific coastal ranges of Guerrero and southern Oaxaca, colors are variable, but generally darker. Specifically a series from Zacatecas, interior Jalisco, and Nayarit (apparently a migrant from a breeding population of Zacatecas or Jalisco) is distinctly darker than any of 66 from Durango., Nayarit, etc., and warmer and darker than southern Oaxaca birds. A long series from Michoacgn and Est. Mxico is slightly paler than the preceding and the following groups, and also slightly duller, less green than the following. The Guerrero series is slightly darker again, and slightly greener; the southern Oaxaca group is grayer, less brownish than the three preceding groups. The populations from Zacatecas to southern Oaxaca are all a yellowish-brown Olive. In eastern Mxico lives the dark olive race phaeocercus (yellowish- brown Olive again in the color standard). Although 100% from 100% distinguishable from the Sonora to Nayarit series above (darker and greener), it is not prominently differentiated from the Zacatecas to Oaxaca series. To the north a series from Tamaulipas and northern Puebla is slightly paler and browner than that from west central Vera Cruz and northern Oaxaca, and the series from Vera Cruz is slightly greener than any other. As to distinction from Zacatecas to Oaxaca populations (bur- leighi), phaeocercus is slightly greener northward (Tamaulipas-Puebla versus Est. Mxico-Michoacgn) and slightly greener as well as darker southward (Vera Cruz-northern Oaxaca versus Guerrero-southern Oaxaca), with the sharpest contrast in the state of Oaxaca. The description by Sutton and Burleigh (1940) of hidalgensis was based upon a lack of enough freshly taken topotypes from Vera Cruz; here I must emphasize that all the specimens considered above were taken in 1941 or later except for some from Sonora and Sinaloa that date back as far as 1931. The March series from Hidalgo* and a single March bird from Cafiada Grande, southern San Luis Potosi*, I have classified as worn but recent. The latter is precisely between Est. Mxico burleighi and Tamaulipas-Hidalgo-Puebla phaeocercus. The former fit in per- fectly with th'e October to February Tamaulipas-Puebla series and are, in fact, also indistinguishable from the palest individual from Vera Cruz. A special comparison* of all available recently taken April-June speci- mens from eastern Mexico (2 Tamaulipas, 3 San Luis Potosl, 6 Hidalgo, 6 Puebla, 7 Vera Cruz, 1 northern Oaxaca) confirmed the submergence of hidalgensis. The 5 greenest specimens came from Vera Cruz (4) and Puebla (1). In justification of Sutton and Burleigh's 1940 action, it should be noted that the only freshly taken topotype of phaeocercus available to them (Cornell 8294, 29 April 1939, Jalapa) is the brownest, least green recently taken Vera Cruz specimen I have seen--almost as brown as foxed skins of 1880. South of the isthmus of Tehuantepec lives the darkest population, that of Chiapas, which is blackish Olive, distinctly darker than all populations to the north and averaging darker than series from Guatemala, Honduras, and E1 Salvador. Old specimens (1909) from Nicaragua* are indistin- guishable from the paler individuals from Honduras and E1 Salvador. (2) Little variation can be seen in this class, geographic or otherwise. However, the brownest single specimen, and also one of the darkest, is from Cartago province, central Costa Rica. The old (January 1926)* or somewhat worn (March 1951)* specimens from central Panamg are duller and greener and slightly darker than those from Costa Rica and western Panamfi. (3) A well marked cline of darkness and greenness occurs within this class. Eastern Panama specimens are the darkest, duskiest, least green; Colombian specimens are greener (near Lime but less yellowish) and paler; Peruvian specimens are still paler and greener. The gap between groups (2) and (3) is prominent, with the eastern Panam/[ birds dis- tinctly greener than those from western and central Panam/[. Color oJ juvenal plumage.---A series of 43 specimens from all subspecies except vividus and berlepschi showed prominent geographical variation. Ventrally a smooth cline from pale Buffy Brown in Sonora darkened southeastwardly to deep tawny Buffy Brown to brownish Tawny in Chiapas and Nicaragua; in Costa Rica and eastern Panam/t the under- parts were a little paler again and distinctly yellowish Buffy Brown; in Peru tawny Buffy Brown. Dorsally, a smooth cline ran from pale Sepia tipped with pale Tawny in Sonora, darker southeastward to dark Sepia tipped with Tawny in Chiapas, Guatemala, Nicaragua, and Honduras; in Costa Rica and eastern Panama the upperparts were a little paler again, and had more yellowish Tawny tippings. In Peru the upperparts were still paler and buffier, Buffy Brown tipped with pale Tawny. Other characters.--I am unable to correlate with geography the con- trast between crest coloration and that of the back. I)ISCUSSION The inverse relationship in Central and South America, the opposite of Gloger's Rule, might be explained by assuming that a shift from a brown to a greener color resulted in more additional protection than a shift from a paler to a darker shade. For a bird of the upper story of the forest like Mitrephanes, I prefer to express it in a different way. The green coloration would seem to be an adaptation to always-green sub- tropical and humid tropical forests and the brown or tawny-and-olive coloration to partly brown pine-oak forests, with this adaptation over- riding Gloger's Rule. Zimmer (1930) stated that the brown juvenal plumage in the southern forms of Mitrephanes indicates that the brown northern forms are nearer the ancestral type. I agree and suggest a hypothetical history of the genus. I suggest that the genus originated in the late Tertiary in Central America or Mexico, from the same section of th'e family Tyrannidae that gave rise in the same region at about the same time to Contopus, Empi- do.nax, Pyrrhomyias, and Xenotriccus. The original form was brown in color and lived in temperate pine-oak forest. During one of the earlier glacial advances when temperate forests were extensive, it spread through- out much of Central America. During an interglacial period it was then restricted to isolated mountains; on one of these it developed green colora- tion as an adaptation to subtropical forest. Subsequently the green form spread southward into South America in almost continuous subtropical forest during Wisconsin times, only to have the range broken up again by the warming trend of Recent climatic change. (Martin, 1958, and Savage, 1966, discuss Pleistocene ecology in Central America.) The in- vasion of subtropical forest by brown forms to the north was a Recent event, unaccompanied by a radical color change. A lessening cline of slight dorsal greenness in the brown forms parallels the amount of sub- tropical forest habitat available, north from Nicaragua. This suggests a northwestward flow of green genes which gives out in Guerrero and San Luis Potosi along with the subtropical forest. RESIJlViE OF SPECIES AND SUBSPECIES (All localities cited in this section refer to specimens examined.) Mitrephanes phaeocercus tenuirostris Brewster 1888 (near Oposura, Sonora, Mxico). Paler throughout and averaging more slender billed than all other forms of the genus. Also larger (wing and tail lengths) than all other forms except burleighi. Range: Mountains of northeastern Sonora (Oposura, Pinos Altos) and north- westeen Chihuahua (Sierra N/tcori, Bravo, Mina Abundancia, Jesfis Maria) south along the western flank of the Sierra Madre Occidental in Chihuahua, Durango, and Sinaloa to Nayarit (Santa Teresa, mountains west of Tepic) and coastal Jalisco (Sierra Autl/tn). Descends in winter to low valleys and the coastal plain. Mitrephanes phaeocercus burIeighi Phillips 1966 (Rio Moli.no near San Miguel Suchistepec, southern Oaxaca, Mxico). Darker than tenuirostris throughout; also the southern populations (Guerrero and Oaxaca) are slightly greener dorsally and the northern populations are duller, browner dorsally. Range: Sierra Madre Occidental, Sierra Madre del Sur, and most of Trans-volcanic Range; from wester.n Zacatecas (west of Milpillas, Monte Escobedo) and central Jalisco (Tapalpa, Mezamitla) east through Michoacfin to western Est. Mxico (Villa Victoria, Temascaltepec) and northern Morelos (Coajomulco); south to near the Pacific coast of Michoacfin (Coalcom{n), Guerrero (Omilteme, Cerro Teotepec), and Oaxaca (near Lachao, Rio Molino). Descending to the valleys in winter and even migrating almost to the coast in Nayarit (mountain west of Tepic). Remarks: This race is a weak one, but recognizing it is convenient; the alternative would be to regard the entire series of populations as intermediate between tenuirostris and phaeocercus. As constituted, about 90% of all individuals can be distinguished in fresh plumage (100% of certain populations). Too few recently taken specimens exist to define precisely the subspecific boundaries in Jalisco or in Oaxaca. To the east, specimens from southern San Luis Potosl (Cafiada Grande) and extreme western Puebla (Los Venerables) are intermediate between burleighi and phaeocercus. Mitrephanes phaeocercus phaeocercus Sclater 1859 (C6rdoba, Vera Cruz, Mxico). Greener than burIeighi dorsally and darker ventrally; smaller (wing and tail lengths) than tenuirostris and burIeighi; also darker dorsally than burIelghi southward. Range: Sierra Madre Oriental from southern Tamaulipas (Rancho Cielo) and south- eastern San Luis Potosl (near Xilitla) south through Hidalgo, eastern Puebla, and western Vera Cruz, in eastern mountains southeast to Cerro Zempoaltepec, Oaxaca (Moctum, Totonotepec), and central Oaxaca (Cerro San Felipe, 24 miles northwest of Oaxaca City, 15 miles west of Oaxaca City). Descending to the valleys in winter. Mitrephanes phaeocercus nicaraguae Miller and Griscom 1925 (San Rafael del Norte, Nicaragua). Darker than phaeocercus throughout, and also smaller. The southernmost popula- tion, from Nicaragua, is also somewhat yellower on the posterior underparts; the tail is shorter from Honduras south. Range: Mountains of northern Chiapas (5 miles north of Jitotol) southeast through Chiapas, Guatemala, E1 Salvador, and Honduras to northeastern Nicaragua (San Rafael del Norte, Matagalpa). Permanent resident in temperate and subtropical forests according to Skutch (1960) and specimen labels. Remarks: The submergence of the familiar race quercinus Dickey and Van Rossem (1927) is a direct result of the large amount of material now available from Central America. The shorter wing claimed by Miller and Griscom as a distinction for nicaraguae from a Guatemala series is not great (see Table 2), and the shorter tail is shared by the series from E1 Salvador, whence quercinus was described. The color characters claimed by Dickey and Van Rossem are slight to my eye, but no fresh specimens from Nicaragua and E1 Salvador have been seen, and it is not clear whether Van Rossem, Griscom, or anyone else compared the Salvador and Nicaragua series directly when they were still unfaded. If the present subspecies is to be split, the new form must certainly be described from Chiapas, so that size variation is coordinated with color, and freshly taken specimens from Nicaragua and E1 Salvador must be compared. Mitrephanes phaeocercus aurantiiventrs (Lawrence 1867) (Tabacales, Costa Rica). Distinctly yellower ventrally and greener dorsally than nicaraguae; also averaging smaller. Range: Mountains of north-central Costa Rica (Villa Quesada, Alajuela Province) to eastern Panama (throughout mountains of Chiriqul Province). Permanent resident in temperate and subtropical forests according to Skutch (1960) and specimen labels. Mtrephanes phaeocercus vlvidus (Griscom 1927) (mountains behind Chitr, Chitr Province, Panama). Smaller than aurantiiventris; also duller, darker, and greener dorsally, duller and less buffy on anterior underparts, paler and more purely yellow on posterior under- parts. Range: Permanent resident of subtropical mountain forests of the central part of Panamir, in the provinces of Chitr (mountains behind Chitrd), Cocl (Cerro La India Dormida, Head of Rio Guabel), and Panama (Cerro Compana). Mitrephanes phaeocercus eminulus (Nelson 1912) (Cana, Daridn Province, Panama). Averaging longer winged than vividus; also greener and paler dorsally and distinctly yellower ventrally. Range: Permanent resident of subtropical zone in eastern Panama, in Darien Prov- ince (Cerro Mall, Cerro Tacarcuna, Cerro Pirre = Cana). Remarks: As noted above, the population of Cerro Pirre differs in one character-- less buffy underparts--from that of the Cerro Tacarcuna area to the north. On the basis of present material this would not justify the description of a new race. Mitrephanes phaeocercus berlepschi (Harterr 1902) (Bulfin, Ecuador). Shorter winged than any other race; as compared with eminulus, tail averaging slightly longer, yellower, less orangish ventrally, and greener and paler dorsally. Range: Humid tropical forest of the Pacific coast of Colombia (Mungarido and Malugita, Choco; La Guayancana, Narifio) and northwestern Ecuador. Mitrephanes olivaceus Berlepsch and Stolzmann 1894 (Gorrita del Sol, Junin Province, Peru). Larger than berlepschi and greener throughout; also paler dorsally and much darker on posterior underparts. Range: Subtropical and upper humid tropical forests of the eastern slope of the Andes from northern Peru (Rio Jelashte, San Martin Province) to eastern Bolivia (Quebrada Honda). S?lCl_Mlls ExArllln Mitrephanes phaeocercus tenuirostris--Mdxico: Sonora 25, Chihuahua 21, Sinaloa 62, Durango 38, Nayarit 34, Jalisco 1. M.p. burleighi--Mxico: Zacatecas 4, Jalisco 20, Michoacn 44, Est. Mxico 25, Morelos 14, Nayarit 1, Guerrero 32, Oaxaca 20. M.p. phaeocercus (including intergrades with burleighi)--Mxico: Tamaulipas 5, San Luis Potosl 17, Hidalgo 7, Puebla 13, Vera Cruz 37, Oaxaca 11. M.p. nicaraguae--Mdxico: Chiapas 25, Guatema!a 19; Honduras 50; E1 Salvador 7; Nicaragua 13. M.p. aurantliventris--Costa Rica 50; Panam& Chiriqui 73. M.p. vividus--PanamA: Chitr 6; Cocl 5, Prov. Panamir 1. M.p. eminulus--Panam& Darien 20. M.p. berlepschi--Colombia: Choco 2; Narifio 2. M. olivaceus--Peru: San Martin 2, Hutnuco 3, Junln 7, Cusco 3, Puno 1; Bolivia: Cochabamba 1. ACKBIO WLEDGi'v[EBITS Allan R. Phillips and George M. Sutton loaned me specimens from their personal collections. The curators of these museums courteously loaned me specimens from the collections under their care: American Museum of Natural History, British Museum (Natural History), California Academy of Sciences, Museum of Vertebrate Zoology (University of California at Berkeley), Carnegie Museum, Dickey Collection (University of California at Los Angeles), Field Museum of Natural History, Museum of Comparative Zoology (Harvard University), Instituto Biologia (Universidad Nacional de Mxico), University of Kansas Museum of Natural History, Louisiana State Museum of Zoology, University of Michigan Museum of Zoology, Minnesota Museum of Natural History, Moore Laboratory of Zoology (Occidental College), Academy of Natural Sciences of Philadelphia, United States National Museum. LITERATURE CITED BERLEPSCXX, H., AD J. STOLZMA. 1894. Descriptions de quelques Espces nouvelles d' Oiseaux du P6rou central. Ibis, ser. 6, 6: 385-405. BREWSTER, W. 1888. On three apparently new subspecies of Mexican birds. Auk, 5: 136-139. CXAPMA, F.M. 1926. The distribution of bird life in Colombia. Bull. Amer. Mus. Nat. Hist., 55: 1-784. CouEs, E. 1882. Note on Mitrephanes, a new generic name. Bull. Nuttall Orn. Club, 7: 55. DICXE3/4, D. R., Am> A. J. VA ROSSEM. 1927. Seven new birds from Salvador. Proc. Biol. Soc. Wash., 40: 1-8. DmxE3/4, D. R., Am> A. J. VA ROSSEM. 1938. The birds of El Salvador. Field Mus. Nat. Hist., Zool. Ser., 23: 1-609. DWXGT, J., An L. Ginscoax. 1927. A new and remarkable flycatcher from Guate- mala. Amer. Mus. Novit., 254: 1-2. GRmcoM, L. 1927. Undescribed or little-known birds from Panama. Amer. Mus. Novit., 280: 1-19. Ginscoax, L. 1932. The distribution of bird life in Guatemala. Bull. Amer. Mus. Nat. Hist., 64: 1-439. HARTEaT, E. 1902. Some further notes on the birds of northwest Ecuador. Novit. Zool., 9: 599-617. HELLMAYa, C.E. 1927. Catalogue of birds of the Americas. Field Mus. Nat. Hist., Zool. Ser., 13: 1-517. LAWRENCE, G. N. 1867. Descriptions of six new species of birds from Central America. Ann. Lyc. Nat. Hist. New York, 8: 170-173. LOWERY, G. H., Ja., Ai,D W. W. DALQUEST. 1951. Birds from the state of Veracruz, Mexico. Univ. Kansas Publs. Mus. Nat. Hist., 3: 531-649. MARTIN, P.S. 1958. Pleistocene ecology and biogeography of North America. In Zoogeography, Amer. Assoc. Advan. Sci. Publ. 51: 375-420. MILLER, A. H., H. FRIEDMANN, L. GRISCOM, AND R. T. MOORE. 1957. Distributional check-list of the birds of Mexico, Part II. Pacific Coast Avif., 33: 1-436. MILLER, W. D., AND L. GRISCOM. 1925. Descriptions of new birds from Nicaragua. Amer. Mus. Novit., 150: 1-9. NELSON, E.W. 1912. Descriptions of new genera, species, and subspecies of birds from Panama, Colombia, and Ecuador. Smiths, Misc. Coll., 60: 1-25. PALMER, R. L., AND E. M. REnCL3/4, JR. 1956. A concise color standard. Albany, New York, A.O.U. Handbook Fund, 1956, pp. 1-8. PHILLIPS, A. R. 1966. Further systematic notes on Mexican birds. Bull. Brit. Orn. Club, 86: 103-112. PORTre, W. H. 1965. Central American rainfall. Geogr. Rev., 55: 68-90. RIDGWAY, R. 1907. The birds of North and Middle America. U.S. Natl. Mus. Bull., 50: 1-973. SAVAGE, J.M. 1966. The origins and history of the Central American herpetofauna. Copeia, 1966: 719-766. SCLATER, P. L. 1859. Descriptions of new species of the American family Tyran- nidae. Proc. Zool. Soc. London, 1859: 40-56. S:uTca, A.F. 1960. Life histories of Central American birds, Part II Pacific Coast Avif., 34: 1-593. SUTTON, G, M., AND T. D. BURLEIGIt. 1940. A new Tufted Flycatcher from Hidalgo. Wilson Bull., 52: 30-31. VAN ROSSEM, A. J. 1945. A distributional survey of the birds of Sonora, Mexico. Occ. Pap., Mus. Zool., Louisiana State Univ., 21: 1-379. ZllVtMEa, J.T. 1930. Birds of the Marshall Field Expedition, 1922-1923. Field Mus. Nat. Hist., Zool. Ser., 17: 1-480. ZIMMER, J. T. 1938a. Studies of Peruvian birds, no. 29, The genera Myiarchus, Mitrephanes, and Cnemotrlccus. Amer. Mus. Novit., 994: 1-32. ZnVrMER, J. T. 1938b. A new genus and species of Mexican flycatcher. Auk, 55: 663-665. Hanover College, Hanover, Indiana, and California Academy of Sciences, San Francisco, California.