362 SYSTEMA TIC SYNOPSIS. — PASSERES — OSCINES. 



VIR'EO. (Lat. rireo, I am green or flourishing.) Greenlets. Vireos. Bill like that of 

 a Shrike in miniature, moderately or very stout, shorter than head, compressed at least toward 

 end, distinctly hooked and notched at tip, sometimes with trace of a tooth behind notch of 

 upper mandible, and usually a nick in under mandible also. Rictal bristles conspicuous, and 

 others present among the frontal and mental feathers. Nasal fossae nearly filled with short 

 erect feathers. Toes extensively coherent at base, as explained under head of the family ; lat- 

 eral toes of unequal lengths ; claws stout, narrowly compressed, much curved and acute. 

 Wing at least as long as tail, more or less rounded ; sometimes much longer and quite pointed ; 

 of 10 primaries, 1st usually evident, though short or spurious, but sometimes (in the section 

 Vireosylvia and in Vireo flavifrons) rudimentary and more or less completely concealed (excep- 

 tionally obvious even in these species). Tail short, even, of narrow feathers. Size small; 

 length usually 5.00-6.00. Coh)ration simple; above olivaceous or grayish, crown like back, 

 or ashy (in one case brown, in another black) ; under parts white, or white and yellow, or 

 partly olivaceous. Sexes quite indistinguishable ; young similar, not spotted or streaked. 

 Migratory in N. Am. Insectivorous, arboricole. Nest jiendulous; eggs w^iite, spotted (except 

 in V. atricapillus) . 



The numerous species of this genus have been divided into several groups, but no violence 

 will be done by considering them all as Vireo — in fact it is ditBcult to do otherwise. For 

 even the seemingly substantial division into two genera, according as there is an evident spu- 

 rious 1st primary or apparently none, separates species, like gilv^is and phUadelphicus, slightly 

 otherwise specifically distinguishable ; while another division into two genera, according to 

 shape of wings and length of spurious 1st primary or its absence, is subject to some uncertainty 

 of determination, and unites species, like oliraceus and flavifrons, most dissimilar in other re- 

 spects. Probably the best way is to recognize three subgenera — Vireosylvia for barbatulus, 

 oUvaceics, flaviviridis, gilvus, and philadelphicus ; Lanivireo iov flavifrons and solitarius ; and 

 Vireo for all the rest. The fact is, that almost every single species of Vireo has its own peculiar 

 form, in shape of bill, proportions of primaries, etc, and these details cannot well be consid- 

 ered as of more than specific value. These slight differences are perfectly tangible and surpris- 

 ingly constant, rendering the determination of the species comparatively easy, though these birds 

 bear to each other a close general resemblance in size and color, and some of the subspecies are 

 not easily discriminated. They are all more or less olivaceous above, sometimes inclining to 

 gray or plumbeous, with crown either like back, or else ashy — in one species, however, brown, 

 and in another black ; and white or whitish below, usually more or less tinged with yellow. 

 The coloration is very constant, the sexes being indistinguishable, and young differing little, if 

 at all, from adults. All are small- birds, — about 5 or 6 inches long. As a group the student 

 will probably have no difficulty in recognizing them by the foregoing diagnosis, as the charac- 

 ter of the feet seems to be peculiar, among North American birds, and is at any rate diagnostic 

 when taken in connection with the character of the bill — all those Oscines, as Wrens, Creep- 

 ers, or Titmice, that show much cohesion of the toes, having an entirely different bill. Some of 

 the weaker-billed species might be carelessly mistaken for Warblers ; but there is no excuse 

 for this, nor for confounding them with any of the little Clamatorial Flycatchers. Vireos were 

 long supposed to possess either 9 or 10 primaries. But that the important character of number 

 of primaries — one marking whole families, as we have seen — should here subside to specific 

 value only, seemed suspicious ; and the fact is that all the species really have 10, only that, in 

 some instances, the 1st is rudimentary and displaced, lying concealed outside the base of the 2d. 

 The North American species are distributed over the temperate portions of this continent, and 

 several of them are abundant birds of the Atlantic States, inhabiting woodland and shrubbery. 

 Tliey are exclusively insectivorous, and are therefore necessarily migratory in our latitudes. 

 They build a neat pensile nest in tiie fork of a branchlet, and commonly lay four or five white, 

 speckled eggs. All are alike in tliis respect, the nest and eggs of none of the species (except- 



