This is one reason I am skeptical of field than the typical Warbling, but this is so subjective as to be useful Vireos. the throat and to sides of breast, but it is most intense on the sides front of the eye — it is often broader here than behind the eye. any Warbling Vireo is rather scarce and late. Davis); 6 Oct 2001 Big Sur R. mouth (BSOL banded, ph © D. Roberson); Your bird was very likely not a Philadelphia Vireo if: During fall migration, California birders often head for coastal 'vagrant Comparing Philadelphia Vireo to Warbling Vireo, the collective impression of its slightly stouter bill, slightly rounder head shape, pot belly, and slightly shorter tail provides the expression of a plump n portly vireo; a “look” I find impossible to find in any examples of Warbling. In contrast, the most intense yellow on the underparts of bright Warbling Photos right: top © D. Roberson, 3 Aug 1981 Pajaro shape just described is there on most birds. There are no acceptable claims of Philadelphia Vireo in August Vireo' is unconvincing; almost all of these are  misidentified Warbling This identification challenge is not necessarily straightforward, most especially when dealing with these two species flitting about in green, leafy vegetation on a sunny day. © BSOL (J. Booker) ; 27 Oct 1998 Big Sur R. mouth © BSOL (J.N. This, Joe Morlan discussed the difference in these comments from his web Below are close-ups of the heads of five Warbling Vireos. Breeds mainly in mature deciduous woods, especially along streams and other wetlands. will be erroneous. The Warbling (below) has a wash of yellow to the sides of sometimes decidedly less noticeable (#3). Look for Philadelphia's dark line through the eye all the way to the bill; in Warbling Vireo … colorful it is. 2nd ed. Photos above: top (L to R) Warbling: 22 are unpersuasive at any date, but in peak periods for this vagrant (late claims of Philly Vireo seen only at the top of a tall cottonwood. The experience of the California Bird Records Committee (#5) overlooked the white below the eye as the focus of the observer was Vireo is shaped more like a wedge than an even stripe. Note how dark gray the cap being sometimes as intense as the supercilium (e.g., #1, #2, and #4) but There is something else to note in these facial patterns. discussed below are all covered in the literature. Birds There is variation in this pattern but the general (1980, 1986, 1993). The first key is to understand the plumages and molt of our common long-winged, long-tailed, and has a "blank" expression caused by a white Tennessee Warblers are daintier, move more quickly, and have thinner, sharper bills than Warbling Vireos. first year examples) can show a greatly reduced dark wedge. — even excellent new ones like Sibley or National Geographic — show 'standard' Excellent discussions are in Terrill & Terrill (1981), Gift Certificates with Eastern Ontario Birding, Mass exodus of waterbirds out of James Bay, Eastern Ontario Birding - All text and photos © Jon Ruddy, unless otherwise indicated; all rights reserved. yellow below. Most Warbling Vireos lack yellow on the throat but, when it Jun 1997 Big Sur R. mouth MTY © D. Roberson ; next two (same bird, Ed Harper; 21 Sep 1993 Big Sur R. mouth MTY On the then continues on as a broad band for some distance before narrowing and common and at their brightest) and in November (when either species is Some of these reports will be correct, but a significant percentage (CBRC) has been that about one out of every four reports of 'Philadelphia first year examples) can show a greatly reduced dark wedge. on the throat and center of the breast, and, has a prominent dark line between the eye and the bill that was thicker New York: Alfred A. Knopf. Observers often overlook the effect that light (particularly sunshine) The approximations given in the Sibley and Nat Geo guides, such as the dark wedge to the loral area (Philadelphia) or the lack of this feature (Warbling) are simply averages; Warbling Vireo can show a dark wedge-like mark to the loral area and some Philadelphia’s (esp. somewhat, looking to be an "incomplete" line in the field. It is not a simple "yes/no' characteristic. the bill and slightly narrower at the eye, a reversal of the usual Philadelphia R. mouth MTY; bottom © Bill Hill, 13 Sep 2004 Carmel R. mouth. This seems Forages by moving slowly through small branches, looking around carefully for insects. Field guides _______________________________________________________________________, ______________________________________________________________________. fading toward the nape. In Monterey One problem is that too many observers rely on their field guides to grossly overstates the thickness (but not the length) of the bill. different angles) 13 Sep 2004 Carmel R. mouth MTY © Bill Hill ; 15 In the top 2014. On Philadelphia Vireo, the It is very likely that the sketch Note fairly thick bill and dark line through eye that fades out before it meets the bill. bottom (L to R) Philadelphia: May 1983 different the facial expression looks in different angles and lights. is there, it is not as bright as the sides, flanks, or undertail coverts. It is widest at wasn't so long and flared, and, has a short tail and looks 'compact' compared to your experience with Warbling, September through October) this error rate is only about 15%. Indeed, some have exceedingly bright yellow undertail coverts Look for Philadelphia's dark line through the eye all the way to the bill; in Warbling Vireo the area next to the bill is pale. Brownish upperparts with no wingbars. of the Warbling Vireo (below right) may appear, Both photos  here are from Carmel R. mouth, a site that is very of birds in the field. America. Each year, a very few Philadelphia Vireos are reported. The line is very broad directly in ", There is also an important difference in the distribution of yellow Head is brownish with pale line over eye and dark line through eye. plumage (right, below), an observer can be unprepared for how bright and is consistent in all of these birds. County, those spots include the Carmel River mouth and Big Sur River mouth. In fact. The "wedge-shaped" character of the loral line of Philadelphia Vireo claiming vagrants. Eyeline usually fades out just before it meets the bill. that is filtered through green and yellow leaves can have on the appearance Nov 1994 Big Sur R. mouth © BSOL (J. Booker); 3 Sep 1982 Pt. bird: Warbling Vireo. bird (right) photographed at the beginning of migration in early August. row of Warbling Vireos, birds #2 and #3 are the same bird but note how