White-lored Warbler is a somewhat large headed warbler with an olive green back, yellow belly and a gray head. Its most distinctive features are a bright yellow crown stripe bordered by two black lateral coronal stripes and a white broken eye ring that forms a pair of spectacles.
There are three other species of warblers in the Sierra Nevada de Santa Marta, however the only one of these that could be confused with the White-lored Warbler is Golden-crowned Warbler (Basileuterus culicivorus). Golden-crowned Warbler is smaller, with a slighter build and shows a completely yellow (not gray) throat. Golden-crowned Warbler also lacks the contrast between the gray head and the olive green upperparts of White-lored Warbler. Golden-crowned Warbler also lacks the distinctive white broken eyering. Rufous-capped Warbler (Basileuterus rufifrons) and Santa Marta Warbler (Myiothlypis basilica) differ in many ways, such as their yellow throats and striking head patterns from White-lored Warbler.
White-lored Warbler measures 14.2 cm (Hilty and Brown 1986), making it one of the larger members of its genus. It is also relatively large headed for a warbler, with short wings, long tail and long legs. The upperparts, rump, tail and wings are a relatively uniform olive green. The underparts including lower breast, belly and undertail coverts are yellow, with flanks washed yellow olive.
The head is distinctively gray, contrasting sharply both with the upper- and underparts. It has a pale gray throat and a bright yellow central crown stripe bordered by two black lateral crown stripes reaching to the nape (Hilty and Brown 1986, Curson 1994). The brightness of the central yellow crown stripe can vary from yellow to bright orange perhaps due to age or sex differences (more study is needed). Otherwise, the sexes are apparently monomorphic. It has blackish lores and a white supraloral stripe connected to a conspicuous and highly distinctive white broken eye ring forming a pair of spectacles (Curson 1994).
Juveniles are similar to the adults but are duller colored throughout and lack the gray head, which they acquire after their first molt (see Molts).
Juveniles have a preformative (postjuvenile) partial molt that includes body feathers, and the lesser, median and typically all of the greater coverts (Gómez et al. 2012). Some birds replace the tertials as well. During this partial molt, juveniles gain the gray coloration on the head. On the second molt cycle (prebasic), birds acquire their definitive (adult) plumage through a complete molt (Gómez et al. 2012). After the complete molt, the fresh wing feathers have bright olive green edges that contrast markedly with the dark inner color of the feathers.
Molt limits are very subtle but can be a useful ageing criterion with enough experience. Some individuals retain a few olive feathers on the head after the preformative molt, which are also a useful guide for ageing. Feather shape is also useful for ageing as young birds tend to have pointy feathers where as adult ones broader and more rounded (particularly visible in the rectrices).
White-lored Warbler has a uniformly dark gray bill, brown iris, and pale orange tarsi.
Average (mean) wing chord and body mass measurements of White-lored Warblers caught in mist nets from 2009 to 2013, and histogram showing relative frequencies of wing chord measurements for 320 individuals:
| || Mean +/- SD || N |
|Wing chord (mm) || 63 ± 3 || 320 |
|Body mass (g) || 13.7 ± 0.9 || 316 |