Exceptionally, in heavily worn plumage, some Bermuda Petrels develop a partially collared appearance that resembles Black-capped.<\/p>

Also exceptionally, the darkest Black cappeds may have a dark nape and extensive partial collar, but not a cowl\u2014which is diagnostic when present.<\/p>

Underwing Pattern:<\/u>\u00a0 At a glance, Black-capped and Bermuda Petrels seem to have the same basic underwing pattern: a white center bordered by a black carpal bar and black trailing edge.\u00a0 However, there are subtle but diagnostic differences, as Bermuda Petrel\u2019s underwing has a distinctive \u201csignature\u201d pattern of two bars (one black, one white) that rarely, if ever, appears on Black-capped.<\/p>

Black-capped varies in the proportions of white and black on the underwing.\u00a0 White-faced birds typically have an extensively white underwing framed by a thin black carpal bar and equally thin black trailing edge.<\/p>

Dark-faced birds typically have a fairly thick carpal bar and a comparably thick black trailing edge, with an equal white strip in the middle\u2014so the net impression is of three bars: black-white-black.<\/p>\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t