Red Warbler
Cardellina rubra
The red warbler is a small passerine, measuring 12.5–13.5 cm (4.9–5.3 in) in length, and weighing from 7.6 to 8.7 g (0.27 to 0.31 oz). As an adult, it is red overall, with either a white or dark gray (depending on the subspecies) auricular patch on each side of its head. Its wings and tail are slightly darker, dusky red, and edged in pinkish-red. Its legs are a dull red-brown, and its thin bill is pinkish-gray with a dark tip. The iris is dark brown to blackish. Plumage varies little between the sexes, although the female tends to be a little duller or more orange-tinged. Voice: The red warbler has several common calls, including a high, thin tsii and a stronger pseet. Its song is a mix of short trills and richer warbles, interspersed with high-pitched chips. Unlike other species in the same habitat zone, it tends to sing only during bright morning hours during the breeding season.
ID text from Wikipedia, CC BY-SA 4.0
Wilson's Warbler
Cardellina pusilla
Wilson's warbler is a small passerine, ranging from 10 to 12 cm (3.9 to 4.7 in) in length, with a wingspan of 14–17 cm (5.5–6.7 in) and a mass of 5–10 g (0.18–0.35 oz). It has a plain green-brown back and yellow underparts. The male has a small black cap. Males of the western race C. p. chryseola are greener above and brighter than males of the eastern, nominate race. Individuals from Alaska and the west-central portion of the species' range average slightly larger than those found in eastern and Pacific coastal populations. Its song is a chattering series of loud descending notes.
ID text from Wikipedia, CC BY-SA 4.0

Where you might meet both
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Play today's Daily BirdPhotos and recordings are credited to their authors under the licence shown. Full profiles: Red Warbler and Wilson's Warbler.