Goldcrest
Regulus regulus
The goldcrest is the smallest European bird, 8.5–9.5 cm (3.3–3.7 in) in length, with a 13.5–15.5 cm (5.3–6.1 in) wingspan and a weight of 4.5–7.0 g (0.16–0.25 oz). It is similar in appearance to a warbler, with olive-green upper-parts, buff-white underparts, two white wing bars, and a plain face with conspicuous black irises. The crown of the head has black sides and a narrow black front, and a bright crest, yellow with an orange centre in the male, and entirely yellow in the female; the crest is erected in display, making the distinctive orange stripe of the male much more conspicuous. Voice: The typical contact call of the goldcrest is a thin, high-pitched zee given at intervals of 1–4 seconds, with all the notes at the same pitch. It sometimes has a more clipped ending, or is delivered more rapidly. The call is higher and less rough than that of the firecrest.
ID text from Wikipedia, CC BY-SA 4.0

Ruby-crowned Kinglet
Corthylio calendula
The ruby-crowned kinglet is a very small bird, being 9 to 11 cm (3.5 to 4.3 in) long, having a wingspan of 16 to 18 cm (6.3 to 7.1 in), and weighing 5 to 10 g (0.2 to 0.4 oz). It has gray-green upperparts and olive-buff underparts. It has two white wingbars and a broken white eye ring. The wingbar on the greater secondary coverts (closer to the wing-tip) is wider, and is next to a dark band. The kinglet has a relatively plain face and head, although the male has a scarlet-red crown patch, which is usually concealed by the surrounding feathers. Voice: The ruby-crowned kinglet's vocalizations are remarkably loud and complex for its size. Its song can be divided into three main parts: a series of high pitched notes (zee-zee-zee or tee-tee-tee), two to five low trills (turr or tu), and a repeated three note "galloping" phrase (tee-da-leet, tee-da-leet).
ID text from Wikipedia, CC BY-SA 4.0

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Play today's Daily BirdPhotos and recordings are credited to their authors under the licence shown. Full profiles: Goldcrest and Ruby-crowned Kinglet.