Flamecrest
Regulus goodfellowi
The flamecrest is a small perching bird, resembling a warbler. Its length is only 9 cm (3.5 in) and weight about 7 g, making it the smallest of all Taiwan's endemic bird species, and the smallest and most colourful member of its family in the world. The top of its head is yellow and orange, with black crown stripes. White feathers encircling the black eye-patches give it the appearance of having two black eyes. The most distinguishing characteristic is the orange-yellow crest on top of the head, for which it is named. Voice: Flamecrests have fine, shrill and high-pitched calls, zi zi yi. Although noisy at close range, the voice is soft and does not carry far.
ID text from Wikipedia, CC BY-SA 4.0
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

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: Flamecrest and Goldcrest.