Black-browed Bushtit
Aegithalos iouschistos
It is a small, long-tailed bird, 11–12 centimetres (4.3–4.7 in) long. It has grey upperparts, rufous breast and flanks and a white belly. The head is buff with a broad black mask, white forehead and a white bib, speckled black in the centre. The subspecies A. b. sharpei has white rather than buff on the head, a dark breastband and a buff belly.
ID text from Wikipedia, CC BY-SA 4.0
Long-tailed Tit
Aegithalos caudatus
This species has been described as a tiny (at only 13–15 cm (5–6 in) in length, including its 7–9 cm (3–3+1⁄2 in) tail), round-bodied tit-like bird with a short, stubby bill and a very long, narrow tail. The sexes look the same and young birds undergo a complete moult to adult plumage before the first winter. The plumage is mainly black and white, with variable amounts of grey and pink. Voice: This species is often identified in the field through hearing its distinctive vocalisations. When they are in flocks, they issue constant contact calls, so they are often heard before they are seen. They have three main calls, a single high pitched pit, a 'triple trill' eez-eez-eez, and a rattling schnuur.
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: Black-browed Bushtit and Long-tailed Tit.