Olive-backed Euphonia
Euphonia gouldi
The olive-backed euphonia is 9 to 10 cm (3.5 to 3.9 in) long and weighs about 11 to 16 g (0.39 to 0.56 oz). It is a small euphonia with a thick stubby bill. The species is sexually dimorphic. Adult males of the nominate subspecies have a yellow forehead; the patch extends to the rear of the eye and sometimes has light black flecks. The rest of their crown, and their nape, upperparts, and tail are olive-green. All of them except the uppertail coverts have a bluish gray gloss. Voice: The olive-backed euphonia's song is "a rapid jumble of chatters, buzzes, and harsh whistles". Its calls "include a chi'chi'chi'cheet and a liquid tsip'please-seeee'up!. Another description of its song is "a rambling medley of whistles, chatters and staccato notes, some dry and chaffy, some musical" that may continue for a long time.
ID text from Wikipedia, CC BY-SA 4.0
Scrub Euphonia
Euphonia affinis
The scrub euphonia is about 10 cm (3.9 in) long. It weighs 8.5 to 12.8 g (0.30 to 0.45 oz). It has a short stubby bill. The species is sexually dimorphic. Adult males of the nominate subspecies have a small yellow forecrown; the color extends just to the eye. The rest of their head and nape are glossy blue-black with a purplish sheen. Their upperparts are glossy blue-black. Their tail is mostly blackish with white inner webs on the outer two pairs of feathers. Their upperwing coverts and flight feathers are blackish with some dark blue gloss. Voice: The scrub euphonia's calls include "1–3 pure thin whistles, dee-dee-dee, sometimes followed by 2 or 3 more on same or slightly lower pitch", a "shorter whit-it-it-it", and a "longer wheeee". It sings less than it calls, with "a weak twittering and chirping medley, e.g. wheetidy-titity-witity-titity". Its song and that of the West Mexican euphonia are similar but this species' is slower.
ID text from Wikipedia, CC BY-SA 4.0
Where you might meet both
Learn this pair in BeakBrain
Photo and call practice, free in any browser.
Play BeakBrainPhotos and recordings are credited to their authors under the licence shown. Full profiles: Olive-backed Euphonia and Scrub Euphonia.