butter butts
n.— «Audubon warblers, the Western form of the yellow-rumped warbler, also were moving through in large numbers early last week. These blue and yellow warblers are affectionately called “butter butts” by many birders due to their flashing yellow rump patch, which is so visible as they flit away from you.» —“Cold spring mornings a tough time for hummers” by Sylvia Brockner Canyon Courier (Evergreen, Colorado) May 24, 2007. (source: Double-Tongued Dictionary)
Further reading
A newscaster covering treacherous driving conditions offered this advice: Keep it between the mustard and the mayo. In other words, “Make sure your car stays between the yellow line and the white line on the road.” This is part of a complete episode...
A Winter Dictionary (Bookshop|Amazon) by Paul Anthony Jones includes some words to lift your spirits. The verb whicken involves the lengthening of days in springtime, a variant of quicken, meaning “come to life.” Another word, breard, is an old term...