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
Residents of Martha’s Vineyard look forward each year to the arrival of pinkletinks, little frogs that herald the arrival of spring. Elsewhere, they’re called spring peepers, tinkletoes, and pink-winks. This is part of a complete episode...
In his delightful memoir Better Living Through Birding: Notes from a Black Man in the Natural World (Bookshop|Amazon), Christian Cooper introduces the vocabulary of birding, including the term warbler neck, an affliction among fellow birders. Cooper...