Verdin

2000, Kenn Kaufman, Verdin, Steven J. Phillips, Patricia Wentworth Comus (editors), A Natural History of the Sonoran Desert, Arizona-Sonora Desert Museum Press, University of California Press, Revised and Updated Edition, page 422, Tiny and rather plain, the Verdin seems quite unremarkable at first sight.

Verdins are yellow-faced desert-dwellers that are commonly encountered in southern Arizona.[…]Although primarily insectivorous, Verdins will also readily consume nectar, which they obtain by piercing tubular flowers or by visiting hummingbird feeders.

Desert-dwelling verdins, forage solitarily, in pairs, or in small groups by actively hopping from twig to twig while sounding their surprisingly loud tseet calls almost continuously.