G. Hofmann & F. Scheffer, Tiny Fox Lab

Gouldian finch chicks have blue opalescent beads on the corners of their mouths, making it easier for their parents to feed them in the dark. – Tiny Fox Lab

Preview photo credit: G. Hofmann & F. Scheffer, Tiny Fox Lab
Source: http://blog.cincinnatizoo.org/2014/01/28/why-are-there-spots-in-these-birds-mouths/