A small, slim endemic warbler common throughout New Zealand. Gray-brown above and paler gray to off-white below. Tail is darker, tipped with white, most noticeable in flight. Adults have a distinctive red eye. Juvenile similar, with yellow coloration and brown eyes. Male has a distinctive long, bubbling musical song. Female gives short “chirp” contact calls. More often heard than seen, this species forages for insects in the forest understory or scrub, sometimes hovering among the outer foliage and twigs. On mainland New Zealand, this is the only host species of the nest parasite Shining Bronze-Cuckoo, and so Gray Gerygone parents can be encountered feeding much larger cuckoo chicks. Despite inhabiting the same areas, distinguishable from Silvereye by slightly larger size, greener upperparts, and lack of a white eye-ring.