I believe that you are talking about the waxwing. There is the Bohemian Waxwing which is grayish brown and the larger waxwing. The Cedar Waxwing is smaller than a robin and more of a brown tint than the Bohemian Waxwing. They both have the black eye band, or mask, and they have a yellow band on the tip of the tail.

Check a field guide for cedar or bohemian waxwing. Also see the pyrrhuloxia.

Japanese Waxwing was created in 1824.

If it's in the Northern Hemisphere and sort of greenish, the size of a Robin, it's probably a either a Bohemian or Cedar Waxwing. See links below.

Cedar Waxwing, Bombycilla cedrorum

Downy Woodpecker, Picoides pubescens

Gray Catbird, Dumetella carolinensis

Northern Cardinal, Cardinalis cardinalis

Orchard Oriole, Icterus spurius

Song Sparrow, Melospiza melodia

Red-winged Blackbird, Agelaius phoeniceus

Eastern Towhee, Pipilo erythrophthalmus

Scarlet Tanager, Piranga olivacea

Wood Thrush, Hylocichla mustelina