crissum

[ kris-uh m ]

/ ˈkrɪs əm /

the region surrounding the cloacal opening beneath the tail of a bird.

the feathers of this region collectively.

Origin of crissum

1870–75; < New Latin, equivalent to Latin criss(āre) to move the haunches + -um noun suffix

Below, pale yellowish wood-brown, straw-yellow on abdomen and crissum.

Life Histories of North American Wood Warblers Part One and Part Two |Arthur Bent
Below grayish buff rapidly fading when older to a greenish gray; abdomen and crissum pale straw-yellow.

Life Histories of North American Wood Warblers Part One and Part Two |Arthur Bent
The rump is also much more yellow (less green) and the crissum is more yellow (less orange).

Life Histories of North American Wood Warblers Part One and Part Two |Arthur Bent
Below, greenish buff paler and yellower on abdomen and crissum.

Life Histories of North American Wood Warblers Part One and Part Two |Arthur Bent

The mature male is purplish-gray below, with a tendency to whitening on the throat, belly and crissum.

Nests and Eggs of Birds of The United States |Thomas G. Gentry

crissum

/ (ˈkrɪsəm) /

the area or feathers surrounding the cloaca of a bird

crissal, adjective

C19: from New Latin, from Latin crissāre to move the haunches