Skip to main content
U.S. flag

An official website of the United States government

Black-capped Chickadee with a mildly deformed beak

Detailed Description

A Black-capped Chickadee with an upper beak slightly longer than the lower beak. Avian keratin disorder (AKD) is a disease characterized by debilitating beak overgrowth and other abnormalities of keratinized tissues. Affected birds have difficulty feeding and preening and may suffer high rates of mortality.


Public Domain.