Brood patch on the owl’s lower abdomen.

Direct Heat Transfer: Feathers are insulators that prevent heat loss; removing them allows warmth from the bird’s body to reach the eggs.

Physiological Changes: The skin often becomes thickened, wrinkled, and highly vascularized (filled with extra blood vessels) to maximize heat transfer.

Development: While usually occurring in females, in many species, males also develop brood patches to help with incubation.

Species Variation: Some birds, such as ducks, pluck feathers to create the patch, while in others, the feathers fall out automatically.

Duration: The patch typically develops just before egg- laying and disappears after the young have hatched and no longer need constant brooding.