Close this search box.

Word of the Week: Operculum

Like what you see? Share this post

Welcome to Word of the Week! Stay tuned for a new word each Friday to amp up your nature vocabulary!

Operculum [oh-PUR-kyuh-luh m] (zoology noun): A lid or flap of skin covering an aperture. For fish or amphibians, this might look like the gill cover and for gastropods, this might look like the plate that closes the opening of the shell.

In this blog, we’ll be focusing more specifically on where this fun word fits into the world of birds! Some birds will have an operculum, which covers their nares or nostrils. This part of their body will usually look like a membranous, horny or cartilaginous flap, sitting near the base of the bird’s beak.

The goal of the operculum is to keep unwanted substances out. Some of these substances include water, dirt, or dust. This is why you are more likely to see this body part on diving birds, or birds that feed on pollen!

For us city dwellers, we hardly have to travel anywhere to find a bird with an operculum. You just have to spot a Rock Dove, also known as a Pigeon!

Pigeon opercula have evolved into a soft swollen mass, sitting at the base of their beaks but above their nares! This evolved opercula is sometimes referred to as a cere which is a different beak structure.

Keep an eye out for pigeons and their opercula, in and around High Park!


In some birds, like the Tawny Frogmouth, the operculum will shrink as the birds age, disappearing completely by the time they reach adulthood.

Tapaculos birds are the only birds that are able to move their opercula