A peacock has been killed at the Calgary Zoo by a pair of the facility's own lions.

It happened when the free-roaming birds were being rounded up for the season.

One of them suddenly managed to fly into the lion habitat, and the two males were quick to notice their visitor.

"This type of behaviour with birds does happen with wild ducks, with geese," said spokeswoman Trish Exton-Parder.

"Often they will come in from the wild and pop into the tiger enclosure and oftentimes the lions, and in this case one of our own peacocks did the same. And I think most people can understand what that conclusion was."

Exton-Parder says the zoo is now examining its protocols.

"Also looking at how we gather up the peacocks, how did this happen?" she said.

"They didn't expect that this peacock could fly that direction and it did. It caught everybody off guard, so we always take it very seriously."

The six remaining peacocks are now safely in their winter holding area.

This is the second time this year a peacock has been killed at the zoo.

One died in June after a red fox sneaked onto the grounds and took it down.

Exton-Parder said despite the deaths, the peacocks will return once again in the spring.