‘Lifer’ is the term used by birdwatchers to describe the first time they saw a specific species of bird. Lifers for the basis for a person’s life list, the list of all the species of bird a person has seen in their lifetime.

Lifers can also be used with a geographic context. For example, the first time a person saw a Mute Swan in Scotland, they may say that the sighting was a lifer for them in Scotland even though they may have already seen the species many times outside of Scotland.