Here are some terms used by birders:
Twitcher – A hard-core birder who goes to great lengths to see a species and add it to his or her list.
Lifer – A first-time sighting for a birder.
Spark bird – A species that triggers a lifelong passion for birding.
Nemesis bird – A species that constantly eludes a birder.
LBJs (little brown jobs) – A blanket term for drab songbirds that are difficult to distinguish from one another.
Vagrant – A bird straying well outside its regular ecological range.
National Audubon Society