Sympatric

[[File:Choughmaps2.png|thumb|318px|The two species of choughs' ranges. Note that there isn't much overlapping.


 * Green: Red-billed Chough
 * Yellow: Alpine Chough
 * Orange: Both species]]

Having overlapping ranges.

Examples

 * William C. Dilger studied five species of N. American thrushes - Wood Thrush, Veery, Hermit Thrush, Swainson's Thrush and Grey-cheeked Thrush - in which males cannot be distinguished outwardly from the females, and discovered that the males and females recognised each other by their behaviour. He also concluded that the songs and calls of the male thrushes, that are different in each species, were the primary signs by which females recognised males of their own kind.