noun
American robin
Refers specifically to the American robin (Turdus migratorius), not the European or Japanese robin.
庭にコマツグミが来ていた。
An American robin came to the garden.
ツグミ is the dusky thrush (Turdus eunomus), a different species common in Japan.
コマドリ is the Japanese robin (Erithacus akahige), not the American robin.
The name likely derives from 駒 (こま, 'horse') + 鶇 (つぐみ, 'thrush'), but the exact origin is uncertain.