canary
noun /kəˈneəri/
  /kəˈneri/
 (plural canaries)
Idioms - a small yellow bird with a beautiful song, often kept in a cage as a petTopics Birdsc1Oxford Collocations DictionaryCanary is used before these nouns:
- yellow
 
Word Originlate 16th cent.: from French canari, from Spanish canario ‘canary’ or ‘person from the Canary Islands’. 
Idioms 
a canary in a/the coal mine 
- something that gives you an early warning of danger
- Among the species at risk is the silvery minnow, the river's equivalent of a canary in a coal mine.
 
 
like the cat that got/ate/swallowed the canary (US English) 
(British English like a cat that’s got the cream)
- very pleased with yourself synonym smug
- She looked like a cat that’s swallowed the canary. She was almost purring with pleasure.