robin redbreast vs Old World robin

robin redbreast and Old World robin both are nouns.

Word	Noun	Adjective	Verb	Adverb
robin redbreast	Yes	No	No	No
Old World robin	Yes	No	No	No

As nouns, robin redbreast and Old World robin are synonyms defined as:

robin redbreast and Old World robin: small Old World songbird with a reddish breast

Other synonyms of robin redbreast include Erithacus rubecola, redbreast, robin.

robin redbreast (noun)	Old World robin (noun)
small Old World songbird with a reddish breast	small Old World songbird with a reddish breast