a little bird told (someone)

Translations
птичка на хвосте принесла
A little bird told me that you are getting married.
Птичка на хвосте принесла мне, что ты собираешься жениться.
Definitions
This phrase is used to indicate that the speaker has received information from a secret or undisclosed source, often implying that the information is gossip or rumor.