Heard the male cardinal's song followed by an identical return song from another male cardinal - but no, the return was made by our resident mockingbird perched on his usual uppermost tip of a tall evergreen tree.
Many birds visit our heated to just above freezing birdbath / drinking pool . These include, cardinals , the mockingbird, bluejays, starlings , sparrows, brownheaded cowbird, chickadees, robins and our frequently visiting cooper's hawk.
On a sunny day starlings and sparrows will bathe and spash until the pool is emptied of water.
Also visiting our feeders are house finches, goldfinches, mourning doves and juncos.
A pair of red tailed hawks perched for a brief period in our front maple tree.
Jim