Oopsie - High Wizardry

In the book "High Wizardry," the third book of Diane Duane's Young Wizards series there seems to be a discrepancy. Page two and three has Nita conversing with a "catbird" in the back yard elm tree which was making "an enthusiastic but substandard imitation of a blue jay."  She promises the bird a half a muffin to take a message to Kit.

Then, in the next-to-last page of the story, just after returning to the back yard, we read: "In the elm tree, a mockingbird was doing blue jay imitations and demanding muffins."

Presumably this is the same bird.  So, is it supposed to be the Gray Catbird (Dumetella Carolinensis) or the Northern Mockingbird (Mimus Polyglottos)?  The description on page three, "In a whir of white-barred wings, the catbird was gone," tells us it is a mockingbird and not a catbird. The Northern Mockingbird has white bars on the underside of its wings, but the Gray Catbird does not.

This oopsie is probably not something you would notice unless you, like me, have read the book at least five times.