Blue Bird toby jug produced by Lefton China of Chicago, Illinois, circa 1970. Bluebirds are a North American group of medium-sized, mostly insectivorous or omnivorous birds and one of the few thrush genera in the Americas. Bluebirds nest from March all the way through August. Bluebirds have blue, or blue and rose beige, plumage. Female birds are less brightly colored than males, although color patterns are similar and there is no noticeable difference in size.