Somewhere over the rainbow bluebirds fly! The Bluebird Collection by Serendipity is comfy and cute in soft, cotton knit and blue and white gingham. The Bluebird Flutter Dress is a whimsical style for girls featuring coral pom pom trim and an elastic back for ease of wear. Cotton/Elastane blend. See Size Guide. xxs(12m-18m),xs(2t-3t),s(4t-5t),m(5-6),l(7-8),xl(9-10),xxl(11-12).