What is "cerulean warbler"

The cerulean warbler (Setophaga cerulea) is a small songbird of the New World warbler family. Adult males have pale cerulean blue and white upperparts with a black necklace across the breast and black streaks on the back and flanks. Females and immature birds have greyer or greenish upperparts, a pale stripe over the eye, and no streaking on the back and no necklace. All of these birds have wing bars and a thin pointed bill. They are found in deciduous forests of eastern North America during the breeding season and then migrate to forested mountain areas in South America. The species is considered threatened with an IUCN status of Vulnerable (VU), indicating it is considered to be facing a high risk of extinction in the wild.