Context clues:
* ornithologist: A person who studies birds.
* feathered: Covered in feathers.
* long, slender beak: A distinctive feature of birds.
* vibrant plumage: Bright and colorful feathers.
* rare, migratory bird: A bird that travels long distances and is not commonly seen.
* never before been documented: Indicates the bird is unusual and previously unknown in the area.
These clues all point to the sentence being about a rare bird discovery.