According to the magical AI I asked, this is the Great Frigatebird, and Here’s some information about it:

• Appearance: They are large, black seabirds with a distinctive long, deeply forked tail. Males have a striking red throat pouch that they inflate to attract mates. Females are slightly larger than males and have a white chest. As you can see in your photo, this one has a white chest, indicating it’s a female.  
• Habitat: They are found throughout tropical and subtropical oceans. In American Samoa, they are commonly seen soaring along the coastlines and offshore.  
• Behavior: Frigatebirds are known for their impressive aerial skills. They are masters of soaring and gliding, and can stay aloft for long periods without flapping their wings. They are kleptoparasites, meaning they often harass other seabirds to steal their food.  
• Nesting: They nest in colonies on islands and atolls.  

Interesting facts:

• Frigatebirds have the largest wingspan-to-body-weight ratio of any bird.  
• They can sleep while soaring by shutting down one half of their brain at a time.