Caspian gull
A large gull species (Larus cachinnans). The name describes its yellow legs, black back, and gull family.
The Caspian gull is a rare winter visitor in Japan.
Katakana spelling is standard for bird names; usually written in kana.
Kanji spelling is rare and mainly used in specialized contexts; learners should recognize the katakana form.
The name is descriptive: 黄足 (yellow legs), 背黒 (black back), and 鴎 (gull). The exact derivation is uncertain, but it follows the typical pattern of Japanese bird names.