What is "fork-tailed gull"

Fork-tailed \Fork"-tailed`\, a. (Zo["o]l.) Having the outer tail feathers longer than the median ones; swallow-tailed; -- said of many birds.

Fork-tailed flycatcher (Zo["o]l.), a tropical American flycatcher ( Milvulus tyrannus).

Fork-tailed gull (Zo["o]l.), a gull of the genus Xema, of two species, esp. X. Sabinii of the Arctic Ocean.

Fork-tailed kite (Zo["o]l.), a graceful American kite ( Elanoides forficatus); -- called also swallow-tailed kite.