What is "larus atricilla"

Laughing \Laugh"ing\, a. & n. from Laugh, v. i. Laughing falcon (Zo["o]l.), a South American hawk ( Herpetotheres cachinnans); -- so called from its notes, which resemble a shrill laugh. Laughing gas (Chem.), hyponitrous oxide, or protoxide of nitrogen Laughing goose (Zo["o]l.), the European white-fronted goose. Laughing gull. (Zo["o]l.)

1. A common European gull ( Xema ridibundus); -- called also pewit, black cap, red-legged gull, and sea crow.

2. An American gull ( Larus atricilla). In summer the head is nearly black, the back slate color, and the five outer primaries black.

   Laughing hyena (Zo["o]l.), the spotted hyena. See Hyena.

   Laughing jackass (Zo["o]l.), the great brown kingfisher ( Dacelo gigas), of Australia; -- called also giant kingfisher, and gogobera.

   Laughing owl (Zo["o]l.), a peculiar owl ( Sceloglaux albifacies) of New Zealand, said to be on the verge of extinction. The name alludes to its notes.