Flying distances of the tracked gulls.

CI = Confidence interval.*ND = Not determine; because the migratory route started from Thailand to Cambodia and Vietnam, and it took 39 days from Vietnam to China.CI为置信区间（Confidence interval），ND为未确定（Not determine）；因该迁徙路线始于泰国，途经柬埔寨与越南，且从越南至中国的行程耗时39天。