It is a very big generalization, and some species are exceptions, but generally first summer individuals can only be separated by retained juvenile remiges and rectrices or by moult limits in the greater coverts 这是一个很概括的看法,且某些鸟种是例外,但一般而言一龄夏羽个体只能以还留著的幼鸟飞羽和尾羽,或大覆羽的换羽界限来区分
Adult winter heuglin's gull : the primary moult begins much later than in other big gulls and progresses slowly through the winter, and moult limits can usually be seen into january-february of the following year ( p9-10 ) 灰林银鸥成鸟冬羽:初级飞羽换羽时间较其他种为迟而且整个冬季都在缓慢换羽,所以第二年一二月一般都还可以看到换羽的界限(p9-10)。
Adult winter heuglin's gull : the primary moult begins much later than in other big gulls and progresses slowly through the winter, and moult limits can usually be seen into january-february of the following year ( p9-10 ) 灰林银鸥成鸟冬羽:初级飞羽换羽时间较其他种为迟而且整个冬季都在缓慢换羽,所以第二年一二月一般都还可以看到换羽的界限(p9-10)。