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
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