多年来他一直观察鸟类的行为。

He has been observing the behavior of birds for many years.

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他经常观察鸟类的行为。

He often observes the behavior of birds.

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观鸟者观察各种新的物种，从中他们不止能认识不同的鸟种，还能学到关于迁徙、鸟类行为学、食性、求爱还有鸟类领地的知识。

As birders observe new species, they not only learn about different birds, but they also learn about migration, bird behavior, feed preferences, courtship and bird territories.

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