There are four different species of swallow which visit us-the swift, the chimney swallow, the house martin, and the sand martin.

我们见到的燕子有四种——褐雨燕、烟囱雨燕、家燕和崖沙燕。

Four brothers had watched with indignation the felonious attempts of a sparrow to possess himself of the nest of a house martin, in which lay its young brood of four unfledged birds.

四兄弟愤怒地看到一只麻雀试图夺取一只燕子的巢窠，里面有四只羽翼未丰的小燕子。