Indeed,if you take baby tree swallows out of a nest for an hour (feeding half the set and starving the other half), when the birds are replaced in the nest, the starved youngsters beg more loudly than the fed birds, and the parent birds feed the active beggars more than those who beg less vigorously. (TPO11, 56)

tree swallow n. 双色树燕，白杜燕

youngster /'jʌŋstə/ n. 小孩子，年轻人

vigorous /'vɪɡərəs/ adj. 精力充沛的;有力的，猛烈的toefl报名

我是分界线，大家先自己速读哦。

Indeed, (if you take baby tree swallows out of a nest for an hour) (feeding half the set and starving the other half),(when the birds are replaced in the nest), the starved youngsters beg more loudly than the fed birds, and the parent birds feed the active beggars more than those (who beg less vigorously).

长难句分析：

这句话的主干其实就是后面的一个并列结构，A and B

the starved youngsters beg more loudly than the fed birds, and the parent birds feed the active beggars more than those (who beg less vigorously)

修饰一：(if you take baby tree swallows out of a nest for an hour) ，从句

中文：如果你把小的双色树燕拿出鸟巢一小时

修饰二：(when the birds are replaced in the nest)，从句

中文：当这些鸟被放回鸟巢时

修饰三：(feeding half the set and starving the other half)，非谓语动词

中文：喂养一半，使另一半挨饿

修饰四：(who beg less vigorously) ，从句

中文：乞叫没那么大声

参考翻译：

确实，如果你把小的双色树燕拿出鸟巢一小时(喂养一半，使另一半挨饿)，当这些鸟被放回鸟巢时，挨饿的雏鸟就会比喂饱的鸟叫得更大声，它们的父母也会喂积极的乞食者要多于那些不积极的。

这个句子的主要修饰成分就是从句和非谓语动词，大家务必想清楚，每一个修饰成分修饰的是什么，才能看清楚这个句子的结构。