48．The common kestrel roosts and hunts alone，but the lesser kestrel roosts andhunts in flocks，possibly soone bird can learn from others where to find insect swarms．

(possibly so=possibly so that)

普通红隼单独栖息和狩猎，但较小的红隼群栖群食，很可能因此一只鸟可以从其他鸟那儿了解到在哪儿可以找到成群的昆虫。

分句1：the common kestrel…

分句2：but

分句3：possibly so…

分句4：where to…

1，2和3并列

3和4嵌套