nest building behavior

例句：

1. 1. Birds build their nests intrees to protect their eggs and chicks.
   鸟在树上筑巢以保护它们的蛋和雏鸟。
2. 2. Some animals, such assquirrels, build elaboratenests for warmth and protection.
   一些动物，如松鼠，建造复杂的巢穴以保暖和保护。
3. 3. The study of nest buildingbehavior is important for understanding animal ecology.
   研究筑巢行为对于理解动物生态学非常重要。