Baby Names Beginning With "C": Meaning: Dove?

Questions

Mallard ---------- are sometimes built at a height of 40 feet above ground. Surprisingly, when leaving their nests for the first time, chicks are very rarely hurt due to falling to the ground.?

Fish travel in schools, whales travel in pods or ----------?

Because birds carrying messages were often killed in flight by hawks, medieval Arabs made a habit of sending important messages ----------?

Many corals receive nourishment from algae which grow inside their ----------?

---------- feel safest when they are crowded together, hundreds in a group.?