How Are Pesticides Passed Through The Food Chain?

A plant may absorb the pesticides from the ground or air. The plants may be eaten by bugs and insects. And then be eaten by a bird or other insectivore. That animal would then absorb
whatever of the pesticide the bug hadn't metabolised . From
there, it would be passed on through the food chain as normal, the
amount of poison transferred lowering bit by bit - assuming that no
animals in the chain ate any more infected bugs or plants.