When the red fox eats a rabbit, the fox is at a higher feeding level than it is when it eats berries from a bush. The plants are at the first feeding level. Their source of food is the sun. Herbivores or plant eaters are at the second feeding level. It is possible for an animal to feed at different levels.
Omnivores are at different feeding levels depending upon what they are eating.
When a robin is eating earthworms or insects, it is feeding at a higher level than when it is picking seeds off a bush. Carnivores are at the third or fourth feeding level, depending on whether they are eating herbivores or other carnivores. The Great Horned Owl might feed on mice, or it might kill a weasel, which also preys on mice. So the feeding level depends on what the owl is eating.