Uricotelism is found in

The correct option is birds, land reptiles and insects.

Excretion of nitrogenous wastes can be classified into three major types based on the primary excretory product: ammonotelism (excreting ammonia), ureotelism (excreting urea), and uricotelism (excreting uric acid).

Uricotelism is the process of excreting nitrogenous waste primarily in the form of uric acid. Uric acid is the least toxic and the least soluble in water among the primary nitrogenous wastes (ammonia, urea, and uric acid). Because of its low solubility, it requires very little water for its elimination from the body and is typically excreted as a semi-solid paste or pellet.

This is a vital evolutionary adaptation for water conservation in animals inhabiting terrestrial habitats with limited water availability. Therefore, uricotelism is typically found in:
1. Birds
2. Land reptiles (such as lizards and snakes)
3. Insects and some land snails

Let us look at the other options to understand why they are incorrect:
- Frogs and toads: Adult amphibians are mostly ureotelic (excreting urea), while their aquatic larvae (tadpoles) are ammonotelic (excreting ammonia).
- Mammals: Mammals are ureotelic, excreting urea as their primary nitrogenous waste.
- Fish and freshwater protozoans: Most aquatic animals, including bony fishes and protozoans, are ammonotelic because ammonia is highly toxic but highly soluble, requiring large volumes of water for excretion, which is readily available in their environment.