1. Internal vs. External Fertilization:
* Birds: Birds lay eggs, which means fertilization is external. The female lays an egg that has been fertilized by the male.
* Mammals: Mammals give birth to live young, meaning fertilization is internal. The male's sperm fertilizes the female's egg inside her body.
2. Parental Care:
* Birds: While there's a lot of variation, many bird species have extensive parental care. Both parents often share the responsibility of incubating eggs, feeding and protecting chicks, and teaching them essential skills for survival.
* Mammals: Mammals typically have more intensive parental care than birds. They nourish their young through lactation, providing milk from their mammary glands. Many mammals also provide significant care and protection after birth, teaching offspring essential behaviors and skills.
Important Note: There are exceptions within both bird and mammal groups. For example, some birds, like ostriches, lay their eggs and have minimal parental care, while some mammals, like platypuses, lay eggs.