Coenozoic era is the correct answer.

The era age of birds and mammals is the Coenozoic era. Let's delve into the details of this era and understand why it is the correct answer.

Coenozoic Era:
The Coenozoic era is the current era, also known as the Age of Mammals. It began around 66 million years ago and continues to the present day. This era is characterized by the dominance and diversification of mammals and the rise of birds.

Key Points:
1. Geological Time Scale: The Coenozoic era is the most recent era on the geological time scale, following the Mesozoic era (age of dinosaurs) and the Paleozoic era (age of early life forms).

2. Age of Mammals: The Coenozoic era is often referred to as the Age of Mammals because it is during this era that mammals experienced significant diversification and became the dominant group of animals on Earth. Mammals evolved various adaptations and filled ecological niches previously occupied by dinosaurs.

3. Rise of Birds: The Coenozoic era is also the time when birds evolved and diversified. Birds are descendants of a group of small, feathered theropod dinosaurs, and their evolution and diversification occurred during this era.

4. Extinction of Dinosaurs: The Coenozoic era began with a mass extinction event, known as the Cretaceous-Paleogene extinction event, which wiped out the dinosaurs and many other organisms. This extinction event opened up ecological opportunities for mammals and birds to thrive and evolve.

5. Geological Events: The Coenozoic era is marked by various geological events, including the formation of the Himalayas, the opening and closing of ocean basins, and the development of modern climate patterns.

Conclusion:
In conclusion, the era age of birds and mammals is the Coenozoic era. This era is characterized by the dominance and diversification of mammals and the rise of birds. It began around 66 million years ago and continues to the present day.