Biotic elements are the living components of an ecosystem. They include all living organisms, such as plants, animals, and microorganisms, that interact with each other and their environment. In the given options, birds and animals are the biotic elements, while air is an abiotic element.

Explanation:

1. Birds:
Birds are living organisms and belong to the animal kingdom. They are warm-blooded vertebrates and play a crucial role in the ecosystem. Birds contribute to pollination, seed dispersal, and pest control. They also help in nutrient cycling by scavenging dead animals or feeding on carrion. Birds are an essential part of the food chain, serving as both predators and prey. They interact with other biotic elements, such as plants and insects, and their presence or absence can greatly impact the ecosystem.

2. Animals:
Animals, including mammals, reptiles, amphibians, and insects, are biotic elements. They are an integral part of the ecosystem and interact with other living organisms and their environment. Animals contribute to various ecological processes, such as pollination, seed dispersal, predation, and decomposition. They are involved in nutrient cycling and play a vital role in maintaining the balance of the ecosystem. Animals also serve as indicators of environmental health and can help monitor the overall well-being of an ecosystem.

3. Air:
Air is not a biotic element; it is an abiotic element. Abiotic elements are non-living components of an ecosystem, such as air, water, soil, sunlight, and temperature. While air is essential for the survival of living organisms, it is not considered a biotic element because it does not possess life or engage in biological processes. However, air quality can have a significant impact on the health and well-being of biotic elements.

Correct answer:
The correct answer is option 'A': 1 and 2 only.
Birds and animals are biotic elements, while air is an abiotic element.