Water bird is a term used to describe a bird species that is adapted to living in or near water. They are commonly found in wetlands, marshes, lakes, rivers, and coastal areas. These birds have various adaptations that allow them to swim, dive, wade, and catch prey in aquatic environments.

Among the given options, the correct answer is option 'A' - Crane.

Crane is a water bird that belongs to the family Gruidae. It is known for its tall stature, long legs, and long neck. Cranes are found in various parts of the world and are known for their distinctive calls and elaborate courtship dances. They are highly adapted for wading in shallow water, where they feed on fish, frogs, insects, and other small aquatic animals.

Here are the characteristics and features of cranes that make them water birds:

1. Adapted for wading: Cranes have long legs that allow them to wade in shallow water without getting wet. Their long toes and sharp claws help them maintain balance on uneven surfaces.

2. Long neck: The long neck of cranes enables them to reach down into the water to catch prey. It also aids in alertness and provides a better view of their surroundings.

3. Beak shape: The beak of a crane is long, slender, and pointed, which is ideal for capturing small aquatic creatures like fish and insects.

4. Waterproof feathers: Cranes have a special gland that produces oil, which they spread on their feathers to make them waterproof. This adaptation helps them stay dry and buoyant while swimming or wading in water.

5. Strong wings: Cranes have strong wings that allow them to fly over long distances, migrating between breeding and wintering grounds. They often form V-shaped formations during migration, which helps reduce air resistance and conserve energy.

6. Habitat preference: Cranes are commonly found in wetland habitats, such as marshes, swamps, and riverbanks. These environments provide them with ample food sources and nesting sites.

In conclusion, the correct answer is option 'A' - Crane, as it possesses all the characteristics and adaptations that define a water bird.

A