Solution:

Introduction:
In this question, we are given a list of four birds - Sparrow, Parrot, Cuckoo, and Duck. We need to identify the odd one out from the given options.

Analysis:
To find the odd one out, we need to carefully observe the characteristics or features of each bird and compare them.

Sparrow:
- Sparrows are small-sized birds.
- They have brown or gray feathers.
- They are known for their chirping sound.
- Sparrows have a diet consisting of seeds and insects.

Parrot:
- Parrots are colorful birds.
- They have a strong beak.
- They are known for their ability to mimic human speech.
- Parrots primarily feed on fruits and nuts.

Cuckoo:
- Cuckoos are medium-sized birds.
- They have a slender body and long tail feathers.
- Male cuckoos make a 'cuckoo' sound.
- Cuckoos are known for laying their eggs in other bird's nests.

Duck:
- Ducks are aquatic birds.
- They have a flat bill and webbed feet.
- They are known for their ability to swim and dive.
- Ducks feed on plants, small fish, and insects.

Odd One Out:
From the analysis, we can see that all the birds - Sparrow, Parrot, and Cuckoo - share common characteristics such as being small or medium-sized birds and having feathers. However, the odd one out is the Duck because it is the only bird that is aquatic and has unique features like a flat bill and webbed feet.