The birds at the beginning of the story are described as "calling softly." Let's explore this in more detail.

Introduction:
The story starts by mentioning the birds and their behavior at the beginning. It is important to understand what the author means by "calling softly" in order to determine the correct answer.

What does "calling softly" mean?
When birds call softly, it means they are making low or quiet sounds. These sounds are usually melodic and gentle. It is a way for birds to communicate with each other or to establish their presence in an area. Birds use different types of calls for various purposes, such as attracting mates, warning others of danger, or simply maintaining contact with their flock.

Explanation:
Given that the birds are calling softly at the beginning of the story, it suggests that they are not singing loudly, flying around, or sleeping. Let's examine each option in more detail:

a) Singing loudly:
If the birds were singing loudly, the author would have used different wording to describe their behavior. Singing loudly usually indicates a more energetic and vibrant behavior, which is not mentioned in this context.

b) Flying around:
The story does not mention the birds flying around. While birds do fly, it is not specified in the given scenario. Additionally, the question is specifically asking about their behavior at the beginning of the story.

c) Sleeping:
The birds are not mentioned as sleeping in the given scenario. Sleeping birds are usually depicted as quiet and still, rather than calling softly.

d) Calling softly:
This is the correct answer. The story explicitly states that the birds are calling softly at the beginning. This behavior suggests that the birds are communicating with each other in a gentle and melodic manner.

Conclusion:
Based on the given information, the correct answer is option 'd) Calling softly.' The birds at the beginning of the story are described as making low, gentle sounds to communicate with each other.