1. A flock of birds: This could represent Doodle's fragile nature, as a young ibis, a type of bird known for its delicate beauty, is found dead in the story. The flock symbolizes the larger context of nature's indifference to individual lives.
2. A swarm of memories: This could describe the protagonist's memories of his brother, both happy and painful. The swarm represents the overwhelming nature of these memories, how they persist and sometimes feel uncontrollable.
3. A knot of guilt: This could describe the narrator's feelings of responsibility for his brother's death. The knot signifies the tangled and oppressive nature of his guilt, which he carries with him throughout the story.
4. A cloud of grief: This could represent the atmosphere of sorrow and sadness that envelops the narrator after Doodle's death. The cloud symbolizes the pervasive nature of his grief, which seems to darken everything around him.
5. A web of expectations: This could be used to describe the pressure the narrator feels to make Doodle "normal." The web represents the complex and sometimes suffocating network of expectations that the narrator places on his brother.
These are just a few examples, and it's important to remember that the beauty of language lies in its flexibility. You can use collective nouns creatively to express different themes and emotions within the story.