1 bird: 6 flew away, leaving 1 dead bird.

2 birds: 5 flies flew away, leaving 1 dead birds and 1 live birds.

3 birds: 4 flew away, leaving 1 dead birds and 2 live birds.

4 birds: 3 flew away, leaving 1 dead birds and 3 live birds.

5 birds: 2 flew away, leaving 1 dead birds and 4 live birds.

6 birds: 1 flew away, leaving 1 dead birds and 5 live birds.

Hypothesis 2: A dead bird falls from a tree bird.

Fly away at 0: 7, no birds.

1 bird: 6 flew away, leaving 1 live bird.

2 birds: 5 flies flew away, leaving 2 live birds.

It flew away at 3: 4, leaving three live birds.

Fly away at 4: 3, leaving four live birds.

Five birds: two flew away, leaving five live birds.

6 birds: 1 flew away, leaving 6 live birds.

N birds: None flew away, but n-6 birds flew in, leaving N live birds.

Suppose 1: The dead bird didn't fall from the tree.

1 bird: 9 flew away, leaving 1 dead bird.

2 birds: 8 flew away, leaving 1 dead birds and 1 live birds.

3 birds: 7 flew away, leaving 1 dead birds and 2 live birds.

4 birds: 6 flew away, leaving 1 dead birds and 3 live birds.

5 birds: 5 flew away, leaving 1 dead birds and 4 live birds.

6 birds: 4 flew away, leaving 1 dead birds and 5 live birds.

7 birds: 3 flew away, leaving 1 dead birds and 6 live birds.

8 birds: 2 flew away, leaving 1 dead birds and 7 live birds.

9 birds: 1 flew away, leaving 1 dead birds and 8 live birds.

10: None flew away, leaving 1 dead birds and 9 live birds.

1 1: None flew away, 1 only flew in, leaving 1 dead birds and 10 live birds.

12 birds: not one flew away, but two flew in, leaving 1 dead bird1/live bird.

N birds: none flew away, and n- 10 birds flew in, leaving 1 dead birds and n- 1 live birds.

Hypothesis 2: A dead bird falls from a tree bird.

Fly away at 0: 9, no birds.

1: 8 birds flew away, leaving 1 live birds.

2 birds: 7 birds flew away, leaving 2 live birds.

Three: Six flew away, leaving three live birds.

4 birds: 5 flies flew away, leaving 4 live birds.

Five birds: four flew away, leaving five live birds.

Six birds: three flew away, leaving six live birds.

Seven birds: two flew away, leaving seven live birds.

8 birds: 1 flew away, leaving 8 live birds.

Nine: None of them flew away, leaving nine live birds.

10: None flew away, 1 only flew in, leaving 10 live birds.

1 1: No one flew away, but two flew in, leaving 1 1 live birds.

N birds: No one flew away, but N-9 birds came, leaving N live birds.

It depends on time and place, types of weapons and birds, climate and physical conditions.