Counting at daybreak

An original explanation of an invented wildlife survey.

Just before sunrise on Saturday, volunteers will count the birds living among the reeds beside the river. Each pair of volunteers will remain in one marked section for twenty minutes and record every bird they detect. They may write notes to one another, but they have been asked not to talk until the count has finished.

The reeds hide many birds from view, so volunteers often recognise them from their calls. A conversation could cover a short or quiet call and cause a bird to be missed. Human voices might also make some birds fall silent or move into another section while counting is still taking place. This would alter the results rather than provide an accurate record of the birds that were present at the start.

Volunteers may discuss their observations as soon as the twenty minutes are over. The request for silence applies only during the count and is not a general rule for visitors to the riverside.

In your own words, explain two reasons why the volunteers are asked not to talk during the count.