In the last decade, the country of Alumba has undergone a massive construction boom. In one city, Semanta, hundreds of new buildings have been erected and, as a result, the ambient light at night has increased from 0.10 lux to 10 lux, causing migratory birds flying to alter their traditional path and fly into Semanta, where they often crash into buildings. The mayor believes that to ensure the birds keep to their traditional flight path while flying through Alumba, the city should turn off lights throughout the city at night during the bird`s migratory season, so that ambient light is around 0.10 lux. Which of the following, is necessary, to evaluate the mayor`s proposal for limiting the amount of night light that Semanta emits?
【选项】Whether the period in which birds migrate is consistent each year.