Although this behavior may be harmless, from a cultural point of view, it may bring bad luck to people. Therefore, if pigeons are found defecating on the windowsill, it is best to take measures to clean them up, maintain good hygiene habits and avoid any possible health risks.
In short, although it is not necessarily unlucky for pigeons to shit on the windowsill, it is usually considered unlucky from a cultural point of view, so we should pay attention to cleanliness and maintain hygienic habits.