What is a clear sign of an active bed bug infestation?

Small blood spots on bedding are indeed a clear sign of an active bed bug infestation. This occurs because bed bugs feed on human blood during the night, and after feeding, they may leave behind tiny blood spots on sheets or mattress covers. These stains are a direct indicator of their presence, highlighting feeding activity and the likelihood of an infestation.

The other options do not clearly indicate an active bed bug infestation. Excessive scratching of skin can be caused by various irritations, including allergies or other insect bites, but it does not specifically point to bed bugs. The presence of fur and feathers typically suggests the presence of rodents or birds, rather than bed bugs, as these pests do not produce such materials. Frequent insect sightings during the day is also misleading; bed bugs are primarily nocturnal and are less likely to be spotted during daylight hours. Thus, the small blood spots on bedding serve as a definitive and direct sign of bed bug activity.