What is a common sign of infestation by carpenter ants?

A common sign of infestation by carpenter ants is sawdust trails. Carpenter ants tunnel through wood to create their nests, and as they excavate the wood, they discard fine wood particles and frass, which can resemble sawdust. This accumulation of sawdust around areas where these ants are nesting or traveling is a telltale indication of their presence.

The other options refer to characteristics of different pests or specific behaviors that do not apply to carpenter ants. Clear droppings are more associated with other insects like cockroaches, while feeder tubes are related to termites, which creates mud tubes as a protective structure leading to their food sources. Noise during the day might be expected from certain pests like rodents, but carpenter ants tend to be more active at night and are less likely to cause noticeable noise during daylight hours.