 The presence of bristles near the bill (rictal bristles) in some flycatchers may be an adaptation for hawking insects; scientists are not sure of the function but they may help protect the eyes or they might actually help provide the bird sensory information as to the location of the prey.Swallows, swifts, and nightjars do not have large bills, but they have wide-gaping mouths.Some nightjars also have bristles around the bill (the common poorwill does, the common nighthawk does not).