Sparrows, Starlings, and Pigeons have discovered that nesting in stove, bathroom, and dryer vents is extremely safe. This problem is not discovered until nesting material, ectoparasites, bird feathers, and bird droppings start to appear in and around the vents. This can cause serious damage to the dryer, stove or bathroom fans. When this happens, the nesting material need to be removed, and the vent should be bird-proofed.