Yes they can, and I’ve had success in doing this myself. Here are some tips for machine washing and drying a feather pillow:

• Use a low-sud detergent when washing your pillow
• Use the delicate cycle on your washer, and wash in cold water
• Run the pillow through at least one extra rinse cycle to ensure that all the soap has been washed out of the pillow
• For the dryer, use the low-heat or no-heat setting to avoid singeing the feathers inside the pillow
• Add some wool dryer balls (or clean tennis balls) to the dryer to fluff the pillow during the drying process