A down mattress is actually a layer of feather mattress. And they do come from actual adult birds. The feathers from these birds are known to be good conductors of insulation. And they offer more ” fluff”. For discriminating sleepers, this is one of the better bed add ons to own.

WiseGeek breaks down the properties further:

Down has many properties that make it an excellent additive to textile products. Though down can be packed tightly into small spaces, it is also able to trap air in its layers and provide thermal insulation. Down is considered to be one of the best insulators against cold and is frequently used in outdoor gear such as sleeping bags, coats, and jackets. However superior its insulating properties are to synthetic filler, down falls short of superior in wet conditions because it loses its insulating properties when wet and does not dry quickly.

Down mattress photo from Purelivingcollection.