sentences:  Islands where terrestrial predators have arrived in the form of rats, cats, foxes, etc., have devastated island seabird colonies.One well-studied case of this phenomenon has been the effect on common murre colonies on islands in Alaska, where foxes were introduced for fur farming.Colony-nesting birds have been used by humans as a source of food in the form of eggs and meat, down for bedding, feathers for quill pens, and guano for fertilizer.