The down sweaters - down jacket's younger brother
Down jackets and down pullovers have proven useful: a well-designed down lining simply offers an excellent ratio between thermal output and weight. Goose down, however, is warmer than duck down. Apart from that, down with high bulking power (700-800 Cuin) provides and ideal amount of warmth. Why use this lightweight, cozy and warm material only for outside layers of your clothing? Doesn't make a lot of sense, does it? Down sweaters are the best practical evidence.
Down pullovers - sometimes the outer layer, sometimes the inner layer.
No matter what time of the year, it makes sense to always carry a down sweater along with you. In mild temperatures it can serve as a jacket when it gets windy or when the sun disappears behind the clouds. It will always fit in your hiking backpack. Because of their small packed dimensions and low weight down pullovers are excellent companions. When temperatures drop below freezing your down sweater will be an excellent insulation layer under your outer jacket and keep you warm and cozy.