female ducks who are maturing and ready to mate (or close to it) will present themselves to a potential mate by lowering their heads and fanning the wings out slightly (flattening their backs). They don't really have a "Heat" per say, but more like a season of being hormonally challenged. lol. It usually starts in January or February and goes through summer usually... it's not very specific in time. Females ducks will often start this when they are around 3-5 months old and will start laying around 5 months old IF it aligns with the season. Most ducks born in spring will be ready to start the whole mating business in Jan/Feb, But ducks born really early in the season usually start laying in summer, or they may skip this season and start the following year. Ducks born really late in the summer usually wait longer, or a season before they start laying as well (sometmes they'll start the beginning of the following summer). I have 6 females who all live indoors and most of them are being hormonally challenged right now... lol I'm not entirely sure on this info, it's just my best assumption based on what i've seen so far.