Bringing a new duck into an established group can sometimes be challenging. From my experience and observations, ducks often take time to adjust to new flock members. It's quite common for a new duck to keep to herself initially, especially if she has just arrived in the last 10 days or so. This period allows her to assess her environment and the other ducks without feeling threatened. To help promote bonding, it's helpful to monitor their interactions closely while providing a safe and comfortable space for the new arrival. Gradual introductions, such as letting the new duck observe from a distance at first, can reduce stress for everyone involved. Additionally, ensuring there is enough food, water, and shelter helps minimize competition, which might otherwise cause some ducks to isolate themselves. Offering treats or shared feeding times can encourage positive interactions, as ducks associate each other's presence with good experiences. I also found that spending time near the ducks and speaking softly can make them feel more secure with the newcomer. Sometimes, it takes patience; social bonds can take weeks or even months to fully establish. If you notice prolonged isolation beyond a reasonable adjustment period, it might be worth consulting a vet or an avian expert to rule out health issues. Remember, every duck is unique, and showing empathy towards their feelings can go a long way in helping your flock live harmoniously together.